Antioxidative enzymes, calcium, and ABA signaling pathway are required for the stress tolerance of transgenic wheat plant by the ectopic expression of harpin protein fragment Hpa110–42 under heat stress
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Genetic engineering for heat stress tolerance can promote crop growth and improve yield. One wheat (Triticum aestivum L.) line Y16 (wild type) and two transgenic plants (Y16-3 and Y16-46) that express Hpa110-42, a functional fragment of harpin protein, were used in this study to investigate their possible abiotic stress tolerance under heat stress. Results showed that enhanced thermotolerance was observed in the Y16-3 and Y16-46 lines over the control wheat under stress conditions. However, this increased stress tolerance was significantly abolished by specific inhibitors such as fluridone or sodium tungstate (i.e., arrests abscisic acid (ABA) biosynthesis) and EGTA or La3+ (i.e., arrests Ca2+ signaling pathway) under heat exposure. By contrast, high activities of antioxidant enzymes such as superoxide dismutase, catalase, and ascorbate peroxidase (but not peroxidase) and low levels of oxidative damage (thiobarbituric acid reactive substance (TBARS) and chlorophyll) were detected in transgenic wheat lines compared with the control plant under stress exposure. However, this significant difference diminished after the addition of these specific inhibitors. Furthermore, a slight increase of H2O2 was observed in the transgenic plant, instead of the control, without the addition of chemicals under heat stress. These results suggested that antioxidant enzymes, calcium, and ABA signaling pathways were involved in this Hpa110–42-mediated thermotolerance of transgenic wheat plants under stress exposure. Finally, a hypothetical model based on H2O2 signaling was proposed to illustrate the possible mechanism of this enhanced heat stress tolerance.
KeywordsTriticum aestivum abscisic acid antioxidative enzyme harpin protein high temperature hydrogen peroxide
thiobarbituric acid reactive substance
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