29. Sims, K.; Abedi-Samakush, F.; Szulc, N.; Macias Honti, M.G.; Mattsson, J. (2021) OsARF11 Promotes Growth, Meristem, Seed, and Vein Formation during Rice Plant Development.International Journal of Molecular Sciences 22(8) OsARF11 Promotes Growth, Meristem, Seed, and Vein Formation during Rice Plant Development
The plant hormone auxin acts as a mediator providing positional instructions in a range of developmental processes. Studies in Arabidopsis thaliana L. show that auxin acts in large part via activation of Auxin Response Factors (ARFs) that in turn regulate the expression of downstream genes. The rice (Oryza sativa L.) gene OsARF11 is of interest because of its expression in developing rice organs and its high sequence similarity with MONOPTEROS/ARF5, a gene with prominent roles in A. thaliana development. We have assessed the phenotype of homozygous insertion mutants in the OsARF11 gene and found that in relation to wildtype, osarf11 seedlings produced fewer and shorter roots as well as shorter and less wide leaves. Leaves developed fewer veins and larger areoles. Mature osarf11 plants had a reduced root system, fewer branches per panicle, fewer grains per panicle and fewer filled seeds. Mutants had a reduced sensitivity to auxin-mediated callus formation and inhibition of root elongation, and phenylboronic acid (PBA)-mediated inhibition of vein formation. Taken together, our results implicate OsARF11 in auxin-mediated growth of multiple organs and leaf veins. OsARF11 also appears to play a central role in the formation of lateral root, panicle branch, and grain meristems. Link DOI PubMed
28. Zhou, C; Mattsson, J. (2021) Development of Micropropagation in Bigleaf Maple (Acer macrophyllum).Horticulturae 7 Development of Micropropagation in Bigleaf Maple (Acer macrophyllum)
TDZ; apical dominance; figured wood
Natural populations of bigleaf maple (Acer macrophyllum Pursh) trees contain, at low frequency, individuals with stems that have attractive and valuable wavy grain in the wood. To maintain the genotype of these individuals, vegetative propagation is desired. To enable propagation from the limited amount of plant tissue that is often available, an in vitro micropropagation procedure was developed. A mix of wild trees was used as source material to generate a procedure that is genotype unspecific. Among tested basal media, DKW medium resulted in the highest frequency of growing shoots. For multiplication of shoots, removal of the apex of shoot explants was instrumental, presumably because this treatment broke a strong apical dominance in this species. Of tested hormone and hormone combinations, 0.1 mu M thidiazuron produced the best results with an average of 3.2 axillary shoots per explant with an average of 3.7 nodes per axillary shoot after 1 month. Although rooting did not require hormone treatment, a 68% frequency of rooting was obtained on 1/2 MS supplemented with 1 mu M IBA, 27% higher than hormone-free media. Taken together, we have developed a procedure for propagation of bigleaf maple from a limited amount of tissues that can be used to multiply various genotypes of interest. DOI
27. Tasnim, S; Gries, R; Mattsson, J. (2020) Identification of Three Monofunctional Diterpene Synthases with Specific Enzyme Activities Expressed during Heartwood Formation in Western Redcedar (Thuja plicata) Trees.Plants-Basel 9 Identification of Three Monofunctional Diterpene Synthases with Specific Enzyme Activities Expressed during Heartwood Formation in Western Redcedar (Thuja plicata) Trees
diterpene synthase; heartwood; secondary metabolites; western redcedar
Upon harvest, Western redcedar (WRC;Thuja plicata) trees have a high incidence and extent of heartwood rot. While monoterpenoids and lignans have been linked to rot resistance in this species, other specialized metabolites, such as diterpenes, are likely to contribute to rot resistance. Here we report the cloning and functional assessment of three putative diterpene synthase (TpdiTPS) genes expressed during heartwood formation in WRC. The predicted proteins of the three genes lack either of the two catalytically independent active sites typical of most diTPS, indicating monofunctional rather than bifunctional activity. To identify potential catalytic activities of these proteins, we expressed them in genetically engineeredEscherichia colistrains that produce four potential substrates, geranylgeranyl diphosphate (GGDP),ent, syn,and normal stereoisomers of copalyl diphosphate (CDP). We found that TpdiTPS3 used GGDP to produce CDP. TpdiTPS2 used normal CDP to produce levopimaradiene. TpdiTPS1 showed stereoselectivity as it used normal CDP to produce sandaracopimaradiene andsyn-CDP to producesyn-stemod-13(17)-ene. These genes and protein enzymatic activities have not been previously reported in WRC and provide an opportunity to assess their potential roles in heartwood rot resistance in this economically important species. DOI PubMed
26. Arshad, M; Biswas, K; Bisgrove, S; Schroeder, WR; Thomas, BR; Mansfield, SD; Mattsson, J; Plant, A. (2019) Differences in drought resistance in nine North American hybrid poplars.Trees-Struct. Funct. 33: 1111-1128 Differences in drought resistance in nine North American hybrid poplars
