PREDOC2023 (CM) - Evolution of stress tolerance in plants

An algal ancestor of all land plants colonised land 500 million years ago. In order to survive in the new terrestrial environment, dehydration tolerance was crucial for success. Therefore, the first land plants had to enhance their tolerance to dehydration tolerance. In land plants, abscisic acid (ABA) is the key signalling molecule regulating plant adaptation to abiotic stresses, including dehydration. The components of the ABA pathway are well conserved in land plants: the PYL/PP2C receptor complex, the SnRK2 protein kinases and key bZIP transcription factors (TF). In contrast, although algae synthesise ABA, they do not respond to it. This has led to the hypothesis that acquisition of ABA-modulation of an ancient desiccation tolerance pathway by an aero-terrestrial algal ancestor paved the way for the evolution of land plants. The first land plants, such as extant non-vascular Bryophytes, evolved a strong dehydration tolerance. In contrast to Bryophytes, in plants such as angiosperms, desiccation tolerance is mostly restricted in seeds. Indeed, in angiosperms such as the model Arabidopsis thaliana, the bZIP transcription factors key in promoting ABA-mediated desiccation tolerance are only expressed in seeds. ABI5 is the primary TF mediating ABA-mediated tolerance. AtABI5 belongs to a functional redundant gene family of at least 6 members. Therefore, we proposed to analyze Marchantia, a new model non-vascular plant enabling to infer features of the common ancestor.