Regulation of plant sesquiterpene biosynthesis
Gao-Jie Hong, Zong-Xia Yu, Xiao-Ya Chen*
National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032; Plant Science Research Center, Shanghai Chenshan Botanical Garden, Shanghai 201602, P. R. China
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Terpenoids play important roles in plant-insect, plant-pathogen, and plant-plant interactions. Some terpenoids are of medicinal value, such as the anti-malaria drug Qinghaosu (artemisinin) which is an endoperoxide sesquiterpene lactone isolated from the traditional herb Artemisia annua.
Sesquiterpenes are derived from the cytosolic mevalonate pathway, and sesquiterpene synthases catalyze the key step of converting farnesyl diphosphate into mostly cyclic sesquiterpenes. In plants expression of sesquiterpene synthase genes is often inducible by the phytohormone jasmonate (JA). We found that in A. annua, the JA-responsive AP2 family transcription factors—AaERF1 and AaERF2 are involved in transcriptional regulation of AaADS (encoding amorpha-4,11-diene synthase) and CYP71AV1 of the artemisinin pathway. In Arabidopsis thaliana, the bHLH transcription factor MYC2 plays an important role in transcriptional regulation of AtTPS21 and AtTPS11, both are responsible for floral production of volatile sesquiterpenes. Interestingly, in addition to JA, the growth regulator gibberellin (GA) is also able to induce the AtTPS21 and AtTPS11 expression. MYC2 interacts with DELLA proteins which are GA signaling repressors, integrating both GA and JA signals into transcriptional regulation of sesquiterpene synthase genes. Considering that secondary metabolites vary among different organs and along with the plant life cycle, further research will be directed to explore the relationship between plant development and secondary metabolism regulation.
Key Words: Sesquiterpene, artemisinin, MYC2, gibberellins, jasmonate