Temperature-sensitive alleles of RSW2 link the KORRIGAN endo-1,4-beta-glucanase to cellulose synthesis and cytokinesis in arabidopsis

An 8.5-kb: cosmid containing the KORRIGAN gene complements the cellulose-de ficient rsw2-1 mutant of Arabidopsis. Three temperature-sensitive allies of rsw2 show single amino acid mutations in the putative endo-1,4-beta -gluca nase encoded by KOR. The F-1 from crosses between kor-1 and rsw2 alleles sh ows a weak, temperature-sensitive root phenotype. The shoots of rsw2-1 seed lings produce less cellulose and accumulate a short chain, readily Extracta ble glucan resembling that reported for rsw1 (which is defective in a putat ive glycosyltransferase required for cellulose synthesis). The double mutan t (rsw2-1 rsw1) shows further reductions in cellulose production relative t o both single mutants, constitutively slow root growth, and enhanced temper ature-sensitive responses that are typically more severe than in either sin gle mutant. Abnormal cytokinesis and severely reduced birefringent retardat ion in elongating root cell walls of rsw2 link the enzyme to cellulose prod uction for primary cell walls and probably cell plates. The Rsw2(-) phenoty pe generally resembles the Kor(-) and cellulose-deficient Rsw1(-) phenotype s, but anther dehiscence is impaired in Rsw2-1(-). The findings link a seco nd putative enzyme activity to cellulose synthesis in primary cell walls of Arabidopsis and further increases the parallels to cellulose synthesis in Agrobacterium tumefaciens where the celA and celC genes are required and en code a putative glycosyltransferase and an endo-1,4-beta -glucanase related to RSW1 and KOR, respectively.