Photosynthesis Research最新文献_第4页

Resolving the contributions of photosystem II, photosystem I, and phycobilisomes to the in vivo fluorescence yield in the red alga Cyanidioschyzon merolae. 解析光系统II、光系统I和藻胆体对红藻体内荧光产率的贡献。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-26 DOI: 10.1007/s11120-026-01212-6

Han-Yi Fu, Ying-Yu Chen

{"title":"Resolving the contributions of photosystem II, photosystem I, and phycobilisomes to the in vivo fluorescence yield in the red alga Cyanidioschyzon merolae.","authors":"Han-Yi Fu, Ying-Yu Chen","doi":"10.1007/s11120-026-01212-6","DOIUrl":"10.1007/s11120-026-01212-6","url":null,"abstract":"Analysis of in vivo fluorescence yield measured in the red and far-red regions is widely used to estimate photosynthetic parameters related to photosystem II (PSII). Besides PSII, photosystem I (PSI) and phycobilisomes (PBS), the latter present in cyanobacteria, red algae, and glaucophytes, also emit fluorescence. Real-time fluorescence responses of PSI and PBS have not been fully characterized, as practical methods to resolve fluorescence contributions from PSII, PSI, and PBS are limited. To resolve the contributions of PSII, PSI, and PBS to the in vivo fluorescence yield, an analytical workflow is proposed based on fluorescence induction curves and variable fluorescence kinetics measured across four detection wavebands. The fluorescence induction curves and variable fluorescence kinetics were measured using blue and amber lights, which preferentially excited the photosystems (PSII and PSI) and PBS, respectively, in the unicellular red alga Cyanidioschyzon merolae. Both PSI and PBS contributed small but measurable portions to the fluorescence induction curves, enabling estimation of the relative fluorescence amplitudes across detection wavebands through constrained non-negative matrix factorization (NMF). The relative fluorescence amplitudes were used to estimate the relative fluorescence yields of PSII, PSI, and PBS, as well as the PSII-related parameter ΦPSII through least-squares fitting of variable fluorescence data. The resulting kinetics obtained from the optimal NMF models revealed multiple processes associated with nonphotochemical quenching of PSII and provided insights into the regulation of excitonic energy transfer among PSII, PSI, and PBS. The analytical workflow serves as an effective approach to uncover PSI and PBS fluorescence yield kinetics across diverse photosynthetic organisms.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147521675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Excitation dynamics in B800-B850 antenna: hierarchical equation versus perturbative approaches. B800-B850天线的激励动力学：层次方程与微扰方法。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-26 DOI: 10.1007/s11120-026-01213-5

Vladimir I Novoderezhkin

引用次数: 0

Can continuous light mitigate the detrimental actions of salinity stress in facultative CAM plants? 连续光照能减轻兼性CAM植物中盐胁迫的有害作用吗？

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-23 DOI: 10.1007/s11120-026-01211-7

Michał Nosek, Katarzyna Gawrońska, Jakub Oliwa, Andrzej Kalisz, Iwona Ciereszko, Alicja Piotrowska-Niczyporuk, Piotr Rozpądek, Andrzej Kornaś

{"title":"Can continuous light mitigate the detrimental actions of salinity stress in facultative CAM plants?","authors":"Michał Nosek, Katarzyna Gawrońska, Jakub Oliwa, Andrzej Kalisz, Iwona Ciereszko, Alicja Piotrowska-Niczyporuk, Piotr Rozpądek, Andrzej Kornaś","doi":"10.1007/s11120-026-01211-7","DOIUrl":"10.1007/s11120-026-01211-7","url":null,"abstract":"Facultative CAM plants possess a unique ability to reversibly initiate and suppress β-carboxylation, a metabolic pathway characterised by nocturnal stomatal opening and high water-use efficiency. In the present study, we focused on determining how continuous light modifies the interaction of the Mesembryanthemum crystallinum, a model CAM facultative species, with salinity stress – an ever-growing global-scale plant diversity and productivity threat. Expression of stress-dependent PEPC form and RbcL, chlorophyll a fluorescence, pigment composition and antioxidant enzyme activity were analysed. Expression of both mentioned genes was predictably influenced by salinity stress, with stress-dependent PEPC amount increase accompanied by a concurrent RbcL decline. However, exposing plants already affected by salinity stress to continuous light resulted in a limited RbcL decline – a side-effect exclusively induced by salinity stress. Moreover, a limited expression of salinity-dependent PEPC was concomitantly observed; in M. crystallinum leaves, the content of cryptoxanthin, β-carotene, α-carotene, zeaxanthin, violaxanthin, antheraxanthin and neoxanthin has increased, especially in the case of salinity with continuous light treatments. The total SODs activity was increased in plants exposed to salinity combined with continuous light. This study unravels novel evidence that continuous light treatment may alleviate the detrimental effects of high salinity in facultative CAM plants; these conclusions, however, may potentially be extrapolated to other plant groups, including glycophytes.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147504103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mechanistic insights into photosynthetic linear electron transport flow: a mathematical modeling approach. 光合作用线性电子传递流的机理：一种数学建模方法。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-18 DOI: 10.1007/s11120-026-01205-5

