Surviving the Potato Stems: Differences in Genes Required for Fitness by Dickeya dadantii and Dickeya dianthicola

Abstract

Bacteria belonging to the Dickeya genus cause blackleg and soft rot symptoms on many plant hosts, including potato. Although there is considerable knowledge about the genetic determinants that allow Dickeya to colonize host plants, as well as the genes that contribute to virulence, much is still unknown. To identify the genes important for fitness in potato stems, we constructed and evaluated randomly-barcoded transposon mutant (RB-TnSeq) libraries of Dickeya dadantii and Dickeya dianthicola. We identified 169 and 157 genes important for growth in D. dadantii and D. dianthicola in stems, respectively. This included gene related to metabolic pathways, chemotaxis and motility, transcriptional regulation, transport across membranes, membrane biogenesis, detoxification mechanisms, and virulence-related genes including a potential virulence cluster srfABC, c-di-GMP modulating genes, and pectin degradation genes. Comparing the results of the stem assay with other datasets, we identified genes important for growth in stems versus tubers and in vitro conditions. Additionally, our data showed differences in fitness determinants for D. dadantii and D. dianthicola. This data provides important insights into the mechanisms used by Dickeya when interacting with and colonizing plants, and thus might provide targets for management.