Cell death‐inducing DNA fragmentation factor alpha (DFFA)‐like effectors (CIDEs) improve lipid droplet (LD) formation and oil accumulation in plant tissues

The cell death-inducing DNA fragmentation factor alpha (DFFA)-like effectors (CIDEs), including CIDEA, CIDEB and CIDEC, regulate the number and size of lipid droplets (LDs) in vertebrates. However, no homologue of CIDE has been reported in plants. Here, we expressed the coding sequences of CIDEA, CIDEB and CIDEC from Mus musculus in tobacco leaves and Brassica napus seeds. The results showed that the size and number of LDs in transiently transformed tobacco leaves were 2.8-3.1 times larger and 24-25 fold more numerous compared to mock-infiltrated leaves, respectively. The total fatty acid (FA) content in CIDE-expressing leaves was increased by more than 50%, and the triacylglycerol (TAG) content was increased by 2-3 fold compared to that of mock-infiltrated leaves. In B. napus seeds, the number of LDs was significantly decreased while the size of LDs was greatly enlarged in CIDE-expressing lines, and the TAG was increased by 10.5%-15.3%. However, the contents of phosphatidylcholine (PC), phosphatidic acid (PA), and phosphatidylserine (PS) were significantly reduced. Almost all metabolites in the glycolytic pathway and some metabolites in the tricarboxylic acid (TCA) cycle were higher in CIDE-expressing seeds compared with WT, and the transcript levels of the related genes were significantly higher than those in WT. The results suggest that the expression of mammalian CIDEs can alter the morphology of LDs and increase oil content in different plant tissues. By enhancing the seed oil content in B. napus, our results offer a new biotechnology strategy to improve oil yield.