Cytochrome P450 monooxygenases (CYP

Cytochrome P450 monooxygenases (CYPs) are a group of redox proteins that catalyze various oxidative reactions in plant secondary metabolism. To explore the function of the CYP71 gene in Ginkgo biloba under biotic and abiotic stresses, a full-length CYP gene, designated GbCYP71, was first isolated and characterized from leaves of G. biloba. It contained a 1512-bp open reading frame (ORF) encoding 503 amino-acid-deduced polypeptide whose theoretical molecular weight was 56.9 kDa. The genomic DNA sequence of GbCYP71 contained two exons and one intron. The cDNA of GbCYP71 was subcloned in a pET-32a vector and then transformed into E. coli strain BL21 (DE3). A protein with a molecular weight of 76.4 kDa was subsequently identified and found to be consistent with the above theoretical value. Transient expression analysis revealed that the GbCYP71 protein may be located in the G. biloba cell cytoplasm. GbCYP71 was expressed in almost all ginkgo tissues, including leaves, stamens, gynoecia, stems and, preferentially, roots. Expression-profiling analyses revealed that GbCYP71 can be induced by salinity stress and phytohormone signals, including salicylic acid, abscisic acid, methyl jasmonate and ethephon, but is repressed by heat and cold stresses. These results indicate that GbCYP71 mainly functions in responding to biotic and abiotic stresses.