Proteomic responses of wheat root tissues to salt stress in relation to root physiology

Wheat is a staple food crop, and its early growth is particularly salt sensitive. Salinity stress causes adverse effects on plant growth and development at both physiological and biochemical levels. To date, numerous studies have focused on plant metabolic responses to salinity in above ground tissues, however surprisingly little is known about the metabolic responses of wheat roots exposed to salt. This project investigates the impact of salt stress on root physiology and metabolism. We exposed Scepter wheat variety to 150mM NaCl for 3 days and 6 days through gradual increment of salt and assessed changes in growth parameters. Targeted and un-targeted proteomic approaches were conducted to depict temporal proteomic changes in root tips and mature root tissues. Scepter showed significant reduction in fresh weight and dry weight after 6 days of treatment with 150 mM NaCl, with a reduction in relative growth rate, chlorophyll content compared to the respective controls. Shot-gun proteomic analysis in root tips and mature roots revealed that most proteins were assigned to protein synthesis and degradation category which was followed by carbon and energy metabolism. GO and Kegg pathway analysis further confirmed that most of the enrichment was observed in pathways involved in genetic information processing, carbon, energy and amino acid metabolism. Significant up-regulation in proteins involved in of sugar metabolism and amino acid metabolism observed by targeted MRM approach indicated that these metabolic pathways could play prominent roles in root tissues to generate energy for growth and maintenance under salt stress. Overall, the proteomic level changes suggests that the salt stress impacts largely on the actively growing root tissue rather than the mature part of the root as well as the proteomic changes follow a time dependent manner which also highlights the importance of considering the root physiology, time-course changes in stress related omics studies.