14‐3‐3 protein mediates plant seed oil biosynthesis through interaction with AtWRI1

Summary Plant 14‐3‐3 proteins are phosphopeptide‐binding proteins, belonging to a large family of proteins involved in numerous physiological processes including primary metabolism, although knowledge about the function of 14‐3‐3s in plant lipid metabolism is sparse. WRINKLED 1 ( WRI 1) is a key transcription factor that governs plant oil biosynthesis. At present, At WRI 1‐interacting partners remain largely unknown. Here, we show that 14‐3‐3 proteins are able to interact with At WRI 1, both in yeast and plant cells. Transient co‐expression of 14‐3‐3‐ and At WRI 1‐encoding cDNA s led to increased oil biosynthesis in Nicotiana benthamiana leaves. Stable transgenic plants overproducing a 14‐3‐3 protein also displayed increased seed oil content. Co‐production of a 14‐3‐3 protein with At WRI 1 enhanced the transcriptional activity of At WRI 1. The 14‐3‐3 protein was found to increase the stability of At WRI 1. A possible 14‐3‐3 binding motif was identified in one of the two AP 2 domains of At WRI 1, which was also found to be critical for the interaction of At WRI 1 with an E3 ligase linker protein. Thus, we hypothesize a regulatory mechanism by which the binding of 14‐3‐3 to At WRI 1 interferes with the interaction of At WRI 1 and the E3 ligase, thereby protecting At WRI 1 from degradation. Taken together, our studies identified At WRI 1 as a client of 14‐3‐3 proteins and provide insights into a role of 14‐3‐3 in mediating plant oil biosynthesis.