Plant Pathogen-Induced Water-Soaking Promotes Salmonella enterica Growth on Tomato Leaves

Abstract

c Plant pathogen infection is a critical factor for the persistence of Salmonella enterica on plants. We investigated the mechanisms responsible for the persistence of S. enterica on diseased tomato plants by using four diverse bacterial spot Xanthomonas species that differ in disease severities. Xanthomonas euvesicatoria and X. gardneri infection fostered S. enterica growth, while X. perforans infection did not induce growth but supported the persistence of S. enterica. X. vesicatoria-infected leaves harbored S. enterica populations similar to those on healthy leaves. Growth of S. enterica was associated with extensive water-soaking and necrosis in X. euvesicatoria-and X. gardneri-infected plants. The contribution of water-soaking to the growth of S. enterica was corroborated by an increased growth of populations on water-saturated leaves in the absence of a plant pathogen. S. enterica aggregates were observed with bacterial spot lesions caused by either X. euvesicatoria or X. vesicatoria; however, more S. enterica aggregates formed on X. euvesicatoria-infected leaves as a result of larger lesion sizes per leaf area and extensive watersoaking. Sparsely distributed lesions caused by X. vesicatoria infection do not support the overall growth of S. enterica or aggregates in areas without lesions or water-soaking; S. enterica was observed as single cells and not aggregates. Thus, pathogeninduced water-soaking and necrosis allow S. enterica to replicate and proliferate on tomato leaves. The finding that the pathogen-induced virulence phenotype affects the fate of S. enterica populations in diseased plants suggests that targeting of plant pathogen disease is important in controlling S. enterica populations on plants.

TALE-induced bHLH transcription factors that activate a pectate lyase contribute to water soaking in bacterial spot of tomato

“…Whether or not bacteria such as human pathogens can survive in the plant apoplast as a result of AvrHah1-induced water soaking will need to be determined. This finding is particularly important in the light of previous work that described how increased water soaking and foliar damage from xanthomonad pathogens facilitated the growth of the human pathogen Salmonella enterica on tomato leaves (38). Because bacterial manipulation of the leaf apoplast to promote an aqueous environment is required for pathogenesis (39), improving the tolerance of food crops from water-soaked lesion development as part of a multilayered disease management strategy may help reduce yield losses and even prevent the colonization of human pathogens on diseased crops.…”

Cellulose-Derived Oligomers Act as Damage-Associated Molecular Patterns and Trigger Defense-Like Responses

“…Disease-associated water 588 soaking was estimated by measuring ion leakage 3 days post-inoculation (Potnis et al, 2015;589 Ishiga et al, 2016). Infections were performed via the flood inoculation method (Ishiga et al,590 2011) with minor modifications.…”

The role of water in plant–microbe interactions

“…induced water-soaking is associated with greatly increased release of Xcm bacteria from infected plant tissues (Yang et al, 1994). In addition, it was recently reported that water-soaking and necrosis in leaves infected by Xanthomonas euvesicatoria and X. gardneri, can promote colonization of the human pathogen Salmonella enterica inside plant tissues (Potnis et al, 2015). This is interesting in light of the finding by Xin et al (2016) that the levels and abundance of leaf endophytic bacterial communities are altered in plant genotypes that are prone to water-soaking under high humidity.…”