Role of the putative membrane-bound endo-1,4-beta-glucanase KORRIGAN in cell elongation and cellulose synthesis in Arabidopsis thaliana
Sato, S. (Mitsui Plant Biotechnology Research Inst., Tsukuba, Ibaraki (Japan)) | Kato, T. | Kakegawa, K. | Ishii, T. | Liu, Y.G. | Awano, T. | Takabe, K. | Nishiyama, Y. | Kuga, S. | Sato, S. | Nakamura, Y. | Tabata, S. | Shibata, D.
A temperature-sensitive, elongation-deficient mutant of Arabidopsis thaliana was isolated. At the nonpermissive temperature of 31 deg C, the mutation impaired tissue elongation; otherwise, tissue development was normal. Hypocotyl cells that had established cell walls at 21 deg C under light-dark cycles ceased elongation and swelled when the mutant was shifted to 31 deg C and darkness, indicating that the affected gene is essential for cell elongation. Analysis of the cell walls of mutant plants grown at 31 deg C revealed that the cellulose content was reduced to 40% and the pectin content was increased to 162% of the corresponding values for the wild type grown at the same temperature. The increased amounts of pectin in the mutant were bound tightly to cellulose microfibrils. No change in the content of hemicellulose was apparent in the 31 deg C-adapted mutant. Field emission-scanning electron microscopy suggested that the structure of cellulose bundles was affected by the mutation; X-ray diffraction, however, revealed no change in the crystallite size of cellulose microfibrils. The regeneration of cellulose microfibrils from naked mutant protoplasts was substantially delayed at 31 deg C. The recessive mutation was mapped to chromosome V, and map-based cloning identified it as a single G -> A transition (resulting in a Gly**429 ->Arg substitution) in KORRIGAN, which encodes a putative membranebound endo-1, 4-bata-glucanase. These results demonstrate that the product of this gene is required for cellulose synthesis.
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