AOBPreview originally published online on May 16, 2008
Annals of Botany 2008 102(2):221-226; doi:10.1093/aob/mcn077
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β-1,3 : 1,4-Glucan Synthase Activity in Rice Seedlings under Water
1 Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan
2 Department of Biology and Geosciences, Graduate School of Science, Osaka City University, 3-3-138, Sugimoto-cho, Sumiyoshi-ku, Osaka 558-8585, Japan
* For correspondence. E-mail kotake{at}molbiol.saitama-u.ac.jp
Received: 1 February 2008 Returned for revision: 31 March 2008 Accepted: 17 April 2008 Published electronically: 18 May 2008
Background and Aims: The metabolism of β-1,3 : 1,4-glucan regulates the mechanical properties of cell walls, and thereby changes the elongation growth of Poaceae plants. A previous study has shown that elongation growth of rice coleoptiles under water is enhanced by increased activity of β-1,3 : 1,4-glucan hydrolases; however, the involvement of β-1,3 : 1,4-glucan synthase activity in elongation growth under water has not yet been clarified.
Methods: The β-1,3 : 1,4-glucan synthase activity in a microsomal fraction prepared from rice seedlings grown under water was compared with that from control seedlings grown in air. The change under water in the relative expression level of CslF6, a major isoform of the β-1,3 : 1,4-glucan synthase genes, was examined by quantitative reverse-transcriptase PCR.
Key Results: The level of β-1,3 : 1,4-glucan synthase activity in submerged seedlings decreased to less than 40 % of that of the control seedlings and was accompanied by a significant reduction in the amount of β-1,3 : 1,4-glucan in the cell walls. Under water, the expression of CslF6 was reduced to less than 20 % of the unsubmerged control. Bubble aeration partially restored both β-1,3 : 1,4-glucan synthase activity and the expression of CslF6 under water, correlating with suppression of the submergence-induced elongation growth of coleoptiles.
Conclusions: Submergence down-regulates the expression of the CslF6 gene, leading to a decreased level of β-1,3 : 1,4-glucan synthase activity. Together with the increased activity of β-1,3 : 1,4-glucan hydrolases, the decreased activity of β-1,3 : 1,4-glucan synthase contributes to the decrease in the amount of β-1,3 : 1,4-glucan in the cell walls under water. The suppression of β-1,3 : 1,4-glucan synthesis under water may be mainly due to oxygen depletion.
Key words: β-1,3 : 1,4-glucan, rice, Oryza sativa, elongation growth, cell wall, β-1,3 : 1,4-glucan synthase, CslF gene
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