Populus; Physiology; Gene expression; ABA; Ranking; Indicator gene
Poplar hybrids are cultivated in North America for environmental applications, agroforestry, and the pulp and paper industry primarily because of their fast growth and limited nutrient requirement. For the same reasons, they have been identified as suitable species for carbon sequestration and as a potential feedstock for carbon-neutral production of energy. The clones deployed on the Canadian prairies are generally regarded as drought sensitive, which poses a problem as water availability has steadily decreased in this region over the past century and a severe water crisis has been predicted. To approach this problem, we tested nine commonly deployed North-American hybrid poplars, developed for large-scale cultivation in the Canadian prairies, for their physiological responses to drought, resulting in a ranking of drought resistance. The difference between the clones showing the most and the least response of drought stress was large, and we used these clones to further examine the differences in the expression of genes known to be up-regulated in response to drought stress. This interrogation showed significant differences in transcript abundance that largely reflected the physiological status of the tested clones, but also many genes being down rather than up-regulated in response to drought stress in the drought-tolerant clone. In particular, putative positive and negative regulators of abscisic acid signaling were expressed at levels consistent with a potential role in observed differences in drought resistance. DOI
25. Schuetz, M; Fidanza, M; Mattsson, J. (2019) Identification of Auxin Response Factor-Encoding Genes Expressed in Distinct Phases of Leaf Vein Development and with Overlapping Functions in Leaf Formation.Plants-Basel 8 Identification of Auxin Response Factor-Encoding Genes Expressed in Distinct Phases of Leaf Vein Development and with Overlapping Functions in Leaf Formation
MONOPTEROS; auxin response factor; ARF; shoot meristem; leaf initiation; vascular; procambium; Arabidopsis
Based on mutant phenotypes the MONOPTEROS (MP)/Auxin Response Factor 5 (ARF5) gene acts in several developmental processes including leaf vein development. Since overlapping functions among ARF genes are common, we assessed the related ARF 3-8 and 19 genes for potential overlap in expression during vein development using in-situ hybridization. Like MP/ARF5, ARF3 was expressed in preprocambial and procambial cells. ARF7 was also expressed in procambial cells, close to and during vein differentiation. ARF19 was expressed in differentiating vessel elements. To assess if genes with vein expression have overlapping functions, double mutants were generated. While arf3, 5 and 7 mutants formed leaves normally, double mutant combinations of mp/arf5 with arf3 or arf7 resulted in a breakdown of leaf formation. Instead, novel structures not present in any of the single mutants formed. The results implicate ARF3 and ARF7 in rosette leaf formation and suggest that their functions overlap and act in parallel with MP/ARF5 in this process. The observed vascular expression patterns suggest unique functions (ARF7 and 19) and potentially overlapping functions (ARF3 and 5) in vein development. Since arf3 arf5 double mutants do not form leaves, assessment of their potential combined action in vein development will require the use of conditional mutants. DOI PubMed
24. van den Top, GG; Reynolds, JD; Prins, HHT; Mattsson, J; Green, DJ; Ydenberg, RC. (2018) From salmon to salmonberry: The effects of salmon-derived nutrients on the stomatal density of leaves of the nitriphilic shrub Rubus spectabilis.Funct. Ecol. 32 From salmon to salmonberry: The effects of salmon-derived nutrients on the stomatal density of leaves of the nitriphilic shrub Rubus spectabilis
Great Bear Rainforest; nutrient subsidy; Rubus spectabilis; salmonberry; salmon-derived nutrients; stomata; stomatal density
Nutrients derived from the carcasses of Pacific salmon have been shown to have wide-ranging effects on riparian systems. These include changes in community species composition and an increase in leaf nitrogen concentration, with the latter effect pronounced in the nitriphilic shrub Rubus spectabilis (salmonberry). Experimental work with other species has shown that leaf stomatal density increases in response to nitrogen fertilization. We predicted that the stomatal density of salmonberry leaves would vary directly with the density of spawning salmon in salmonberry leaves collected from 16 streams in the vicinity of Bella Bella, on British Columbia's central coast. We estimated the stomatal density along each stream, and quantified stream characteristics, including the number of spawning salmon (Oncorhynchus spp.), canopy cover, stem density and soil moisture. We found that salmon have both direct and indirect effects on stomatal density, the latter mediated by canopy cover and stem density. Salmonberry stomatal density increased by 1.12 stomata per mm(2) (similar to 0.5%) for every kg of salmon per metre of stream. Over the range of salmon densities observed (1.8-49.0 kg per metre of stream), stomatal density increased by almost 45 mm(-2), or more than 20%. These data confirm that the stomatal density in salmonberry responds positively to the opportunity for greater productivity provided by salmon carcasses. The data provide insight into the physiological and morphological processes supporting nitrogen uptake, which in turn influences plant community composition. A is available for this article. DOI
