Unraveling the mutualistic interaction between endophytic Curvularia lunata CSL1 and tomato to mitigate cadmium (Cd) toxicity via transcriptomic insights

In this study, endophytic fungus Curvularia lunata strain SL1 was used to explore its bioremediation potential and growth restoration of tomato (Solanum lycopersicum) under cadmium (Cd) stress. Our findings demonstrate that SL1 establishes a symbiotic relationship with tomato plants, which modulates the antioxidant system, secondary metabolites, and gene expression in tomato plants exposed to Cd stress. Under Cd stress, tomato seedling growth was significantly reduced by up to 42.8 %, although this reduction was mitigated by up to 25 % after SL1 inoculation. Similar to this, SLI inoculation inhibits Cd absorption and translocation to the upper parts of the plant. Additionally, during Cd stress, phytohormones related to stress, including jasmonic acid (JA), abscisic acid (ABA), and ethylene (ET), were elevated; however, SL1 inoculation lowered their level. RNA-Seq data revealed that the highest number of differentially expressed genes (DEGs) was detected in the comparison between control and 1 mM Cd, followed by 2 mM Cd stress. These DEGs were mostly related to oxidoreductase activity, catalytic activity, plant hormones transduction, and photosynthesis. The findings also suggested that SL1 could improve tomato tolerance to Cd stress by modulating Ca2+ signaling, phytohormone biosynthesis, MAPK signaling pathway, and some transcription factors.