Engineering bacteriocin‐mediated resistance against the plant pathogenPseudomonas syringae

Abstract

Summary The plant pathogen, Pseudomonas syringae (Ps), together with related Ps species, infects and attacks a wide range of agronomically important crops, including tomato, kiwifruit, pepper, olive and soybean, causing economic losses. Currently, chemicals and introduced resistance genes are used to protect plants against these pathogens but have limited success and may have adverse environmental impacts. Consequently, there is a pressing need to develop alternative strategies to combat bacterial disease in crops. One such strategy involves using narrow‐spectrum protein antibiotics (so‐called bacteriocins), which diverse bacteria use to compete against closely related species. Here, we demonstrate that one bacteriocin, putidacin L1 (PL1), can be expressed in an active form at high levels in Arabidopsis and in Nicotiana benthamiana in planta to provide effective resistance against diverse pathovars of Ps. Furthermore, we find that Ps strains that mutate to acquire tolerance to PL1 lose their O‐antigen, exhibit reduced motility and still cannot induce disease symptoms in PL1‐transgenic Arabidopsis. Our results provide proof‐of‐principle that the transgene‐mediated expression of a bacteriocin in planta can provide effective disease resistance to bacterial pathogens. Thus, the expression of bacteriocins in crops might offer an effective strategy for managing bacterial disease, in the same way that the genetic modification of crops to express insecticidal proteins has proven to be an extremely successful strategy for pest management. Crucially, nearly all genera of bacteria, including many plant pathogenic species, produce bacteriocins, providing an extensive source of these antimicrobial agents.

Current Knowledge on Microviridin from Cyanobacteria

“…Hilder et al (1987) [96] were the first to use these organisms to express serine protease inhibitors with the potential to kill predatory larvae insects. There is a considerable number of works employing plants as hosts of ribosomally synthesized and post-translationally modified peptides [97][98][99]. Plant-based microviridins have promises for future applications, since they can replace the use of pesticides to help control insect pests with low costs and low environmental impacts.…”

Bacteriocins Targeting Gram-Negative Phytopathogenic Bacteria: Plantibiotics of the Future

“…(B) Non-transgenic (NT) vs. transgenic expression of PL1 in both Arabidopsis seedlings (upper panel) and Nicotiniana benthamiana leaves (lower panel) provides robust resistance against strains of P. syringae that are susceptible to PL1. These images were adapted from Rooney et al (2019).…”

“…As we have recently shown, bacteriocins can be expressed transgenically in planta to provide resistance against P. syringae. Expression of PL1 in two model plant species provided a strong resistance phenotype in plants challenged with several unrelated PL1-sensitive P. syringae field isolates ( Figure 2B; Rooney et al, 2019) with bacterial titres in PL1 transgenic lines 1.5 log-units lower than in non-transgenic controls (Rooney et al, 2019).…”

“…One potential issue in utilizing bacteriocins as a direct treatment is the requirement for large scale bacteriocin production. This maybe technically difficult for multi-component bacteriocins (e.g., tailocins) but should not be a problem for LLBs and CLBs where successful production in planta has already been demonstrated (Schulz et al, 2015;Paškevičius et al, 2017;Rooney et al, 2019).…”

Variation at the common polysaccharide antigen locus drives lipopolysaccharide diversity within the Pseudomonas syringae species complex

“…It has been shown recently that there is a high degree of variation in the sensitivity to tailocins within P. syringae (Baltrus et al ., 2019). Understanding the molecular basis of this variation is important if we are to implement novel methods such as the use of phage therapy or tailocins for biological control of this pathogen (Frampton et al ., 2014; Frampton et al ., 2015; Baltrus et al ., 2019; Pinheiro et al ., 2019; Rooney et al ., 2020; Holtappels et al ., 2020).…”