23. Foster, AJ; Aloni, R; Fidanza, M; Gries, R; Gries, G; Mattsson, J. (2016) Foliar phase changes are coupled with changes in storage and biochemistry of monoterpenoids in western redcedar (Thuja plicata).Trees-Structure and Function 30: 1361-1375 Foliar phase changes are coupled with changes in storage and biochemistry of monoterpenoids in western redcedar (Thuja plicata)
Western redcedar; Thuja plicata; Monoterpenes; Ontogeny; Metamorphic heteroblasty; Resin ducts; Resin glands; alpha-Thujone; Herbivory
The monoterpenoid content of Thuja plicata needles and scales differs both quantitatively and qualitatively. Resin storage structures are associated with anatomical modifications that suggest facilitated exit of monoterpenoids. Western redcedar (Thuja plicata) is a highly valued source of lumber. T. plicata trees planted in reforestations efforts are often heavily damaged by extensive ungulate browsing. Research has shown that high foliar content of monoterpenoids deters browsing, providing an avenue for resistance selection in young plants. T. plicata foliage undergoes, however, extensive phase changes during early growth. Currently it is unknown whether the anatomical basis of monoterpenoid storage and release, and the content and composition of stored monoterpenoids, also change at the same time. Here, we studied these aspects of T. plicata seedling biology. Cotyledons lack storage structures for terpenoids. Needles contain a single longitudinal terpenoid duct with (+)-sabinene and (-)-alpha-pinene as prevalent monoterpenoids. In contrast, scales contain enclosed resin glands and have a monoterpenoid profile that is markedly different from needles, with alpha-thujone as the most prevalent monoterpenoid and no detectable levels of (-)-alpha-pinene. Both ducts and glands are close to the epidermis and vascular tissues, frequently companioned by gaps in the sub-epidermal fiber layer, suggesting paths of facilitated diffusion of monoterpenoids out of tissues. We conclude that foliar phase changes are coupled with equally significant changes in resin storage structure anatomy, monoterpenoid levels and composition. Our findings provide a framework for reproducible sampling and selection not only for high levels of monoterpenoids but also for anatomical markers that may affect release of these compounds. DOI
22. Gesell, A; Blaukopf, M; Madilao, L; Yuen, MMS; Withers, SG; Mattsson, J; Russell, JH; Bohlmann, J. (2015) The Gymnosperm Cytochrome P450 CYP750B1 Catalyzes Stereospecific Monoterpene Hydroxylation of (+)-Sabinene in Thujone Biosynthesis in Western Redcedar.Plant Physiology 168: 94-U776 The Gymnosperm Cytochrome P450 CYP750B1 Catalyzes Stereospecific Monoterpene Hydroxylation of (+)-Sabinene in Thujone Biosynthesis in Western Redcedar
Western redcedar (WRC; Thuja plicata) produces high amounts of oxygenated thujone monoterpenoids associated with resistance against herbivore feeding, particularly ungulate browsing. Thujones and other monoterpenoids accumulate in glandular structures in the foliage of WRC. Thujones are produced from (+)-sabinene by sabinol and sabinone. Using metabolite analysis, enzyme assays with WRC tissue extracts, cloning, and functional characterization of cytochrome P450 monooxygenases, we established that transsabin- 3-ol but not cis-sabin-3-ol is the intermediate in thujone biosynthesis in WRC. Based on transcriptome analysis, full-length complementary DNA cloning, and characterization of expressed P450 proteins, we identified CYP750B1 and CYP76AA25 as the enzymes that catalyze the hydroxylation of (+)-sabinene to trans-sabin-3-ol. Gene-specific transcript analysis in contrasting WRC genotypes producing high and low amounts of monoterpenoids, including a glandless low-terpenoid clone, as well as assays for substrate specificity supported a biological role of CYP750B1 in alpha- and beta-thujone biosynthesis. This P450 belongs to the apparently gymnosperm-specific CYP750 family and is, to our knowledge, the first member of this family to be functionally characterized. In contrast, CYP76AA25 has a broader substrate spectrum, also converting the sesquiterpene farnesene and the herbicide isoproturon, and its transcript profiles are not well correlated with thujone accumulation.Website DOI
21. Arshad, M; Mattsson, J. (2014) A putative poplar PP2C-encoding gene negatively regulates drought and abscisic acid responses in transgenic Arabidopsis thaliana.Trees-Structure and Function 28: 531-543 A putative poplar PP2C-encoding gene negatively regulates drought and abscisic acid responses in transgenic Arabidopsis thaliana
Drought tolerance; Poplar; PP2CA; Abscisic acid; Arabidopsis thaliana
