Heterologous Overexpression of Apple <i>MdKING1</i> Promotes Fruit Ripening in Tomato
2023
Qianyu Yue | Xinyue Yang | Pengda Cheng | Jieqiang He | Wenyun Shen | Yixuan Li | Fengwang Ma | Chundong Niu | Qingmei Guan
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 <i>MdKING1</i> during fruit ripening, which can promote fruit ripening through the ethylene pathway. Our findings reveal that <i>MdKING1</i> 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 <i>MdKING1</i> (<i>MdKING1</i> 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 <i>MdKING1</i> OE and WT fruits. However, <i>MdKING1</i> 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 (<i>SlACO1</i>, <i>SlACS2</i>, and <i>SlACS4</i>), carotenoid biosynthesis (<i>SlPSY1</i> and <i>SlGgpps2a</i>), and fruit firmness regulation (<i>SlPG2a</i>, <i>SlPL</i>, and <i>SlCEL2</i>) was also increased in the fruits of <i>MdKING1</i> OE plants. In conclusion, our results suggest that <i>MdKING1</i> 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.
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