Characterization of bHLH transcription factors that control tissue differentiation in Physcomitrella patens
Year: 2012
Type: dissertation
Abstract: The evolution of developmental and physiological processes in plants made possible the colonization of the terrestrial environment. The development of a rooting system was critical for the spread of plants on land. Rhizoids and caulonema are cells with rooting function that are present in early diverging groups of land plants, such as mosses. In Physcomitrella patens the development of these cells is controlled by auxin, which positively regulates PpRSL (Physcomitrella patens RHD SIX-LIKE) Class I genes. The closest relatives of PpRSLs in higher plants control root hair development. In higher plants LRL (LjRHL-LIKE) genes also control root hair development but their function in P. patens is unknown. I show here that PpLRL genes are present in P. patens and are required for caulonema and rhizoid development. In A. thaliana, RSL Class I genes positively regulate the expression of AtLRL3, and this gene is also positively regulated by auxin. I demonstrate that auxin-induced rhizoid and caulonema cell development in P. patens requires the activity of PpLRL genes, but unlike A. thaliana both PpLRL genes are negatively regulated by auxin. I also found that expression of PpLRL genes is independent of RSL Class I. These findings suggest that there exists a gene network that is conserved between A. thaliana and P. patens, but the interactions between its components are different in the two species. These different topologies observed in the network that controls the development of rooting systems may explain the diversity observed in land plant rooting systems. I also generated a knock-out mutant, Pphol, which will be used to understand the role and evolution of methyl halides production in land plants. Altogether, this work supports the hypothesis that the evolution of novel developmental and physiological processes was partly driven by the reutilization of ancient developmental and physiological mechanisms.
Author: Bruno Catarino
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2257056610