Spatial and developmental regulation of putative genes associated with the biosynthesis of sesquiterpenes and pyrethrin I in Chrysanthemum cinerariaefolium

Abstract

Pyrethrum (Chrysanthemum cinerariaefolium) is a plant from the Asteraceae family discovered as a plant-based insecticidal source which is producing beneficial secondary metabolites such as sesquiterpenes and pyrethrins, hence raised attention due to the insecticidal properties of its secondary metabolites. To improve our knowledge about the biosynthesis of sesquiterpenes and pyrethrin I, we directed a survey to analyze the gene expression in different developmental stages of leaves and also in chloroform dipped leaves (to remove glandular trichomes). Along with this, histochemical experiments were carried out on leaves to detect the accumulation site of lipids, monoterpene phenols, and sesquiterpenes. Gene expression results showed that chrysanthemyl diphosphate synthase (CDS), farnesyl diphosphate synthase (FDS), and 13-Lipoxygenase (13-LOX) putative genes were highly expressed in intact leaves (leaves with glandular trichomes). In contrast, their expression significantly decreased in chloroform dipped leaves (without glandular trichomes). Also, the higher expression of genes that are related to the biosynthetic pathways of sesquiterpenes and pyrethrin I was observed in young leaves compared with the leaflets and fully-expanded leaves. The obtained results demonstrate that glandular trichomes’ relative density changes markedly during the developmental stages of leaves and, consequently, influences the transcript levels of trichome-specific genes.