Auxin signaling in the epidermis regulates stem growth via interactions with the brassinosteroid pathway
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ABSTRACT:
ORGANISM(S): Arabidopsis thaliana Brassica rapa
PROVIDER: GSE79881 | GEO | 2016/06/30
SECONDARY ACCESSION(S): PRJNA317322
REPOSITORIES: GEO
Similar Datasets
Project description:Growth of a complex multicellular organism requires coordinated changes in diverse cell types. These cellular changes generate organs of the correct size, shape and functionality. During plant development, the growth hormone auxin induces stem elongation; however, which cell types of the stem perceive the auxin signal and contribute to organ growth is poorly understood. Here, we show that auxin signalling is required in many cell types for correct hypocotyl stem growth, with a key role for the epidermis. Combining genetic manipulations in Arabidopsis thaliana with transcriptional profiling of the hypocotyl epidermis from Brassica rapa, we show that auxin functions in the epidermis in part by inducing activity of the locally-acting, growth-promoting brassinosteroid pathway. Our findings clarify cell-specific auxin function in the hypocotyl, and highlight the complexity of cell-type interactions within a growing organ. We performed whole-genome transcriptome (mRNA-Seq) on 5 d-old W light-grown Arabidopsis thaliana plants (CER6pro>>axr3-1::mCit experimental plants and UAS::axr3-1::mCit hemizygous control plants; whole-seedling tissue) treated for 4 h W light or low R:FR shade. In addition, we performed mRNA-Seq on 4 d-old Brassica rapa plants (FPsc strain) treated for 9 h W light or shade. Brassica tissues collected were hypocotyl epidermal peels or whole hypocotyls.
2016-06-30 | E-GEOD-79881 | biostudies-arrayexpress
Project description:The mechanisms ensuring balanced growth remain a critical question in developmental biology. In plants, this balance relies on spatiotemporal integration of hormonal signaling pathways, but the understanding of the precise contribution of each hormone is just beginning to take form. Brassinosteroid (BR) hormone, is shown here to have opposing effects on root meristem size, depending on its site of action. BR is demonstrated to both delay and promote onset of stem cell daughter differentiation, when acting in the outer tissue of the root meristem, the epidermis, and the inner-most tissue, the stele, respectively. To understand the molecular basis of this phenomenon, a comprehensive spatiotemporal translatome mapping of Arabidopsis roots was performed. Analyses of wild type and mutants featuring different distributions of BR, revealed autonomous, tissue-specific gene responses to BR, implying its contrasting tissue-dependent impact on growth. BR-induced genes were primarily detected in epidermal cells of the basal meristem zone and were enriched by auxin-related genes. In contrast, repressed BR genes prevailed in the stele of the apical meristem zone. Furthermore, auxin was found to mediate the growth-promoting impact of BR signaling originating in the epidermis, while BR signaling in the stele buffered this effect. We propose that context-specific BR activity and responses are oppositely interpreted at the organ level, ensuring coherent growth.
2015-01-04 | GSE64410 | GEO
Project description:The mechanisms ensuring balanced growth remain a critical question in developmental biology. In plants, this balance relies on spatiotemporal integration of hormonal signaling pathways, but the understanding of the precise contribution of each hormone is just beginning to take form. Brassinosteroid (BR) hormone, is shown here to have opposing effects on root meristem size, depending on its site of action. BR is demonstrated to both delay and promote onset of stem cell daughter differentiation, when acting in the outer tissue of the root meristem, the epidermis, and the inner-most tissue, the stele, respectively. To understand the molecular basis of this phenomenon, a comprehensive spatiotemporal translatome mapping of Arabidopsis roots was performed. Analyses of wild type and mutants featuring different distributions of BR, revealed autonomous, tissue-specific gene responses to BR, implying its contrasting tissue-dependent impact on growth. BR-induced genes were primarily detected in epidermal cells of the basal meristem zone and were enriched by auxin-related genes. In contrast, repressed BR genes prevailed in the stele of the apical meristem zone. Furthermore, auxin was found to mediate the growth-promoting impact of BR signaling originating in the epidermis, while BR signaling in the stele buffered this effect. We propose that context-specific BR activity and responses are oppositely interpreted at the organ level, ensuring coherent growth. 24 samples of polyribosome-associated mRNA (following 0, 3, and 8 hours of BR treatment, in two biological repetitions), were collected. RNA samples were sequenced on an Illumina HiSeq 2500, to obtain 50 bp single-end reads. These reads were aligned to the TAIR10 assembly of the Arabidopsis thaliana genome, using Tophat2 v2.0.9. Transcript coordinates from the TAIR10 reference set were used to guide the alignment process. After alignment, the numbers of reads per transcript were estimated using HTSeq v0.5.3p3, and DESeq2 v1.2.8 was used to normalize read counts and call differentially expressed genes.
