iTRAQ - based proteomic and physiological analyses of broccoli sprouts in response to the stresses of heat, hypoxia and heat plus hypoxia

Aims Stressful conditions, such as heat and hypoxia stresses, could enhance glucosinolate metabolism, but impacted plant growth and productivity. It is very important to identify the differences in physiological and proteomic changes in broccoli sprouts under the stresses of heat, hypoxia and heat plus hypoxia. Methods Physiological properties, antioxidant enzyme activity and glucosinolates and sulforaphane were studied. The iTRAQ technique was applied to identify the differentially abundant proteins. Results A total of 145, 92 and 105 proteins in broccoli sprouts showed differential relative abundance under the stresses of heat, hypoxia and heat plus hypoxia, respectively. These proteins were mainly involved in energy, defense/stress, carbohydrate catabolism and protein biosynthesis. Compared with heat- and hypoxia-stress, heat plus hypoxia stress resulted in 102 and 17 differentially abundant proteins, respectively. Conclusions Heat and heat plus hypoxia stresses might modulate stress-triggered ROS homeostasis and MDA by activating heat shock proteins and antioxidant enzymes as well as by inducing of glucosinolates and sulforaphane. Hypoxia stress induced antioxidant enzymes and glucosinolates metabolism to strengthen the defense system in broccoli sprouts. Heat plus hypoxia stress did not have the synergistic effect of heat and hypoxia both in physiological changes and in proteomic analysis; and it was similar to hypoxia stress.