aeruginosa PAO1 and Flg22-1, and Flg22-2 from P. (A) Sequence alignment of Flg22_Pa from P.
Plant immunity induced by Flg22-1 and Flg22-2. All experiments were repeated three times with similar results. Different letters indicate statistically significant differences between different treatments (one-way ANOVA, Tukey’s test P < 0.05). (D) Quantitative analysis of primary root length, number of lateral roots, and lateral root density. kilonensis F113 and its fliC mutants on shoot and root growth in A. The fraction under each image indicates the number of times that the HR was inhibited compared to the number of test inoculations. After 6 h, an overlapping inoculation of 5 × 10 6 CFU/mL of the HR-inducing strain Pst DC3000 (lower circles) was made.
benthamiana leaves with 1 × 10 8 CFU/mL of the test Pseudomonas strains (upper circles). (B) Challenge-inoculation HR assays for functional PTI were conducted by first infiltrating N. kilonensis F113, and the fliC mutants in N. Our findings on the divergence of duplicated flagellins provide a conceptual framework for better understanding the functional determinant flagellin and its peptide in multiple-flagellin plant-growth-promoting rhizobacteria.įlg22 Pseudomonas flagella flagellin motility plant immunity plant-microbe interactions.Ĭontribution of the duplicated flagellins to plant immunity and root growth. This work focuses on flagellin duplication in some plant-associated Pseudomonas. IMPORTANCE Flagellins have emerged as important microbial patterns. These findings suggest that Pseudomonas has evolved duplicate flagellins, with only FliC-1 contributing to motility and plant immune elicitation. Also, Flg22-2 epitopes in the other 11 Pseudomonas strains were presumed to have low binding affinity due to the same change in the 19th amino acid. A change in the 19th amino acid in Flg22-2 reduced its binding affinity to the FLS2/brassinosteroid insensitive 1-associated kinase 1 complex. Compared to the Flg22-2 epitope (relative to FliC-2), Flg22-1 (relative to FliC-1) induced stronger FLAGELLIN SENSING 2 (FLS2)-mediated microbe-associated molecular pattern-triggered immunity and significantly inhibited plant root growth. In silico prediction revealed that all fliC-2 genes in the 12 Pseudomonas strains have a poorly conserved promoter motif. The transcriptional expression of fliC-2 was significantly lower than that of fliC-1 in medium and in planta, most likely due to variations in promoter activity. Only the fliC-1 gene but not the fliC-2 gene in strain F113 is responsible for flagellar biogenesis, motility, and plant immune elicitation. We demonstrate that the two flagellins (FliC-1 and FliC-2) in 12 Pseudomonas strains, including F113, are evolutionarily distinct. Here, the model plant-growth-promoting bacterium Pseudomonas kilonensis F113 was used to decipher the divergent functions of duplicated flagellins. Although the functions of flagellins have been extensively studied in bacteria with a single flagellin-encoding gene, the function of multiple flagellin-encoding genes in a single bacterial species is largely unknown.
Flagellins are the main constituents of the flagellar filaments that provide bacterial motility, chemotactic ability, and host immune elicitation ability.
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