Here we link for the first time a poplar gene with putative function in ABA signaling to the regulation of drought responses, providing a target for drought tolerance improvement in poplars. Populus species are valued for their fast growth and are cultivated widely. Many of the commonly used species and hybrids are, however, regarded as drought sensitive, which poses a problem for large-scale cultivation particularly in light of climate change-induced drought spells in areas of poplar growth. While many hundreds of drought-induced genes have been identified in Populus species, very little is known about the genes and the signaling process that leads to a drought response in these species. Based on sequence similarity, the poplar G059200 gene is a potential ortholog of AtPP2CA, an inhibitor of drought and abscisic acid (ABA) responses in Arabidopsis thaliana. To test if G059200 has a similar function, we generated transgenic A. thaliana plants overexpressing this gene. These transgenic lines exhibited reduced responses to exogenous ABA and reduced tolerance to osmotic stress. Finally, drought tolerance of plants was also significantly reduced. Taken together, these data provide evidences that G059200 acts as a negative regulator of ABA responses. The ability to negatively regulate drought stress responses suggests that G059200 may be targeted for drought tolerance breeding, for example, by identification of individuals harboring natural or induced loss-of-function alleles, or by RNA interference technology, to generate poplar plants with reduced activity of G059200. DOI
20. Aloni, R; Foster, A; Mattsson, J. (2013) TRANSFUSION TRACHEIDS IN THE CONIFER LEAVES OF THUJA PLICATA (CUPRESSACEAE) ARE DERIVED FROM PARENCHYMA AND THEIR DIFFERENTIATION IS INDUCED BY AUXIN.American Journal of Botany 100: 1949-1956 TRANSFUSION TRACHEIDS IN THE CONIFER LEAVES OF THUJA PLICATA (CUPRESSACEAE) ARE DERIVED FROM PARENCHYMA AND THEIR DIFFERENTIATION IS INDUCED BY AUXIN
VASCULAR DIFFERENTIATION; TRANSPORT INHIBITORS; LEAF VEIN; TISSUE; GIBBERELLIN; ARABIDOPSIS; FOLIAR; PHLOEM; PINUS
Premise of the study: Conifer leaves are characterized by the differentiation of transfusion tracheids either adjacent to the vascular bundle or away from bundles. Toward uncovering the mechanism regulating this differentiation, we tested the hypotheses that transfusion tracheids differentiate from parenchyma rather than from procambium and that auxin acts as an inducer of this process. Methods: Transfusion tracheids were studied at different developmental stages in both dissected and cleared juvenile and mature leaves. Auxin accumulation was induced by application of either auxin to juvenile leaves or of auxin transport inhibitors in lanolin to stems. Key results: Transfusion tracheids originate from parenchyma cells during late stages of leaf development, after the activity of the procambium has ceased. Transfusion tracheids differentiate also in the leaf tip, a region in which there are no procambial cells. Application of either auxin or auxin transport inhibitors resulted in a significant increase in transfusion tracheids in leaves. Disruption of the leaf vascular bundle combined with auxin application resulted in direct differentiation of transfusion tracheids from parenchyma cells; the regeneration of a vascular bundle around the disruption was polar and supports both hypotheses. Conclusions: The results provide experimental support for a parenchymatic origin of the transfusion tracheids in a conifer leaf and for auxin acting as an inducer of these cells. Our results suggest a new model in which auxin production in the leaf apex continues after primary tracheids and parenchyma cells have differentiated, and this late auxin flow induces transfusion tracheids from parenchyma cells. DOI
19. Baylis, T; Cierlik, I; Sundberg, E; Mattsson, J. (2013) SHORT INTERNODES/STYLISH genes, regulators of auxin biosynthesis, are involved in leaf vein development in Arabidopsis thaliana.New Phytologist 197: 737-750 SHORT INTERNODES/STYLISH genes, regulators of auxin biosynthesis, are involved in leaf vein development in Arabidopsis thaliana
Arabidopsis; auxin; cotyledon; leaf; SHORT INTERNODES; STYLISH; vein
Leaves depend on highly developed venation systems to collect fixed carbon for transport and to distribute water. We hypothesized that local regulation of auxin biosynthesis plays a role in vein development. To this effect, we assessed the role of the SHORT INTERNODES/STYLISH (SHI/STY) gene family, zinc-finger transcription factors linked to regulation of auxin biosynthesis, in Arabidopsis thaliana leaf vein development. Gene functions were assessed by a combination of high-resolution spatio-temporal expression analysis of promoter-marker lines and phenotypic analysis of plants homozygous for single and multiple mutant combinations. The SHI/STY genes showed expression patterns with variations on a common theme of activity in incipient and developing cotyledon and leaf primordia, narrowing to apices and hydathode regions. Mutant analysis of single to quintuple mutant combinations revealed dose-dependent defects in vein patterning affecting multiple vein traits, most notably in cotyledons. Here we demonstrate that local regulation of auxin biosynthesis is an important aspect of leaf vein development. Our findings also support a model in which auxin synthesized at the periphery of primordia affects vein development. DOI