2015-01-04 | E-GEOD-64410 | biostudies-arrayexpress
Project description:In plants, an elevation in ambient temperature induces morphological changes including elongation hypocotyls, considered to be adaptive responses to alleviate the heat-induced damages. The high temperature-induced morphological changes are called thermomorphogenesis, which is predominantly regulated by a bHLH transcription factor PIF4. Although PIF4 is expressed in all aerial tissues including the epidermis, mesophyll, and vascular bundle, its tissue-specific functions in thermomorphogenesis are not known. Here, we found that epidermis-specific expression of PIF4 induced constitutive long hypocotyls, while vasculature-specific expression of PIF4 had no effect on hypocotyl growth. Consistently, RNA-Seq and qRT-PCR analyses revealed that auxin responsive genes and growth-related genes were highly activated by epidermal, but not by vascular, PIF4. The epidermal, but not vascular, inactivation of PIF4 by a PIF4 artificial microRNA or a dominant negative form of PIF4 suppressed thermoresponsive gene expression and hypocotyl growth. Additionally, both the block of epidermal auxin signaling and the epidermal overexpression of a thermosensor phytochrome B (phyB) inhibited thermoresponsive growth, indicating that epidermal PIF4-auxin pathway are essential for the temperature responses. We further show that epidermal PIF4 is increased by high temperatures mainly through the transcriptional activation of PIF4. Taken together, our study demonstrates that the epidermis regulates thermoresponsive growth through the phyB-PIF4-auxin pathway.
2020-01-26 | GSE133564 | GEO
Project description:Auxin signaling in the epidermis regulates stem growth via interactions with the brassinosteroid pathway
| PRJNA317322 | ENA
Project description:In response to neighbor proximity plants increase growth of specific organs (e.g. hypocotyl) to enhance access to sunlight. Shade enhances the activity of Phytochrome Interacting Factors (PIFs) by releasing those bHLH transcription factors from phytochrome B-mediated inhibition. PIFs promote elongation by inducing auxin production in cotyledons. In order to elucidate spatiotemporal aspects of the neighbor proximity response, we analyzed changes in transcript abundance at different time points during a shade treatment in dissected cotyledons and hypocotyls. We concentrated our analysis on these two organs because the former is considered as the primary shade-sensing organ while elongation is rapidly triggered in the hypocotyl. We conclude that PIFs initiate transcriptional reprogramming in both organs within 15 minutes comprising regulated expression of several early auxin response genes. This suggests that hypocotyl growth is elicited by both local and distal auxin signals. With time the transcriptional response diverges increasingly between organs. We identify genes whose differential expression may underlie organ-specific elongation. Finally, we uncover a growth promotion gene expression signature shared between responses to different environments and organs.
2017-01-17 | GSE81202 | GEO
Project description:Plants are known for their outstanding capacity for recovering from various wounds and injury. However, it remains largely unknown how plants sense diverse forms of injury and canalize existing developmental processes into the execution of a correct regenerative response. Auxin, a cardinal plant hormone with morphogenlike properties, has been previously implicated in recovery from diverse types of wounding and organ loss. Here, through a combination of cellular imaging and in silico modelling, we demonstrate that vascular stem cell death obstructs the polar auxin flux, much alike rocks in a stream, and causes it to accumulate in the endodermis. This in turn grants the endodermal cells the capacity to undergo periclinal cell division that repopulate the vascular stem cell pool. Replenishment of the vasculature by the endodermis depends on the transcription factor ERF115, a wound inducible regulator of stem cell divisions. Although not being the primary inducer, auxin is required to maintain ERF115 expression. Reversely, ERF115 sensitizes cells to auxin by activating ARF5/MONOPTEROS, an auxin responsive transcription factor involved in the global auxin response, tissue patterning and organ formation. Combined, the wound induced auxin accumulation and ERF115 expression grant the endodermal cells stem cell activity. Our work provides a mechanistic model for wound induced stem cell regeneration in which ERF115 acts as a wound-inducible stem cell organizer that interprets wound-induced auxin maxima.
