OsBC1L4 encodes a COBRA-like protein that affects cellulose synthesis in rice

Abstract

Plant morphogenesis is highly dependent on the regulation of cell division and expansion. The organization of the cellulose microfibrils in the cell wall is a key determinant of cell expansion. Previously, a dwarf mutant with fewer tillers, Osbc1l4 (Oryza sativa brittle culm 1 like 4), was identified by screening a rice T-DNA insertion mutant library. It is reported here that OsBC1L4 encodes a COBRA-like protein that exhibits typical structural features of a glycosylphosphatidylinositol-anchor protein. The T-DNA insertion in OsBC1L4 results in abnormal cell expansion. A decrease in cellulose content but the increase in pectin and starch contents was identified in Osbc1l4 mutants by measuring the content of wall components. OsBC1L4 was expressed in all tissues/organs examined, with a low level in leaves. OsBC1L4 protein is mainly located in the cell wall and plasma membrane. Correlation analysis indicated that the expression of OsBC1L4 was highly correlated to that of several primary wall-forming cellulose synthase genes (CESAs). Moreover, the expression level of several cellulose-related genes is increased in Osbc1l4 mutants, which suggests that a feedback mechanism may exist during cellulose synthesis.

The Arabidopsis COBRA Protein Facilitates Cellulose Crystallization at the Plasma Membrane

“…5). It has been shown that the reduction of cellulose in the cobra mutant is accompanied by overproduction of starch, preventing osmotic stress by the excess of glucose that cannot be incorporated into the cell wall (36). Analysis of galacturonic acid (GalA) levels revealed a significant increase in the cobra mutant (Fig.…”

COBRA-LIKE2, a Member of the Glycosylphosphatidylinositol-Anchored COBRA-LIKE Family, Plays a Role in Cellulose Deposition in Arabidopsis Seed Coat Mucilage Secretory Cells ,

“…In other developmental contexts, COBL gene products have been shown to affect crystalline cellulose deposition (Schindelman et al, 2001;Li et al, 2003;Dai et al, 2011). Schindelman and colleagues elegantly employed polarized light microscopy to demonstrate a substantial reduction in crystalline cellulose deposition at the elongation zone of cob-1 mutant roots under restrictive conditions, a phenotype associated with the perturbation in anisotropic cell expansion (Schindelman et al, 2001;Roudier et al, 2005).…”

“…Mutations in cobra (cob) result in reduced levels of crystalline cellulose and disorganized deposition of cellulose microfibrils at the root elongation zone, leading to short and swollen roots (Benfey et al, 1993;Hauser et al, 1995;Schindelman et al, 2001;Roudier et al, 2005;Sorek et al, 2014). Other characterized COBL family members have been assigned similar functions in other contexts: COBL9, in root hair elongation (Parker et al, 2000;Ringli et al, 2005;Jones et al, 2006), COBL10 and 11 in pollen tube elongation through the transmitting tract , and COBL4, initially identified through its coexpression with CESA4, CESA7 and CESA8 (as well as its orthologs from rice and maize) in secondary cell wall deposition in xylem cells (Li et al, 2003;Brown et al, 2005;Persson et al, 2005;Ching et al, 2006;Sato et al, 2010b;Dai et al, 2011;Liu et al, 2013). Of the twelve COBL family members, seven remain uncharacterized.…”

SEMI-ROLLED LEAF1 Encodes a Putative Glycosylphosphatidylinositol-Anchored Protein and Modulates Rice Leaf Rolling by Regulating the Formation of Bulliform Cells

“…Transcript levels were normalized with the ACTIN transcription and relative expression levels were compared with that in Nip (set as 1), respectively. Mean values were calculated from three independent experiments and error bars indicate SD. of COBRA in rice, regulates the synthesis of secondary cell wall and affects the mechanical strength of rice plants (Li et al, 2003;Dai et al, 2011). However, SRL1 belongs to none of these groups and does not contain any conserved domain.…”