18. Foster, AJ; Hall, DE; Mortimer, L; Abercromby, S; Gries, R; Gries, G; Bohlmann, J; Russell, J; Mattsson, J. (2013) Identification of Genes in Thuja plicata Foliar Terpenoid Defenses.Plant Physiology 161: 1993-2004 Identification of Genes in Thuja plicata Foliar Terpenoid Defenses
WHITE-PINE WEEVIL; HIGH-QUALITY RNA; CONIFER DEFENSE; SITKA SPRUCE; WESTERN REDCEDAR; FUNCTIONAL-CHARACTERIZATION; CHAMAECYPARIS-NOOTKATENSIS; BIOSYNTHESIS; METABOLISM; DEER cedar
Thuja plicata (western redcedar) is a long-lived conifer species whose foliage is rarely affected by disease or insect pests, but can be severely damaged by ungulate browsing. Deterrence to browsing correlates with high foliar levels of terpenoids, in particular the monoterpenoid a-thujone. Here, we set out to identify genes whose products may be involved in the production of a-thujone and other terpenoids in this species. First, we generated a foliar transcriptome database from which to draw candidate genes. Second, we mapped the storage of thujones and other terpenoids to foliar glands. Third, we used global expression profiling to identify more than 600 genes that are expressed at high levels in foliage with glands, but can either not be detected or are expressed at low levels in a natural variant lacking foliar glands. Fourth, we used in situ RNA hybridization to map the expression of a putative monoterpene synthase to the epithelium of glands and used enzyme assays with recombinant protein of the same gene to show that it produces sabinene, the monoterpene precursor of a-thujone. Finally, we identified candidate genes with predicted enzymatic functions for the conversion of sabinene to a-thujone. Taken together, this approach generated both general resources and detailed functional characterization in the identification of genes of foliar terpenoid biosynthesis in T. plicata.Website DOI
15. Dolgosheina, EV; Morin, RD; Aksay, G; Sahinalp, SC; Magrini, V; Mardis, ER; Mattsson, J; Unrau, PJ. (2008) Conifers have a unique small RNA silencing signature.RNA-Publ. RNA Soc. 14: 1508-1515 Conifers have a unique small RNA silencing signature
RNA silencing; Dicer (DCL); small RNA processing; plant evolution; gymnosperms
Plants produce small RNAs to negatively regulate genes, viral nucleic acids, and repetitive elements at either the transcriptional or post-transcriptional level in a process that is referred to as RNA silencing. While RNA silencing has been extensively studied across the different phyla of the animal kingdom (e. g., mouse, fly, worm), similar studies in the plant kingdom have focused primarily on angiosperms, thus limiting evolutionary studies of RNA silencing in plants. Here we report on an unexpected phylogenetic difference in the size distribution of small RNAs among the vascular plants. By extracting total RNA from freshly growing shoot tissue, we conducted a survey of small RNAs in 24 vascular plant species. We find that conifers, which radiated from the other seed-bearing plants; 260 million years ago, fail to produce significant amounts of 24-nucleotide (nt) RNAs that are known to guide DNA methylation and heterochromatin formation in angiosperms. Instead, they synthesize a diverse population of small RNAs that are exactly 21-nt long. This finding was confirmed by high-throughput sequencing of the small RNA sequences from a conifer, Pinus contorta. A conifer EST search revealed the presence of a novel Dicer-like (DCL) family, which may be responsible for the observed change in small RNA expression. No evidence for DCL3, an enzyme that matures 24-nt RNAs in angiosperms, was found. We hypothesize that the diverse class of 21-nt RNAs found in conifers may help to maintain organization of their unusually large genomes. DOI PubMed
13. Wenzel, CL; Hester, Q; Mattsson, J. (2008) Identification of genes expressed in vascular tissues using NPA-Induced vascular overgrowth in Arabidopsis.Plant and Cell Physiology 49: 457-468 Identification of genes expressed in vascular tissues using NPA-Induced vascular overgrowth in Arabidopsis
auxin; vascular expression; vascular overgrowth
The genetic basis of vascular differentiation and function is relatively poorly understood, partly due to the difficulty of screening for mutants defective in internal vascular tissues. Here we present an approach based on a predicted increase in vascular-related gene expression in response to an auxin transport inhibitor-induced vascular overgrowth. We used microarray analyses to identify 336 genes that were up-regulated 2-fold in shoot tissues of Arabidopsis thaliana showing vascular overgrowth. Promotermarker gene fusions revealed that 38 out of 40 genes with 4-fold up-regulation in vascular overgrowth tissues had vascular-related expression in transgenic Arabidopsis plants. Obtained expression patterns included cambial tissues and differentiating xylem, phloem and fibers. A total of 15 genes were found to have vascular-specific expression patterns in the leaves and/or inflorescence stems. This study provides empirical evidence of the efficiency of the approach and describes for the first time the in situ expression patterns of the majority of the assessed genes. DOI
