Bioorganic studies on the nyctinastic leaf-movement of plants

Nyctinasty, a circadian-regulated leaf movement observed in legumes, has long intrigued scientists. This study identified genus-specific endogenous chemical factors, leaf-closing factors (LCFs) and leaf-opening factors (LOFs), that control this rhythmic behavior. In Samanea saman, a model for nyctinasty, the LCF 12-hydroxyjasmonic acid glucoside induces leaf-folding by selectively targeting extensor motor cells and activating reactive oxygen species (ROS)-dependent K⁺ efflux via the SPORK2 channel. Functional analyses revealed that SPORK2 and the SsSLAH1/SsSLAH3 anion channel complex are key effectors in the regulation of leaf movement. Remarkably, SPORK2 also functions as a temperature-sensitive K⁺ channel, inactivating at low temperatures to mediate rain-induced leaf folding, a phenomenon underlying the nickname "rain tree". These findings provide a chemical entry point to dissect the molecular machinery of nyctinasty and reveal a previously unrecognized role for plant K⁺ channels in temperature sensing.