The impacts of drought stress on crop yield and quality are substantial. Drought priming during the early growth stage of plants has been shown to improve tolerance to drought stress during the reproductive stage, although its effects on grain quality remain elusive. This study investigated the influence of drought priming on starch and protein levels in grains under drought stress during grain filling. Our results revealed that drought stress leads to a reduction in the contents of starch and its constituents, while simultaneously increasing glutenin macropolymers and protein fractions. Notably, drought primed plants under drought stress (PD) exhibited mitigated declines in the contents of starch and its components, leading to improvements in starch swelling power and pasting properties. In addition, PD resulted in a slight increase in the protein fractions, limiting the overall rise in total protein content compared to drought stress alone. The results of our study underscore the efficacy of drought priming as a strategy to counteract the negative effects of drought stress on grain quality, particularly by minimizing starch losses and restraining protein content elevation.

Frequent drought events severely restrict global crop productivity, especially those occurring in the reproductive stages. Moderate drought priming during the earlier growth stages is a promising strategy for allowing plants to resist recurrent severe drought stress. However, the underlying mechanisms remain unclear. Here, we subjected wheat plants to drought priming during the vegetative growth stage and to severe drought stress at 10 days after anthesis. We then collected leaf samples at the ends of the drought priming and recovery periods, and at the end of drought stress for transcriptome sequencing in combination with phenotypic and physiological analyses. The drought-primed wheat plants maintained a lower plant temperature, with higher stomatal openness and photosynthesis, thereby resulting in much lower 1,000-grain weight and grain yield losses under the later drought stress than the non-primed plants. Interestingly, 416 genes, including 27 transcription factors (e.g., MYB, NAC, HSF), seemed to be closely related to the improved drought tolerance as indicated by the dynamic transcriptome analysis. Moreover, the candidate genes showed six temporal expression patterns and were significantly enriched in several stress response related pathways, such as plant hormone signal transduction, starch and sucrose metabolism, arginine and proline metabolism, inositol phosphate metabolism, and wax synthesis. These findings provide new insights into the physiological and molecular mechanisms of the long-term effects of early drought priming that can effectively improve drought tolerance in wheat, and may provide potential approaches for addressing the challenges of increasing abiotic stresses and securing food safety under global warming scenarios.