11. Wenzel, CL; Schuetz, M; Yu, Q; Mattsson, J. (2007) Dynamics of MONOPTEROS and PIN-FORMED1 expression during leaf vein pattern formation in Arabidopsis thaliana.Plant Journal 49: 387-398 Dynamics of MONOPTEROS and PIN-FORMED1 expression during leaf vein pattern formation in Arabidopsis thaliana
MONOPTEROS; PIN-FORMED1; vascular patterning; auxin transport
Genetic evidence links the Arabidopsis MONOPTEROS (MP) and PIN-FORMED1 (PIN1) genes to the patterning of leaf veins. To elucidate their potential functions and interactions in this process, we have assessed the dynamics of MP and PIN1 expression during vascular patterning in Arabidopsis leaf primordia. Both genes undergo a dynamic process of gradual refinement of expression into files one to two cells wide before overt vascular differentiation. The subcellular distribution of PIN1 is also gradually refined from a non-polar distribution in isodiametric cells to strongly polarized in elongated procambial cells and provides an indication of overall directions of auxin flow. We found evidence that MP expression can be activated by auxin exposure and that PIN1 as well as DR5::GUS expression is defective in mp mutant leaves. Taken together the results suggest a feedback regulatory loop that involves auxin, MP and PIN1 and provide novel experimental support for the canalization-of-auxin-flow hypothesis. DOI
10.Mattsson, J; Ckurshumova, W; Berleth, T. (2003) Auxin signaling in Arabidopsis leaf vascular development.Plant Physiology 131: 1327-1339 Auxin signaling in Arabidopsis leaf vascular development
A number of observations have implicated auxin in the formation of vascular tissues in plant organs. These include vascular strand formation in response to local auxin application, the effects of impaired auxin transport on vascular patterns and suggestive phenotypes of Arabidopsis auxin response mutants. In this study, we have used molecular markers to visualize auxin response patterns in developing Arabidopsis leaves as well as Arabidopsis mutants and transgenic plants to trace pathways of auxin signal transduction controlling the expression of early procambial genes. We show that in young Arabidopsis leaf primordia, molecular auxin response patterns presage sites of procambial differentiation. This is the case not only in normal development but also upon experimental manipulation of auxin transport suggesting that local auxin signals are instrumental in patterning Arabidopsis leaf vasculature. We further found that the activity of the Arabidopsis gene MONOPTEROS, which is required for proper vascular differentiation, is also essential in a spectrum of auxin responses, which include the regulation of rapidly auxin-inducible AUX/IAA genes, and discovered the tissue-specific vascular expression profile of the class I homeodomain-leucine zipper gene, AtHB20. Interestingly, MONOPTEROS activity is a limiting factor in the expression of AtHB8 and AtHB20, two genes encoding transcriptional regulators expressed early in procambial development. Our observations connect general auxin signaling with early controls of vascular differentiation and suggest molecular mechanisms for auxin signaling in patterned cell differentiation.PDF
9. Berleth, T; Mattsson, J. (2000) Vascular development: tracing signals along veins.Current Opinion in Plant Biology 3: 406-411 Vascular development: tracing signals along veins
The plant hormone auxin has been implicated in vascular development, but the molecular details of patterned vascular differentiation have remained elusive. Research in the past year has identified new genes that control vascular patterning, and auxin transport and perception. New experimental strategies have been employed to study vascular development. Together, these findings have generated a conceptual framework and experimental tools for the exploration of vascular-tissue patterning at the molecular level.PDF
8. Berleth, T; Mattsson, J; Hardtke, CS. (2000) Vascular continuity, cell axialisation and auxin.Plant Growth Regulation 32: 173-185 Vascular continuity, cell axialisation and auxin
Arabidopsis mutants; auxin; vascular development; polarity; embryogenesis
Phytohormones have been implicated in vascular development in various ways, but their precise function and the extent of their influence is still controversial. Recent results from experimental manipulation of developing organs and Arabidopsis developmental genetics support a role for polar auxin flow in cell axis formation within the vascular system and, interestingly, also in the embryonic establishment of the plant body axis. Vascular responses to auxin transport inhibition indicate patterns of auxin distribution during leaf development and new technologies may enable these predictions to be tested within the near future. Moreover, recently discovered Arabidopsis axialisation mutants seem to identify essential genes that relay auxin signals in vascular development. A first gene in this class, MONOPTEROS (MP) has been cloned and encodes a transcription factor capable of binding to auxin response elements in the control regions of auxin regulated genes. Molecular identification of further axialisation genes may provide access to a mechanistic understanding of plant cell axis formation.
