Project description:The balance between cell proliferation, differentiation and elongation rates emerges from gene regulatory networks coupled to various signal transduction pathways, including reactive oxygen species (ROS) and transcription factors, to respond to environmental cues. The Arabidopsis thaliana primary root has become a valuable system to unravel such networks and the role of transcription factors mediating the inhibition of primary root growth by ROS is just beginning to be studied. In this study, we demonstrate that the MADS-box transcription factor XAANTAL1 (XAL1) mediates the role of hydrogen peroxide (H2O2) in primary root growth and root stem cell niche identity. Interestingly, our findings suggest that XAL1 acts as a positive regulator of H2O2 concentration in the root meristem by directly regulating genes involved in oxidative stress response, such as PEROXIDASE 28 (PER28). Moreover, we found that XAL1 is necessary for the H2O2-induced inhibition of primary root growth through the negative regulation of peroxidase and catalase activities. Furthermore, we found that XAL1 together with RETINOBLASTOMA-RELATED (RBR), is also necessary to positively regulate the differentiation of columella stem cells triggered by a moderate oxidative stress induced by H2O2 treatment.
Project description:MADS-domain transcription factors play pivotal roles in numerous developmental processes in Arabidopsis thaliana. While their involvement in flowering transition and floral development has been extensively examined, their functions in root development remain relatively unexplored. Here, we explored the function and genetic interaction of three MADS-box genes (XAL2, SOC1 and AGL24) in primary root development. Our findings revealed that SOC1 and AGL24, both critical components in flowering transition, redundantly act as repressors of primary root growth as the loss of function of either SOC1 or AGL24 partially recovers the primary root growth, meristem cell number, cell production rate, and the length of fully elongated cells of the short-root mutant xal2-2. Furthermore, we observed that the simultaneous overexpression of AGL24 and SOC1 leads to short-root phenotypes, affecting meristem cell number, cell production rate, fully elongated cell size, but only the overexpression of SOC1 affects distal root stem cell differentiation. Additionally, these genes exhibit distinct modes of transcriptional regulation in roots compared to what has been previously reported for aerial tissues. Moreover, our findings revealed that the expression of certain genes involved in cell differentiation, as well as stress responses, which are either upregulated or downregulated in the xal2-2 mutant, reverted to WT levels in the absence of SOC1 or AGL24.
Project description:Lateral root organogenesis plays an essential role in defining plant root system architecture. In Arabidopsis, the AP2-family transcription factor PUCHI controls cell proliferation in lateral root primordia. To identify downstream targets of PUCHI, we engineered a transgenic line with inducible PUCHI activity by expressing a fusion protein of PUCHI and rat glucocorticoid receptor (GR) under the control of its own regulatory region (gPUCHI-GR) in the puchi-1 mutant.
Project description:Root hairs are frequently reported to be plastic in response to nutrient supply, but relatively little is known about their development in response to magnesium (Mg) availability, and evidence is scarce about the signals involved in this process. Here, we showed that both density and length of root hairs of Arabidopsis decreased logarithmically with increasing Mg supply in the media , which correlated with the initiation of new trichoblast files and likelihood of trichoblasts to form hairs. Low Mg resulted in greater concentrations of reactive oxygen species (ROS) and Ca2+ in the roots and displayed a stronger tip-focused gradient of ROS and cytosolic Ca2+ concentration ([Ca2+]c) during initiation and elongation of root hairs. This gradient could be eliminated by DPI or BAPTA. Application of either DPI or BAPTA to low Mg treatment blocked the enhanced development of root hairs. The opposite was true when the plants under high Mg were supplied with Ca2+ or PMS. Whole-genome transcriptome data revealed that the maximum differential expressed genes involved in ‘stress’, ‘oxidation reduction’, ‘ion transport and homeostasis’ and ‘cell wall organization’. A greater fraction of morphogenetic H-genes and root hair -specific genes as well as genes involved in ‘cell wall structure’ were up-regulated by 7-d treatment of 0.5 μM Mg but down-regulated by 7-d treatment of 10,000 μM Mg. It is concluded that a distinct and previously poorly characterized response of root hair development to Mg availability is presented in Arabidopsis where ROS and Ca2+ are the signaling molecules that control this response.
Project description:Stem cells are defined by their ability to self-renew and produce daughter cells that proliferate and mature. These maturing cells transition from a proliferative state to a terminal state through the process of differentiation. In the Arabidopsis thaliana root the transcription factors SCARECROW and SHORTROOT regulate specification of the bi-potent stem cell that gives rise to the cortical and endodermal progenitors. Subsequent progenitor proliferation and differentiation generates mature endodermis, marked by the Casparian Strip: a cell wall modification that prevents ion diffusion into and out of the vasculature. We identified a transcription factor, MYB36 that regulates the transition from proliferation to differentiation in the endodermis. We show that SCARECROW directly activates MYB36 expression, which in turn directly regulates essential Casparian Strip formation genes. In addition, MYB36 represses extra divisions within the endodermis. Our results demonstrate that MYB36 is a critical positive regulator of differentiation and negative regulator of cell proliferation. 12 samples analyzed: 3 biological replicates each from 1) wild type (Col-0) whole root, 2) mutant (myb36-1) whole root, 3) wild type (Col-0) sorted endodermis, 4) mutant (myb36-1) sorted endodermis
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.