Crosstalk of phenylpropanoid biosynthesis with hormone signaling in Chinese cabbage is key to counteracting salt stress

Salt stress limits the regional distribution of Chinese cabbage, yet the molecular factors that confer tolerance to salt stress in Chinese cabbage remain poorly understood. To further investigate this issue, salt-tolerant and salt-sensitive Chinese cabbage cultivars were selected, and their responses to salt stress were tested. Then, comparative transcriptome profiling was performed on the roots of salt-tolerant and salt-sensitive Chinese cabbage cultivars under salt stress. The results showed that Qinghua and Biyu are considered to be salt-tolerant and salt-sensitive Chinese cabbage cultivars, respectively. Qinghua had higher water content and lower Na⁺/K⁺ in roots and leaves, better root development, higher lignin content and higher abscisic acid content in roots than Biyu. Comparative transcriptome profiling showed that the abscisic acid and ethylene signaling pathways of Qinghua roots were more actively expressed than those of Biyu. During root adaptation to salt stress, abscisic acid crosstalk with suberin biosynthesis and ethylene signaling crosstalk with lignin biosynthesis were observed. Suberin development and lignin accumulation in the Qinghua roots were found to be important strategies for resisting salt stress in this study. These strategies are not independent, but rather coordinate to promote salt tolerance in Chinese cabbage. The increased lignin content in the roots of Qinghua under salt stress may prevent embolism. Embolism prevention can maintain the flow of water transport, and thus compensate for the reduction in water permeability of these suberized cells in a process that occurs concurrently with greater sodium ion limitation. These results provide novel insight into the crosstalk of phenylpropanoid biosynthesis with hormone signaling under salt stress, and facilitate further dissection of molecular mechanism of adaptive response to salt stress in Chinese cabbage.