2026-09-25 神戸大学
神戸大学・京都大学の研究グループは、植物が寒冷条件下で光合成装置を損傷する「低温PSI光阻害」について、新たな分子機構を解明した。イネとキュウリを用いた実験から、葉緑体のNDH複合体が光化学系I（PSI）に蓄積する余剰電子を逃がす「安全弁」として機能し、低温下でPSIを保護することを明らかにした。NDHを欠損したイネではPSI損傷が進行した一方、別経路で電子を逃がすFLVタンパク質を導入すると光阻害がほぼ抑制された。また、キュウリでは低温と光への曝露後1時間以内にNDH複合体が崩壊し、その機能低下が活性酸素の発生とPSI光阻害につながることも示した。低温ストレスに強い作物の探索・開発につながる基礎的知見である。
図1 寒さで壊れる光合成の安全弁（竹内航、神戸大学大学院農学研究科 植物栄養学研究室）。
＜関連情報＞
- https://www.kobe-u.ac.jp/ja/news/article/20260925-68295/
- https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.71594
PSI–NDH超複合体は低温ストレスによるPSI光阻害を抑制する The PSI-NDH supercomplex prevents chilling-induced PSI photoinhibition
Ko Takeuchi, Shintaro Harimoto, Kentaro Ifuku
New Phytologist Published: 20 September 2026
DOI:https://doi.org/10.1111/nph.71594
Summary
- Chilling stress induces photosystem I (PSI) photoinhibition in cucumber (Cucumis sativus L.). This process is associated with insufficient activity of the chloroplast NADH dehydrogenase-like complex (NDH). However, whether the importance of NDH can be generalized to other species and how NDH function is impaired remain unclear.
- We first examined whether NDH is essential for PSI protection under chilling stress using an NDH-deficient rice (Oryza sativa L.) mutant.
- The NDH-deficient rice exhibited pronounced PSI photoinhibition under chilling stress. By contrast, rice expressing flavodiiron protein (FLV), which functions as an alternative electron acceptor downstream of PSI, did not exhibit PSI photoinhibition under chilling stress, demonstrating that the electron sink capacity of NDH is important for PSI protection under chilling stress. Furthermore, in cucumber, chilling stress destabilizes the PSI-NDH supercomplex, leading to NDH monomerization and a consequent loss of NDH activity. This NDH monomerization is likely attributable to chilling-induced damage to the light-harvesting complex Lhca, which mediates the association between PSI and NDH.
- Together, these results indicate that NDH protects PSI from photoinhibition under chilling stress, and that chilling-induced destabilization of the PSI-NDH supercomplex represents a key molecular mechanism underlying PSI over-reduction and photoinhibition in cucumber.
