Desert Endophytic Fungi Differentially Modulate Reactive Oxygen Species and Antioxidant Responses to Heat Stress in Tomato

Increasing temperature is a major stress factor associated with climate change, strongly limiting agricultural productivity, particularly in sensitive crops such as tomato (Solanum lycopersicum L.). High temperatures promote the accumulation of reactive oxygen species (ROS), leading to oxidative damage and disruption of key physiological processes. Here, we evaluated whether desert-derived endophytic fungi differentially modulate oxidative stress responses in tomato plants exposed to heat stress. Plants were inoculated with either Talaromyces minioluteus or Serendipita indica and grown under control (22/19 °C) or heat stress conditions (35/19 °C). Heat stress reduced growth and increased oxidative damage, whereas endophyte inoculation mitigated these effects. Inoculated plants showed higher shoot and root biomass, lower levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and enhanced enzymatic and non-enzymatic antioxidant systems, including increased activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), as well as greater accumulation of phenolic compounds and flavonoids. However, the magnitude and direction of these responses depended on the endophyte species. Overall, endophytic fungi modulated ROS homeostasis through coordinated enzymatic and non-enzymatic antioxidant mechanisms. These findings indicate that desert endophytic fungi enhance tolerance to heat stress through endophyte-specific regulation of oxidative balance, highlighting their potential to improve crop resilience under climate change.