Nonuniform Salt Distribution in the Root Zone Alleviates Salt Damage in Wheat

Furrow sowing could significantly decrease salt damage to wheat. However, the underlying molecular mechanism is not well known. A split-root system was applied to simulate non-uniform root zone salinity in this study. Hydroponic results showed that wheat seedlings under non-uniform salt stress may take a salt avoidance method to ensure growth. RNA sequencing analysis showed that 1648 and 3245 differentially expressed genes were identified in the 0/150 and 75/75 salt treatments, respectively, with an intersection of 690. GO terms which represent normal growth were specifically enriched by up-regulated genes in the 0/150 treatment or down-regulated genes in the 75/75 treatment, while terms which represent phytoremediation were specifically enriched by up-regulated genes in the 75/75 treatment or down-regulated genes in the 0/150 treatment. Besides, differentially expressed genes between the 0/150 and 75/75 treatments known as marker genes for salt tolerance and transcription factors all showed a significantly higher expression level in the 75/75 treatment. All these suggest that a uniform salt treatment causes wheat to initiate a more complex salt-tolerance mechanism to confront salt stress. In addition, 11 genes annotated to peroxidase were more highly expressed in the 0/150 treatment, and the enzyme activity showed the same trend. This indicates that peroxidase may play some role in the better performance of wheat plants undergoing non-uniform salt stress. Lastly, pot culture experiment showed that wheat plants under non-uniform salt stress attained higher yields, further indicating that inducing unequal salt distribution in the soil could provide significant improvements in wheat cultivation.