A nuclear-localized cysteine desulfhydrase plays a role in fruit ripening in tomato

Hydrogen sulfide(H_(2)S)is a gaseous signaling molecule that plays multiple roles in plant development.However,whether endogenous H_(2)S plays a role in fruit ripening in tomato is still unknown.In this study,we show that the H_(2)S-producing enzyme L-cysteine desulfhydrase SILCD1 localizes to the nucleus.By constructing mutated forms of SILCD1,we show that the amino acid residue K24 of SILCD1 is the key amino acid that determines nuclear localization.Silencing of SILCD1 by TRV-SILCD1 accelerated fruit ripening and reduced H_(2)S production compared with the control.A SILCD1 gene-edited mutant obtained through CRISPR/Cas9 modification displayed a slightly dwarfed phenotype and accelerated fruit ripening.This mutant also showed increased cysteine content and produced less H_(2)S,suggesting a role of SILCD1 in H_(2)S generation.Chlorophyll degradation and carotenoid accumulation were enhanced in the SILCD1 mutant.Other ripening-related genes that play roles in chlorophyll degradation,carotenoid biosynthesis,cell wall degradation,ethylene biosynthesis,and the ethylene signaling pathway were enhanced at the transcriptional level in the lcd1 mutant.Total RNA was sequenced from unripe tomato fruit treated with exogenous H_(2)S,and transcriptome analysis showed that ripening-related gene expression was suppressed.Based on the results for a SILCD1 gene-edited mutant and exogenous H_(2)S application,we propose that the nuclear-localized cysteine desulfhydrase SILCD1 is required for endogenous H_(2)S generation and participates in the regulation of tomato fruit ripening.