With global warming and water shortage, drought stress is provoking an increasing impact on plant growth, development, and crop productivity worldwide.
Pipecolic acid (Pip) is an emerging
lysine catabolite in plants, acting as a critical
element in
disease resistance with a related signal pathway of
phytohormone salicylic acid (SA). While SA plays a vital role in various abiotic stresses, the role of Pip in plant response to abiotic stresses, especially drought, remains largely unknown. To address this issue, Pip biosynthetic gene Slald1 mutants and hydroxylated modification gene Slfmo1 mutants were generated using CRISPR-Cas9 gene-editing approaches. Drought resistance dramatically increased in Slald1 mutants compared with wild-type, which was associated with increased CO2 assimilation, photosystems activities,
antioxidant enzymes activities, ascorbate and
glutathione content, and reduced
reactive oxygen species accumulation, lipid peroxidation and
protein oxidation. On the contrary, Slfmo1 mutants were more sensitive to drought, showing damaged photosystems and impaired
antioxidant systems, which were significantly alleviated by exogenous ascorbate. Our results demonstrate that Pip biosynthesis and hydroxylated modification pathways play a critical role in drought tolerance through the
antioxidant system in tomato. This knowledge can be helpful to breed improved crop cultivars that are better equipped with drought resistance.