FORMING FILAMENTS WITH ENZYMES: A POTENTIAL MECHANISM FOR PLANTS TO ADJUST TO STRESSFUL ENVIRONMENTAL CONDITIONS

Abstract

We are interested in understanding the molecular mechanisms of how plants respond to environmental stress. The focus of this study is on how plant roots grow in different concentrations of nitrogen. Through a collaboration with a proteomics group, we identified around fifty proteins that interact with XIP1/CEPR1, a receptor protein that is involved in sensing nitrogen levels and regulating lateral root growth in Arabidopsis. Of these interactors, we selected eight that we hypothesize are important for lateral root growth. A review of the literature of some of these proteins involved in sugar and amino acid metabolism in Arabidopsis and other organisms found that many were found in unexpected, highly-concentrated structures called filaments. Filaments are made from multimers of the enzymes, sometimes forming large helices. These filaments can be visualized as foci when the proteins are made as translational fusions to Green Fluorescent Protein. Although there have been studies on these filaments, little is known about the formation and function of these structures. To better understand these interacting proteins, we created constructs using cDNAs flanked with 35S Promoter region driving the expression of these eight proteins, which are translationally fused to Green Fluorescent Protein. We then transformed these constructs into Arabidopsis plants using Agrobacterium. To understand how the receptors might regulate filament formation, we inserted these constructs into the wild type and cepr1;cepr2 double mutant Arabidopsis. Next we will test whether these enzymes form filaments in mutants and in wildtype controls, test if filaments affect enzyme function, and whether phosphorylation of these enzymes results in filamentation.