S S Khruschev, T Yu Plyusnina, P V Fursova, R N Chervitsov, A A Volgusheva, G Yu Riznichenko, A B Rubin

{"title":"Mechanistic insights into photosynthetic linear electron transport flow: a mathematical modeling approach.","authors":"S S Khruschev, T Yu Plyusnina, P V Fursova, R N Chervitsov, A A Volgusheva, G Yu Riznichenko, A B Rubin","doi":"10.1007/s11120-026-01205-5","DOIUrl":"10.1007/s11120-026-01205-5","url":null,"abstract":"A mathematical model of a photosynthetic electron transport chain part comprising photosystem II (PSII), cytochrome b6 f complex (Cyt b6 f), and the plastoquinone (PQ) pool was developed to investigate the dependence of linear electron flow (LEF) on light intensity in proposition that special regulatory mechanisms are absent. The model predicts a nonmonotonic relationship between LEF rate and light intensity, driven by the imbalance of PSII and Cyt b6 f activity, which causes over-reduction of the PQ pool and further impedes electron transport through Cyt b6 f. These effects arise from the Q-cycle mechanism, where electron transport through the high- and low-potential branches must be balanced. Under PQ pool over-reduction, LEF blockage occurs being still reversible upon lowering light intensity. The mechanism under consideration is an internal property of the system, and its functioning is not associated with the generation of an electrical and proton gradient on the membrane. The model reproduces experimentally observed switching between active and blocked states of the electron transport chain under intense light. These findings demonstrate that rather complex behavior in response to external factors can emerge in a biological system even in the absence of explicit regulation due to the intrinsic properties of complex network of chemical reactions subject to the mass action law.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147481151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

GSNOR mediates NO signaling to enhance salt tolerance in tobacco by regulating redox and photosynthesis. GSNOR通过调控氧化还原和光合作用，介导NO信号增强烟草耐盐性。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-13 DOI: 10.1007/s11120-026-01209-1

Yu Zhang, Yixuan Feng, Yanjie Liu, Yongzheng Qiu, Xiaoyu Zhang, Jieyun Cheng, Yue Wang

