Tall fescue (Festuca arundinacea) is a widely cultivated cool-season turfgrass and forage species worldwide, thriving best between 15°C and 25°C. Temperature above 35°C can cause irreversible damage, including premature leaf senescence. Heat-induced leaf senescence reduces both the forage yield and turf quality. As global temperatures rise, this problem will get worse.
To investigate the molecular mechanisms underlying heat-induced leaf senescence for breeding tall fescue varieties that can resist heat-induced leaf senescence, researchers from the Wuhan Botanical Garden (WBG) of the Chinese Academy of Sciences conducted studies and discovered the role of the FaNAC047-FaNAC058 module in regulating heat-induced leaf senescence in tall fescue. Their findings were published in the Journal of Integrative Plant Biology.
The study identifies that FaNAC047, a key gene previously found to show significant up-regulation in response to long-term heat stress and natural leaf senescence, acts as a positive regulator of heat-induced leaf senescence in tall fescue. FaNAC047 is a bifunctional transcription factor with both transcriptional activation and repression domains: it directly activates the expression of FaCCGs (chlorophyll catabolic genes) while simultaneously repressing Catalases 2 (FaCAT2) expression, thereby coordinating chlorophyll degradation and reactive oxygen species accumulation during heat-induced leaf senescence.
Additionally, FaNAC058, another positive regulator of heat-induced leaf senescence, is identified as physically interacting with FaNAC047 to enhance its regulatory effects on FaCCGs and FaCAT2. The study reveals that FaNAC047 can transcriptionally activate FaNAC058 expression, thus forming a regulatory module that enhances the control over the expression of FaCCGs and FaCAT2.
This study uncovers a molecular mechanism by which the FaNAC047-FaNAC058 module accelerates heat-induced leaf senescence in tall fescue through coordinated regulation of chlorophyll catabolism and reactive oxygen species homeostasis. The findings provide valuable clues for the genetic modification of tall fescue in response to heat-induced leaf senescence and facilitate the breeding of heat-resistant plants.
This work was financially supported by the National Natural Science Foundation of China and the Major Science and Technology Innovation Project of Shandong Province, among other sources.
The regulatory model of the FaNAC047-FaNAC058 protein complex in mediating heat-induced leaf senescence in tall fescue (Image by WBG)
