Photoperiod-entrained circadian regulation of downstream transporter networks mediates nyctinastic leaf movement in peanut.

The nightly closure or downward folding of leaves, a process known as sleep movement or nyctinasty, is a widespread phenomenon in legumes that helps optimize photosynthesis, conserve water, and reduce pathogen susceptibility. Although the physical process has been well characterized, the molecular regulation of nyctinasty remains poorly understood. Here, we combined temporal transcriptome profiling, photoperiod manipulation, and tissue-specific gene expression analysis to dissect the regulatory network in peanut (Arachis hypogaea) during nyctinastic leaf movement. Under normal light/dark cycles, leaves displayed distinct nyctinastic behavior, which was suppressed under continuous light, underscoring the importance of photoperiod for this process. Transcriptome analysis identified conserved light- and circadian-related genes exhibiting rhythmic expression patterns. Key candidates included light-responsive SWEET and aquaporin genes with distinct tissue-specific expression patterns, along with a pulvinus-enriched MYB transcription factor gene. Promoter-binding and reporter assays supported transcriptional links between circadian/light-signaling components and these candidate downstream genes. Together, these findings support a working model in which photoreceptors and the circadian clock coordinate the expression of transporter and regulatory genes, which may contribute to nyctinastic leaf movement in peanut. These findings provide a molecular framework for future functional investigations of nyctinasty in legumes.