Cloning and characterization of a cabbage <i>BoAOS</i> gene with enhanced drought tolerance

Allene oxide synthase (AOS), which is a cytochrome P450 (CYP74A), catalyses the first step in the biosynthesis of jasmonic acid from lipoxygenase-derived hydroperoxides of free fatty acids. The full-length cDNA of an AOS-like gene was cloned from Brassica oleracea using rapid amplification of cDNA ends and was designated as BoAOS. The BoAOS expression level was higher in alabastrums and flowers than in other tissues of cabbage, as determined by real-time reverse transcription polymerase chain reaction (RT-PCR). To characterize the BoAOS gene, Arabidopsis was transformed via Agrobacterium tumefaciens with a vector to express the gene under the control of a strong constitutive promoter, CaMV35S (Cauliflower Mosaic Virus). Based on analyses of tolerance to drought stress, compared with control plants, the overexpression of BoAOS in transgenic plants increased the endogenous jasmonic acid level and conferred higher tolerance to drought stress. Therefore, we suggest that BoAOS may be a suitable candidate gene to produce transgenic plants with tolerance to drought stress.