Molecular characterization of a novel type of lipoxygenase (LOX) gene from common wheat (Triticum aestivum L.)

Lipoxygenases (LOXs) are key enzymes catalyzing the oxidation of polyunsaturated fatty acids, and play an important role in grain storage, seed vigor and bread-making. In this study, we report cloning and characterization of TaLOX3, the homolog gene of barley LoxB, from common wheat (Triticum aestivum L.). The full-length cDNA sequence of TaLOX3 had an open reading frame of 2,634 bp encoding a deduced polypeptide of 878 amino acid residues with a predicted molecular weight of 99,549.79 Da and an estimated isoelectric point of 6.26. TaLOX3 was assigned to chromosome 4A. The multiple alignment result showed that TaLOX3 protein had an identity of 91.3% to barley LOX3 (encoded by LoxB). Profile analyses revealed that the three TaLOX genes are expressed in unique patterns in various organs. Furthermore, the expression profiles of the TaLOX3 gene were determined by q-PCR using the high and low seed LOX activity of different wheat varieties. The result showed that TaLOX3 transcript levels increased significantly during the development of wheat grain. Further analysis indicated genotypes with high LOX activity were associated with higher expression levels than the low LOX activity ones. This indicates that TaLOX3 may contribute to the total LOX activity in common wheat seeds. Phylogenetic analysis conducted with LOXs from rice, maize, Brachypodium distachyon genome, barley and wheat seeds (TaLOX1, TaLOX2 and TaLOX3) revealed that LOXs could be well resolved into two clades (G1 and G2). Moreover, G1 can be divided to three subgroups, with each TaLOX in one subgroup. Collectively, these results can extent our knowledge of the molecular characterization of LOXs, and will provide a valuable resource for wheat quality improvement and breeding.