A a ORA , a trichome‐specific AP 2/ ERF transcription factor of A rtemisia annua , is a positive regulator in the artemisinin biosynthetic pathway and in disease resistance to B otrytis cinerea

Summary Six transcription factors of APETALA2/ethylene‐response factor ( AP 2/ ERF ) family were cloned and analyzed in A rtemisia annua . Real‐time quantitative polymerase chain reaction ( RT ‐ Q ‐ PCR ) showed that Aa ORA exhibited similar expression patterns to those of amorpha‐4,11‐diene synthase gene ( ADS ), cytochrome P450‐dependent hydroxylase gene ( CYP71AV1 ) and double bond reductase 2 gene ( DBR2 ) in different tissues of A . annua . A a ORA is a trichome‐specific transcription factor, which is expressed in both glandular secretory trichomes ( GST s) and nonglandular T ‐shaped trichomes ( TST s) of A . annua . The result of subcellular localization shows that A a ORA is targeted to the nuclei and the cytoplasm. Overexpression and RNA interference ( RNA i) of A a ORA in A . annua regulated, positively and significantly, the expression levels of ADS , CYP 71 AV 1 , DBR 2 and A a ERF 1 . The up‐regulated or down‐regulated expression levels of these genes resulted in a significant increase or decrease in artemisinin and dihydroartemisinic acid. The results demonstrate that A a ORA is a positive regulator in the biosynthesis of artemisinin. Overexpression of A a ORA in A rabidopsis thaliana increased greatly the transcript levels of the defense marker genes PLANT DEFENSIN1.2 ( PDF1.2 ), HEVEIN‐LIKE PROTEIN ( HEL ) and BASIC CHITINASE ( B‐CHI ). After inoculation with B otrytis cinerea , the phenotypes of A a ORA overexpression in A . thaliana and Aa ORA RNA i in A . annua demonstrate that A a ORA is a positive regulator of disease resistance to B . cinerea .