Physio-biochemical and proteomic mechanisms of coronatine induced potassium stress tolerance in xylem sap of cotton

Potassium (K) is a major plant nutrient, and its deficiency can limit plant growth and development. Coronatine (COR) could increase cotton seedling tolerance to K deficiency, which was hypothesized to be in relation to improving the physiological and proteomic profile of xylem sap. To test this hypothesis, cotton seedlings growth, physio-biochemical and proteomic profile of xylem sap treated with (0 and 10 nM COR) under deficient K solution (0.05 mM KCl) were explored. Compared with control, COR treatment significantly increased lateral root number and root diameter and decreased contents of malondialdehyde (MDA), some cations like potassium and calcium in xylem sap and its volume. These morphological and physiological presentations were well evidenced by differentially expressed proteins (DEPs) in the xylem sap. For instance, increasing the average root diameter and lateral roots were related to up-regulation of cobalamin-independent methionine synthase family proteins, auxin-responsive protein, and cell wall remodeling proteins such as dirigent-like protein, laccase, and the pectin lyase; lessening xylem sap volume and some cations contents was in connections with down-regulation of uclacyanin 1 and up-regulation of calmodulin-domain protein kinase 7; the MDA content reducing was associated with many PCD-related proteins’ down-regulation or loss. Furthermore, COR potentially weakened plant defense, owing to lessening or disappearing lipid-transfer proteins, signaling proteins, and other proteins positively involved in plant defense.