New research in perennial ryegrass identifies LpCbDR1, a drought-responsive transcription factor, as a molecular switch that helps the plant decide when old leaves should yellow and when stress defenses should rise. The study shows that LpCbDR1 activates the chlorophyll b reductase gene LpNOL , triggering chlorophyll breakdown and leaf senescence under prolonged drought. At the same time, it directly stimulates the stress-related genes LpPLA7 and LpERF1B , helping plants survive water shortage. By separating the visible “stay-green” trait from the deeper machinery of drought resilience, the work offers a more precise route for breeding turf and forage grasses that remain productive as dry periods intensify and irrigation becomes less reliable.
Perennial ryegrass ( Lolium perenne L.) is widely grown for turf, sports fields, and forage, where a dense green canopy is central to both appearance and yield. Yet the species is highly sensitive to drought, and prolonged water deficit often causes chlorophyll (Chl) loss, premature leaf senescence, and declining grass quality. Senescence is not simply damage: it can help plants conserve water and move nutrients from aging leaves. But if the process begins too early or runs too strongly, growth and recovery suffer. Based on these challenges, there is a need to investigate how perennial ryegrass coordinates leaf yellowing, senescence timing, and drought tolerance at the molecular level.
Researchers from the College of Agro-grassland Science, Nanjing Agricultural University, published (DOI: 10.1093/hr/uhag093) their findings in Horticulture Research on March 9, 2026. Focusing on perennial ryegrass ( Lolium perenne L.), the study investigated how the NAM, ATAF1/2, and CUC2 (NAC) transcription factor LpCbDR1 coordinates drought-induced leaf senescence and drought tolerance. The team showed that LpCbDR1 directly activates the chlorophyll b reductase gene LpNOL to promote chlorophyll breakdown, while also activating stress-related genes such as LpPLA7 and LpERF1B to enhance osmotic stress tolerance in this important turf and forage grass.
The team first found that suppressing LpNOL delayed drought-induced leaf yellowing, allowing leaves to retain higher chlorophyll (Chl) content. To uncover how LpNOL is controlled, they screened its promoter using yeast one-hybrid (Y1H) assays and identified LpCbDR1 as an upstream activator. Subcellular localization showed that LpCbDR1 functions in the nucleus, while electrophoretic mobility shift assay (EMSA) and Cleavage Under Targets and Tagmentation (CUT&Tag)-quantitative polymerase chain reaction (qPCR) confirmed its direct binding to the LpNOL promoter. Functional tests then revealed a clear split: induced overexpression of LpCbDR1 accelerated senescence in older leaves, while RNA interference (RNAi) suppression produced a stay-green phenotype. Under drought, however, LpCbDR1-overexpressing plants had lower electrolyte leakage (EL) and higher survival than wild-type (WT) plants, whereas RNAi lines were more drought-sensitive. Integrated RNA sequencing (RNA-seq) and CUT&Tag analyses detected 3,130 differentially expressed genes and 157 overlapping candidate targets, with enrichment in hormone-mediated and ethylene-activated signaling. Among them, LpPLA7 and LpERF1B emerged as direct downstream genes. Their promoters were validated as LpCbDR1 binding sites, and both genes responded to drought-related osmotic stress, although with different expression patterns across tissues. Overexpressing either gene improved osmotic stress tolerance, including in the LpCbDR1 -RNAi background, placing them downstream of LpCbDR1 in the drought-response pathway.
The authors said the findings reveal why drought-stressed grasses do not simply stay green or turn yellow, but instead manage a regulated trade-off. They said LpCbDR1 appears to connect two branches of plant response: one branch activates LpNOL to initiate Chl degradation and leaf senescence, while another activates LpPLA7 and LpERF1B to strengthen stress tolerance. This dual role, they said, gives researchers a clearer target for adjusting the timing and strength of senescence rather than turning the process fully on or off, a key step for improving grasses without sacrificing recovery.
Application and implications: The findings could inform molecular breeding and gene-editing strategies for turfgrass and forage improvement, especially as heat and drought make canopy maintenance more difficult. A stay-green plant may look healthier during drought, but appearance alone does not guarantee survival. The LpCbDR1-centered network points to a more practical strategy: modify the LpCbDR1 – LpNOL branch to delay unwanted yellowing, while strengthening drought-defense outputs through genes such as LpPLA7 and LpERF1B . Future studies in stable transgenic or edited ryegrass lines will be important for testing whether this balance can improve canopy quality, regrowth, field persistence, and performance under recurring drought.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhag093
Funding information
This research was supported by the National Natural Science Foundation of China, 32441041, 32271755, 32371778.
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.
Horticulture Research
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LpCbDR1 regulates leaf senescence and drought tolerance by activating the chlorophyll b reductase gene and stress-related genes in perennial ryegrass
9-Mar-2026
The authors declare that they have no competing interests.