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Yun L, Zegarac R, Ducat DC. Impact of irradiance and inorganic carbon availability on heterologous sucrose production in Synechococcus elongatus PCC 7942. FRONTIERS IN PLANT SCIENCE 2024; 15:1378573. [PMID: 38650707 PMCID: PMC11033428 DOI: 10.3389/fpls.2024.1378573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 03/27/2024] [Indexed: 04/25/2024]
Abstract
Cyanobacteria have been proposed as a potential alternative carbohydrate feedstock and multiple species have been successfully engineered to secrete fermentable sugars. To date, the most productive cyanobacterial strains are those designed to secrete sucrose, yet there exist considerable differences in reported productivities across different model species and laboratories. In this study, we investigate how cultivation conditions (specifically, irradiance, CO2, and cultivator type) affect the productivity of sucrose-secreting Synechococcus elongatus PCC 7942. We find that S. elongatus produces the highest sucrose yield in irradiances far greater than what is often experimentally utilized, and that high light intensities are tolerated by S. elongatus, especially under higher density cultivation where turbidity may attenuate the effective light experienced in the culture. By increasing light and inorganic carbon availability, S. elongatus cscB/sps produced a total of 3.8 g L-1 of sucrose and the highest productivity within that period being 47.8 mg L-1 h-1. This study provides quantitative description of the impact of culture conditions on cyanobacteria-derived sucrose that may assist to standardize cross-laboratory comparisons and demonstrates a significant capacity to improve productivity via optimizing cultivation conditions.
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Affiliation(s)
- Lisa Yun
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
- Department of Energy-Michigan State University Plant Research Laboratories, Michigan State University, East Lansing, MI, United States
| | - Robert Zegarac
- Department of Energy-Michigan State University Plant Research Laboratories, Michigan State University, East Lansing, MI, United States
| | - Daniel C. Ducat
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
- Department of Energy-Michigan State University Plant Research Laboratories, Michigan State University, East Lansing, MI, United States
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Su J, Jiao Q, Jia T, Hu X. The photosystem-II repair cycle: updates and open questions. PLANTA 2023; 259:20. [PMID: 38091081 DOI: 10.1007/s00425-023-04295-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 11/15/2023] [Indexed: 12/18/2023]
Abstract
MAIN CONCLUSION The photosystem-II (PSII) repair cycle is essential for the maintenance of photosynthesis in plants. A number of novel findings have illuminated the regulatory mechanisms of the PSII repair cycle. Photosystem II (PSII) is a large pigment-protein complex embedded in the thylakoid membrane. It plays a vital role in photosynthesis by absorbing light energy, splitting water, releasing molecular oxygen, and transferring electrons for plastoquinone reduction. However, PSII, especially the PsbA (D1) core subunit, is highly susceptible to oxidative damage. To prevent irreversible damage, plants have developed a repair cycle. The main objective of the PSII repair cycle is the degradation of photodamaged D1 and insertion of newly synthesized D1 into the PSII complex. While many factors are known to be involved in PSII repair, the exact mechanism is still under investigation. In this review, we discuss the primary steps of PSII repair, focusing on the proteolytic degradation of photodamaged D1 and the factors involved.
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Affiliation(s)
- Jinling Su
- International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
- Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, 225009, China
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, China
| | - Qingsong Jiao
- International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
- Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, 225009, China
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, China
| | - Ting Jia
- International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China.
- Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, 225009, China.
| | - Xueyun Hu
- International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China.
- Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, 225009, China.
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, China.
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Koskinen S, Kurkela J, Linhartová M, Tyystjärvi T. The genome sequence of Synechocystis sp. PCC 6803 substrain GT-T and its implications for the evolution of PCC 6803 substrains. FEBS Open Bio 2023; 13:701-712. [PMID: 36792971 PMCID: PMC10068330 DOI: 10.1002/2211-5463.13576] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 02/02/2023] [Accepted: 02/07/2023] [Indexed: 02/17/2023] Open
Abstract
Synechocystis sp. PCC 6803 is a model cyanobacterium, glucose-tolerant substrains of which are commonly used as laboratory strains. In recent years, it has become evident that 'wild-type' strains used in different laboratories show some differences in their phenotypes. We report here the chromosome sequence of our Synechocystis sp. PCC 6803 substrain, named substrain GT-T. The chromosome sequence of GT-T was compared to those of two other commonly used laboratory substrains, GT-S and PCC-M. We identified 11 specific mutations in the GT-T substrain, whose physiological consequences are discussed. We also provide an update on evolutionary relationships between different Synechocystis sp. PCC 6803 substrains.