7. Berleth, T; Mattsson, J; Hardtke, CS. (2000) Vascular continuity and auxin signals.Trends in Plant Science 5: 387-393 Vascular continuity and auxin signals
Plant vascular tissues form systems of interconnected cell files throughout the plant body. Vascular tissues usually differentiate at predictable positions but the wide range of functional patterns generated in response to abnormal growth conditions or wounding reveals partially self-organizing patterning mechanisms. Signals ensuring aligned cell differentiation within vascular strands are crucial in self-organized vascular patterning, and the apical-basal flow of indole acetic acid has been suspected to act as an orienting signal in this process. Several recent advances appear to converge on a more precise definition of the role of auxin flow in vascular tissue patterning.PDF
6.Mattsson, J; Sung, ZR; Berleth, T. (1999) Responses of plant vascular systems to auxin transport inhibition.Development 126: 2979-2991 Responses of plant vascular systems to auxin transport inhibition
Arabidopsis thaliana; auxin transport; provascular tissue; vascular development; eir1-1; aux1-7; pin1; mp
To assess the role of auxin flows in plant vascular patterning, the development of vascular systems under conditions of inhibited auxin transport was analyzed. In Arabidopsis, nearly identical responses evoked by three auxin transport inhibitor substances revealed an enormous plasticity of the vascular pattern and suggest an involvement of auxin hows in determining the sites of vascular differentiation and in promoting vascular tissue continuity. Organs formed under conditions of reduced auxin transport contained increased numbers of vascular strands and cells within those strands were improperly aligned. In leaves, vascular tissues became progressively confined towards the leaf margin as the concentration of auxin transport inhibitor was increased, suggesting that the leaf vascular system depends on inductive signals from the margin of the leaf. Staged application of auxin transport inhibitor demonstrated that primary, secondary and tertiary veins became unresponsive to further modulations of auxin transport at successive stages of early leaf development. Correlation of these stages to anatomical features in early leaf primordia indicated that the pattern of primary and secondary strands becomes fixed at the onset of lamina expansion. Similar alterations in the leaf vascular responses of alyssum, snapdragon and tobacco plants suggest common functions of auxin flows in vascular patterning in dicots, while two types of vascular pattern alterations in Arabidopsis auxin transport mutants suggest that at least two distinct primary defects can result in impaired auxin how We discuss these observations with regard to the relative contributions of auxin transport, auxin sensitivity and the cellular organisation of the developing organ on the vascular pattern.PDF
5. Przemeck, GKH; Mattsson, J; Hardtke, CS; Sung, ZR; Berleth, T. (1996) Studies on the role of the Arabidopsis gene MONOPTEROS in vascular development and plant cell axialization.Planta 200: 229-237 Studies on the role of the Arabidopsis gene MONOPTEROS in vascular development and plant cell axialization
Arabidopsis; cell axialization; MONOPTEROS gene; PIN-FORMED gene; polar auxin transport; vascular development
In the embryo of Arabidopsis thaliana (L.) Heynh., formation of the hypocotyl/root axis is initiated at the early-globular stage, recognizable as oriented expansion of formerly isodiametric cells. The process depends on the activity of the gene MONOPTEROS (MP); Inp mutant embryos fail to produce hypocotyl and radicle. We have analyzed the morphology and anatomy of mp mutant plants throughout the Arabidopsis life cycle. Mutants form largely normal rosettes and root systems, but inflorescences either fail to form lateral flowers or these flowers are greatly reduced. Furthermore, the auxin transport capacity of inflorescence axes is impaired and the vascular strands in all analyzed organs are distorted. These features of the mutant phenotype suggest that the MP gene promotes cell axialization and cell file formation at multiple stages of plant development.
4. Soderman, E; Mattsson, J; Engstrom, P. (1996) The Arabidopsis homeobox gene ATHB-7 is induced by water deficit and by abscisic acid.Plant Journal 10: 375-381 The Arabidopsis homeobox gene ATHB-7 is induced by water deficit and by abscisic acid
Homeodomain-leucine zipper (HD-Zip) proteins are putative transcription factors encoded by a class of recently discovered homeobox genes as yet found only in plants. This paper reports on the characterization of one of these genes, ATHB-7, in Arabidopsis thaliana. ATHB-7 transcripts were present in all organs of the plant at low levels, but expression was induced several-fold by water deficit, osmotic stress as well as by exogenous treatment with abscisic acid (ABA), a response being detectable at 10(-8) M and reaching a maximum at 10(-6) M ABA. The ATHB-7 transcript was detected within 30 min after treatment with ABA and the transcript level was rapidly reduced after removal of the hormone. The induction of ATHB-7 was shown to be mediated strictly via ABA, since no induction of ATHB-7 was detectable in the ABA-deficient mutant aba-3 subjected to drought treatment. Induction levels in two ABA-insensitive mutants abi2 and abi3 were similar to the wild-type response. In the abi1 mutant, however, induction was impaired as 100-fold higher concentrations of ABA were required for a maximum induction as compared with wild-type. In this mutant the ATHB-7 response was reduced also after drought and osmotic stress treatments. These results indicate that ATHB-7 is transcriptionally regulated in an ABA-dependent manner and may act in a signal transduction pathway which mediates a drought response and also includes ABl1.
