AUTHOR=Robic Kévin , Munier Euphrasie , Effantin Géraldine , Lachat Joy , Naquin Delphine , Gueguen Erwan , Faure Denis 

TITLE=Dissimilar gene repertoires of Dickeya solani involved in the colonization of lesions and roots of Solanum tuberosum

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1154110

DOI=10.3389/fpls.2023.1154110

ISSN=1664-462X

ABSTRACT=<p><italic>Dickeya</italic> and <italic>Pectobacterium</italic> species are necrotrophic pathogens that macerate stems (blackleg disease) and tubers (soft rot disease) of <italic>Solanum tuberosum</italic>. They proliferate by exploiting plant cell remains. They also colonize roots, even if no symptoms are observed. The genes involved in pre-symptomatic root colonization are poorly understood. Here, transposon-sequencing (Tn-seq) analysis of <italic>Dickeya solani</italic> living in macerated tissues revealed 126 genes important for competitive colonization of tuber lesions and 207 for stem lesions, including 96 genes common to both conditions. Common genes included <italic>acr</italic> genes involved in the detoxification of plant defense phytoalexins and <italic>kduD, kduI, eda</italic> (<italic>=kdgA</italic>)<italic>, gudD, garK, garL</italic>, and <italic>garR</italic> genes involved in the assimilation of pectin and galactarate. In root colonization, Tn-seq highlighted 83 genes, all different from those in stem and tuber lesion conditions. They encode the exploitation of organic and mineral nutrients (<italic>dpp</italic>, <italic>ddp</italic>, <italic>dctA</italic>, and <italic>pst</italic>) including glucuronate (<italic>kdgK</italic> and <italic>yeiQ</italic>) and synthesis of metabolites: cellulose (<italic>celY</italic> and <italic>bcs</italic>), aryl polyene (<italic>ape</italic>), and oocydin (<italic>ooc</italic>). We constructed in-frame deletion mutants of <italic>bcsA, ddpA, apeH</italic>, and <italic>pstA</italic> genes. All mutants were virulent in stem infection assays, but they were impaired in the competitive colonization of roots. In addition, the Δ<italic>pstA</italic> mutant was impaired in its capacity to colonize progeny tubers. Overall, this work distinguished two metabolic networks supporting either an oligotrophic lifestyle on roots or a copiotrophic lifestyle in lesions. This work revealed novel traits and pathways important for understanding how the <italic>D. solani</italic> pathogen efficiently survives on roots, persists in the environment, and colonizes progeny tubers.</p>