Abstract
DEK1 consists of a calpain cystein proteinase linked to a 21 transmembrane protein module. Dek1 is an essential gene for plant development that specify epidermal cell fate in all organs by a position dependant, cell autonomous mechanism. Its essential role in plant development is supported by the fact that Dek1 is a single gene in all plant species investigated so far, as well as its remarkable conservation between modern angiosperms, e.g. maize and Arabidopsis on one hand and the moss Physcomitrella patens, separated by 500 million years of evolution on the other. Mounting evidence support a role for epidermis as ?organizer? of underlying tissues. Our working hypothesis is that a fusion between genes encoding the calpain module and a gene(s) for the trans-membrane module gave rise to DEK1 and that this event(s) represented a key step in land plant evolution, facilitating the differentiation of an epidermal cell layer in multicellular organisms with identical cells. Single celled green algae basal to the land plant lineage possess calpain genes, but not Dek1. Calapins are ubiquitous enzymes found in all lineages of living organisms, but DEK1 is consistently present only in land plants. The primary objective of this project is to determine the origin of the Dek1 gene in the land plant lineage and the functionality that DEK1 added to the plant body in the group(s) where it first appeared. To achieve the primary goal, we will sequence calpain and Dek1 genes in species that are basal to Physcomitrella in the land plant lineage, including Bryophytes and green algae. Identification of calapin and Dek1 function in key species will be carried out using RNAi technology, resulting mutant phenotypes will be studied by morphological, molecular and cell biology tools. Finally, attempt will be made to crystallize recombinant protein for selected DEK1 domains.
Norway