Assessing the ability of Salmonella enterica to translocate Type III effectors into plant cells

Authors: CHALUPOWICZ, LAURA - Volcani Center (ARO); NISSAN, GAL - Volcani Center (ARO); Brandl, Maria; MCCLELLAND, MICHAEL - University Of California; SESSA, GUIDO - Tel Aviv University; BARASH, ISAAC - Tel Aviv University; MANULIS-SASSON, SHULAMIT - Volcani Center (ARO); POPOV, GEORGY - Tel Aviv University

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2017
Publication Date: 2/15/2018
Citation: Chalupowicz, L., Nissan, G., Brandl, M., McClelland, M., Sessa, G. Popov G., Barash, I., Manulis-Sasson, S. 2018. Assessing the ability of Salmonella enterica to translocate Type III effectors into plant cells. Molecular Plant-Microbe Interactions. 31(2):233-239. https://doi.org/10.1094/MPMI-07-17-0166-R.
DOI: https://doi.org/10.1094/MPMI-07-17-0166-R

Interpretive Summary: Salmonella enterica, the causal agent of numerous outbreaks of foodborne illness linked to fresh fruit and vegetables, has the ability to multiply and survive endophytically in plants. It has been hypothesized that S. enterica genes belonging to the type III secretion system (T3SS) or its effectors (T3Es), which are essential for its pathogenicity in animal hosts, may contribute to this colonization. We used two molecular reporter systems to assess whether S. enterica effectors can be translocated via the T3SS apparatus of S. enterica. Whereas evidence was obtained from our two reporter systems that are based on two different plant species, that bacterial plant pathogen effectors were translocated into beet root or pepper leaf cells via the plant pathogen T3SS, S. enterica T3SS failed to translocate these effectors. This lack of delivery of effectors by S. enterica indicates that its secretion apparatus, which has evolved separately from that of plant pathogens, lacks the ability to interact directly with plant cells.

Technical Abstract: Salmonella enterica, a human enteric pathogen, has the ability to multiply and survive endophytically in plants, and mutations in genes encoding the type III secretion system (T3SS) or its effectors (T3Es) may contribute to this colonization. Two reporter plasmids for T3E translocation into plant cells that are based on HR domains of avirulence proteins from the Pantoea agglomerans/beet and Xanthomonas euvesicatoria/pepper pathosystems were employed in this study to investigate the role of T3Es in the interaction of S. enterica with plants. The T3Es of S. Typhimurium 14028, SipB and SifA, which are known to be translocated into animal cells, could not be delivered into cells of beet roots or pepper leaves. In contrast, these effectors were translocated into plant cells by the phytopathogenic bacteria P. agglomerans pv. betae, Erwinia amylovora and X. euvesicatoria. Similarly, HsvG, a T3E of P. agglomerans pv. gypsophilae and XopAU of X. euvesicatoria could be translocated into beet roots and pepper leaves, respectively, by the plant pathogens but not by S. Typhimurium. Mutations in S. Typhimurium T3SS genes, invA, ssaV, sipB or sifA, did not affect its endophytic colonization of lettuce leaves, supporting the notion that S. enterica cannot translocate T3Es into plant cells.