The evolution of hydrophobic barriers among land plantsCumulative thesis
Date of Examination:2023-05-25
Date of issue:2023-08-03
Advisor:Prof. Dr. Ivo Feussner
Referee:Prof. Dr. Ivo Feussner
Referee:Prof. Dr. Andrea Polle
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EnglishThe terrestrialization of plants required major physiological and metabolic adaptations, including the capacity to deposit extracellular hydrophobic barriers that shield plant surfaces against various abiotic and biotic stresses. The plant cuticle covers the outermost primary surfaces of almost all aerial plant organs and is composed of the core scaffolding cutin and a mixture of cuticular waxes. In contrast, the biopolymer suberin is mainly associated with belowground tissues, controlling water and ion transport. Substantial progress has been made in understanding the molecular mechanisms of hydrophobic barrier formation in vascular plants, such as Arabidopsis thaliana. However, only a limited number of studies addressed the function of genetic orthologs involved in cuticle biosynthesis in bryophytes. While many of the gene families involved in cuticle biosynthesis are less represented in bryophytes, they gradually increased in gene numbers among vascular plants. To understand the origins and evolution of hydrophobic barriers among land plants, homologs of cuticle biosynthetic enzymes were characterized by reverse-genetic approaches in two model bryophyte species. Furthermore, the role of the R2R3-type Myeloblastosis (MYB) transcription factor AtMYB41 in the formation of hydrophobic barriers has been studied throughout plant development. Previous reports implicated AtMYB41 in the regulation of cutin and endodermal suberin biosynthesis. Here, the characterization of an Atmyb41ge mutant collection has shown that AtMYB41 functions as a dual-function transcription factor of lipid metabolism. Thereby, AtMYB41 acts as a negative regulator of cuticle and fatty acid biosynthesis in leaves and seeds, respectively, but also as a positive regulator of wax production in A. thaliana stems.
Keywords: Arabidopsis thaliana; Marchantia polymorpha; Physcomitrium patens; Cuticular waxes; Cutin; Suberin; Evolution; Plant development; Abiotic stress