Stage-dependent heat priming mitigates reproductive heat stress via proteomic regulation in Oryza sativa L.

This study investigates the effects of heat-priming during the tillering and booting stages of rice and associated changes in proteome expression. Heat stress, particularly during reproductive stages, significantly impacts rice yields, with temperature rises predicted to reduce crop production globally. Plants use priming to mitigate abiotic stress, whereby pre-exposure to moderate stress enhances their responses to subsequent stress. This process, known as 'stress memory' or heat-priming, enables plants to acquire thermotolerance, allowing them to mount a more effective defense against future extreme heat. However, studies on stress memory have not been sufficiently conducted. We identified several physiological and proteomic alterations in heat-primed N22 at the tillering or booting stages under heat stress applied at the flowering stage. The heat priming increased shoot length, tiller number, dry weight, and leaf area regardless of the growth period. Moreover, the fertility rate, reduced by heat stress, was increased by heat priming. Through LC/MS-MS analysis, 334 common proteins were identified. Through Gene Ontology and KEGG pathway analysis, it was found that translation, structural constitution of ribosome, cytoplasm, and metabolic pathway were most involved in heat stress in heat-primed rice. The up-expression of these proteins may suggest alleviation of heat priming through more energy generation, restoration of misfolded proteins, and effective ROS regulation. Through mRNA validation, it was discovered that proteins are regulated by not only their transcript level but also post-transcriptional modification. Our study provided a molecular perspective on the complex mechanism of heat priming that can alleviate heat stress.