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. Therefore, investigating the molecular mechanisms underlying heat-induced leaf senescence for breeding tall fescue varieties that can resist heat-induced leaf senescence is a major goal. 

Recently, researchers from the Wuhan Botanical Garden, Chinese Academy of Sciences revealed the role of FaNAC047-FaNAC058 module in regulating heat-induced leaf senescence in tall fescue.

The study identifies that FaNAC047, a key gene previously found to show significant up-regulation in response to both 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. 

Subsequently, FaNAC058, another positive regulator of heat-induced leaf senescence, is identified physically interacting with FaNAC047 to enhance its regulatory effects on FaCCGs and FaCAT2. Additionally, FaNAC047 can transcriptionally activate FaNAC058 expression, forming a regulatory module that amplifies the control over the expression of FaCCGs and FaCAT2.

Overall, 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.

Results have been published in the Journal of Integrative Plant Biology entitled“FaNAC047-FaNAC058 module coordinately promotes chlorophyll degradation and reactive oxygen species production during heat-induced leaf senescence in tall fescue”. 

This work was supported by the National Natural Science Foundation of China, the Major Science and Technology Innovation Project of Shandong Province, the National Science Foundation for Distinguished Young Scholars of Hubei Province, International Science and Technology Cooperation Project of Hubei Province, and the Science & Technology Specific Projects in Agricultural High-tech Industrial Demonstration Area of the Yellow River Delta.

The regulatory model of the FaNAC047-FaNAC058 protein complex in mediating heat-induced leaf senescence in tall fescue (Image by WBG)