AUTHOR=Li Zhan , Xu Jungui , Gao Yue , Wang Chun , Guo Genyuan , Luo Ying , Huang Yutao , Hu Weimin , Sheteiwy Mohamed S. , Guan Yajing , Hu Jin 

TITLE=The Synergistic Priming Effect of Exogenous Salicylic Acid and H2O2 on Chilling Tolerance Enhancement during Maize (Zea mays L.) Seed Germination

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01153

DOI=10.3389/fpls.2017.01153

ISSN=1664-462X

ABSTRACT=<p>Chilling stress is an important constraint for maize seedling establishment in the field. To examine the role of salicylic acid (SA) and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) in response to chilling stress, we investigated the effects of seed priming with SA, H<sub>2</sub>O<sub>2</sub>, and SA+H<sub>2</sub>O<sub>2</sub> combination on maize resistance under chilling stress (13°C). Priming with SA, H<sub>2</sub>O<sub>2</sub>, and especially SA+H<sub>2</sub>O<sub>2</sub> shortened seed germination time and enhanced seed vigor and seedling growth as compared with hydropriming and non-priming treatments under low temperature. Meanwhile, SA+H<sub>2</sub>O<sub>2</sub> priming notably increased the endogenous H<sub>2</sub>O<sub>2</sub> and SA content, antioxidant enzymes activities and their corresponding genes <italic>ZmPAL, ZmSOD4, ZmAPX2, ZmCAT2</italic>, and <italic>ZmGR</italic> expression levels. The α-amylase activity was enhanced to mobilize starch to supply metabolites such as soluble sugar and energy for seed germination under chilling stress. In addition, the SA+H<sub>2</sub>O<sub>2</sub> combination positively up-regulated expressions of gibberellic acid (GA) biosynthesis genes <italic>ZmGA20ox1</italic> and <italic>ZmGA3ox2</italic>, and down-regulated GA catabolism gene <italic>ZmGA2ox1</italic> expression; while it promoted GA signaling transduction genes expressions of <italic>ZmGID1</italic> and <italic>ZmGID2</italic> and decreased the level of seed germination inhibitor gene <italic>ZmRGL2</italic>. The abscisic acid (ABA) catabolism gene <italic>ZmCYP707A2</italic> and the expressions of <italic>ZmCPK11</italic> and <italic>ZmSnRK2.1</italic> encoding response receptors in ABA signaling pathway were all up-regulated. These results strongly suggested that priming with SA and H<sub>2</sub>O<sub>2</sub> synergistically promoted hormones metabolism and signal transduction, and enhanced energy supply and antioxidant enzymes activities under chilling stress, which were closely relevant with chilling injury alleviation and chilling-tolerance improvement in maize seed.</p><p><bold>Highlights:</bold>Seed germination and seedling growth were significantly improved under chilling stress by priming with SA+H<sub>2</sub>O<sub>2</sub> combination, which was closely relevant with the change of reactive oxygen species, metabolites and energy supply, hormones metabolism and regulation.</p>