{"title":"GSNOR mediates NO signaling to enhance salt tolerance in tobacco by regulating redox and photosynthesis.","authors":"Yu Zhang, Yixuan Feng, Yanjie Liu, Yongzheng Qiu, Xiaoyu Zhang, Jieyun Cheng, Yue Wang","doi":"10.1007/s11120-026-01209-1","DOIUrl":"10.1007/s11120-026-01209-1","url":null,"abstract":"High salt stress can hinder plant growth and development, thus reducing crop yield and quality. As an important signaling molecule, NO is involved in regulating various physiological and biochemical processes in plants. In this study, tobacco seedlings treated with 200 mmol/L NaCl exhibited leaf etiolation, sharp increases in superoxide anion (O2−) and peroxynitrite anion (ONOO−) contents, reduced activities of photosystem I (PSI) and II (PSII) reaction centers, and obstructed electron transfer. However, overexpression of the gene encoding the NO regulator nitrosoglutathione reductase (GSNOR) reduced the excessive accumulation of nitric oxide (NO) and S-nitrosothiol (GSNO) during NaCl stress. It also enhanced antioxidant enzyme activity and the contents of antioxidant substances, thereby maintaining the homeostasis of reactive oxygen species and reactive nitrogen species. Moreover, GSNOR also promoted photosynthesis in tobacco leaves at the transcriptional level. Through enrichment analysis of differentially expressed genes (DEGs) and weighted gene co-expression network analysis (WGCNA) based on physiological and RNA-seq data, it was found that photosynthesis-related pathways, including “Porphyrin and chlorophyll metabolism”, “Carbon fixation in photosynthetic organisms,” and “Photosynthesis,” were significantly enriched. In GSNOR-overexpression plants, the expression of genes encoding proteins involved in chlorophyll synthesis, the Calvin cycle, PSII, and PSI were upregulated. Meanwhile, leaf chlorophyll increased, and the net photosynthetic rate, stomatal conductance, and activity of the reaction centers were enhanced. In contrast, GSNOR-inhibited plants exhibited the opposite trends. These results indicate that NO enhances the salt tolerance of tobacco seedlings by promoting photosynthesis and enhancing antioxidant capacity.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147444666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of different light intensities on photosynthetic properties of endangered Primula filchnerae seedlings. 不同光照强度对濒危报春花幼苗光合特性的影响。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-12 DOI: 10.1007/s11120-026-01210-8

Ling Wei, Jiali Xue, Jiaxin Quan, Xueyan Zhao, Ming Yue, Qian Li

{"title":"Effects of different light intensities on photosynthetic properties of endangered Primula filchnerae seedlings.","authors":"Ling Wei, Jiali Xue, Jiaxin Quan, Xueyan Zhao, Ming Yue, Qian Li","doi":"10.1007/s11120-026-01210-8","DOIUrl":"10.1007/s11120-026-01210-8","url":null,"abstract":"As a rare and endangered species, Primula filchnerae Knuth faces high seedling-stage mortality that likely contributes significantly to its threatened status. The study aims to investigate the effects of different light intensities under controlled conditions on the photosynthetic traits of P. filchnerae seedlings, elucidate its mechanism of light response and identify optimal light environments for seedlings survival, thereby providing a basis for scientific protection. The three light-intensity treatments were established through artificial shading to simulate the constant light intensity of natural habitat conditions observed in the field: intermediate light intensity (L1, 162 µmol·m⁻²·s⁻¹, control), semi-open area (L2, 324 µmol·m⁻²·s⁻¹) and understory (L3, 5.4 µmol·m⁻²·s⁻¹). Our study revealed that P. filchnerae seedlings exhibited significantly reduced Pnmax and PIABS under both L2 and L3 treatments relative to L1. Specifically, the decrease in photosynthetic rate under L2 was caused by stomatal limitation, while that under L3 was induced by non-stomatal limitation. In contrast, P. filchnerae seedlings maintained high antioxidant enzyme activity and stable accumulation of osmoregulatory substances in L1 treatment. Transcriptomic profiling indicated that flavonoid biosynthesis pathway genes were highly expressed under L2 compared to L1, while photosynthesis-related genes were downregulated under L3 condition. Based on the findings, the L1 treatment represents the optimal growth condition for P. filchnerae seedlings, where photosynthetic efficiency, light energy utilization capacity and stress resistance achieve their most favorable synergistic state. In contrast, both the L2 and L3 conditions were shown to be suboptimal, adversely affecting seedlings growth and physiological performance.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147444596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Research progress on the structure of photosynthetic reaction centers-mobile electron carrier supercomplexes. 光合反应中心-移动电子载体超配合物结构的研究进展。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-09 DOI: 10.1007/s11120-026-01208-2

