Genome-Wide Analysis of Oleosin Gene Family in 22 Tree Species: An Accelerator for Metabolic Engineering of BioFuel Crops and Agrigenomics Industrial Applications?

Abstract

Trees contribute to enormous plant oil reserves because many trees contain 50%-80% of oil (triacylglycerols, TAGs) in the fruits and kernels. TAGs accumulate in subcellular structures called oil bodies/droplets, in which TAGs are covered by low-molecular-mass hydrophobic proteins called oleosins (OLEs). The OLEs/TAGs ratio determines the size and shape of intracellular oil bodies. There is a lack of comprehensive sequence analysis and structural information of OLEs among diverse trees. The objectives of this study were to identify OLEs from 22 tree species (e.g., tung tree, tea-oil tree, castor bean), perform genome-wide analysis of OLEs, classify OLEs, identify conserved sequence motifs and amino acid residues, and predict secondary and threedimensional structures in tree OLEs and OLE subfamilies. Data mining identified 65 OLEs with perfect conservation of the ''proline knot'' motif (PX5SPX3P) from 19 trees. These OLEs contained >40% hydrophobic amino acid residues. They displayed similar properties and amino acid composition. Genome-wide phylogenetic analysis and multiple sequence alignment demonstrated that these proteins could be classified into five OLE subfamilies. There were distinct patterns of sequence conservation among the OLE subfamilies and within individual tree species. Computational modeling indicated that OLEs were composed of at least three ahelixes connected with short coils without any b-strand and that they exhibited distinct 3D structures and ligand binding sites. These analyses provide fundamental information in the similarity and specificity of diverse OLE isoforms within the same subfamily and among the different species, which should facilitate studying the structurefunction relationship and identify critical amino acid residues in OLEs for metabolic engineering of tree TAGs.

Genome-wide identification and analysis of Oleosin gene family in four cotton species and its involvement in oil accumulation and germination

“…It is also reported that the OLEOs could be induced by water stress, jasmonic acid, ABA, and osmotic stabilizer [ 35 ], indicating that OLEOs might play an essential role in engineering salt, cold, and drought tolerance in plants. Shimada et al (2008) found that the OLEOs could maintain the germination rate (GR) of Arabidopsis seeds and improve their overwintering viability by inhibiting the oil body fusion.…”