The function of the WRI1-TCP4 regulatory module in lipid biosynthesis.

The plant-specific TCP transcription factors play pivotal roles in various processes of plant growth and development. However, little is known regarding the functions of TCPs in plant oil biosynthesis. Our recent work showed that TCP4 mediates oil production via interaction with WRINKLED1 (WRI1), an essential transcription factor governing plant fatty acid biosynthesis. WRI1 (AtWRI1) physically interacts with multiple TCPs, including TCP4, TCP10, and TCP24. Transient co-expression of with , but not or , represses oil accumulation in leaves. Increased TCP4 in transgenic plants overexpressing a miR319-resistant () decreased the expression of AtWRI1 target genes. The knockout mutant, the mutant with significant reduction of expression, and a triple mutant, display increased seed oil contents compared to the wild-type . The APETALA2 (AP2) transcription factor WRI1 is characterized by regulating fatty acid biosynthesis through cross-family interactions with multiple transcriptional, post-transcriptional, and post-translational regulators. The interacting regulator modules control the range of AtWRI1 transcriptional activity, allowing spatiotemporal modulation of lipid production. Interaction of TCP4 with AtWRI1, which results in a reduction of AtWRI1 activity, represents a newly discovered mechanism that enables the fine-tuning of plant oil biosynthesis.