Expression Profiles of Rice Soluble Starch Synthase Isoform Genes in Response to High Temperature

Under mean daily temperature of 32°C (high temperature) and 22°C (normal temperature) controlled in growth chambers, the expression responses of 8 soluble starch synthase (SSS) isoform genes involving starch synthesis metabolism in rice (Oryza sativa L.) endosperms were detected using real-time fluorescence quantitative PCR (FQ-PCR). The expression patterns of SSS genes under high temperature stress were isoform-dependent, in which some isoform genes, such as SSS IIb, SSS IIc, SSS IIIb, and SSS IVa, were up-regulated with relatively high expression levels, and other genes, such as SSS IIa and SSS IIIa, showed down-regulated patterns with relatively low expression levels. SSS I and SSS IIIa were highly expressed in rice endosperms during the whole filling period in both temperature treatments, implying that they are the major isoform genes of SSS. The expressions of SSS IIb, SSS IIIa, and SSS IVa genes were much more sensitive to high temperature stress than those of SSS I, SSS IIc, SSS IIIb, and SSS IVb.