Wounding alters gene expression of secoiridoid glucosides metabolic pathway in leaves of common centaury

Abstract

Common centaury (Centaurium erythraea Rafn) is rich in secoiridoid glucosides (SG’s): sweroside, swertiamarin and gentiopicrin. These glycosides are believed to be a part of dual defense system in which the SG’s are bio-activated by hydrolytic enzymes. Upon tissue disruption, SG’s are released from storage compartments and hydrolyzed via β-glucosidase to yield unstable and highly reactive aglycones. This two-component system provides plants with an immediate chemical defense against herbivore-induced wounding of leaves. Plants react to mechanical damage by activating a set of genes, the products of which are involved in defensive functions. Current study was conducted in order to determine how wounding affects the expression of SG metabolic pathway genes. Gene expression patterns of five SG biosynthetic pathway-related genes (CeGPPS, CeGES, Ce8HG0, CeIS, and Ce7DLGT) and of β-glucosidase (CeBglu) were examined in a time-dependent manner to determine the molecular mechanisms underlying wounding-induced changes in SG metabolism. Gene expression results were correlated with SG profiles in centaury shoots. The relative expression of CeGES, Ce8HGO and Ce7DLGT showed an increasing trend, reaching maximum at 24h/48h after wounding. Interestingly, two enzymes of the pathway with opposite functions, Ce7DLGT catalyzing the glycosylation reaction, and CeBglu having role in deglycosylation, showed opposite gene expression profiles. In conclusion, severe changes in gene expression profiles in response to wounding might lead to the reprogramming of SG metabolism in centaury leaves, and thus alter its defense strategies against herbivores.