Potential protein biomarkers for heat tolerance in wheat at seedling and ear peep stages

Heat stress is a major threat to global wheat (Triticum aestivum L.) production, adversely affecting crop yields and grain quality. Understanding wheat's heat tolerance mechanisms is crucial for developing resilient cultivars. This study used targeted proteomics to validate heat-induced changes to protein abundances in seedling and flag leaves of heat-tolerant (Vixen-T) and heat-sensitive (HD2329-S) wheat genotypes. Proteomics samples were collected on days 1, 3 and 5 of heat exposure (32/16 °C day/night for 3 hours per day over 5 days) and day 12 post-recovery. Flag leaf gas exchange was studied under heat treatment during ear peep and significant genotype × heat treatment interactions were observed for all traits. Significant protein abundance changes occurred under heat stress for 15 and 14 proteins at the seedling and ear peep stages, respectively. Two key proteins-DM2 domain-containing protein (r = 0.99) and Rubisco activase (r = 0.96)-showed consistent responses across both developmental stages. Redox homeostasis and protein chaperone pathways emerged as major contributors to wheat heat tolerance. These findings highlight critical protein biomarkers that can support breeding efforts to develop heat-tolerant wheat varieties, offering valuable strategies for sustaining wheat productivity under climate change. SIGNIFICANCE: This study identifies and validates novel protein biomarkers associated with heat tolerance in wheat. These proteins were discovered in our previous study in the flag leaves of four genotypes with contrasting heat responses (tolerant: RAJ3765, HD2932; susceptible: HD2329, HD2733) under short-term heat stress at the ear peep stage. These biomarkers were further validated in two genotypes (tolerant: Vixen; susceptible: HD2329) under short-term heat stress at both seedling and ear peep stages. The validated protein isoforms span key biological processes, including photosynthesis, redox regulation, chromatin remodelling, protein folding, and carbohydrate and secondary metabolism. This panel of protein biomarkers offers a novel molecular framework for breeding heat-tolerant wheat, providing a strategic avenue, utilising targeted proteomics, to sustain yield under rising temperatures.