Abstract
Salicylic acid (SA) can induce plant resistance to biotic and abiotic stresses through cross talk with other signaling molecules, whereas the interaction between hydrogen peroxide (H2O2) and abscisic acid (ABA) in response to SA signal is far from clear. Here, we focused on the roles and interactions of H2O2 and ABA in SA-induced freezing tolerance in wheat plants. Exogenous SA pretreatment significantly induced freezing tolerance of wheat via maintaining relatively higher dark-adapted maximum photosystem II quantum yield, electron transport rates, less cell membrane damage. Exogenous SA induced the accumulation of endogenous H2O2 and ABA. Endogenous H2O2 accumulation in the apoplast was triggered by both cell wall peroxidase and membrane-linked NADPH oxidase. The pharmacological study indicated that pretreatment with dimethylthiourea (H2O2 scavenger) completely abolished SA-induced freezing tolerance and ABA synthesis, while pretreatment with fluridone (ABA biosynthesis inhibitor) reduced H2O2 accumulation by inhibiting NADPH oxidase encoding genes expression and partially counteracted SA-induced freezing tolerance. These findings demonstrate that endogenous H2O2 and ABA signaling may form a positive feedback loop to mediate SA-induced freezing tolerance in wheat.
Highlights
As one of the major food crops, wheat (Triticum aestivum L.) frequently suffers from freezing stress, especially during jointing stage
To evaluate the alleviation effects of exogenous Salicylic acid (SA) on freezing tolerance, we sprayed the foliage of wheat plants with different concentrations of SA and subjected the plants to freezing stress
The morphology, maximum PS II quantum yield (Fv/Fm), electron transport rates (ETR), MDA content, and Electrolyte leakage (EL) were used for evaluation of freezing tolerance
Summary
As one of the major food crops, wheat (Triticum aestivum L.) frequently suffers from freezing stress, especially during jointing stage. SA has been widely investigated for its crucial role in mediating plant responses to pathogen infection, such as inducing host cell death and systemic acquired resistance (SAR) (Yoshimoto et al, 2009; Kalachova et al, 2013). Pretreated with SA biosynthesis inhibitors significantly down-regulated the expression of cold-responsive genes in cucumber (Dong et al, 2014), decreased the capacity of antioxidant in watermelon (Fei et al, 2016), resulting in a reduction in cold tolerance. These findings demonstrated that endogenous SA plays an important role in plant response to low temperature stress. The mechanism of SA-induced tolerance mediated by signaling molecules in response to freezing stress remain to be investigated
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