Spatial specificity of auxin responses coordinates wood formation

AbstractStem cells are one of the foundational evolutionary novelties that allowed the independent emergence of multicellularity in the plant and animal lineages. In plants, the homeodomain (HD) transcription factor WUSCHEL (WUS) is essential for the maintenance of stem cells in the shoot apical meristem. WUS has been reported to bind to diverse DNA motifs and to act as transcriptional activator and repressor. However, the mechanisms underlying this remarkable behavior have remained unclear. Here, we quantitatively delineate WUS binding to three divergent DNA motifs and resolve the relevant structural underpinnings. We show that WUS exhibits a strong binding preference for TGAA repeat sequences, while retaining the ability to weakly bind to TAAT elements. This behavior is attributable the formation of dimers through interactions of specific residues in the HD that stabilize WUS DNA interaction. Our results provide a mechanistic basis for dissecting WUS dependent regulatory networks in plant stem cell control.

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“…EMSAs were carried out as described in Brackmann et al 53 Oligonucleotides sequences are listed in Supplementary Table 4.…”

Section: Electrophoretic Mobility Shift Assay (Emsa)mentioning

confidence: 99%

Structural basis for the complex DNA binding behavior of the plant stem cell regulator WUSCHEL

Sloan

Hankenjos

Gebert

et al. 2020

Preprint

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“…From these data, physiological and developmental features of stem tissues can be reveled and the organ can be characterized as a functional unit. Although several studies have provided transcriptome profiles from several stem tissues and stages Suh et al, 2005;Brackmann et al, 2018), a systematic analysis has not been performed and stem-specific tissues like the pith or the phloem cap have not been targeted at all.…”

Section: Introductionmentioning

confidence: 99%

Tissue-specific transcriptome profiling of theArabidopsis thalianainflorescence stem reveals local cellular signatures

Shi¹,

Jouannet²,

Agustí

et al. 2020

Preprint

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One sentence summary:A genome-wide high-resolution gene expression map of the Arabidopsis inflorescence stem is established. AbstractGenome-wide gene expression maps with a high spatial resolution have substantially accelerated molecular plant science. However, the number of characterized tissues and growth stages is still small because of the limited accessibility of most tissues for protoplast isolation. Here, we provide gene expression profiles of the mature inflorescence stem of Arabidopsis thaliana covering a comprehensive set of distinct tissues. By combining fluorescence-activated nucleus sorting and laser-capture microdissection with next generation RNA sequencing, we characterize transcriptomes of xylem vessels, fibers, the proximal and the distal cambium, phloem, phloem cap, pith, starch sheath, and epidermis cells. Our analyses classify more than 15,000 genes as being differentially expressed among different stem tissues and reveal known and novel tissue-specific cellular signatures. By determining transcription factor binding regions enriched in promoter regions of differentially expressed genes, we furthermore provide candidates for tissue-specific transcriptional regulators. Our datasets predict expression profiles of an exceptional amount of genes and allow generating hypotheses toward the spatial organization of physiological processes. Moreover, we demonstrate that information on gene expression in a broad range of mature plant tissues can be established with high spatial resolution by nuclear mRNA profiling.

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“…Lack of auxin signaling results in impaired vascular tissue development, while application of exogenous auxin can induce the formation of new vascular bundles (Sachs, 1969;Krogan et al, 2012;Donner et al, 2009;Jacobs, 1952). Auxin and its key transcriptional effector MP are therefore often regarded as master regulators of vascular development (Brackmann et al, 2018). Here we asked if this prominent role also pertains to the earliest steps in vascular tissue specification in the embryo.…”

Section: Discussionmentioning

confidence: 99%

“…A signaling molecule that is strongly correlated with vascular development is auxin. Vascular tissue can be initiated by a source of auxin in cut stems (Sachs, 1969), and as a result, auxin maxima are often associated with vascular development (Brackmann et al, 2018, Miyashima et al, 2019Scarpella et al, 2006;Wabnik et al, 2013). Conversely, lack of the AUXIN RESPONSE FACTOR5/MONOPTEROS (MP) transcription factor causes impaired vascular development in the Arabidopsis embryo, seedling, leaf and stem (Berleth and Jürgens, 1993;Hamann et al, 1999;Hardtke and Berleth, 1998;Mayer et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Initiation and regulation of vascular tissue identity in theArabidopsisembryo

Smit

Llavata-Peris

Roosjen

et al. 2019

Preprint

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Development of plant vascular tissues involves tissue specification, growth, pattern formation and cell type differentiation. While later steps are understood in some detail, it is still largely unknown how the tissue is initially specified. We have used the early Arabidopsis embryo as a simple model to study this process. Using a large collection of marker genes, we find that vascular identity is established in the 16-cell embryo. After a transient precursor state however, there is no persistent uniform tissue identity. Auxin is intimately connected to vascular tissue development. We find that while AUXIN RESPONSE FACTOR5/MONOPTEROS/ (ARF5/MP)-dependent auxin response is required, it is not sufficient for tissue establishment. We therefore used a large-scale enhanced Yeast One Hybrid assay to identify potential regulators of vascular identity.Network and functional analysis of suggest that vascular identity is under robust, complex control. We found that one candidate regulator, the G-class bZIP transcription factor GBF2, modulates vascular gene expression, along with its homolog GBF1.Furthermore, GBFs bind to MP and modulate its activity. Our work uncovers components of a gene regulatory network that controls the initiation of vascular tissue identity, one of which involves the interaction of MP and GBF2 proteins.

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Spatial specificity of auxin responses coordinates wood formation

Cited by 110 publications

References 79 publications

Structural basis for the complex DNA binding behavior of the plant stem cell regulator WUSCHEL

Structural basis for the complex DNA binding behavior of the plant stem cell regulator WUSCHEL

Tissue-specific transcriptome profiling of theArabidopsis thalianainflorescence stem reveals local cellular signatures

Initiation and regulation of vascular tissue identity in theArabidopsisembryo

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