By 2100, global temperatures are projected to rise by 1.8 to 4.0°C. In major wheat-growing regions, a 2°C increase during the growing season can accelerate leaf senescence and cut grain yields by up to 50%. Soybeans suffer similar losses — nearly 30% — as heat triggers premature aging. Yet the molecular details of how plants sense and execute heat-induced leaf death have remained largely obscure. Chlorophyll loss is the hallmark of this process, but the upstream regulators that flip the switch have been elusive. Given these challenges, there is an urgent need for in-depth research into the regulatory networks that control heat-triggered chlorophyll breakdown and leaf senescence.
A team from the College of Horticulture and Landscape Architecture at Yangzhou University, China, reports (DOI: 10.1093/hr/uhag135) these findings on 13 April 2026 in Horticulture Research, a peer-reviewed journal published by Oxford University Press on behalf of Nanjing Agricultural University. The researchers combined gene silencing, overexpression, protein interaction assays, and promoter analysis to dissect the PlMYB3RL–PlSGRL pathway in herbaceous peony under controlled high-temperature stress (42/37°C day/night).
The study began with PlSGRL, a protein belonging to the Stay-green family — known regulators of chlorophyll catabolism. Under heat stress, PlSGRL expression surged more than fourfold by day six. When the team silenced PlSGRL using virus-induced gene silencing, the plants kept their leaves greener longer: chlorophyll degradation rates dropped from 14% to just 8–9%, while photosystem II efficiency remained higher and oxidative damage — measured by malondialdehyde, electrical conductivity, and reactive oxygen species — was significantly reduced. Conversely, overexpressing PlSGRL in tobacco accelerated yellowing, with chlorophyll loss reaching 58% compared to 37% in wild-type plants.
The researchers then traced PlSGRL’s activation to PlMYB3RL, an atypical MYB transcription factor that binds directly to the PlSGRL promoter. Heat stress boosted PlMYB3RL expression in parallel with PlSGRL. Silencing PlMYB3RL produced the same protective effect as silencing PlSGRL — delayed senescence, higher chlorophyll retention, and less oxidative damage.
Most strikingly, PlMYB3RL does not work alone. Yeast two-hybrid, luciferase complementation, and bimolecular fluorescence complementation assays all confirmed that PlMYB3RL forms homodimers through self-interaction. And this dimerization matters: when the team increased PlMYB3RL levels stepwise, PlSGRL promoter activity rose in a dose-dependent manner. The more PlMYB3RL present, the more homodimers form, and the stronger the activation of chlorophyll degradation.
“What surprised us most was the dose-dependent nature of this regulation,” the authors said. “PlMYB3RL doesn’t just turn on PlSGRL — it dials the response up or down based on how much of the protein is available. Under mild heat, only a few homodimers form and senescence stays in check. But when heat stress intensifies, more PlMYB3RL accumulates, more homodimers assemble, and the plant commits to leaf aging. It’s a finely tuned rheostat, not an on-off switch. For a perennial like peony, that makes perfect sense — you wouldn’t want to sacrifice leaves prematurely unless the stress truly warrants it.”
This discovery opens new avenues for crop improvement. By targeting the PlMYB3RL–PlSGRL module, breeders could develop varieties that delay heat-induced senescence without compromising normal development — a strategy that may prove especially valuable for perennial ornamentals and medicinal plants where leaf longevity directly impacts belowground storage and next-season flowering. Moreover, because Stay-green proteins and MYB transcription factors are conserved across plants, similar regulatory mechanisms likely operate in staple crops like wheat, rice, and soybean. The findings provide both theoretical foundations and practical gene targets for enhancing heat tolerance in an era of accelerating climate change.
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References
DOI
10.1093/hr/uhag135
Original Source URL
https://doi.org/10.1093/hr/uhag135
Funding information
This work was supported by the Jiangsu Province Seed Industry Revitalization Unveiled Project (JBGS(2021)020), Forestry Science, Technology Innovation and Promotion Project of Jiangsu Province (LYKJ[2021]01), National Forest and Grass Science and Technology Innovation and Development Research Project (2023132012).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.