SlCHP16 promotes root growth and enhances saline-alkali tolerance of tomato

With the increasing salinization in the world, crop growth and yield had a serious threat. Roots as the organ of the plant direct contact the saline-alkali environment has received more and more attention. The Divergent C1 (DC1) domain protein plays an important role in plant growth, development, and stress response. In this study, overexpression of SlCHP16 promoted tomato root growth, while knocking out SlCHP16 inhibited tomato root growth. In the roots of SlCHP16 overexpressing plants, the auxin synthesis key gene SlTAA2 was significantly up-regulated, which increased auxin synthesis and accumulation and promoted root cell elongation. Meanwhile, the expression levels of cell expanding-related genes SlLRP, SlXTH9 and SlEXPB1 were up-regulated. The opposite was observed in SlCHP16 knockout plants. Under saline-alkali stress, the root growth rate of SlCHP16 overexpressed lines was significantly higher than that of AC, and SlCHP16 knockout lines had poor root development during seed germination and seedling growth. At the same time, after saline-alkali stress treatment, SlCHP16-overexpressing lines showed higher tolerance, while SlCHP16 knockout plants were more sensitive to saline-alkali stress. In conclusion, SlCHP16 promoted root growth and enhanced saline-alkali tolerance in tomato. This work provides new insights into the mechanism of tomato root development and provides resources for developing new salt-alkali tolerant tomato varieties.