The decoration of specialized metabolites influences stylar development

Plants produce many different specialized (secondary) metabolites that function in solving ecological challenges; few are known to function in growth or other primary processes. 17-Hydroxygeranylinalool diterpene glycosides (DTGs) are abundant herbivory-induced, structurally diverse and commonly malonylated defense metabolites in plants. By identifying and silencing a malonyltransferase, involved in DTG malonylation, we found that DTG malonylation percentages are normally remarkably uniform, but when disrupted, result in DTG-dependent reduced floral style lengths, which in turn result from reduced stylar cell sizes, IAA contents, and YUC activity; phenotypes that could be restored by IAA supplementation or by silencing the DTG pathway. Moreover, the genus-specific JA-deficient short-style phenotype also results from alterations in DTG malonylation patterns. Decorations of plant specialized metabolites can be tuned to remarkably uniform levels, and this regulation plays a central but poorly understood role in controlling the development of specific plant parts, such as floral styles.