How a Bacterial Protein Weakens Plant Defenses by Targeting Key Plant Proteins

Jim Crocker
14th June, 2024

How a Bacterial Protein Weakens Plant Defenses by Targeting Key Plant Proteins

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Gyeongsang National University found that the effector protein AvrRps4C from Pseudomonas syringae targets specific WRKY transcription factors in Arabidopsis to weaken plant immunity
  • AvrRps4C suppresses the immune-positive regulator WRKY54, preventing it from binding to the SARD1 promoter and thus inhibiting its role in plant defense
  • The study reveals that AvrRps4C causes WRKY transcription factors to form complexes in the cytoplasm, further disrupting their function in plant immunity
Pathogens generate and secrete effector proteins into host plant cells during infection to promote their virulence and colonization. If the plant carries resistance (R) proteins that recognize these effectors, it activates effector-triggered immunity (ETI), resulting in a robust immune response and hypersensitive response (HR). The bipartite effector AvrRps4 from Pseudomonas syringae pv. pisi has been well studied for its avirulence function. In planta, AvrRps4 is processed into two parts, with the C-terminal fragment (AvrRps4C) inducing HR in turnip and being recognized by the paired resistance proteins AtRRS1/AtRPS4 in Arabidopsis. A recent study by researchers at Gyeongsang National University[1] has shown that AvrRps4C targets a group of Arabidopsis WRKY transcription factors, including WRKY46, WRKY53, WRKY54, and WRKY70, to induce its virulence function. In particular, AvrRps4C suppresses the general binding and transcriptional activities of the immune-positive regulator WRKY54 and WRKY54-mediated resistance. This interference suggests that AvrRps4C sequesters WRKY54 from the SARD1 promoter, inhibiting its function in plant immunity. The WRKY transcription factor family in Arabidopsis thaliana, consisting of 74 members, is known to regulate various physiological processes, including plant defense and senescence[2]. WRKY53 and WRKY70 have been implicated as positive and negative regulators of senescence, respectively. The current study reveals that AvrRps4C enhances the formation of homo-/heterotypic complexes of WRKY46, WRKY53, WRKY54, and WRKY70, sequestering them in the cytoplasm and thus inhibiting their function in plant immunity. This study builds on previous research that has highlighted the importance of WRKY transcription factors in plant defense mechanisms[2]. The new findings provide a detailed mechanism of how AvrRps4C disrupts WRKY-mediated resistance, offering insights into the sophisticated defense system of plants. The ability of AvrRps4C to suppress the binding activity of WRKY54 to the SARD1 promoter in vitro is a critical piece of evidence that underscores the virulence strategy employed by Pseudomonas syringae pv. pisi. Furthermore, the study aligns with earlier research on plant-pathogen interactions, which emphasizes the complexity of plant innate immunity and the role of effector proteins in modulating this immunity[3]. The identification of multiple HaRxL effectors from the pathogenic oomycete Hyaloperonospora arabidopsidis that suppress pathogen-associated molecular pattern-triggered immunity (PTI) and localize to different subcellular compartments[4] parallels the multilayered suppression of immunity observed with AvrRps4C. In conclusion, the research conducted by Gyeongsang National University elucidates the virulence mechanism of AvrRps4 through its C-terminus, enhancing our understanding of how pathogens manipulate plant immune responses. This study not only advances our knowledge of plant-pathogen interactions but also provides potential targets for developing disease-resistant crops, contributing to sustainable agriculture and food security.

GeneticsBiochemPlant Science

References

Main Study

1) The processed C-terminus of AvrRps4 effector suppresses plant immunity via targeting multiple WRKYs.

Published 13th June, 2024

https://doi.org/10.1111/jipb.13710

Related Studies

2) WRKY54 and WRKY70 co-operate as negative regulators of leaf senescence in Arabidopsis thaliana.

https://doi.org/10.1093/jxb/err450

3) Plant Innate Immunity Multicomponent Model.

https://doi.org/10.3389/fpls.2015.00987

4) In planta effector competition assays detect Hyaloperonospora arabidopsidis effectors that contribute to virulence and localize to different plant subcellular compartments.

https://doi.org/10.1094/MPMI-06-12-0154-R


Related Articles

An unhandled error has occurred. Reload 🗙