Analysis of Artemisia annua transcriptome for BAHD alcohol acyltransferase genes: Identification and diversity of expression in leaf, stem and root

Alcohol acyltransferases (AATs) of BAHD gene superfamily play diverse roles in plant secondary metabolism like synthesis of volatile esters, modified anthocyanins, terpene indole alkaloids, benzylisoquinoline alkaloids and capsacinoids. Artemisia annua is an important medicinal and aroma plant synthesizing monoterpene oil and several non-volatile sesquiterpenes including anti-malarial artemisinin. These AATs are characterized by two key structural motifs-HXXXD and DFGWG. ESTscan of A. annua trascriptome yielded 43 contigs homologous to BAHDs. Removal of redundant sequences led to identification of 16 discrete BAHD family AATs and assembly of 3 full length cDNA of BAHD acyltransferases. RT-PCR analysis confirmed the expression of these genes. The in silico assembled putative full length AATs were validated by PCR amplification, sequencing and matching the sequences with the assembled genes. Cross-species comparison of AAT amino acid sequences gave an updated account of conserved residues in BAHDs including the novel homologues identified in this study. Presence of several AATs in this plant underpins their co-necessity for acylation assisted extension of the diverse secondary metabolites. Functional characterization of the AATs are necessary to understand the subtle differences in motifs vis-a-vis catalytic specificities among these AATs.