12-Hydroxyjasmonic acid glucoside causes leaf-folding of Samanea saman through ROS accumulation

Foliar nyctinasty, a circadian rhythmic movement in plants, is common among leguminous plants and has been widely studied. Biological studies on nyctinasty have been conducted using Samanea saman as a model plant. It has been shown that the circadian rhythmic potassium flux from/into motor cells triggers cell shrinking/swelling to cause nyctinastic leaf-folding/opening movement in S. saman. Recently, 12-hydroxyjasmonic acid glucoside (JAG) was identified as an endogenous chemical factor causing leaf-folding of S. saman. Additionally, SPORK2 was identified as an outward-rectifying potassium channel that causes leaf-movement in the same plant. However, the molecular mechanism linking JAG and SPORK2 remains elusive. Here, we report that JAG induces leaf-folding through accumulation of reactive oxygen species in the extensor motor cells of S. saman, and this occurs independently of plant hormone signaling. Furthermore, we show that SPORK2 is indispensable for the JAG-triggered shrinkage of the motor cell. This is the first report on JAG, which is believed to be an inactivated/storage derivative of JA, acting as a bioactive metabolite in plant.