The new function of FaSRT2-1 protein in energy metabolism: Promoting strawberry fruit quality and ripening

Sirtuins (SRTs) are nicotinamide adenine dinucleotide (NAD⁺) dependent II histone deacetylases (HDACs) that have been understudied in horticultural crops. However, their functions in regulating mitochondrial energy metabolism and influencing fruit development and quality formation remain unclear. In this study, we found that FaSRT2-1 exhibits diverse subcellular localizations. Overexpression of FaSRT2-1 promoted strawberry fruit quality formation (soluble sugars, organic acids, anthocyanins) and accelerated ripening. Conversely, knockout of FaSRT2-1 yielded opposite results. During fruit ripening, ATP content and ATP/ADP ratio gradually increased, and FaSRT2-1 promoted ATP accumulation and decreased before and after the deep red stage, respectively, indicating its role in fruit ripening and senescence. FaSRT2-1 interacted with energy-related proteins (FaRPT4a, FaATPβ and FaATPγ) to increase ATP content and the ATP/ADP ratio. Additionally, FaSRT2-1 collaborated with FaGDH2 and FaWDR5B to increase the accumulation of soluble sugars, organic acids and anthocyanins. Meanwhile, FaRPT4a, FaATPγ, FaGDH2 and FaWDR5B were co-localized with FaSRT2-1, while FaATPβ was localized in both the cytoplasm and mitochondria. Transient overexpression experiments further highlight the roles of FaRPT4a and FaGDH2/FaWDR5B in modulating ATP accumulation and fruit ripening, respectively. In summary, FaSRT2-1 plays important roles in promoting strawberry fruit ripening, senescence and quality formation by regulating energy metabolism.