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Affiliation(s)
- Satu Koskinen
- Department of Life Sciences/Molecular Plant Biology, University of Turku, Finland
| | - Juha Kurkela
- Department of Life Sciences/Molecular Plant Biology, University of Turku, Finland
| | - Markéta Linhartová
- Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czech Republic
| | - Taina Tyystjärvi
- Department of Life Sciences/Molecular Plant Biology, University of Turku, Finland
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Dey D, Nishijima M, Tanaka R, Kurisu G, Tanaka H, Ito H. Crystal structure and reaction mechanism of a bacterial Mg-dechelatase homolog from the Chloroflexi Anaerolineae. Protein Sci 2022; 31:e4430. [PMID: 36173179 PMCID: PMC9514216 DOI: 10.1002/pro.4430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 08/22/2022] [Accepted: 08/24/2022] [Indexed: 11/05/2022]
Abstract
Chlorophyll degradation plays a myriad of physiological roles in photosynthetic organisms, including acclimation to light environment and nutrient remobilization during senescence. Mg extraction from chlorophyll a is the first and committed step of the chlorophyll degradation pathway. This reaction is catalyzed by the Mg-dechelatase enzyme encoded by Stay-Green (SGR). The reaction mechanism of SGR protein remains elusive since metal ion extraction from organic molecules is not a common enzymatic reaction. Additionally, experimentally derived structural information about SGR or its homologs has not yet been reported. In this study, the crystal structure of the SGR homolog from Anaerolineae bacterium was determined using the molecular replacement method at 1.85 Å resolution. Our previous study showed that three residues-H32, D34, and D62 are essential for the catalytic activity of the enzyme. Biochemical analysis involving mutants of D34 residue further strengthened its importance in the functioning of the dechelatase. Docking simulation also revealed the interaction between the D34 side chain and central Mg ion of chlorophyll a. Structural analysis showed the arrangement of D34/H32/D62 in the form of a catalytic triad that is generally found in hydrolases. The probable reaction mechanism suggests that deprotonated D34 side chain coordinates and destabilizes Mg, resulting in Mg extraction. Besides, H32 possibly acts as a general base catalyst and D62 facilitates H32 to be a better proton acceptor. Taken together, the reaction mechanism of SGR partially mirrors the one observed in hydrolases.
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Affiliation(s)
- Debayan Dey
- Graduate School of Life ScienceHokkaido UniversitySapporoJapan
- Institute of Low Temperature ScienceHokkaido UniversitySapporoJapan
| | | | - Ryouichi Tanaka
- Institute of Low Temperature ScienceHokkaido UniversitySapporoJapan
| | - Genji Kurisu
- Institute for Protein ResearchOsaka UniversitySuitaJapan
| | - Hideaki Tanaka
- Institute for Protein ResearchOsaka UniversitySuitaJapan
| | - Hisashi Ito
- Institute of Low Temperature ScienceHokkaido UniversitySapporoJapan
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Lin YP, Shen YY, Shiu YB, Charng YY, Grimm B. Chlorophyll dephytylase 1 and chlorophyll synthase: a chlorophyll salvage pathway for the turnover of photosystems I and II. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 111:979-994. [PMID: 35694901 DOI: 10.1111/tpj.15865] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 06/02/2022] [Indexed: 06/15/2023]
Abstract
Chlorophyll (Chl) is made up of the tetrapyrrole chlorophyllide and phytol, a diterpenoid alcohol. The photosynthetic protein complexes utilize Chl for light harvesting to produce biochemical energy for plant development. However, excess light and adverse environmental conditions facilitate generation of reactive oxygen species, which damage photosystems I and II (PSI and PSII) and induce their turnover. During this process, Chl is released, and is thought to be recycled via dephytylation and rephytylation. We previously demonstrated that Chl recycling in Arabidopsis under heat stress is mediated by the enzymes chlorophyll dephytylase 1 (CLD1) and chlorophyll synthase (CHLG) using chlg and cld1 mutants. Here, we show that the mutants with high CLD1/CHLG ratio, by different combinations of chlg-1 (a knock-down mutant) and the hyperactive cld1-1 alleles, develop necrotic leaves when grown under long- and short-day, but not continuous light conditions, owing to the accumulation of chlorophyllide in the dark. Combination of chlg-1 with cld1-4 (a knock-out mutant) leads to reduced chlorophyllide accumulation and necrosis. The operation of CLD1 and CHLG as a Chl salvage pathway was also explored in the context of Chl recycling during the turnover of Chl-binding proteins of the two photosystems. CLD1 was found to interact with CHLG and the light-harvesting complex-like proteins OHP1 and LIL3, implying that auxiliary factors are required for this process.
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Affiliation(s)
- Yao-Pin Lin
- Institute of Biology/Plant Physiology, Humboldt-Universität zu Berlin, Philippstraße 13 Building 12, 10115, Berlin, Germany
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 11529, Taiwan, ROC
| | - Yu-Yen Shen
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 11529, Taiwan, ROC
| | - Yen-Bin Shiu
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 11529, Taiwan, ROC
| | - Yee-Yung Charng
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 11529, Taiwan, ROC
| | - Bernhard Grimm
- Institute of Biology/Plant Physiology, Humboldt-Universität zu Berlin, Philippstraße 13 Building 12, 10115, Berlin, Germany
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