Overexpression of SlPYR1 and SlPYL8 confers ABA hypersensitivity, plant dwarfing, and delayed senescence in tomato

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Abscisic acid (ABA) functions as a master regulator in plant developmental processes and stress responses through signal transduction components. Extensive mechanistic dissection of PYR/PYL receptors has centered on stress adaption and fruit ripening. However, the roles of ABA receptors in regulating vegetative growth and floral organogenesis remain poorly characterized. Herein, 15 SlPYR/PYLs were identified and classified into three subfamilies in tomato. Expression profiling revealed that SlPYR1.1 and SlPYL8.1 were significantly downregulated under ABA, salt stress, and ethylene treatment while showing tissue-specific dominance in roots/leaves and dynamic reduction during fruit ripening. Subcellular localization confirmed their dual nuclear and cytoplasmic distribution. Functional characterization of overexpression lines demonstrated ABA hypersensitive phenotypes, including declined seed germination rate and root elongation in the presence of ABA. SlPYR1.1-overexpressing transgenics exhibited plant dwarfing, which might be attributed to SlGID1 downregulation, while SlPYL8.1-OX lines showed enhanced chlorophyll retention and mesophyll cell proliferation, thereby delaying leaf senescence. Notably, SlPYL8.1-OX tomatoes displayed reproductive abnormalities, including inflorescence stem orthogravitropism, and floral bud abortion in first- and higher-order inflorescences. In addition, SlPYL8.1 led to lycopene overaccumulation in fruit. These findings establish SlPYR1.1 and SlPYL8.1 as pivotal regulators of ABA-mediated growth-defense trade-offs, integrating phytohormone signaling with developmental plasticity in vegetative and reproductive organs.