Abstract
Rising global temperatures are increasingly affecting plant performance, leading to reduced growth, altered metabolism, and compromised membrane integrity. Although plant growth-promoting bacteria (PGPB) show promise in enhancing thermotolerance, the underlying mechanisms remain insufficiently explored. Therefore, this study investigated the effects of PGPB inoculation on Zea mays under control (26 °C) and heat stress (36 °C) conditions. Maize plants were inoculated with two thermotolerant bacterial strains and their effects were compared to non-inoculated plants through morphometric, biochemical, and lipidomic analyses. Heat stress negatively affected germination (-35.9%), increased oxidative stress (+46% for LPO, +57% for SOD, +68% for GPx), and altered leaf lipid composition, particularly fatty acids, glycerolipids, and sphingolipids. Inoculation with Pantoea sp. improved germination by 15% for seeds exposed to heat stress, increased growth (+28% shoot and +17% root), enhanced antioxidant defenses (+35% for CAT and +38% for APx), and reduced membrane damage by 65% compared with the control. Lipidomic profiling revealed that inoculation mitigated temperature-induced lipid alterations by reducing triacylglycerol accumulation and preserving the levels of polyunsaturated galactolipids and hexosylceramides. Notably, Pantoea sp.-inoculated plants under heat stress exhibited lipid profiles that were more similar to those of control plants, suggesting enhanced heat resilience. These results underscore the importance of specific plant-microbe interactions in mitigating heat stress and highlight PGPB inoculation as a promising strategy to enhance crop performance and resilience under projected climate warming scenarios.