相分離による細胞膜の「濡れ」が植物の種子形成に重要であることを発見

相分離による細胞膜の「濡れ」が植物の種子形成に重要であることを発見

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細胞制御工学研究センター Alexander I. May特任助教の国際共著論文

”Wetting of phase-separated droplets on plant vacuole membranes leads to a competition between tonoplast budding and nanotube formation”

が、Proceedings of the National Academy of Sciences  にオンライン掲載されました。(DOI:10.1073/pnas.2024109118

種子形成の過程において、液液相分離が貯蔵タンパク質の相分離と液胞膜の形態変化に貢献していることを明らかにしました。将来はこの研究が作物収量の上昇につながると期待されます。

詳しくはこちら 

 

<Abstract>

Seeds of dicotyledonous plants store proteins in dedicated membrane-bounded organelles called protein storage vacuoles (PSVs). Formed during seed development through morphological and functional reconfiguration of lytic vacuoles in embryos [M. Feeney et al.Plant Physiol. 177, 241–254 (2018)], PSVs undergo division during the later stages of seed maturation. Here, we study the biophysical mechanism of PSV morphogenesis in vivo, discovering that micrometer-sized liquid droplets containing storage proteins form within the vacuolar lumen through phase separation and wet the tonoplast (vacuolar membrane). We identify distinct tonoplast shapes that arise in response to membrane wetting by droplets and derive a simple theoretical model that conceptualizes these geometries. Conditions of low membrane spontaneous curvature and moderate contact angle (i.e., wettability) favor droplet-induced membrane budding, thereby likely serving to generate multiple, physically separated PSVs in seeds. In contrast, high membrane spontaneous curvature and strong wettability promote an intricate and previously unreported membrane nanotube network that forms at the droplet interface, allowing molecule exchange between droplets and the vacuolar interior. Furthermore, our model predicts that with decreasing wettability, this nanotube structure transitions to a regime with bud and nanotube coexistence, which we confirmed in vitro. As such, we identify intracellular wetting [J. Agudo-Canalejo et al., Nature 591, 142–146 (2021)] as the mechanism underlying PSV morphogenesis and provide evidence suggesting that interconvertible membrane wetting morphologies play a role in the organization of liquid phases in cells.