Wx蛋白缺失对水稻颖果和剑叶生理活性的影响

Effects of Wx Protein Loss on the Physiological Activities of Caryopsis and Flag Leaf in Rice

以转反义耽基因粳稻和籼稻为材料的研究结果表明，直链淀粉含量降低后的转基因水稻颖果的光合和呼吸活性在发育前期显著高于亲本，但下降较快，到发育中期（花后15～18d）以后，则低于同期的亲本。但其SOD和CAT活性比其亲本下降得慢，从花后9d开始一直保持着比亲本高的水平。花后转基因水稻剑叶的叶绿素含量、光合速率和SOD及CAT活性下降也比其亲本慢，至颖果发育中后期，均高于其亲本。说明Wx蛋白缺失影响了颖果的生理活性，以至颖果储藏物质的积累最终使千粒重下降。

The content of amylose in rice caryopsis is determined by Wx protein, one kind of granule-bound starch synthetase which is encoded by Wx gene. Different rice types and species have different levels of Wx gene expression and have different content of amylose in their caryopsis. Wuyunjing 7（2200）, the japonica rice whose amylose content is 17% and its transgenic rice with antisense Wx gene （2201, 2203, amylose content is 8.5% and 2% respectively）, and Longtefu （LP03）, the indica rice of high amylose content （28%） and its transgenic rice with antisense Wx gene （A199, amylose content 9% ） were used to investigate the effects of Wx protein loss on development of rice caryopsis and accumulation of photosynthate. The photosynthetic and respiratory rate of these rice were determined by methods of oxygen electrode in regular days after flowering. The results indicated that the photosynthetic and respiratory rate of transgenic rice caryopses were markedly higher than their parents in the beginning, and then decreased quickly, and at the 15th - 18th days after flowering（DAF） were markedly lower than their parents （ Fig. 1, Fig. 2）. In indica transgenic caryopsis, the SOD and CAT activities were apparently higher, while in japonica transgenic caryopses, lower than their parents in the early stage. The SOD and CAT activities were decreased slowly in transgenic caryopses and higher than their parents at the 12th - 15th DAF （Fig. 3, Fig.4）. In addition, the chlorophyll content and SOD activity in flag leaves were increased slightly in the early filling stage, and then decreased continuously. While the photosynthesis rate and CAT activity in flag leaves decreased gradually after flowering. In transgenic rice, the chlorophyll content, photosynthesis rate, SOD and CAT activities of flag leaves were all decreased more slowly than their parents, and thus were higher than their parents in later filling stage （Fig. 5, Fig. 6） . In conclusion, the physiological activities of caryopsis and flag leaves are affected by Wx protein, whose loss will decrease the accumulation of photosynthates in caryopsis, and lead to the reduction of the grain weight at last.