Down-regulation of the cotton endo-1,4-β-glucanase gene KOR1 disrupts endosperm cellularization, delays embryo development, and reduces early seedling vigour.

Xiaoguang Shang,Tianzhen Zhang,Wangzhen Guo,Jianxiong Jiang,Qichao Chai,Yong-Ling Ruan,Qinghu Zhang

doi:10.1093/jxb/erv111

Abstract

Towards the aim of examining the potential function of KORRIGAN (KOR), a highly conserved membrane-bound endoglucanase, in reproductive development, here transgenic evidence is provided that a cotton (Gossypium hirsutum) endoglucanase, GhKOR1, plays significant roles in endosperm and embryo development. RNA interference (RNAi)- and co-suppression-mediated down-regulation of GhKOR1 resulted in smaller filial tissue and reduced seed weight, which were characterized by disrupted endosperm cellularization and delayed embryo development, leading to a delayed germination and a weak growth of seedlings early in development. The transgenic seeds exhibited fewer and smaller endosperm cells with irregular and brittle cell walls, and their embryos developed only to the globular stage at 10 days post-anthesis (DPA) when the wild-type endosperm has become highly cellularized and the embryo has progressed to the heart stage. The transgenic seed also displayed a significant reduction of callose in the seed coat transfer cells and reduced cellulose content both in the seed coat and in mature fibres. These findings demonstrate that GhKOR1 is required for the developmental of both seed filial and maternal tissues and the establishment of seedling vigour.

Highlights

In addition to the cellulose synthase complex, KORRIGAN (KOR), a plasma membrane-bound endo-1,4-β-glucanase, is another protein required for complete and correct cellulose biosynthesis and cell wall formation (Nicol et al, 1998; Zuo et al, 2000)
RNA interference (RNAi)and co-suppression-mediated down-regulation of GhKOR1 resulted in smaller filial tissue and reduced seed weight, which were characterized by disrupted endosperm cellularization and delayed embryo development, leading to a delayed germination and a weak growth of seedlings early in development
The GhKOR1 gene shares a similar structure with AtKOR1, both of which contain the same number of exons and introns with similar nucleotide number in the exons (Supplementary Fig. S1 at JXB online)

Summary

Introduction

In addition to the cellulose synthase complex, KORRIGAN (KOR), a plasma membrane-bound endo-1,4-β-glucanase, is another protein required for complete and correct cellulose biosynthesis and cell wall formation (Nicol et al, 1998; Zuo et al, 2000). KOR was initially isolated from the Arabidopsis thaliana dwarf mutant, kor, which displayed pronounced architectural alterations in the primary cell wall (Nicol et al, 1998). Mutations in KOR resulted in the reduction of cellulose content in both the primary and secondary cell wall and, various phenotypes in Arabidopsis mutants, including dwarfism (Nicol et al, 1998), radial swelling of root tips (Lane et al, 2001), and collapse of xylem vessels (Szyjanowicz et al, 2004). The altered cell wall 1 (acw1) mutant characterized by a mutation in AtKOR1, for example, exhibited impaired

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Conclusion