Enhancement of Wx Gene Expression and the Accumulation of Amylose in Response to Cool Temperatures during Seed Development in Rice

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The wx (waxy) locus controls amylose synthesis in the endosperm of rice (Oryza sativa). We found that Wx gene expression was activated reversibly in response to a cool temperature (18℃);that is, the steady state-level of the transcript from the wx locus (Wx transcript) was higher at a cool temperature (18℃) than at a normal temperature (28℃). The longer that raice plants were exposed to a cool temperature, the higher the levels of Wx protein and the greater the accumulation of amylose. These results indicated that the activation of the Wx gene resulted in the increase in amylose content at the cool temperature, which caused the reduction in the quality of rice. Since the activation was not observed in seeds grown at 4 or 35℃, the response of the rice Wx gene to a cool temperature was different from the responses to cold stress or heat shock. In transgenic plants that carried the gene for β-glucuronidase (GUS) under the control of the promoter of the Wx gene, enhancement of GUS activity was also detected at a cool temperature, suggesting that the Wx promoter is responsive to a cool temperature.
日本植物生理学会の論文