Heterologous Overexpression of Apple Promotes Fruit Ripening in Tomato.

Fruit ripening is governed by a complex regulatory network, and ethylene plays an important role in this process. MdKING1 is a γ subunit of SNF1-related protein kinases (SnRKs), but the function was unclear. Here, we characterized the role of during fruit ripening, which can promote fruit ripening through the ethylene pathway. Our findings reveal that has higher expression in early-ripening cultivars than late-ripening during the early stage of apple fruit development, and its transcription level significantly increased during apple fruit ripening. Overexpression of ( OE) in tomatoes could promote early ripening of fruits, with the increase in ethylene content and the loss of fruit firmness. Ethylene inhibitor treatment could delay the fruit ripening of both OE and WT fruits. However, OE fruits turned fruit ripe faster, with an increase in carotenoid content compared with WT. In addition, the expression of genes involved in ethylene biosynthesis (, , and ), carotenoid biosynthesis ( and ), and fruit firmness regulation (, , and ) was also increased in the fruits of OE plants. In conclusion, our results suggest that plays a key role in promoting tomato fruit ripening, thus providing a theoretical basis for apple fruit quality improvement by genetic engineering in the future.