The architecture of the root system fulfills multiple essential roles, enabling plants to explore the soil, interact with abiotic and biotic components of the soil, and absorb water and nutrients. Root branching is a key process that influences root architecture. It relies on the formation of a new organ from selected cells in existing roots, the lateral root primordium (LRP).
The AP2/ERF transcription factor PUCHI has been shown to participate in this organogenesis process in the model plant Arabidopsis thaliana. Loss of PUCHI function alters SRP initiation density, developmental program regulation, and SRP functional structuring. Inference of PUCHI-dependent regulatory networks suggested that it induces the very long-chain fatty acid (VLCFA) biosynthesis pathway in SRPs, which was subsequently confirmed by experimental data. The overall objective of my thesis was to decipher the PUCHI-dependent regulatory network targeting VLCFAs during PRL development and to elucidate its impact on lateral root formation.
I discovered that the induction of expression of a large proportion of the genes linked to cutin synthesis, including key genes involved in the formation of the root cuticle cap (RCC), depends on PUCHI during PRL organogenesis. Furthermore, I demonstrated that RCC formation on LPRs depends on PUCHI, defining the specific diffusion barrier properties of its outermost cell layer. I also showed that the transcription factors MYB94 and MYB96, whose expression is stimulated by PUCHI during PRL development, are necessary for this induction of VLCFA and cutin metabolism gene expression, as well as for RCC formation on PRLs. Finally, our results suggest that this RCC influences the expression of genes involved in the functional structuring of the PRL and that part of PUCHI’s influence on the development and functional organization of the PRL is most likely explained by its impact on RCC formation.
Overall, this work has contributed to elucidating the PUCHI-dependent regulatory network during PRL formation in Arabidopsis thaliana.
Keywords: lateral root, gene regulatory network, very long-chain fatty acids (VLCFAs), root cuticle cap (RCC), PUCHI transcription factor