3. SODERMAN, E; MATTSSON, J; SVENSON, M; BORKIRD, C; ENGSTROM, P. (1994) EXPRESSION PATTERNS OF NOVEL GENES ENCODING HOMEODOMAIN LEUCINE-ZIPPER PROTEINS IN ARABIDOPSIS-THALIANA.Plant Molecular Biology 26: 145-154 EXPRESSION PATTERNS OF NOVEL GENES ENCODING HOMEODOMAIN LEUCINE-ZIPPER PROTEINS IN ARABIDOPSIS-THALIANA
CDNA; DEVELOPMENT; HOMEOBOX; IN SITU HYBRIDIZATION; TRANSCRIPTION FACTOR
A recently discovered class of genes in Arabidopsis thaliana encode putative transcription factors which contain a homeodomain closely linked to a leucine zipper motif. We have previously reported on the cloning and cDNA sequence of one gene of this class, Athb-3. In this article we show this gene to be expressed predominantly in the cortex of the root and the stem. Using the Athb-3 clone as a probe we have isolated cDNA clones corresponding to three novel homeodomain-leucine zipper proteins. These clones, Athb-5, Athb-6 and Athb-7, hybridized to transcripts that were relatively abundant in the leaf, but also present in other vegetative organs, as well as in the flower. Only weak hybridization was observed to seed pod samples. These observations indicate that these Athb genes have major functions in the mature plant, and therefore, in contrast to homeobox genes in other eukaryotes and to the kn-1 gene in maize, are unlikely to function in the primary control of developmental processes during embryogenesis or organogenesis. The deduced amino acid sequences of Athb-5, Athb-6 and Athb-7 are highly similar to the previously isolated Athb-1, Athb-2 and Athb-3 in the homeodomain and leucine-zipper parts of the proteins, whereas the similarities to homeodomain proteins from other eukaryotes are limited. The Athb proteins thus constitute a new and well defined class of homeodomain proteins, apparently unique to plants. DOI
2. MATTSSON, J; BORKIRD, C; ENGSTROM, P. (1992) SPATIAL AND TEMPORAL EXPRESSION PATTERNS DIRECTED BY THE AGROBACTERIUM-TUMEFACIENS T-DNA GENE-5 PROMOTER DURING SOMATIC EMBRYOGENESIS IN CARROT.Plant Molecular Biology 18: 629-637 SPATIAL AND TEMPORAL EXPRESSION PATTERNS DIRECTED BY THE AGROBACTERIUM-TUMEFACIENS T-DNA GENE-5 PROMOTER DURING SOMATIC EMBRYOGENESIS IN CARROT
BETA-GLUCURONIDASE; CELL AND ORGAN SPECIFICITY; DAUCUS-CAROTA; GENE FUSIONS; TRANSCRIPTION
We have analysed the patterns of expression of a gene encoding beta-glucuronidase (GUS) fused to the promoter of the Agrobacterium tumefaciens T-DNA gene 5 during embryogenesis in carrot, Daucus carota L. Gene expression was monitored by a histochemical assay of beta-glucuronidase activity. The gene 5 promoter, although of bacterial origin, conferred expression upon the marker gene in all stages of embryo development. The patterns of expression however, differed between embryos in different stages of development. In the globular stage expression was confined to the basal part of the embryo, suggesting that the promoter is sensitive to regulatory functions active in the primary establishment of polarity in the radially symmetric globular embryo. In the heart and torpedo stages of development GUS expression was high in the entire embryonic axis, but not in the cotyledons. During germination expression was reduced in the elongating hypocotyl and radicle, and high levels of expression were detected only in the shoot and root apices. Among the transformed cell lines analysed, one was found that showed an aberrant pattern of GUS expression during embryogenesis, in that expression in the upper part of the embryo was undetectable, and expression was restricted to the root apex in later stages of development. This difference in organ specificity of expression is likely due to a large deletion of the promoter. DOI
1. MATTSSON, J; SODERMAN, E; SVENSON, M; BORKIRD, C; ENGSTROM, P. (1992) A NEW HOMEOBOX-LEUCINE ZIPPER GENE FROM ARABIDOPSIS-THALIANA.Plant Molecular Biology 18: 1019-1022 A NEW HOMEOBOX-LEUCINE ZIPPER GENE FROM ARABIDOPSIS-THALIANA
ARABIDOPSIS; HOMEOBOX; HOMEODOMAIN; LEUCINE ZIPPER
We have isolated a homeobox-containing gene from Arabidopsis thaliana using a degenerate oligonucleotide probe corresponding to the most conserved region of the homeodomain. This strategy has been used previously to isolate homeobox-containing genes from Caenorhabditis, and recently from A. thaliana. The Arabidopsis genes have an unusual structure in that they have a leucine zipper motif adjacent to the carboxy terminal region of the homeo domain, a feature not found in homeobox-containing genes isolated from animals. We report the isolation and primary structure of a new member of this Arabidopsis homeobox-leucine zipper gene family. This new member has the homeodomain and leucine-zipper motif similar to the two genes previously identified, but differs from these genes in the part corresponding to the carboxy terminus of the polypeptide, as well as in size and isoelectric point of the protein. DOI
