Peanut leaves stretch during the day and close at night, and this nocturnal movement that varies with day and night is a direct reflection of plants coordinating environmental signals and physiological activities. The opening and closing of leaves mainly rely on the changes in turgor pressure of leaf pillow movement cells, while the biological clock provides internal time information for plants to perceive and respond to circadian rhythms. However, how light and biological clock signals are transmitted to genes related to material transport and further involved in leaf movement still requires further analysis.
Recently, the Institute of Modern Agriculture at Peking University and Liu Xiaoqin The team is aBIOTECH Published an article titled “ Photoperiod-entrained circadian regulation of downstream transporter networks mediates nyctinastic leaf movement in peanut ” The research paper. By combining phenotype observation under different light conditions, time series transcriptome analysis, and molecular experiments, the regulatory relationship between clock factors CCA1 and MYB transcription factors and sugar and water transport related genes was identified, and a working model was proposed for the involvement of light signals and biological clocks in leaf movement. This study provides new molecular clues for understanding how plants link day night time information with organ movement.
In order to clarify the effect of light dark cycles on peanut leaf movement, researchers compared the leaf opening and closing states under normal light dark alternation and continuous light conditions. Under the condition of 16 hours of light and 8 hours of darkness every day, the leaves gradually closed after turning off the lights at 21:30 and fully closed by 23:00; After turning on the lights at 5:30 the next day, gradually unfold and resume stretching around 7:00. Under continuous illumination, typical opening and closing movements are suppressed, and the leaves remain largely unfolded, showing only slight up and down movements (Figure 1). This result indicates that under the conditions of this study, the normal light dark cycle plays an important role in maintaining the opening and closing of peanut leaves.
To further track the temporal signals behind leaf movement, researchers sampled 14 time points within a day and conducted gene expression analysis on creeping and upright peanuts. Under normal light dark cycles, clock related genes such as LHY/CCA1 are mainly expressed in the early morning, while some PRR genes reach their peak expression in the afternoon. TOC1 and other genes are active in the evening or night, showing an ordered temporal expression pattern. Under continuous illumination, the expression fluctuations of some clock related genes weaken, but the order of morning and evening expression is still largely preserved, indicating that visible leaf movement is inhibited, but it does not mean that all molecular time signals have disappeared.
On this basis, the author screened candidate genes related to SWEET sugar transporter and PIP aquaporin from those whose expression changes were similar to light signaling and circadian clock related genes. Two types of proteins are respectively related to sugar transport and water transmembrane flow, providing potential entry points for linking time signals with changes in leaf pillow turgor pressure. To investigate whether there is a transcriptional regulatory relationship between candidate genes, the authors further used yeast one hybrid and dual luciferase reporter assays to analyze the interactions between relevant transcription factors and candidate gene promoters, as well as their effects on promoter activity.
Research has found that clock protein CCA1 can recognize EE elements in some SWEET and MYB gene promoters. Electrophoretic Mobility Shift Analysis (EMSA) further showed that after the addition of CCA1, DNA probes containing normal EE sequences formed protein DNA complexes with slower migration; After changing the EE sequence or adding an excessive amount of unlabeled competitive probes, the binding signal weakened (Figure 2). These results support the sequence specific binding of CCA1 to the corresponding promoter fragment, providing molecular evidence for the direct connection of clock factors to downstream regulatory networks.
The dual luciferase reporter assay also showed that CCA1 and some MYB factors can enhance the activity of the promoter of the tested PIP aquaporin gene, further supporting the regulatory relationship between clock factors, transcription factors, and transport related genes. Organizational expression analysis showed that the two PIP genes detected were mainly expressed in the occipital region of compound leaves, while one MYB gene was more enriched in the occipital region of compound leaves and small leaves, and the two SWEET candidate genes were more inclined towards leaf expression. These spatial distribution characteristics suggest that the relevant regulatory networks may involve collaboration between leaves and leaf pillows.
Based on the above results, the author proposed a working model for the involvement of light signals and biological clock in peanut leaf movement (Figure 3): CCA1 and related MYB factors are involved in transcriptional regulation of SWEET sugar transporter and aquaporin genes, which may participate in leaf opening and closing by affecting sugar distribution, water transport, and cell turgor pressure. This model links the upstream time signal with the downstream transportation process; Some transcriptional regulatory relationships have been experimentally supported, but further functional validation is needed to determine how sugar, water transport, and turgor pressure changes actually drive leaf movement.
This study provides interconnected evidence for understanding the diurnal opening and nocturnal closing of peanut leaves from the perspectives of phenotype, temporal expression patterns, and molecular regulatory relationships. Among them, the direct binding of CCA1 to candidate downstream gene promoters, as well as the regulation of promoter activity of aquaporin genes by CCA1 and MYB factors, provide specific research targets for understanding how plant time signals are transmitted to transport related processes. These findings also lay the research foundation for further exploring the relationship between leaf posture regulation, water use, and environmental adaptation.
Title:Photoperiod-entrained circadian regulation of downstream transporter networks mediates nyctinastic leaf movement in peanut
Journal Name: aBIOTECH
DOI: 10.1016/j.abiote.2026.100089
URL: https://scholarcast.cast.org.cn/news/2103013591479988224
aBIOTECH
Photoperiod-entrained circadian regulation of downstream transporter networks mediates nyctinastic leaf movement in peanut
24-Sep-2026