Understanding the Physiological and Transcriptional Mechanism of Reproductive Stage Soybean in Response to Heat Stress

Understanding the physiological and molecular processes in response to heat in soybean is important to implement strategies to breed more heat tolerant soybean. In this study, physiological and RNA-Seq analysis were used to dissect the physiological alterations and molecular responses in the leaves of reproductive stage soybean grown at heat condition. Stomata conductance and transpiration rate were increased but photosynthesis and relative water content were reduced in response to heat. Among the three measured antioxidant enzymes, the activity of peroxidase was increased but no changes were detected for catalase and superoxide dismutase. A total of 633 annotated genes were found to be differentially expressed in heat stressed plants in which the expression levels of 417 genes were up-regulated and 216 were down-regulated. Most dramatic responses are related to flowering, oxidative stress, protein and mRNA folding and degradation, protective compounds synthesis, and ethylene biosynthesis and signaling. The diverse pathways identified in this study indicated that soybean employs complicated mechanisms to cope with heat. A few of the identified genes and pathways may be manipulated to improve heat resistance ability in soybean via either genetic engineering or molecular breeding method.