Transcriptomic changes in sapx tapx, pgr5, and triple mutants under high-light stress
Ontology highlight
ABSTRACT:
ORGANISM(S): Arabidopsis thaliana
PROVIDER: GSE156883 | GEO | 2020/08/26
REPOSITORIES: GEO
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Project description:PGR5 is a small chloroplast protein that performs cyclic electron flow (CEF) around photosystem I and it is required for the proton gradient generation across the thylakoid membrane. The level of this protein is closely regulated by PGRL1. However, the molecular mechanism of PGR5 is still elusive. In this work, we have generated a new pgr5 mutant in Arabidopsis using CRISPR-Cas9 technology, pgr5-Cas, completely devoid of PGR5. We performed comparative proteomic analysis on pgr5-1 and pgr5-Cas lines (#1 and #2), as well as on pgrl1ab mutant.
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Project description:PROTON GRADIENT REGULATION 5 (PGR5) plays a critical role in generating proton motive force across thylakoid membranes and supporting photoprotection under fluctuating light in C3 plants. It is proposed that this function is achieved by regulating cyclic electron flow around Photosystem I. During the evolutionary transition from C3 to C4 photosynthesis, PGR5 abundance in leaves has increased, coinciding with an enhancement in cyclic electron flow rate. To investigate the role of PGR5 in C4 photosynthesis and photoprotection, we generated Setaria viridis (a model C4 monocot) lines with null PGR5 alleles. We demonstrate that loss of PGR5 severely impairs the establishment of proton motive force, photosynthetic control, and energy-dependent non-photochemical quenching at high irradiances, leading to a loss of Photosystem I activity under light stress. Furthermore, plants lacking PGR5 exhibit drastically reduced growth and photosynthesis when grown under fluctuating daylight; however, they are less severely affected than C3 pgr5 mutants. This relative tolerance arises from the ability of S. viridis lacking PGR5 to maintain significant levels of photosynthetic control, in contrast to C3 mutants. Additionally, in the absence of PGR5 and qE, a slower-relaxing, zeaxanthin-dependent form of non-photochemical quenching supports survival under fluctuating light, albeit at the cost of reduced photochemical efficiency and assimilation. Our findings highlight the essential role of PGR5 in enabling efficient C4 photosynthesis under fluctuating light by regulating photosynthetic control and energy-dependent non-photochemical quenching. This study also uncovers the interplay between multiple photoprotective mechanisms safeguarding C4 photosynthesis under light stress.
2025-10-21 | GSE287975 | GEO
Project description:The light reactions of photosynthesis couple electron and proton transfers across the thylakoid membrane, generating NADPH for carbon fixation and a proton motive force (dominated by ΔpH in chloroplasts) to drive ATP production by the ATP synthase complex. Regulation of NADPH and ATP levels to meet metabolic requirements alongside the dissipation of excess solar energy when it exceeds these requirements are critical to plant growth under fluctuating light environments. To investigate mechanisms involved in the regulation of the light reactions of photosynthesis, we describe proteomic comparisions between two mutant Arabidopsis strains and their respective wild-type background strains: (1) hope2 (ATP synthase γ1-subunit G143D mutant vs. wild-type background Col-0) and (2) pgr5 (impaired stability of the Proton Gradient Regulation 5 (PGR5) protein vs. wild-type background gl1).
2023-03-06 | PXD033007 | Pride
Project description:Microalgae are natural biocatalysts of Hydrogen. Their ability to convert solar energy to valuable compounds with minimal ecological footprint potentially puts them as significant contributors to clean energy transition. Currently, this process, although promising, is not scalable because it is limited to oxygen-free conditions and is short-lived due to electron loss to other processes, mainly carbon fixation. Here we show that a strain, defected in thylakoid proton gradient regulation, ∆pgr5, bypasses both challenges simultaneously, leading to a prolonged 12-day hydrogen production under ambient mixotrophic conditions in a one-liter set-up. We report that ∆pgr5 possess a repressed ability to fixate carbon and this limitation is counterbalanced by an enhanced chloroplast-mitochondrion energetic exchange. This unique physiology supported the simplistic, yet robust and scalable hydrogen production capability of ∆pgr5.
