Land plants evolved from green algae predecessors around 470 million years ago, a key evolutionary step facilitated by their novel ability to perceive positional information and translate this into 3D growth patterns. The exact mechanism(s) for positional signaling in plants is still unknown. DEFECTIVE KERNEL 1 (DEK1), a large multi-domain protein with membrane-anchored calpain, has been proposed as a key regulator of oriented cell division and positional cell fate specification in land plants.
We aim to contribute to the understanding of DEK1 function by determining the structure of DEK1 protein and to identify its downstream targets,including in vivo substrates of the calpain protease. We have proposed that DEK1, a 240 kDa protein have evolved from ancient TML-calpains (existed 1.5 billion yrs ago) by fusion of genes encoding a Major facilitator superfamily membrane protein, an LG3 domain containing protein and a calpain. We aim to express and purify the full-length DEK1 recombinant protein as well as its calpain catalytic core, to determine the structure of DEK1 using cryo-EM and X-ray crystallography. Experimental systems for functional dissection of DEK1 using genetics and cell biology include the moss Physcomitrella patens and Arabidopsis thaliana.