Project description:We combined transcriptomic profiling of auxin related mutants with genetic and biochemical approaches and live-cell imaging techniques of Arabidopsis roots to understand the role of auxin-driven gibberellin level changes during root development, particularly root cell elongation. We show that auxin negatively regulates the level of gibberellin in root elongation zone. Auxin signalling steers the expression of gibberellin deactivating enzymes - GIBBERELLIN 2-OXIDASES (GA2OX) exclusively in root elongation zone. Interestingly, GA2OX8 expression is high in tissues with elevated auxin levels, such as vasculature or stem cell niche, fitting with the observed effect of auxin on gibberellin level. Here we show that GA2OX enzymes are negative regulators of root cell elongation. Gibberellin decrease caused by GA2OX8 overexpression inhibits root cell elongation. In contrast, roots missing GA2OX genes elongate faster. These findings indicate that GA2OX8 enzymes represent an integration core of auxin and gibberellin signalling pathway in root elongation zone, vascular development and regulation of stem cell niche. Our results enhance understanding of complex mechanisms controlling root cell elongation.
Project description:Injured plant somatic tissues regenerate themselves by establishing the shoot or root meristems. In Arabidopsis (Arabidopsis thaliana) a two-step culture system ensures regeneration by first promoting the acquisition of pluripotency and subsequently specifying the fate of new meristems. Although previous studies have reported the importance of phytohormones auxin and cytokinin in determining the fate of new meristems, it remains elusive whether and how the environmental factors influence this process. In this study, we investigated the impact of light signals on shoot regeneration using Arabidopsis hypocotyl as explants. We found that light signals promote shoot regeneration while inhibiting root formation. ELONGATED HYPOCOTYL 5 (HY5), the pivotal transcriptional factor in light signaling, plays a central role in this process by mediating the expression of key genes controlling the fate of new meristems. Specifically, HY5 directly represses root development genes and activates shoot meristem genes, leading to the establishment of shoot progenitor from pluripotent callus. We further demonstrated that the early activation of photosynthesis is critical for shoot initiation, and this is transcriptionally regulated downstream of the HY5-dependent pathways. In conclusion, we uncovered the intricate molecular mechanisms by which light signals control the establishment of new meristem through the regulatory network governed by HY5, thus, highlighting the influence of light signals on plant developmental plasticity.
Project description:Phosphate (Pi) deficiency alters root hair length and frequency as a means of increasing the absorptive surface area of roots. Three partly redundant single R3 MYB proteins, CAPRICE (CPC), ENHANCER OF TRY AND CPC1 (ETC1) and TRIPTYCHON (TRY), positively regulate the root hair cell fate by participating in a lateral inhibition mechanism. To identify putative targets and processes that are controlled by these three transcription factors (TFs), we conducted transcriptional profiling of roots from Arabidopsis thaliana wild-type plants, and cpc, etc1 and try mutants grown under Pi-replete and Pi-deficient conditions using RNA-seq.