Jiasheng Jiang, Jie Wang, Xing Han, Xiaochun Qin, Shishang Dong

{"title":"Research progress on the structure of photosynthetic reaction centers-mobile electron carrier supercomplexes.","authors":"Jiasheng Jiang, Jie Wang, Xing Han, Xiaochun Qin, Shishang Dong","doi":"10.1007/s11120-026-01208-2","DOIUrl":"10.1007/s11120-026-01208-2","url":null,"abstract":"In photosynthesis, transient supercomplexes formed between reaction centers (RCs) and mobile electron carriers provide the physical interfaces that enable directional electron transfer. Recent advances in cryo-electron microscopy have substantially expanded the structural available information for these short-lived assemblies in both oxygenic and anoxygenic photosynthetic systems. This review summarizes and integrates recent high-resolution structural studies of representative RCs-mobile electron carrier supercomplexes, including Photosystem I (PSI) with plastocyanin (PC), ferredoxin (Fd), and flavodoxin (Fld) in oxygenic organisms, and RC-Light-Harvesting complex 1 (LH1) with high-potential iron-sulfur protein (HiPIP) in anoxygenic photosynthetic bacteria. Across these systems, common design features of supercomplex formation emerge, including electrostatic-hydrophobic interplay, assembly symmetry, and environmental adaptability. In oxygenic systems, the PSI-PC supercomplex follows a dynamic \"electrostatic guidance-hydrophobic stabilization\" model, with binding affinity modulated by the redox state of PC. PSI-Fd and PSI-Fld supercomplexes rely on synergistic electrostatic, hydrophobic, and hydrogen-bonding interactions, with Fld exhibiting symmetric, high-affinity binding under iron-deficient conditions as a functional substitute for Fd. In anoxygenic bacteria, the HiPIP-RC-LH1 supercomplex is primarily stabilized by hydrophobic interactions and hydrogen bonds, featuring a conserved transmembrane electron transfer pathway. Together, these studies provide a structural framework for understanding how interface interactions and conformational variability are related to electron transfer efficiency in photosynthetic supercomplexes, and, in doing so, outline key directions for future investigation into regulatory mechanisms, environmental adaptation, and biomimetic applications.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147390592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Protein/linker dynamics facilitates the structural adaptation of the orange carotenoid protein in cyanobacterial photoprotection: a neutron scattering study. 蛋白质/连接体动力学促进了蓝藻光保护中橙色类胡萝卜素蛋白的结构适应：中子散射研究。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-07 DOI: 10.1007/s11120-026-01204-6

Maksym Golub, Marcus Moldenhauer, Franz-Josef Schmitt, Tilo Seydel, Markus Appel, Olga Matsarskaia, Sylvain Prevost, Dmitry Zlenko, Eugene G Maksimov, Roberta Spadaccini, Thomas Friedrich, Jörg Pieper

{"title":"Protein/linker dynamics facilitates the structural adaptation of the orange carotenoid protein in cyanobacterial photoprotection: a neutron scattering study.","authors":"Maksym Golub, Marcus Moldenhauer, Franz-Josef Schmitt, Tilo Seydel, Markus Appel, Olga Matsarskaia, Sylvain Prevost, Dmitry Zlenko, Eugene G Maksimov, Roberta Spadaccini, Thomas Friedrich, Jörg Pieper","doi":"10.1007/s11120-026-01204-6","DOIUrl":"10.1007/s11120-026-01204-6","url":null,"abstract":"The orange carotenoid protein (OCP) plays a pivotal role in the photoprotection of cyanobacteria and undergoes a structural change after photoactivation. Here, we report a solution structure of the active state differing significantly from that known upon binding to the phycobilisome. In solution, the N-terminal domains are clearly detached and reoriented by about 90° relative to the C- terminal domains. This apparent structural difference implies the need for a previously unknown structural rearrangement. A rarely considered aspect is the internal protein dynamics facilitating this structural transition. Therefore, we directly probe protein dynamics in a wide observation time range in the dark and under illumination. After photoactivation to the active state, the internal dynamics is enhanced, while the global diffusion is slowed down. A residue-resolved molecular dynamics simulation indicates that the interdomain linker becomes more flexible and may mediate the structural adaptation to the phycobilisome binding site. In turn, the β-sheet structures remain the most rigid part of the active state structure, which is essential for protein dimerization.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147373020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

State transitions in Physcomitrium patens studied with time-resolved fluorescence. 用时间分辨荧光法研究了斑立菌的态转变。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-06 DOI: 10.1007/s11120-026-01206-4

