Genome-Wide Identification of WRKY Genes in Artemisia annua: Characterization of a Putative Ortholog of AtWRKY40

Artemisia annua L. is well-known as the plant source of artemisinin, a sesquiterpenelactone with eective antimalarial activity. Here, a putative ortholog of the Arabidopsis thalianaWRKY40 transcription factor (TF) was isolated via reverse transcription-polymerase chain reactionand rapid amplification of cDNA ends in A. annua and named AaWRKY40. A putative nuclearlocalization domain was identified in silico and experimentally confirmed by using protoplasts ofA. annua transiently transformed with AaWRKY40-GFP. Agenome-wide analysis identified 122 WRKYgenes in A. annua, and a manually curated database was obtained. The deduced proteins werecategorized into the major WRKY groups, with group IIa containing eight WRKY members includingAaWRKY40. Protein motifs, gene structure, and promoter regions of group IIa WRKY TFs of A. annuawere characterized. The promoter region of AaWRKY group IIa genes contained several abioticstress cis-acting regulatory elements, among which a highly conservedW-box motif was identified.Expression analysis of AaWRKY40 compared to AaWRKY1 in A. annua cell cultures treated withmethyl jasmonate known to enhance artemisinin production, suggested a possible involvementof AaWRKY40 in terpenoid metabolism. Further investigation is necessary to study the role ofAaWRKY40 and possible interactions with other TFs in A. annua.