Analysis of mRNA-miRNA networks in soybean lipid metabolism and the regulatory role of gma-miRNA396b based on transcriptomics

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Soybean ( Glycine max (Linn.) Merr.) is a globally important crop. It is extensively utilized in food processing, feed production, and various industrial applications. miRNAs are involved in various plant biological processes, particularly in growth, development, differentiation, and biotic and abiotic stress responses. However, their involvement in lipid synthesis in soybean has rarely been reported. In this study, the soybean cultivar ‘JN18’ and its low linolenic acid mutant ‘MT72’ were used as experimental material at R4 (pod filling stage), R5 (initiation of seed formation), and R6 (peak of seed formation) for whole-transcriptome sequencing. miRNAs related to lipid synthesis were identified and miRNA-mRNA network was constructed. Overexpression of gma - miR396b leaded to a significant reduction in oleic acid content and total hydrolyzed amino acids in the seeds. The interaction between gma-miR396b and GmLACS1 was validated by rapid amplification of cDNA ends mediated and β -glucuronidase (GUS) histochemical staining assays. Our results provide a new perspective on the molecular network of soybean lipid metabolism. • An interaction network of miRNAs and their target genes involved in soybean oil biosynthesis was screened and constructed. • Overexpression of gma-miR396b resulted in a significant decrease in seed oleic acid content, a 21.9 % reduction in total hydrolyzed amino acid content, and a 17.76 % increase in thousand-seed weight. • Mature miR396b cleaves GmLACS1 at its binding site, thereby suppressing GmLACS1 expression. • gma-miR396b directly participates in lipid metabolism by reversibly regulating the expression of the key oil biosynthesis gene GmACCA-1 .