Purpose To reveal the key genes and regulatory pathways regulating the formation and accumulation of resistant starch (RS) in the grains of high-RS rice variety Gongmi 3, providing a theoretical basis for the selection of high-quality functional rice varieties with high RS content.
Methods The high-RS content rice variety Gongmi 3 and the low-RS content rice variety Diantun 502 were used as objects and control, respectively. Transcriptome sequencing and comparative analysis were carried out at multiple periods (the 10th, 17th and 24th day after flowering), revealing the molecular regulatory mechanism of RS formation in Gongmi 3.
Results In the two varieties, the number of differentially expressed genes (DEGs) of the 24th day after flowering was substantially higher than the previous two stages. GO and KEGG enrichment analysis showed that lipid transport and binding items were significantly enriched across all three stages, with non-specific lipid transport proteins being the main ones, regulating lipid accumulation. Starch and sucrose metabolism pathway were significantly enriched at the 10th and 24th day after flowering, with glycosyl hydrolase genes as the main, regulating the content of reducing sugars. Venn diagram analysis identified 635 genes consistently differentially expressed in all three developmental stages, annotation and enrichment analysis of these genes showed significant enrichment for the lipid transport and binding items. Among these, six key genes, including a novel gene (Oryza_ sativa_newGene_1652), were consistently upregulated in Gongmi 3, serving as critical candidate genes for regulating RS content in subsequent functional validation.
Conclusion It is speculated that RS accumulation in Gongmi 3 grains is coordinately regulated by lipid metabolism and starch biosynthesis pathways, likely through enhanced formation of RS5 (starch-lipid complexes), and the 3rd developmental stage serves as a critical window orchestrating RS accumulation.
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