Comparative analysis of the function and regulation of the ZOU/ICE protein complex in Arabidopsis thaliana and Marchantia polymorpha

Abstract

In angiosperms, the development of the seed and the accumulation of reserves require the establishment of close communication between the embryo and the endosperm. In Arabidopsis thaliana, this coordination is regulated by a protein complex made up of two transcription factors: ZHOUPI and INDUCER OF CBF EXPRESSION (ZOU/ICE). The ZOU/ICE complex controls the degradation of the endosperm and thus the optimal development of the embryo, and regulates the establishment of a complex interface between the endosperm and the embryo composed of an extracuticular sheath and of the embryonic cuticle. In a first part of my work, the analysis of the regulation and the function of the ZOU/ICE complex made it possible to highlight the regulation underlying a cryptic redundancy in seed development between the two ICE genes in Arabidopsis thaliana, as well as to explore the post-translational regulation of their proteins, in particular the potential role of ubiquitination in their degradation via the HOS1 protein. Secondly, genetic and molecular and cellular biology analyses in the bryophyte Marchantia polymorpha, which does not produce seeds, provided a better understanding of the ancestral function of the ZOU/ICE complex. Indeed, this study revealed two potential ancestral functions of this complex, firstly in the control of the development of pegged rhizoids involved in the transport of water and secondly in the biogenesis of the cuticle. The study of the composition of the cuticle of Marchantia polymorpha, and of the transcriptional targets of the ZOU/ICE complex involved in its establishment, made it possible to formulate innovative hypotheses about the importance of the modification of the composition of the wall, and the production of reactive oxygen species in plant cuticle biogenesis.