Beyond heat stress: the heat shock factor family orchestrates multifaceted abiotic stress responses in perennial ryegrass

Perennial ryegrass (Lolium perenne L.) is a vital cool-season forage and turfgrass species whose productivity is increasingly threatened by climate change-induced abiotic stresses. The Heat Shock Factor (HSF) family are key transcription factors known to mediate plant stress responses, yet their functional landscape in perennial ryegrass remains poorly characterized, especially beyond heat stress. In this study, genome-wide identification revealed 26 LpHSF genes in perennial ryegrass, harboring abundant stress-responsive cis-elements. Moving beyond a singular focus on thermotolerance, the study established a comprehensive spatio-temporal expression atlas of LpHSFs. The findings demonstrate that specific LpHSFs, particularly members of the LpHSFA2 subclass, LpHSFA3, LpHSFC1.3, and LpHSFC1.4, are significantly upregulated under a broad spectrum of abiotic stresses, including salinity, alkalinity, and heavy metal exposure, indicating their roles as broad-spectrum stress regulators. Furthermore, this study uncovered distinct tissue-specific expression patterns, with Class A genes predominantly expressed in leaves and Classes B and C in roots and crowns, implicating their roles in organ development and stress adaptation. Notably, the expression of numerous LpHSFs during leaf senescence and their induction by hormones such as ABA and MeJA further highlights their functional diversity. This study provides the first integrated expression atlas of the LpHSF family, revealing their versatile roles in coordinating responses to diverse environmental and developmental signals. This work lays a crucial foundation for future functional studies and positions LpHSFs as prime targets for molecular breeding aimed at enhancing multi-stress resilience in perennial ryegrass.