Abstract：As a key enzyme of plant eighteen carbonate metabolic pathway, lipoxygenase (LOX), which is closely related with seed aging. Onion (Allium cepa) seeds are a short-lived seeds. In order to study the mechanism of LOX gene in the process of onion seeds aging, the full length cDNA of LOX gene (GenBank accession No. KU363822) in onion seeds was cloned by RT-PCR and rapid-amplification of cDNA ends (RACE) technology. The bioinformatics methods were used to analyze the sequence characteristics of this gene and the combination of RT-PCR and qRT- PCR methods were used to investigate the temporal and spatial expression pattern of AcLOX1 gene. The cloned full-length cDNA of AcLOX1 was 2 847 bp in length, containing a 2 616 bp ORF which encodes 872 amino acids. Amino acid sequence analysis showed that AcLOX1 contained a PLAT_LH2(polycystin-1, lipoxygenase, alpha-toxin_lipoxygenase homology) domain and a Lipoxygenase domain. Protein sequence identity search showed that AcLOX1 was similar to LOX gene of Eucalyptus grandis, Prunus dulcis, Vitis vinifera with similarities of 66%~73%. Phylogenetic tree reconstructed by neighbor joining method clearly showed that AcLOX1 protein was classified into 9-LOX subgroup. RT-PCR and qRT-PCR analysis showed that AcLOX1 were expressed in onion tissues and there were differences in expression. The expression was increasing from 5 day to 25 day after pollination, but there was a small amount of sustained expression in the seeds from 25 days after pollination to maturation and seeds stored a year. In this study it is demonstrated that is somewhat related to the onion seeds aging and can promote the development of onion seeds, which lay the foundation for elucidating the mechanism of seed aging and provide theoretical basis for improving the storage of seed.
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