Dynamic regulation of pectin catabolism in the pathogenicity of Dickeya dadantii
Debra Ruth David
Date of Issue2012
School of Biological Sciences
Institute National des Sciences Appliquées de Lyon
Dickeya dadantii is a phytopathogen responsible for causing soft rot in many agricultural crops. With its increasing emergence in Europe, research efforts are aimed at understanding mechanisms used by D.dadantii. Large amounts of pectinase production are required to colonise plants before host defence can be triggered and D.dadantii is suspected to utilise bistability as a form of memory for this pathogenic strategy. In this paper, we mimic conditions where D.dadantii has established primary colonisation of a plant by pre-incubation with polygalacturonic acid to study effects on memory. Enzymatic assays showed an increase in pectate lyases activity in pre-incubated wild type and all KdgR mutant samples on secondary polygalacturonic acid exposure. This demonstrates a positive feedback loop involving KdgR for pectinase synthesis as a form of pathogenic memory. A pulse experiment performed on pre-incubated WT samples indicated that memory persisted for seven generations before returning to baseline activity. At the transcriptional level, q-PCR identified Pel B, D and E as major Pel genes synthesised on secondary exposure to polygalacturonic acid. These genes likely have memory and contribute to increased pathogenicity observed. Further studies will focus on modelling the regulatory network of D.dadantii pectate lyases and virulence to discover therapeutic targets.
Final Year Project (FYP)
Nanyang Technological University