Receptor-like kinase SlRLK-like positively regulates sugar accumulation and fruit ripening in tomato

Jiaqi Sun^1,2Xinsheng Zhang^1,3Miaofei Yang¹Xin Liu^1*Jing Jiang^1*

• ¹Shenyang Agricultural University, Shenyang, China
• ²Liaodong University, Dandong, China
• ³Jilin Agricultural University, Changchun, China

The ripening process of tomato fruits contains lots of complex changes. The elucidation of the ripening pathways contributes to reduce post-harvest losses and improve fruit quality. However, there is still much unknown about how tomato plants precisely synchronize metabolic regulation and fruit maturation. In this study, SlRLK-like, a member of the Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) in tomato was found to be involved in the regulation of sugar transport, lycopene content, and synthesis of ethylene. Overexpression (OE) or virus-induced gene silencing (VIGS) of SlRLK-like increases or decreases sugar accumulation in tomato fruits, respectively. Meanwhile, overexpressing SlRLK-like causes the acceleration in ripening process of tomato fruit, which also results in upregulating the ethylene production and lycopene content. SlRLK-like can interact with SlSWEETs (SlSWEET7a and SlSWEET14), and further alter their sucrose transport ability to modulate sugar accumulation. Furthermore, during tomato fruit ripening, SlRLK-like also can interact with ethylene and lycopene biosynthesis related proteins (SlACS2, SlSAMS4, and SlPSY1), by controlling their gene expression level and protein abundance to promote the process of lycopene and ethylene production. More importantly, the sugar accumulation in fruit can enhance the ethylene production, which can also speed up the tomato fruit ripening process. As a result, SlRLK-like acts as a positive regulator of tomato ripening. The study provides novel insights in the molecular regulatory networks of tomato fruit quality and ripening, which can be applied to improve tomato cultivation.