Arabidopsis 2010: Determination of Biological Functions of the NPH3/RPT2 Family

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Because of their sessile nature, plants have evolved a wide range of strategies to respond to changes in their environment. For a number of these responses plants have co-opted (or co-evolved) systems that are shared with other taxa. However, many of the environmental (both biotic and abiotic) response systems plants utilize are apparently specific to plants and are often comprised of novel molecular components. With the recent completion of the Arabidopsis genome sequencing project we are now in a unique position to ask fundamental questions about the functions of these latter set of regulatory proteins in plants. Of the ~11,000 protein families formed by the 25,498 predicted genes of Arabidopsis, only ~150 families appear to be plant-specific. One of these plant-specific families is the NPH3/RPT2 family. This family, which is comprised of 32 novel proteins (for more information about these proteins/genes, including GenBank accession numbers, see http://www.biosci.missouri.edu/liscum/nph3-rpt2figs.html), was first identified with the cloning of NPH3 (NONPHOTOTROPIC HYPOCOTYL 3) and RPT2 (ROOT PHOTOTROPISM 2) - genes identified in screens for mutants with altered phototropic responses. NPH3 and RPT2 function in early phototropic signaling and appear to act as modular scaffold proteins to recruit or activate enzymatic components of the transduction chains, including the respective photoreceptors themselves, mediating phototropic responses. Given the high degree of similarity in primary sequence and secondary structure between all members of the NPH3/RPT2 family it seems appropriate to hypothesize that these plant-specific proteins may act as scaffolds for sensor-containing signaling complexes utilized in a variety of abiotic and/or biotic responses. The major goals proposed for this project are to determine mRNA and protein expression patterns, and biological functions for each member of the NPH3/RPT2 family. The expression studies are proposed as a means of developing logical and focused analyses of loss- and gain-of-function mutants. In such a way we expect to be able to determine what biological processes require the function of each member of the NPH3/RPT2 family. All project data will be publicly available through a project database (http://www.biosci.missouri.edu/liscum/NPH3-RPT2family.html), as well as The Arabidopsis Information Resource (TAIR) (http://www.arabidopsis.org/home.html). Given the plant-specific and novel nature of the NPH3/RPT2 family, it is likely that elucidation of biological functions for the family will represent an important step in understanding fundamental aspects of plant growth and development.