Heat Shock Factor HsfA1a Is Essential for Gene-Mediated Nematode Resistance and Triggers HO Production.

Plants generate reactive oxygen species (ROS) in the apoplast in response to pathogen attack, especially following resistance () gene-mediated pathogen recognition; however, the mechanisms activating ROS generation remain unknown. Here, we demonstrate that RKN () infection rapidly induces ROS accumulation in the roots of tomato () plants that contain the gene but rarely induces ROS accumulation in the susceptible or -silenced resistant genotypes. RNK also induces the hypersensitive response, a form of programmed cell death, in plants. RKN induces the expression of numerous class-A heat shock factor (HsfA) genes in resistant tomato plants. Silencing compromises -mediated resistance, apoplastic HO accumulation, and the transcription of (), which encodes a respiratory burst oxidase homolog. HsfA1a regulates transcription by binding to the promoter, and silencing of compromises -mediated resistance. HsfA1a and Wfi1 are involved in Mi-1.2-triggered Hsp90 accumulation and basal defense in susceptible tomato. Thus, HsfA-1aWfi1-dependent ROS signaling functions as a crucial regulator of plant defense responses.