A bHLH7-PDF2 module mediates transcriptional regulation to repress seed oil accumulation in Arabidopsis thaliana.

Seed oil accumulation requires precise coordination of multiple factors, and transcription factors (TFs) play crucial roles in governing this process. However, the knowledge of how TFs and the crosstalk between different TF families coordinate the transcriptional network associated with seed oil accumulation is still lacking. Here, we report that both basic helix-loop-helix7 (bHLH7) and PROTODERMAL FACTOR2 (PDF2) TFs, highly expressed in the developing embryos, negatively control seed oil accumulation. bHLH7 and PDF2 physically interact and cooperatively inhibit the transcription of MYB96, PYRUVATE DEHYDROGENASE E1 BETA1 (PDH-E1β1), PDH-E1β2, and BIOTIN CARBOXYL CARRIER PROTEIN1 (BCCP1) by directly binding to their promoters. Further genetic findings demonstrated that bHLH7 and PDF2 act in an additive manner to repress seed oil accumulation, and this effect is partially dependent on PDH-E1β1 that significantly promotes seed oil deposition. Collectively, we provide insights into the mechanisms by which transcriptional regulation mediated by the bHLH7-PDF2 module controls oil accumulation in A. thaliana seeds.