A plasma membrane-bound putative endo-1,4-beta -D-glucanase is required for normal wall assembly and cell elongation in Arabidopsis

Abstract

Endo-1,4-β-D-glucanases (EGases) form a large family of hydrolytic enzymes in prokaryotes and eukaryotes. In higher plants, potential substrates in vivo are xyloglucan and non-crystalline cellulose in the cell wall. Gene expression patterns suggest a role for EGases in various developmental processes such as leaf abscission, fruit ripening and cell expansion. Using Arabidopsis thaliana genetics, we demonstrate the requirement of a specialized member of the EGase family for the correct assembly of the walls of elongating cells. KORRIGAN (KOR) is identified by an extreme dwarf mutant with pronounced architectural alterations in the primary cell wall. The KOR gene was isolated and encodes a membrane-anchored member of the EGase family, which is highly conserved between mono-and dicotyledonous plants. KOR is located primarily in the plasma membrane and presumably acts at the plasma membrane-cell wall interface. KOR mRNA was found in all organs examined, and in the developing darkgrown hypocotyl, mRNA levels were correlated with rapid cell elongation. Among plant growth factors involved in the control of hypocotyl elongation (auxin, gibberellins and ethylene) none significantly influenced KOR-mRNA levels. However, reduced KOR-mRNA levels were observed in det2, a mutant deficient for brassinosteroids. Although the in vivo substrate remains to be determined, the mutant phenotype is consistent with a central role for KOR in the assembly of the cellulose-hemicellulose network in the expanding cell wall.

GALACTURONOSYLTRANSFERASE-LIKE5 Is Involved in the Production of Arabidopsis Seed Coat Mucilage

“…The idea of a hydrolase functioning in plant cell wall polysaccharide synthesis has been proposed before. KORRIGAN (KOR), an endo-1,4-b-glucanase, cannot only degrade cellulose but also appears to play a role in plant cellulose synthesis, as evidenced by the reduction in cellulose content observed in the kor mutant (Nicol et al, 1998;Lane et al, 2001). However, glycosylhydrolases involved in cell wall polysaccharide reconstruction and modification after biosynthesis that have been identified to date are located in the cell wall or in the plasma membrane (Minic and Jouanin, 2006).…”

Specialized Roles of the Conserved Subunit OST3/6 of the Oligosaccharyltransferase Complex in Innate Immunity and Tolerance to Abiotic Stresses

“…Another candidate protein that is sensitive to alterations in glycosylation is the endo-b-1,4-glucanase KOR1 (Nicol et al, 1998), which plays a yet unclear role during cell wall formation and cellulose synthesis. KOR1 has eight potential glycosylation sites in its extracellular domain, and genetic interactions of the weak KOR1 allele rsw2-1 (Lane et al, 2001) with different N-glycan-processing mutants indicate that Nglycans play a crucial role for KOR1 (Kang et al, 2008;Liebminger et al, 2009).…”

CHITINASE-LIKE1/POM-POM1 and Its Homolog CTL2 Are Glucan-Interacting Proteins Important for Cellulose Biosynthesis in Arabidopsis

“…The cellulose crystalline/amorphous ratio also influences in muro interaction between XGs and cellulose (Hanus and Mazeau, 2006). Only one protein has been reported to alter that ratio; KORRIGAN (KOR), a membrane-bound b-1,4-glucanase, which increases the amount of noncrystalline cellulose (Nicol et al, 1998;Takahashi et al, 2009). The kor1/lion's tail1 mutant was initially isolated in a screen for mutants with anisotropic growth defects (Nicol et al, 1998).…”