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, details of how TFs and crosstalk between different TF families coordinate the transcriptional network associated with seed oil accumulation remain to be clarified. Here, we report that basic helix-loop-helix7 (bHLH7) and PROTODERMAL FACTOR2 (PDF2) TFs, both highly expressed in developing embryos, negatively control seed oil accumulation. bHLH7 and PDF2 physically interact and cooperatively inhibit the transcription of MYB DOMAIN PROTEIN 96 (MYB96), PYRUVATE DEHYDROGENASE E1 BETA1 (PDH-E1β1), PDH-E1β2, and BIOTIN CARBOXYL CARRIER PROTEIN1 (BCCP1) by directly binding to their promoters. Additional genetic evidence demonstrated that bHLH7 and PDF2 act in an additive manner to repress seed oil accumulation, and this effect is partially dependent on PDH-E1β1, which significantly promotes seed oil deposition. Collectively, our results provide insights into the mechanisms by which the bHLH7-PDF2 module mediates transcriptional regulation to control oil accumulation in A. thaliana seeds.