Identification, classification and differential expression of oleosin genes in tung tree (605.3)

Abstract

Triacylglycerols (TAG) are the major molecules of energy storage in eukaryotes. TAG are packed in subcellular structures called oil bodies or lipid droplets. Oleosins (OLE) are the major proteins in plant oil bodies. Multiple isoforms of OLE are present in plants such as tung tree (Vernicia fordii), whose seeds are rich in novel TAG with many industrial applications. We identified five tung tree OLE genes coding for small hydrophobic proteins. Genome‐wide phylogenetic analysis and multiple sequence alignment demonstrated that the five OLE genes represent the five OLE subfamilies and all contained the “proline knot” motif (PX5SPX3P) shared among 65 OLE from 19 tree species, including the sequenced genomes of cacao, castor bean, grapevine, peach and poplar. TaqMan and SYBR Green qPCR methods studied the differential expression of OLE genes in tung tree. Expression results demonstrated that 1) All five OLE genes were expressed in developing tung seeds, leaves and flowers; 2) OLE mRNA levels were much higher in the seeds than leaves or flowers; 3) OLE1‐3 genes were expressed in tung seeds at much higher levels than OLE4‐5 genes; 4) the amounts of OLE mRNA rapidly increased during seed development; and 5) the expression levels of OLE genes were well‐coordinated with tung oil accumulation in the seeds. These results suggest that tung OLE genes 1‐3 probably play major roles in tung oil accumulation and/or oil body development. Grant Funding Source: USDA‐Agricultural Research Service Quality and Utilization of Agricultural Products Research Program