Patatin-Related Phospholipase pPLAIIIβ-Induced Changes in Lipid Metabolism Alter Cellulose Content and Cell Elongation in Arabidopsis

The release of fatty acids from membrane lipids has been implicated in various plant processes, and the patatin-related phospholipases (pPLAs) constitute a major enzyme family that catalyzes fatty acid release. The Arabidopsis thaliana pPLA family has 10 members that are classified into three groups. Group 3 pPLAIII has four members but lacks the canonical lipase/esterase consensus catalytic sequences, and their enzymatic activity and cellular functions have not been delineated. Here, we show that pPLAIII beta hydrolyzes phospholipids and galactolipids and additionally has acyl-CoA thioesterase activity. Alterations of pPLAIII beta result in changes in lipid levels and composition. pPLAIII beta-KO plants have longer leaves, petioles, hypocotyls, primary roots, and root hairs than wild-type plants, whereas pPLAIII beta-OE plants exhibit the opposite phenotype. In addition, pPLAIII beta-OE plants have significantly lower cellulose content and mechanical strength than wild-type plants. Root growth of pPLAIII beta-KO plants is less sensitive to treatment with free fatty acids, the enzymatic products of pPLAIII beta, than wild-type plants; root growth of pPLAIII beta-OE plants is more sensitive. These data suggest that alteration of pPLAIII beta expression and the resulting lipid changes alter cellulose content and cell elongation in Arabidopsis.