2020-06-30 | GSE139715 | GEO
Project description:The phytohormone auxin controls a myriad of processes in plants, at least in part through its regulation of cell expansion. The "acid growth hypothesis" has been proposed to explain auxin-stimulated cell expansion for five decades, but the mechanism underlying auxin-induced cell wall acidification is poorly characterized. Auxin induces the phosphorylation and activation of the plasma membrane (PM) H+-ATPase that pumps protons into the apoplast, yet how auxin activates its phosphorylation remains elusive. Here, we show that the transmembrane kinase (TMK) auxin signaling proteins interact with PM H+-ATPases and activate their phosphorylation to promote cell wall acidification and hypocotyl cell elongation in Arabidopsis. Auxin induced TMK's interaction with H+-ATPase on the plasma membrane within 1-2 minutes as well as TMK-dependent phosphorylation of the penultimate Thr residue. Genetic, biochemical, and molecular evidence demonstrates that TMKs directly phosphorylate PM H+-ATPase and are required for auxin-induced PM H+-ATPase activation, apoplastic acidification, and cell expansion. Thus, our findings reveal a crucial connection between auxin and PM H+-ATPase activation in regulating apoplastic pH changes and cell expansion via TMK-based cell surface auxin signaling.
2021-07-14 | MSV000087822 | MassIVE
Project description:Root meristem organization is maintained by an interplay between hormone signaling pathways that both interpret and determine their accumulation and distribution. The interacting hormones Brassinosteroids (BR) and auxin control the number of meristematic cells in the Arabidopsis root. BR was reported both to promote auxin signaling input and to repress auxin signaling output. Whether these contradicting molecular outcomes co-occur and what their significance in meristem function is remain unclear. Here, we established a dual effect of BR on auxin, with BR simultaneously promoting auxin biosynthesis and repressing auxin transcriptional output, which is essential for meristem maintenance. Blocking BR-induced auxin synthesis resulted in rapid BR-mediated meristem loss. Conversely, plants with reduced BR levels were resistant to a critical loss of auxin biosynthesis, maintaining their meristem morphology. In agreement, injured root meristems, which rely solely on local auxin synthesis, regenerated when both auxin and BR synthesis were inhibited. Use of BIN2 as a tool to selectively inhibit BR signaling yielded meristems with distinct phenotypes depending on the perturbed tissue: meristem reminiscent either of BR-deficient mutants or of high BR exposure. This enabled mapping of the BR-auxin interaction that maintains the meristem to the outer epidermis and lateral root cap tissues and demonstrated the essentiality of BR signaling in these tissues for meristem response to BR. BR activity in internal tissues however, proved necessary to control BR levels. Together, we demonstrate a basis for inter-tissue coordination and how a critical ratio between these hormones determines the meristematic state.
2021-08-07 | GSE179910 | GEO
Project description:We performed an analysis of transcriptomic responses to auxin within four distinct tissues of the Arabidopsis thaliana root. This high-resolution dataset shows how different cell types are predisposed to react to auxin with discrete transcriptional responses. The sensitivity provided by the analysis lies in the ability to detect cell-type specific responses diluted in organ-level analyses. This dataset provides a novel resource to examine how auxin, a widespread signal in plant development, influences differentiation and patterning in the plant through tissue-specific transcriptional regulation. To analyze the effect of auxin in separate spatial domains of the root, early transcriptional changes in response to auxin treatment were assayed by means of fluorescence activated cell sorting (FACS) and microarray analysis in four tissues of the Arabidopsis root (wild type Col-0). The samples covered inner and outer as well as proximal and distal cell populations; including the stele (reporter line pWOL::GFP), xylem-pole (xp) pericycle (enhancer trap line E3754), epidermis/lateral root cap (reporter line pWER::GFP) and columella (enhancer trap line PET111). One-week-old seedlings of the individual lines were treated with auxin (two hours, 5µM indole-3-acetic acid [IAA]) or mock treated, after which roots were harvested and cells were dissociated by cell wall digestion (1 hour; including 5uM IAA) . GFP-positive cells were sorted and used for microarray transcriptome analysis (as in Bargmann and Birnbaum, Plant Phys. 2010). For comparison, transcriptional responses to auxin were also assayed in intact (undigested) roots.
2013-08-06 | E-GEOD-35580 | biostudies-arrayexpress