Distinctiveness of genes contributing to growth of Pseudomonas syringae in diverse host plant species

Authors: Helmann, Tyler; DEUTSCHBAUER, ADAM - Lawrence Berkeley National Laboratory; LINDOW, STEVEN - Lawrence Berkeley National Laboratory

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2020
Publication Date: 9/28/2020
Citation: Helmann, T.C., Deutschbauer, A., Lindow, S. 2020. Distinctiveness of genes contributing to growth of Pseudomonas syringae in diverse host plant species. PLoS ONE. 15(9):e0239998. https://doi.org/10.1371/journal.pone.0239998.
DOI: https://doi.org/10.1371/journal.pone.0239998

Interpretive Summary: The bacterial plant pathogen Pseudomonas syringae causes disease on a wide variety of plant species. It is difficult to simultaneous examine and directly compare the virulence mechanisms for infection on different host plants. We took advantage of recent advances in sequencing technologies to identify the overlap of bacterial genes important for growth in three susceptible hosts: common bean, lima bean, and pepper. We found most genes were important in all plants, though some were significantly host-specific. The results of this study will be useful to understand how a single pathogen can infect multiple plant species.

Technical Abstract: A variety of traits are necessary for bacterial colonization of the interior of plant hosts, including well-studied virulence effectors as well as other phenotypes contributing to bacterial growth and survival within the apoplast. High-throughput methods such as transposon sequencing (TnSeq) are powerful tools to identify such genes in bacterial pathogens. However, there is little information as to the distinctiveness of traits required for bacterial colonization of different hosts. Here, we utilize randomly barcoded TnSeq (RB-TnSeq) to identify the genes that contribute to the ability of Pseudomonas syringae strain B728a to grow within common bean (Phaseolus vulgaris), lima bean (Phaseolus lunatus), and pepper (Capsicum annuum); species representing two different plant families. The magnitude of contribution of most genes to apoplastic fitness in each of the plant hosts was similar. However, 50 genes significantly differed in their fitness contributions to growth within these species. These genes encoded proteins in various functional categories including polysaccharide synthesis and transport, amino acid metabolism and transport, cofactor metabolism, and phytotoxin synthesis and transport. Six genes that encoded unannotated, hypothetical proteins also contributed differentially to growth in these hosts. The genetic repertoire of a relatively promiscuous pathogen such as P. syringae may thus be shaped, at least in part, by the conditional contribution of some fitness determinants.