Transposon insertion upstream of a putative sodium/sulphate symporter is associated with hypervirulence in the soft rot bacterium, Pectobacterium carotovorum

Pathogenesis by Pectobacterium carotovorum and the other soft rot bacteria results mostly from the synthesis and secretion of a plethora of exoproteins including plant cell wall‐degrading enzymes and type III effectors. A mini‐Tn5 transposon mutant of P. carotovorum (KD200) was isolated that is highly increased in activity and transcript levels of extracellular cell wall‐degradative enzymes, pectate lyase, polygalacturonase, cellulase and protease. Accordingly, the mutant was more virulent as it macerated more host tissue than its parent. KD200 mutant harbours a Tn5 insertion directly upstream of nssAEcc₇₁, a putative sodium/sulphate symporter gene and member of a family of divalent anion sodium symporters (DASS). The findings reported here suggest that DASS proteins may be involved in soft rot pathogenesis.