Abstract:Lipoxygenase is a key enzyme involved in the pathway of fatty acid metabolism, and plays an important role in the growth and development of plants, responses to environmental stresses and the synthesis of aroma components. In this study, the red callus from the leaves of 'Zihong 3' was used for PCR amplification of the MdLOX1a gene and its partial promoter sequence. Sequencing analysis revealed that MdLOX1a has an open reading frame of 2592 bp encoding for 863 deduced amino acids, with a predicted protein molecular weight of 97.69 KDa and the isoelectric point of 5.14. The MdLOX1a gene was found to be localized on chromosome 9 of the apple genome, consisting of 8 exons and 7 introns. Phylogenetic tree analysis with amino acid sequence indicated that MdLOX1a and Pb9S-LOX5 were assigned within the same branch. In addition, we obtained the MdLOX1a promoter sequence with a length of 1058 bp, which contained several cis-acting elements in response to various stresses. Subcellular localization revealed that MdLOX1a was localized on both the cell membrane and the nucleus. The tissue disparity analysis showed that the expression level of MdLOX1a gene was abundant in the pericarp, followed by flower and pulp. The expression of MdLOX1a gene gradually increased with fruit ripening, and its transcription has been induced under continuous light treatment. The expression of MdLOX1a gene was significantly reduced after low temperature (16 ℃) and exogenous ABA treatment at different concentrations. The overexpression of MdLOX1a showed that the transgenic lines showed the induction of the aromatic components in relative to the control lines, suggesting that MdLOX1a might associate with the synthesis of aroma components.