Tomato (Solanum lycopersicum) gray mold, caused by the pathogenic fungus Botrytis cinerea, is a devastating post-harvest disease causing billions of dollars in global economic losses annually. As tomatoes ripen, they naturally become more susceptible to this destructive pathogen which is regulated by ethylene response factors (ERFs). Current methods often face limitations regarding safety and sustainability, exploring the molecular mechanism behind tomato fruit resistance is essential for developing new technologies to reduce post-harvest losses and maintain fruit quality.

Researchers at the Wuhan Botanical Garden, Chinese Academy of Sciences, pinpoint SlERF.F4 as a pivotal regulator in tomato's defense against the B. cinerea. The study finds that SlERF.F4 transcripts are detected in mature green fruits and are significantly upregulated upon infection.

Crucially, comparative analysis revealed that knocking out or knocking down SlERF.F4 increased fruit susceptibility to B. cinerea. Conversely, overexpressing SlERF.F4 slightly enhanced resistance, indicating that SlERF.F4 negatively regulates tomato fruits' susceptibility to B. cinerea.

Mechanistically, SlERF.F4 acts as a molecular bridge between fruit immunity and antioxidant defense. Jasmonic acid signaling component MYC2-activated SlERF.F4 induces key pathogenesis-related (PR) genes like PR2a, CHI1, and PR-STH2 to combat the pathogen directly, while simultaneously regulating enzymes such as PR-9 (POD) and superoxide dismutase (SOD) to maintain reactive oxygen species (ROS) homeostasis and prevent oxidative damage. Most importantly, SlERF.F4 enhances disease resistance without compromising fruit ripening or postharvest quality, making it as a highly promising target for breeding disease-resistant tomato varieties.

Results have been published in Postharvest Biology and Technology entitled "SlERF.F4negatively regulates tomato fruit susceptibility toBotrytis cinereaindependently of ripening traits". This research was supported by the National Natural Science Foundation of China, Youth Talent Development Program of Hubei Province, Wuhan Talent Program, and Science Fund for Creative Research Groups of the Natural Science Foundation of Hubei Province.

Schematic model of SlERF.F4-mediated defense against B. cinerea in tomato fruits (Image by WBG)