AaCYPdwf, a new growth regulatory cytochrome p450 gene from Artemissia annua

Artemisia annua L. (A. annua) produces artemisinin (qinghaosu), which is inhibitory against malarial parasite, Plasmodium falciparum. Genetic engineering is thought to be one of the most reasonable approaches to enhance the production of artemisinin by A. annua plant. This study aimed to clone and investigate a growth regulatory cytochrome p450 gene from A. annua. We cloned a cDNA coding growth regulatory gene from A. annua. The gene had high homology with the steroid 23-alpha-hydroxylase produced-gene of A. thaliana, Oryza sativa and Zinnia elegans. The full-length cDNA was 1708 bp long, containing an open reading frame of 1443 bp that encodes 480 amino acids. We transformed A. annua plants with the full-length cDNA driven by 35S promoter through Agrobacterium-mediated transformation. To identify the function of the gene, we applied RNAi gene silencing technique. The plants transformed with the full-length cDNA were normal in growth but the plants transformed with RNAi showed extreme dwarfism. The dwarfism in the gene silenced plants was rescued by the application of brassinolide and gibberellic acid (GA) indicating that the mutants were deficient in the synthesis of a growth regulatory gene, which we named AaCYPdwf. Phenotypic characteristics of mutant and phylogenetic analysis clustered the AaCYPdwf with other brassinolide producing genes. Our results suggest that AaCYPdwf is a new gene, which likely involved in regulation of brassinosteroid biosynthesis in A. annua plants. A further study is needed to precisely elucidate the role of this new gene in biology of the A. annua.