Elucidating the bottlenech of NADP regeneration in plants

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06695
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 44030:Plant molecular biology and physiology-related
• Research Institution: Central Research Institute of Electric Power Industry
• Principal Investigator: Shin-nosuke Hashida 一般財団法人電力中央研究所, サステナブルシステム研究本部, 上席研究員 (60516649)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: NADP+ / NAD+ / NADP+脱リン酸化 / NAD+リン酸化 / ストロマ / pH / NADK / NADPP

Outline of Final Research Achievements

This study was conducted to elucidate the mechanism of chloroplast NADP+ reduction and to identify the NADP+ regeneration pathway. Investigation of enzymatic properties and metabolic analysis involved in chloroplast NADP+ decrease revealed that NADP+ is converted to NAD+ by NADP+ dephosphorylation (NADPP) after shading. By characterizing the activities of both enzymes involved in the increase and decrease of NADP+, we have discovered an adjustment of chloroplastic NADP+ levels by phosphorylation and dephosphorylation in response to stromal pH conditions. Furthermore, the amino acid sequences of the proteins in the purified active fractions were determined, and the related proteins were identified as novel NADPP enzymes, together with their Arabidopsis mutants.

Free Research Field

植物生理学

Academic Significance and Societal Importance of the Research Achievements

光合成の最終電子受容体であるNADP+は光条件によってその量が変動するが、そのメカニズムは不明であり、NADP+とNADPHの総量であるNADPプールサイズの増加と減少の両面からの研究が必要であった。本研究では初めてNADPプールサイズ減少に関わる経路の同定に成功し、光依存性のpH変化に応答してNADPプールサイズが制御されるメカニズムを新たに提唱した。光エネルギーの入力強度に応じて出力が調節される仕組みの一旦が明らかになったことで、NADPプールサイズの調節によって光合成エネルギー収支を最適化できる事が示唆され、最適化に関わる植物育種戦略としても有望である可能性が見出された。