Disruption of the cellulose synthase gene, <i>AtCesA8/IRX1</i>, enhances drought and osmotic stress tolerance in Arabidopsis

Summary Two allelic Arabidopsis mutants, leaf wilting 2‐1 and leaf wilting 2‐2 ( lew2‐1 and lew2‐2 ), were isolated in a screen for plants with altered drought stress responses. The mutants were more tolerant to drought stress as well as to NaCl, mannitol and other osmotic stresses. lew2 mutant plants accumulated more abscisic acid (ABA), proline and soluble sugars than the wild type. The expression of a stress‐inducible marker gene RD29A , a proline synthesis‐related gene P5CS (pyrroline‐5‐carboxylate synthase) and an ABA synthesis‐related gene SDR1 (alcohol dehydrogenase/reductase) was higher in lew2 than in the wild type. Map‐based cloning revealed that the lew2 mutants are new alleles of the AtCesA8/IRX1 gene which encodes a subunit of a cellulose synthesis complex. Our results suggest that cellulose synthesis is important for drought and osmotic stress responses including drought induction of gene expression.