A novel approach to functional genomic studies of the superfamily of receptor-like kinases (RLKs) in Arabidopsis thaliana

Receptor-like kinases (RLKs) form a large monophyletic gene family of approximately 600 members in Arabidopsis. They consist of proteins that contain a single extracellular domain that is thought to be the site of ligand binding, connected to a single kinase domain, via a single transmembrane domain. Upon ligand binding the kinase is capable of generating a phosphorylation cascade. Because of the size of this gene family and of functional redundancy among closely related members, not much is known about the function of many of these important signaling genes. What little that is known shows that RLKs have many diverse roles in plants such as, hormone perception, plant defense, plant development and cell growth.;My objective is to elucidate the function of these genes using a dominant negative approach, circumventing functional redundancy-associated difficulties in gene functional analysis. I constructed a library of dominant negative mutations that encompasses approximately 50% of all the RLKs in Arabidopsis. This library was then screened for morphological, developmental and conditional phenotypes and two strong candidates emerged.;The first belongs to the wall-associated kinase-like (WAKL) subfamily, and its dominant mutant altered senescence associated gene expression under various nutrient and light conditions. Further exploration into this gene family may lead to an understanding of nutrient sensing and signaling via the cell wall in plants.;The other belongs to the STRUBBELIG RECEPTOR FAMILY (SRF), and its dominant negative mutant altered cell wall composition when examined using Fourier Transform Infrared (FT-IR) microspectroscopy and gas chromatography. In this gene subfamily there is also altered cellulose synthase (CesA) gene expression and morphological phenotypes that suggest that this gene subfamily is important in directing the composition of the plant cell wall. The ramification of this research is that these genes may be important to a future cellulose based fuel economy.