Beta-1,3:1,4-glucan synthase activity in rice seedlings under water.
OBJECTIVE
The metabolism of beta-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 beta-1,3 : 1,4-glucan hydrolases; however, the involvement of beta-1,3 : 1,4-glucan synthase activity in elongation growth under water has not yet been clarified.


METHODS
The beta-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 beta-1,3 : 1,4-glucan synthase genes, was examined by quantitative reverse-transcriptase PCR.


RESULTS
The level of beta-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 beta-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 beta-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 beta-1,3 : 1,4-glucan synthase activity. Together with the increased activity of beta-1,3 : 1,4-glucan hydrolases, the decreased activity of beta-1,3 : 1,4-glucan synthase contributes to the decrease in the amount of beta-1,3 : 1,4-glucan in the cell walls under water. The suppression of beta-1,3 : 1,4-glucan synthesis under water may be mainly due to oxygen depletion.
Kimpara
Tomoya
T
Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan.
Aohara
Tsutomu
T
Soga
Kouichi
K
Wakabayashi
Kazuyuki
K
Hoson
Takayuki
T
Tsumuraya
Yoichi
Y
Kotake
Toshihisa
T
D002473:Cell Wall / Q000737:chemistry; D018548:Cotyledon / Q000201:enzymology / Q000254:growth & development; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005964:Glucosyltransferases / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology* / Q000254:growth & development*; D010940:Plant Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D036226:Seedlings / Q000201:enzymology* / Q000254:growth & development*; D014867:Water; D047071:beta-Glucans / Q000378:metabolism
D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D047071:beta-Glucans; D014867:Water; C067858:beta-glucan, (1-3)(1-4)-; D005964:Glucosyltransferases; C040232:glucan synthase