Loss-of-function mutations in WRKY22 and WRKY25 impair stomatal-mediated immunity and PTI and ETI responses against Pseudomonas syringae pv. tomato

• Published in: Plant molecular biology Vol. 112; no. 3; pp. 161 - 177
• Main Authors: Ramos, Romina N., Zhang, Ning, Lauff, Diana B., Valenzuela-Riffo, Felipe, Figueroa, Carlos R., Martin, Gregory B., Pombo, Marina A., Rosli, Hernan G.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.06.2023; Springer; Springer Nature B.V
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biochemistry; Biomedical and Life Sciences; CRISPR; Disease susceptibility; DNA binding proteins; Gene regulation; Genetic aspects; Immune system; Life Sciences; Mutants; Mutation; Pathogens; Physiological aspects; Plant bacterial diseases; Plant Diseases - microbiology; Plant immunity; Plant Immunity - genetics; Plant Pathology; Plant Proteins - metabolism; Plant Sciences; Proteins; Pseudomonas syringae; Pseudomonas syringae - physiology; Solanum lycopersicum - genetics; Stomata; Tomatoes; Transcription factors; Virulence (Microbiology); Stomatal-mediated immunity; pv; CRISPR-Cas9; WRKY transcription factors; Pseudomonas syringae pv. tomato; Solanum lycopersicum
• DOI: 10.1007/s11103-023-01358-0
• ISSN: 0167-4412

Plants defend themselves against pathogens using a two-layered immune system. The first response, pattern-triggered immunity (PTI), is activated upon recognition of microbe-associated molecular patterns (MAMPs). Virulent bacteria such as Pseudomonas syringae pv. tomato ( Pst ), deliver effector proteins into the plant cell to promote susceptibility. However, some plants possess resistance (R) proteins that recognize specific effectors leading to the activation of the second response, effector-triggered immunity (ETI). Resistant tomatoes such as Río Grande-PtoR recognize two Pst effectors (AvrPto and AvrPtoB) through the host Pto/Prf complex and activate ETI. We previously showed that the transcription factors (TF) WRKY22 and WRKY25 are positive regulators of plant immunity against bacterial and potentially non-bacterial pathogens in Nicotiana benthamiana . Here, the CRISPR-Cas9 technique was used to develop three knockout tomato lines for either one or both TFs. The single and double mutants were all compromised in Pto/Prf-mediated ETI and had a weaker PTI response. The stomata apertures in all of the mutant lines did not respond to darkness or challenge with Pst DC3000. The WRKY22 and WRKY25 proteins both localize in the nucleus, but we found no evidence of a physical interaction between them. The WRKY22 TF was found to be involved in the transcriptional regulation of WRKY25 , supporting the idea that they are not functionally redundant . Together, our results indicate that both WRKY TFs play a role in modulating stomata and are positive regulators of plant immunity in tomato. Key message WRKY22 and WRKY25 are required for full activation of PTI and ETI in tomato against Pseudomonas syringae pv. tomato .