Down-Regulation of SSSII-2 Gene Expression Results in Novel Low-Amylose Rice with Soft, Transparent Grains.

Although soft rice, with low amylose content (AC), has high eating and cooking quality (ECQ), its appearance is poor due to the opaque endosperm. Here, a novel soft rice with low AC but a transparent appearance was generated by knocking-down the expression of SSSII-2, a gene encoding one isoform of soluble starch synthase (SSS). The physicochemical properties of the SSSII-2 RNAi rice are quite different from the control but more like the popular soft rice "Nanjing 46". The taste value assay further demonstrated that the ECQ of SSSII-2 RNAi rice was as high as "Nanjing 46", but only SSSII-2 RNAi rice retained the transparent endosperm under low moisture conditions. Further examination showed that the different morphologies and fine structures of the starch granules may contribute to the specific properties of SSSII-2 RNAi rice. Therefore, SSSII-2 has potential application in future high quality rice breeding programs.