日本分子生物学会

May 2023
オジギソウにお辞儀させるカルシウムイオン
Stimulated to the leaves, the sensitive plant (Mimosa pudica) folds its leaves one after another. To elucidate the mechanism, a transgenic M. pudica was produced so that the cytosolic Ca²⁺ concentration can be observed as fluorescence by GCaMP6f (Hagihara et al. (2022) Nat. Commun. 13: 6412, DOI: 10.1038/s41467-022-34106-x). When a leaflet was wounded, the fluorescent signal caused by Ca²⁺ propagated through the veins to the tertiary pulvinus at the base of the leaflet, immediately followed by a movement of the pair of leaflets to fold inwards. And, Ca²⁺ signals were propagated to the adjacent tertiary pulvini sequentially, and the leaflets were also folded successively. At this time, electrical signals were transmitted simultaneously with the fluorescent signals. The authors also observed that the immotile M. pudica was more susceptible to feeding damage by insects, suggesting that the movement above protects the plant from feeding damage.
葉へ刺激を受けたオジギソウ（Mimosa pudica）は次々に葉を折りたたむ。その機構を明らかにするため、細胞質のCa²⁺濃度をGCaMP6fにより蛍光として観察できる遺伝子組換えオジギソウが作製された（Hagihara et al. (2022) Nat. Commun. 13: 6412, DOI: 10.1038/s41467-022-34106-x）。小葉を傷つけると、葉脈を通じてその小葉の付け根の小葉枕へとCa²⁺による蛍光シグナルが伝播し、直後に小葉の対を折りたたむ運動が起こった。そして隣接する小葉枕へも次々とCa²⁺シグナルが伝播し、小葉も続々と折りたたまれていった。さらに、蛍光シグナルと同時に電気シグナルも伝わっていた。著者らは、動かないオジギソウは昆虫に食べられやすいことも観察しており、この動きは植物を食害から守っていると考察している。