Dana Verhoeven, Cleo Bagchus, Lotte Jore, Herbert van Amerongen, Emilie Wientjes

{"title":"State transitions in Physcomitrium patens studied with time-resolved fluorescence.","authors":"Dana Verhoeven, Cleo Bagchus, Lotte Jore, Herbert van Amerongen, Emilie Wientjes","doi":"10.1007/s11120-026-01206-4","DOIUrl":"10.1007/s11120-026-01206-4","url":null,"abstract":"Photosynthetic organisms adapt their light-harvesting apparatus continuously to the ever-changing light environment. The model moss Physcomitrium patens shares acclimation responses with both the vascular plant Arabidopsis thaliana and the green alga Chlamydomonas reinhardtii. In vivo time-resolved fluorescence spectroscopy has previously helped to clarify the mechanisms of acclimation in A. thaliana and C. reinhardtii. However, it has not yet been applied to study acclimation responses in P. patens. In this work, we studied state transitions in P. patens with in vivo time-resolved fluorescence spectroscopy. We found one short (35–45 ps) and one longer (165–190 ps) in vivo photosystem I (PSI)-related fluorescence lifetime. We suggest that the short fluorescence lifetime is associated with PSI with a small, plant-like antenna, whereas the second component arises from PSI with a larger antenna size. The PSI antenna size is affected by state transitions, a dynamic process that balances the energy capture between PSI and photosystem II (PSII). We found that state transitions in P. patens act most strongly at an exceptionally low light intensity of 3 µmol m− 2 s− 1 actinic light. The in vivo time-resolved fluorescence spectra suggest that state transitions at this actinic light intensity mainly affect PSII and PSI-large, despite PSI-large being excited far less than PSI-small. Our findings indicate that state transitions in P. patens rebalance the excitation-energy distribution to a similar level as vascular plants, but at different light intensities. Our results suggest that state 1 to state 2 transitions primarily increase the abundance of PSI-large.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12963178/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147366566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Synthesis of chlorophyll b: a retrospective analysis of chlorophyllide a oxygenase. 叶绿素b的合成：叶绿素内酯a加氧酶的回顾分析。

IF 3.8 3区生物学

Photosynthesis Research Pub Date : 2026-03-05 DOI: 10.1007/s11120-026-01207-3

J Kenneth Hoober, Laura L Eggink, Daniel-Paul Bednarik, Steffen Reinbothe

{"title":"Synthesis of chlorophyll b: a retrospective analysis of chlorophyllide a oxygenase.","authors":"J Kenneth Hoober, Laura L Eggink, Daniel-Paul Bednarik, Steffen Reinbothe","doi":"10.1007/s11120-026-01207-3","DOIUrl":"10.1007/s11120-026-01207-3","url":null,"abstract":"Chlorophyll (Chl) b is essential for maximal capacity of photosynthesis in green algae and plants. Along with broadening the absorbance spectrum, Chl b controls the translocation of light-harvesting complex apoproteins across the chloroplast envelope inner membrane and stabilizes light-harvesting complexes in thylakoid membranes. In the absence of Chl b, these Chl-binding proteins are retracted into the cytosol and degraded. A protein designated chlorophyllide (Chlide) a oxygenase (CAO) is required for Chl b synthesis. Conversion in vitro of Chlide a to Chlide b by purified recombinant CAO occurs at a low rate. In contrast, protochlorophyllide (Pchlide) a is converted rapidly and quantitatively to Chlide b by CAO in a membrane fraction from cells of Chlamydomonas reinhardtii y-1 when incubated in the presence of polyaromatic m-phenanthroline. This is surprising because Pchlide a per se is not a substrate for CAO. A retrospective analysis of our previous data suggests that phenanthroline mimics Chlide a and pairs with Pchlide a to lower its redox potential, thereby activating Pchlide a as a substrate. A conserved tyrosine residue occurs as a stable radical in CAO and initiates the transformation of the 7-methyl group of Pchlide a to the 7-formyl group of Pchlide b. Replacing this tyrosine with alanine abolished CAO activity. We conclude that Pchlide b is synthesized from Pchlide a by an unusual, radical-mediated/based mechanism that directly involves molecular oxygen. In vivo, subsequent reduction of the C17-C18 double bond by a light-independent Pchlide reductase activity would be facilitated by the electronegative carbonyl of the 7-formyl group to generate Chlide b.","PeriodicalId":20130,"journal":{"name":"Photosynthesis Research","volume":"164 2","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12963167/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147355056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0