摘要Temperature sensitivity and tolerance play a key role in plant survival and production.Perennial ryegrass(Lolium perenne L.),widely cultivated in cool-season for forage supply and turfgrass,is extremely sus-ceptible to high temperatures,therefore serving as an excellent grass for dissecting the genomic and ge-netic basis of high-temperature adaptation.In this study,expression analysis revealed that LpHsfA2,an important gene associated with high-temperature tolerance in perennial ryegrass,is rapidly and sub-stantially induced under heat stress.Additionally,heat-tolerant varieties consistently display elevated expression levels of LpHsfA2 compared with heat-sensitive ones.Comparative haplotype analysis of the LpHsfA2 promoter indicated an uneven distribution of two haplotypes(HsfA2Hap1 and HsfA2Hap2)across varieties with differing heat toler-ance.Specifically,the HsfA2Hap1 allele is predom-inantly present in heat-tolerant varieties,while the HsfA2Hap2 allele exhibits the opposite pattem.Over-expression of LpHsfA2 confers enhanced thermotol-erance,whereas silencing of LpHsfA2 compromises heat tolerance.Furthermore,LpHsfA2 orchestrates its protective effects by directly binding to the pro-moters of LpHSP18.2 and LpAPX1 to activate their expression,preventing the non-specific misfolding of intracellular protein and the accumulation of reactive oxygen species in cells.Additionally,LpHsfA4 and LpHsfA5 were shown to engage directly with the promoter of LpHsfA2,upregulating its expression as well as the expression of LpHSP18.2 and LpAPX1,thus contributing to enhanced heat tolerance.Mark-edly,LpHsfA2 possesses autoregulatory ability by directly binding to its own promoter to modulate the self-transcription.Based on these findings,we pro-pose a model for modulating the thermotolerance of perennial ryegrass by precisely regulating the ex-pression of LpHsfA2.Collectively,these findings provide a scientific basis for the development of thermotolerant perennial ryegrass cultivars.