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Project description:Calredoxin (CRX) is a calcium (Ca2+)-dependent thioredoxin (TRX) in the chloroplast of Chlamydomonas reinhardtii. To further elucidate the function of CRX, we performed in-depth quantitative proteomics taking advantage of a crx insertional mutant (IMcrx), two CRISPR/Cas9 KO mutants, CRX rescues and wild type strains. These analyses revealed that the chloroplast NADPH-dependent TRX reductase (NTRC) is co-regulated with CRX. Electron transfer measurements revealed that CRX inhibits NADPH-dependent reduction of oxidized chloroplast 2-Cys peroxiredoxin (PRX1) via NTRC and that the function of the NADPH-NTRC complex is under strict control of CRX. Our data also demonstrated via non-reducing SDS-PAGE assays and redox proteomics that PRX1, Transketolase (TRK1), ATPC and Proton Gradient Related like 1 (PGRL1) are more oxidized under high light (HL) conditions in the absence of CRX. The redox tuning of PRX1 and control of the NADPH-NTRC complex via CRX interconnects redox control with active photosynthetic electron transport and metabolism as well as Ca2+ signaling. In this way, an economic use of NADPH for PRX1 reduction is assured. The finding, that in the absence of CRX, light-driven CO2 fixation is severely inhibited under HL conditions underpins the importance of CRX for redox tuning as well as for efficient photosynthesis.
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Project description:Plasma membrane proton pump maintains proton electrochemical gradient and provides energy to secondary transporters. Arabidopsis mutant plants with reduced proton pump activity grow normal under ideal growth conditions; however their growth are reduced compared with wildtype plants when placed under the conditions that stress on protonmotive force (high external pH or high external potassium).
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Project description:Plasma membrane proton pump maintains proton electrochemical gradient and provides energy to secondary transporters. Arabidopsis mutant plants with reduced proton pump activity grow normal under ideal growth conditions; however their growth are reduced compared with wildtype plants when placed under the conditions that stress on protonmotive force (high external pH or high external potassium). Seedlings of wildtype, aha1, and aha2 mutant plants were grown under ideal growth condition. Total RNA from those seedlings were subjected to transcriptome analyses using Affymetrix Gene Chip.
2015-04-01 | E-GEOD-34202 | biostudies-arrayexpress
Project description:PROTON GRADIENT5 (PGR5) is thought to promote cyclic electron flow (CEF) and its deficiency causes increased photosensitivity of photosystem I (PSI), leading to lethality under fluctuating light (FL). By screening for suppressor mutations that rescue FL lethality of pgr5 plants, we identified a portfolio of mutations affecting 12 photosynthesis-related proteins. Here we performed a proteomic analysis to compare a mutant lacking PGR5 vs wildtype ( at2g04360-1/pfsc1-1 vs. Col-0)
2024-03-15 | PXD047221 | Pride
Project description:Ascorbate (vitamin C) is an important antioxidant in leaves with multiple functions in photosynthesis and its levels are tightly regulated by light quality. The majority of work to date has focussed on regulation of ascorbate levels via biosynthesis. However, the pathway of ascorbate degradation, which is localised in the apoplast may additionally play a significant role. The degradative pathway begins with ascorbate oxidation by the enzyme ascorbate oxidase (AO) and hence we have examined the impact of manipulation of ascorbate oxidase activity on the content of ascorbate and the acclimation of photosynthesis to changing light levels. Leaf ascorbate content was highly light dependent in Nicotiana tobaccum being double in high compared with low light conditions. In contrast ascorbate oxidase activity was not altered by changing light levels. Transgenic tobacco lines with reduced or enhanced AO activity exhibited no morphological phenotype and photosynthesis under high light was similarly impaired irrespective of the measured AO activity. However further investigation between AO activity and leaf acclimation to changing light intensity revealed a suite of metabolic and transcriptome changes indicating a role for the apoplastic ascorbate pool in chloroplast to nucleus communication. In all genotypes, transcripts associated with ascorbate synthesis and recycling were less abundant following transition from high to low light. However transcripts associated with glutathione recycling, light harvesting, reaction centre function and the Calvin cycle were all increased in abundance. Following the transition from high to low light increases in leaf threonate, an ascorbate degradation product, were proportional to AO activity. A number of chloroplast synthesised amino acids were significantly increased both during high light and following transfer back to LL for 12 h. Similarly, several primary carbohydrates and TCA intermediates were significantly enhanced following high light treatment. In addition to light effects, AO activity had a significant impact on ï¢-alanine, aspartate and threonine. Intriguingly, a large number of fatty acids were reduced in antisense AO and wild-type plants immediately after high light stress however the content of these compounds were significantly increased in overexpressing sense lines. We conclude that AO mediated turnover plays an important role in adjusting cellular ascorbate content to photosynthetic need in a fluctuating light environment and that light mediated signals rapidly adjust that the apoplastic ascorbate pool.
2017-03-01 | E-MTAB-4816 | biostudies-arrayexpress
Project description:Transcriptomic changes in sapx tapx, pgr5, and triple mutants under high-light stress
| PRJNA659346 | ENA