Comparative genomics of Pseudomonas syringae pathovar tomato reveals novel chemotaxis pathways associated with motility and plant pathogenicity

Abstract

Comparative genomics of Pseudomonas syringae pathovar tomato reveals novel chemotaxis pathways associated with motility and plant pathogenicity. 15 Abstract 16 The majority of bacterial foliar plant pathogens must invade the apoplast of host plants through 17 points of ingress, such as stomata or wounds, to replicate to high population density and cause 18 disease. How pathogens navigate plant surfaces to locate invasion sites remains poorly 19 understood. Many bacteria use chemical-directed regulation of flagellar rotation, a process 20 known as chemotaxis, to move towards favorable environmental conditions. Chemotactic 21 sensing of the plant surface is a potential mechanism through which foliar plant pathogens home 22 in on wounds or stomata, but chemotactic systems in foliar plant pathogens are not well 23 characterized. Comparative genomics of the plant pathogen Pseudomonas syringae pathovar 24 tomato (Pto) implicated annotated chemotaxis genes in the recent adaptations of one Pto lineage. 25 We therefore characterized the chemosensory system of Pto. The Pto genome contains two 26 primary chemotaxis gene clusters, che1 and che2. The che2 cluster is flanked by flagellar 27 biosynthesis genes and similar to the canonical chemotaxis gene clusters of other bacteria based 28 on sequence and synteny. Disruption of the primary phosphorelay kinase gene of the che2 29 cluster, cheA2, eliminated all swimming and surface motility at 21 o C but not 28 o C for Pto. The 30 che1 cluster is located next to Type IV pili biosynthesis genes but disruption of cheA1 has no 31 observable effect on twitching motility for Pto. Disruption of cheA2 also alters in planta fitness 32 of the pathogen with strains lacking functional cheA2 being less fit in host plants but more fit in a 33 non-host interaction.

Xanthomonas oryzae pv. oryzae chemotaxis components and chemoreceptor Mcp2 are involved in the sensing of constituents of xylem sap and contribute to the regulation of virulence‐associated functions and entry into rice

“…It is pertinent to note that, in Ralstonia solanacearum and Pseudomonas syringae pv. tomato , it has been shown that the mutants defective in the chemotaxis system exhibit reduced virulence when inoculated by the natural mode of infection (spray or dip inoculation), but are virulence proficient when inoculated directly by wound infection (Clarke et al ., ; Tans‐Kersten et al ., ; Yao and Allen, ). In contrast, it has been shown that Dickeya dadantii chemotaxis mutants exhibit defects in entry into plants, as well as reduced virulence, even after wound inoculation (Antunez‐Lamas et al ., ,).…”

Pseudomonas syringae pv. tomato infection of tomato plants is mediated by GABA and l‐Pro chemoperception

“…The genome analysis of PsPto indicates that it has four chemosensory pathways (Gumerov et al, 2019) and currently available data indicate that only one is involved in chemotaxis (Cerna‐Vargas et al, 2019; Clarke et al, 2016). In P. aeruginosa , the four chemosensory pathways appear to be insulated signalling routes (Matilla, Martin‐Mora, et al, 2021; Ortega, Fleetwood, et al, 2017).…”

“…Stomata are the main entry points of PsPto into the plant apoplast, and previous studies have shown that PsPto is able to move towards open stomata (Melotto et al, 2006). It has also been observed that the mutation of cheA2 , encoding CheA of the chemotaxis pathway, causes a loss of chemotaxis and reduced fitness on plant hosts (Cerna‐Vargas et al, 2019; Clarke et al, 2016). This bacterium was found to perform chemotaxis towards amino acids, sugars, organic acids, and amides (Cerna‐Vargas et al, 2019; Cuppels, 1988; Kim et al, 2007).…”

Vfr targets promoter of genes encoding methyl-accepting chemotaxis protein in Pseudomonas syringae pv. tabaci 6605

“…Gathering of Pto DC3000 around open stomata of Arabidopsis thaliana leaves suggested that Pto DC3000 can sense chemical signals released from the stomata [ 14 ]. Actually, the mutation of cheA2 in Pto DC3000 eliminated surface motility and reduced virulence on tomato and Arabidopsis [ 15 ]. We also found the requirements of cheA2 and cheY2 of Pta 6605 in chemotaxis and virulence on host tobacco plant (unpublished results).…”