Interrelationship of the soft rot phytopathogens in the Pectobacterium genus and Caenorhabditis elegans

Bacterial soft rot is one of the most serious diseases affecting potatoes in fields and storages worldwide. Soft rot on potatoes and other crops are caused mainly by Pectobacterium atrosepticum, Pectobacterium carotovorum and several Dickeya species. The disease spreads via many ways and insects are suggested to be important agents in the epidemiology. Evolutionary and geological evidences suggest soil nematodes play essential roles in ecological processes including nutrients cycling, decomposition and disease suppression. Although some studies show that Pectobacteria can survive the digestive tract of the nematodes, it is unclear whether the soil nematodes can be vectors for transmission and dissemination of plant pathogenic bacteria. Moreover, the life span of C. elegans, a free-living and bacterial-feeding nematode, is limited when fed on Pectobacterium. How soft rot bacteria interact with C. elegans and how the nematodes respond to these bacteria are still unknown. Results of this study suggest that Pectobacterium could be disseminated via nematodes on potatoes, indicating that nematodes could serve as vectors in the dissemination of soft rot bacteria on crops. Through the bacterial transmission assay, Pectobacterium is proved to possess a better ability to persist with nematodes compared to E. coli. It seems that pectobacteria have some traits that provide this ability, so Pectobacterium mutants related to Pectobacterium-plant interaction were tested and the expressions C. elegans genes were measured using quantitative polymerase chain reaction (qPCR), aiming to find out genes playing a role in Pectobacterium-nematodes interaction. However, in this study most likely type VI secretion system, putative Flp/Tad-like pilus, flagella, full length lipopolysaccharides, quorum sensing or ExpAS two-component system are not necessary determinants for the interrelationship of Pectobacterium and nematodes