A transcriptional regulatory module controls lipid accumulation in soybean.

Soybean (Glycine max) is one of the most important oilseed crops. However, limited information is known about the regulatory mechanism of oil accumulation in soybean. In this study, a member of tandem CCCH zinc finger (TZF) proteins, GmZF392, from our previous RNA-seq analysis for seed-preferred transcription factors, was found to function as a positive regulator of lipid production. GmZF392 promotes seed oil accumulation in both transgenic Arabidopsis and stable transgenic soybean plants by binding to a bipartite cis-element containing a TG-rich and a TA-rich sequence in promoters and activates expression of genes in lipid biosynthesis pathway. GmZF392 physically interacts with GmZF351, our previously identified transcriptional regulator of lipid biosynthesis, to synergistically promote downstream gene expression. Both GmZF392 and GmZF351 are further up-regulated by GmNFYA, another transcription factor in lipid biosynthesis, through direct and indirect manner, respectively. Promoter sequence diversity analysis showed that the GmZF392 promoter may be selectively adopted at the origination of the genus Glycine and further mildly selected during domestication from wild soybeans to cultivated soybeans. Our study reveals a regulatory module containing three transcription factors in lipid biosynthesis pathway, and manipulation of the module may improve oil production in soybean and other oilseed crops.