Molecular Mechanism Of Jasmonate-Signaling Components In Regulating The Formation Of Cembratriene-Diols In Tobacco

Cembranoids,a group of natural diterpenoid compounds structurally composed of a 14-carbon cembrane ring with featured oxygen-containing substitutes,are widespread in the nature.In recent years,the biological activities of cembranoids in antimicrobial,anti-cancer and anti-inflammation effects,as well as its fascinating architectures,have attracted great interest from researchers of natural product and pharmaceuticals.Nicotiana(tobacco)species are the terrestrial plants most abundant in cembranoids,which are responsible for the characteristic aroma of tobacco.The two main types of cembranoids in tobacco are cembratriene-ol and cembratriene-diol,and there are two kinds of epimers,a-cembratriene-diol and ?-cembratriene-diol,which is the most abundant cembranoids in tobacco.The enzymes catalyzing cembranoid formation in tobacco have been identified,however,the regulatory mechanism underlying this physiological process remains unknown.This study found that MeJA-treatment could increase the expression level of LTP1,CBTS,and P450 genes and the production of a and ?-cembratriene-diol.Our previous studies showed that the trichome secretion of the plants with dysfunction of COI1 was decreased to an extremely lower level.The cembranoid determination showed that the a-and P-cembratriene-diol contents of plants with dysfunction of C.OIl were decreased to an undetectable level.And,the transcriptional analyses revealed that dysfunction of COI1 greatly attenuated the expression LTP1,CBTS,and P450 genes.Further studies showed that either overexpression of the gene encoding bHLH transcription factor MYC2a or that encoding MYB transcription factor MYB305 could enhance the cembranoid production in plants with dysfunction of COI1 and upregulate the cembranoid synthetic genes CBTS,P450 and NtLTP1.Our findings also suggest that COI1 and its downstream regulators MYC2a and MYB305 display roles in controlling the formation of trichome secretion,which is correlated with the production of cembranoids.Taken together,this study has demonstrated a critical role of JA-signaling components in governing the cembratriene-diol formation and the transcription of cembratriene-diol synthetic genes in tobacco.Findings in this study are of great importance to reveal the molecular regulatory mechanism underlying cembranoid synthesis.