Characterizing membrane anchoring of leaf‐form ferredoxin‐NADP+ oxidoreductase in rice. (3rd October 2022)

• Record Type: Journal Article
• Authors: Da, Xiaowen; Guo, Jiangfan; Yan, Peng; Yang, Chao; Zhao, Hongfei; Li, Wei; Kong, Yuzhu; Jiang, Ruirui; He, Yi; Xu, Jiming; Xu, Ouyuan; Mao, Chuanzao; Mo, Xiaorong
• Is Part Of: Plant, cell and environment. Volume 46:Number 4(2023)
• Page Start: 1195
• Page End: 1206
• Publication Date: 2022-10-03
• Subjects: anchors -- LFNRs -- TIC62 -- TROL1; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.14446
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: Leaf‐form ferredoxin‐NADP + oxidoreductases (LFNRs) function in the last step of the photosynthetic electron transport chain, exist as soluble proteins in the chloroplast stroma and are weakly associated with thylakoids or tightly anchored to chloroplast membranes. Arabidopsis thaliana has two LFNRs, and the chloroplast proteins AtTROL and AtTIC62 participate in anchoring AtLFNRs to the thylakoid membrane. By contrast, the membrane anchoring mechanism of rice ( Oryza sativa ) LFNRs has not been elucidated. Here, we investigated the membrane‐anchoring mechanism of LFNRs and its physiological roles in rice. We characterized the rice protein OsTROL1 based on its homology to AtTROL. We determined that OsTROL1 is also a thylakoid membrane anchor and its loss leads to a compensatory increase in OsTIC62. OsLFNR1 attachment through a membrane anchor depends on OsLFNR2, unlike the Arabidopsis counterparts. In addition, OsTIC62 was more highly expressed in the dark than under light conditions, consistent with the increased membrane binding of OsLFNR in the dark. Moreover, we observed reciprocal stabilization between OsLFNRs and their membrane anchors. In addition, unlike in Arabidopsis, the loss of LFNR membrane anchor affects photosynthesis in rice. Overall, our study sheds light on the mechanisms anchoring LFNRs to membranes in rice and highlights differences with Arabidopsis . Summary statement: Leaf‐form ferredoxin‐NADP + oxidoreductases (LFNRs) play an important role in regulating ferredoxin (FD)‐dependent electron partitioning in the chloroplast, acting at the branch of photosynthetic electron transfer and reductive metabolism. However, the membrane‐anchoring mechanism of LFNRs and its physiological roles in rice remains largely elusive. Here, we compared the growth phenotype, fresh weight, chlorophyll content, photosynthetic rate, and electron transfer rate among the wild‐type (WT), Oslfnr1‐1, Oslfnr2‐1, Ostic62, Ostrol1‐1 mutants, and Ostrol1‐1 and Ostic62 double mutant. The results showed that mutation of OsLFNRs and their putative anchor partners affects plant growth and photosynthesis. We found that OsTIC62 is necessary for thylakoid‐bound high‐molecular‐weight LFNR complexes, as low‐molecular‐weight LFNR complexes on OsTROL1 and medium‐molecular‐weight complexes are likely a mixture of OsTROL2‒OsLFNR and OsTIC62‒OsLFNR. OsLFNR tightly bind to the thylakoid membrane through OsTIC62 and OsTROL1, this binding stabilizes OsLFNR; also, OsLFNR and its membrane anchors reciprocally stabilize each other. What is more, loss of OsTROL1 leads to a compensatory increase in OsTIC62. In Oslfnr2 mutants, we could not find any OsLFNR complexes in the thylakoid membrane, whereas the Oslfnr1 mutant still had many OsLFNR complexes, which suggested that OsLFNR2 is required for the binding of OsLFNRs to the thylakoid membrane. As the expression pattern of membrane anchors under diurnal conditions has not been reported, we investigated the expression pattern of OsTIC62 under diurnal condition. Gene expression and protein levels suggested that OsTIC62 is highly expressed under dark than in daylight at both the transcript and protein levels, which means that OsTIC62 expression have day‒night rhythm.