Colonization patterns of an mCherry-Tagged Pectobacterium carotovorum subsp. brasiliense Strain in potato plants

摘要

Pectobacterium carotovorum subsp. brasiliense is a newly identifiedmember of the potato soft rot enterobacteriaceae. The pathogenesis of thispathogen is still poorly understood. In this study, an mCherry-P. carotovorumsubsp. brasiliense-tagged strain was generated to study P.carotovorum subsp. brasiliense—potato plant interactions. Prior to use,the tagged strain was evaluated for in vitro growth, plasmid stability, andvirulence on potato tubers and shown to be similar to the wild type. Fourpotato cultivars were evaluated for stem-based resistance against P. carotovorumsubsp. brasiliense. Confocal laser-scanning microscopy and invitro viable cell counts showed that P. carotovorum subsp. brasiliense isable to penetrate roots of a susceptible potato cultivar as early as 12 hpostinoculation and migrate upward into aerial stem parts. Due to thephenotypic differences observed between tolerant and susceptible cultivars,a comparison of P. carotovorum subsp. brasiliense colonizationpatterns in these cultivars was undertaken. In the susceptible cultivar, P.carotovorum subsp. brasiliense cells colonized the xylem tissue, forming“biofilm-like” aggregates that led to occlusion of some of the vessels. Incontrast, in the tolerant cultivar, P. carotovorum subsp. brasiliense appearedas free-swimming planktonic cells with no specific tissue localization.This suggests that there are resistance mechanisms in the tolerantcultivar that limit aggregation of P. carotovorum subsp. brasiliense inplanta and, hence, the lack of symptom development in this cultivar.