Perennial ryegrass (Lolium perenne L.), widely cultivated in cool-season for forage supply and turfgrass, is extremely susceptible to high temperature. A recent study has discovered a pivotal stress-responsive gene, combating heat stress in perennial ryegrass.

The discovery holds significant potential for advancing the understanding of genetic augmentation and breeding of heat‐tolerant perennial ryegrass cultivars.

This pivotal stress-responsive gene, named LpHsfA2, belongs to the heat shock factors (Hsf) family. Researchers from Wuhan Botanical Garden (WBG) of the Chinese Academy of Sciences reveals that LpHsfA2, directly binds to the promoter of LpHSP18.2 (heat shock protein gene) and LpAPX1 (ascorbate peroxidase gene) to activate their expression through the attenuated reactive oxygen species accumulation and misfolding of proteins, and therefore enhances plant thermotolerance.

Moreover, heat stress-responsive genes, LpHsfA4 and LpHsfA5, together with LpHsfA2, coordinate a molecular cascade to amplifying the expression of pivotal genes, such as LpHSP18.2 and LpAPX1, to enhance the heat tolerance of plants.

Through the comparison of two haplotypes of HsfA2 promotors, named HsfA2^Hap1 and HsfA2^Hap2, the researchers revealed an uneven distribution across different heat-tolerant ryegrass varieties, with HsfA2^Hap1 allele being predominant.

The research team elucidated the synergistic mechanism influencing the heat tolerance of perennial ryegrass. "This finding will greatly enlighten the breeding of heat-tolerant perennial ryegrass cultivars," said Prof. CHEN Liang from WBG, a leading researcher in the study.

Results of the study were published in the Journal of Integrative Plant Biology entitled “TheLpHsfA2-molecular module confers thermotolerance via fine tuning of its transcription in perennial ryegrass (Lolium perenneL.)”.

This work was supported by National Key R&D Program of China, the National Natural Science Foundation of China, the Science & Technology Specific Projects in Agricultural High-tech Industrial Demonstration Area of the Yellow River Delta, the Strategic Priority Research Program of Chinese Academy of Sciences, and the Major Science and Technology Innovation Project of Shandong Province.