A new plant drought tolerance mechanism via glucocerebrosidase

Abstract

Long-chain base phosphates (LCBPs), such as sphingosine-1-phosphate and phytosphingosine-1-phosphate, are known to function as abscisic acid-mediated signaling molecules that regulate stomatal closure in plants. Recently, Os3BGlu6, a glycoside hydrolase family 1 (GH1) β-glucosidase, was shown to improve drought tolerance by stomatal closure in rice, but the biochemical functions of Os3BGlu6 remained unclear. Here we identified Os3BGlu6 as a novel GH1 glucocerebrosidase (GCase) that catalyzes the hydrolysis of glucosylceramide to ceramide. Phylogenetic and enzymatic analyses showed that GH1 GCases are widely distributed in seed plants and that pollen or anthers of all seed plants tested had high GCase activity, but activity was very low in ferns and mosses. The levels of LCBPs synthesized from ceramides, especially the levels of sphingadienine-1-phosphate, correlated with GCase activity in each rice organ and were significantly lower in Os3BGlu6-deficient rice mutants than in the wild type. These results indicate that Os3BGlu6 increases the level of sphingadienine-1-phosphate and subsequently improves drought tolerance via stomatal closure in rice.