Differential Expression Of The Genes Related Storage Proteins In Endosperms Of Rice With Different Ploidy

The contents and compositions of storage protein play important roles in the nutritional quality of rice(Oryza sativa). Most storage protein (seed storage proteins, SSPs) are stored in the endosperm of rice seeds, with a content of approximately5-10%of dry weight, which makes them the second largest storage substance in rice seed after starch. Compared with diploid rice, the storage protein content of autotetraploid rice was higher (more than20%). To gain insight of mechanism for storage protein synthesis and regulation and to provide base theory and experimental support that might facilitate polyploid rice breeding, this study kept a track of storage protein behaviors through the synthesis process in rice endosperm.Firstly, each component of storage protein was analyzed within four groups of autotetraploid and their diploid by SDS-PAGE technology and BCA method. The results showed that the protein content of each fraction, especially glutenin, in endosperm of autotetraploid rice line is mostly higher than that of its corresponding diploid rice line. However, the SDS-PAGE analysis showed that the subunit types of each storage protein of autotetraploid rice line was generally homologous to that of its corresponding diploid rice line. These results suggested that the doubling of chromosome sets changed the protein expression level but not the protein expression profile in the starchy endosperm of autotetraploid rice.Secondly, six genes (GluA-2, GluA-3, GluB-1, GluB-5, Pro114, S18) encoding seed storage proteins in rice endosperm from HN2026-2X, HN2026-4X, Balilla-4X, Balilla-2X and Nipponbare-2X were tracked in the6,9,12,15,18and21days after flowering. RNAs were extracted from developing rice endosperm and analyzed by RT-PCR technology. The results showed that the level of gene expression in diploid rice line was higher than its corresponding autotetraploid rice line during the first6days. Then the level of gene expression in both lines became equal from7to18days. Finally the level of gene expression in autotetraploid rice line became higher than its corresponding diploid rice line since21days after flowering. However, little difference of genes expression was observed between line PMeS HN2026-4X and Balilla-4X.