Drought is the major abiotic stress that decreases plant water status, inhibits photosynthesis, induces oxidative stress, restricts growth and finally lead to the reduction of wheat yield. It has been proven that drought priming during vegetative growth stage could enhance tolerance to drought stress at grain filling in wheat. However, whether drought priming imposed at grain filling in parental plants could induce drought tolerance in the offspring is not known. In this study, drought priming was successively applied in the first, the second and the third generation of wheat to obtain the plants of T1 (primed for one generation), T2 (primed for two generations), T3 (primed for three generations). The differently primed plants were then subjected to drought stress during grain filling in the fourth generation. Under drought stress, the parentally primed (T1D, T2D, T3D) plants, disregarding the number of generations, showed higher grain yield, leaf photosynthetic rate and antioxidant capacity as well as lower ${\mathrm{O}}_{\mathrm{2}}^{\mathrm{•}\mathrm{-}}$ release rate and contents of H₂O₂ and MDA than the non-primed (T0D) plants, suggesting that drought priming induced the transgenerational stress tolerance to drought stress. Moreover, the parentally primed plants showed higher leaf water status, which may result from the higher contents of proline and glycine betaine, and higher activities of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and betaine aldehyde dehydrogenase (BADH), compared with the non-primed plants under drought stress. In addition, there was no significant difference among three generations under drought, and the drought priming in parental generations did not affect the grain yield of the offspring plants under control condition. Collectively, the enhanced accumulation of proline and glycine betaine in the parentally primed plants could have played critical roles in parental priming induced tolerance to drought stress. This research provided a potential approach to improve drought tolerance of offspring plants by priming parental plants.

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.

Nitrogen is one basic element of amino acids and grain protein in wheat. In field experiments, wheat plants were subjected to different timing of nitrogen topdressing treatments: at the stages of emergence of the top fifth leaf (TL5), top third leaf (TL3) and top first leaf (TL1) to test the regulatory effects of nitrogen topdressing timing on grain protein quality. The underlying mechanisms were elucidated by clarifying the relationship between proteolysis in vegetative organs and accumulation of amino acids in the endosperm cavity, conversion of amino acids, and storage protein synthesis in endosperm of wheat grain. Delayed nitrogen topdressing up-regulated gene expression related to nitrogen metabolism and protease synthesis in the flag leaf, followed by more free amino acids being transported to both the cavity and the endosperm from 7 days after anthesis (DAA) to 13 DAA in TL1. TL1 enhanced the conversion between free amino acids in endosperm and upregulated the expression of genes encoding high molecular weight (HMW) and low molecular weight (LMW) subunits and protein disulfide isomerases-like (PDIL) proteins, indicating that the synthesis and folding of glutenin were enhanched by delayed nitrogen topdressing. As a consequense, the content of glutenin macropolymers (GMP) and glutenin increased with delaying nitrogen topdressing. The results highlight the relationship between nitrogen remobilization and final grain protein production and suggest that the nitrogen remobilization processes could be a potential target for improving the quality of wheat grain. Additionally, specific gene expression related to nitrogen topdressing was identified, which conferred more detailed insights into underlying mechanism on the modification protein quality.

Mechanical wounding can cause morphological and developmental changes in plants, which may affect the responses to abiotic stresses. However, the mechano-stimulation triggered regulation network remains elusive. Here, the mechano-stimulation was applied at two different times during the growth period of wheat before exposing the plants to cold stress (5.6 °C lower temperature than the ambient temperature, viz., 5.0 °C) at the jointing stage. Results showed that mechano-stimulation at the Zadoks growth stage 26 activated the antioxidant system, and substantially, maintained the homeostasis of reactive oxygen species. In turn, the stimulation improved the electron transport and photosynthetic rate of wheat plants exposed to cold stress at the jointing stage. Proteomic and transcriptional analyses revealed that the oxidative stress defense, ATP synthesis, and photosynthesis-related proteins and genes were similarly modulated by mechano-stimulation and the cold stress. It was concluded that mechano-stimulated modifications of the chloroplast antioxidant system and proteome changes are related to cold tolerance in wheat. The findings might provide deeper insights into roles of reactive oxygen species in mechano-stimulated cold tolerance of photosynthetic apparatus, and be helpful to explore novel approaches to mitigate the impacts of low temperature occurring at critical developmental stages.