A dual mechanism of cellulose deficiency in shv3svl1

SHAVEN3 (SHV3) and its homolog SHAVEN3-like 1 (SVL1) encode glycosylphosphatidylinositol (GPI)-anchored proteins (GAPs) that are involved in cellulose biosynthesis and hypocotyl elongation in Arabidopsis thaliana. In a recent report, we showed that the cellulose and hypocotyl elongation defects of the shv3svl1 double mutant are greatly enhanced by exogenous sucrose in the growth medium. Further investigation of this phenomenon showed that shv3svl1 exhibits a hyperpolarized plasma membrane (PM) proton gradient that is coupled with enhanced accumulation of sucrose via the PM sucrose/proton symporter SUC1. The resulting high intracellular sucrose concentration appears to favor starch synthesis at the expense of cellulose synthesis. Here, we describe our interpretation of these results in terms of 2 potential regulators of cellulose synthesis: intracellular sucrose concentration and a putative signaling pathway that involves SHV3-like proteins.