Trichomes are specialized structures derived from epidermal cells. Apart from providing protection to plants, trichomes are source of medicinally important compounds. Although genes involved in initiation and patterning of trichomes have been characterized in some plants like Arabidopsis thaliana, but our knowledge about the development of these trichomes is still limited. Recent studies confirm the role of different transcription factors in trichome development of plants. In model plant Arabidopsis different transcription factor families have been studied in detail. It has been found that transcription factors like bHLH, R2R3 MYB form an activation complex with TTG1 which initiate trichome formation while as R3 MYB type transcription factors inhibit the formation of activation complex. The activation complex acts as a major trigger in the regulation of trichome development. It would be interesting to know whether such activation complex occurs in other plants like Nicotiana tobaccum, Lycopersicum esculentum, Artemisia annua etc. In this review, we focus on recent updates on transcriptional regulation of trichome development and conservation of these regulators in various species of pharmacologically and economically important plants. We have briefly discussed the cross talk of transcription factors with different hormones during trichome development. Further we have elaborated fundamental research ideologies on trichome development and translation of this research from model plant to plants of industrial interest.

The wonder drug artemisinin, a sesquiterpene lactone endoperoxide from Artemisia annua is the million‐dollar molecule required to curb the deadliest disease, Malaria. One of the major challenges even today is to increase the concentration of artemisinin within plants. The transcription factors are important regulators of plant secondary metabolites and have the potential to regulate key steps or the whole biosynthetic pathway. In this study, we have identified and characterised two bHLH transcription factors (Aa6119 and Aa7162) from A. annua. Both the transcription factors turned out to be transcriptionally active and nuclear‐localised typical bHLH proteins. In our study, we found that Aa6119 specifically binds to the E‐box element present on the promoter of artemisinin biosynthetic gene, AMORPHA‐4,11‐DIENE SYNTHASE (ADS). The protein‐DNA interaction confirmed by Yeast one‐hybrid assay was specific as Aa6119 was unable to bind to the mutated E‐boxes of ADS. Further, Aa6119 interacted physically with Aa7162, which was confirmed in vitro by Yeast two‐hybrid assay and in vivo by Bimolecular Fluorescent complementation assay. Our quantitative expression studies have confirmed that Aa6119 and Aa7162 act synergistically in the regulation of artemisinin biosynthetic and trichome developmental genes. The higher accumulation of artemisinin content in the transient co‐transformed transgenic plants than in the individual over‐expression transgenic plants has further validated that Aa6119 and Aa7162 act positively and synergistically to regulate artemisinin accumulation.