GmMYB331 regulates seed traits of soybean

Seed traits, including seed size, weight, and quality, are among the most important characteristics in the crop cultivation process. We conducted a comparative analysis of the transcriptome data between high-oil and high-protein soybeans. By constructing a co-expression network of oil-related genes, we identified an MYB-type transcription factor,GmMYB331. Overexpression of the GmMYB331 gene in soybeans results in a series of gradient phenotypes corresponding to its varying expression levels. When GmMYB331 gene is moderately overexpressed (about 10-fold increase compared to wild type plants), the plant morphology remains similar to the wild type, with slightly larger seed size and marginally higher yield per plant, alongside a significant increase in seed fatty acid content. However, when the gene is excessively overexpressed (tens of thousands of times higher than wild type plants), the plant stems exhibit noticeable curling, there is a greater tendency towards increased seed size rather than fatty acid content, and the yield per plant significantly decreases. To reveal the molecular mechanism of GmMYB331, RNA-sequencing was performed to identify downstream genes and the pathway that GmMYB331 is invovled. Overall design: For leaf analysis, young leaves of wild-type and two transgenic plants (overexpression of GmMYB331-3 and overexpression of GmMYB331-4) were chosen for RNA sequencing. For seed analysis, middle stage seeds of wild-type and two transgenic plants were chosen for RNA sequencing.