Physiological and proteomic analyses reveal the protective roles of exogenous hydrogen peroxide in alleviating drought stress in soybean plants

Drought stress is one of the major constraints for soybean growth and productivity worldwide. The study was aimed to investigate drought-induced physiological and proteomic changes in soybeans, as well as drought relief using exogenous hydrogen peroxide (H 2 O 2 ). In drought-stressed plants, H 2 O 2 spray on the leaf surface improved relative water content (RWC), net photosynthetic rate (Pn), and stomatal conductance (Gs). Furthermore, exogenous H 2 O 2 reduced drought stress-induced endogenous MDA and H 2 O 2 levels, as well as increased the key antioxidant enzymes (SOD,CAT, APX and POD) activity and proline content in H 2 O 2 -treated soybean plants. These findings showed that H 2 O 2 treatment significantly reduced drought stress by increasing the antioxidative defense system and osmotic adjustment. Furthermore, using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, a total of 27 differently expressed proteins was identified, wherein 23 were up-regulated and 4 were down-regulated under drought condition. These proteins were found to be involved in photosynthesis, energy and metabolism, plant defense and antioxidant, signaling and transport, and transcription regulation in response to H 2 O 2 treatment in soybean under drought stress, according to in silico interactome analysis. These findings add to our understanding of H 2 O 2 -mediated drought stress alleviation, as well as the physiological and molecular responses of soybean to drought stress.