An Importin Protein SlIMPA3 Interacts with SlLCD1 and Regulates Tomato Fruit Ripening.

A nuclear-localized cysteine desulfhydrase, LCD1, plays a crucial role in mediating endogenous hydrogen sulfide production in tomatoes. However, the mechanism underlying the nuclear localization of SlLCD1 is not yet fully understood. In this study, it was found that SlLCD1 specifically interacted with nuclear import receptor importin α3 (SlIMPA3). Furthermore, it was demonstrated that silencing SlIMPA3 through virus-induced gene silencing or introducing mutations in via CRISPR/Cas9 significantly accelerated fruit ripening. Moreover, enhanced chlorophyll degradation, carotenoid accumulation, and premature upregulation of ripening-associated genes in the mutant indicated SlIMPA3 to be a negative regulator of fruit ripening and leaf senescence. Besides, deletion resulted in excessive hydrogen peroxide accumulation in fruits and leaves, potentially leading to premature leaf senescence and accelerated fruit ripening in the mutant. SlIMPA3 exhibited pronounced nuclear localization with weak distribution in the cytoplasm. SlLCD1 showed specific nuclear localization; however, after GFP tagging in -edited tomato leaves, it migrated to the cytoplasm, suggesting that SlIMPA3 mediated the nuclear localization of SlLCD1. SlLCD1 transient expression in mutant fruits indicated that it did not inhibit tomato ripening following the mutation. In summary, our study revealed that SlIMPA3 interacted with SlLCD1 to facilitate its nuclear entry. Mutations in led to premature fruit ripening and leaf senescence, likely due to disrupted reactive oxygen species homeostasis resulting from SlLCD1 mislocalization in the mutant.