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#34981811   // To Up

Electron transfer via cytochrome b6f complex displays sensitivity to antimycin A upon STT7 kinase activation.

The cytochrome b6f complex (b6f) has been initially considered as the ferredoxin-plastoquinone reductase (FQR) during cyclic electron flow (CEF) with photosystem I that is inhibited by antimycin A (AA). The binding of AA to the b6f Qi-site is aggravated by heme-ci, which challenged the FQR function of b6f during CEF. Alternative models suggest that PROTON GRADIENT REGULATION5 (PGR5) is involved in a b6f-independent, AA-sensitive FQR. Here, we show in Chlamydomonas reinhardtii that the b6f is conditionally inhibited by AA in vivo and that the inhibition did not require PGR5. Instead, activation of the STT7 kinase upon anaerobic treatment induced the AA sensitivity of b6f which was absent from stt7-1. However, a lock in State 2 due to persisting phosphorylation in the phosphatase double mutant pph1;pbcp did not increase AA sensitivity of electron transfer. The latter required a redox poise, supporting the view that state transitions and CEF are not coercively coupled. This suggests that the b6f-interacting kinase is required for structure-function modulation of the Qi-site under CEF favoring conditions. We propose that PGR5 and STT7 independently sustain AA-sensitive FQR activity of the b6f. Accordingly, PGR5-mediated electron injection into an STT7-modulated Qi-site drives a Mitchellian Q cycle in CEF conditions.
Felix Buchert, Martin Scholz, Michael Hippler

2169 related Products with: Electron transfer via cytochrome b6f complex displays sensitivity to antimycin A upon STT7 kinase activation.

100 ug/vial100ug/vial100ug Lyophilized100 ug/vial0.1ml (1mg/ml)1 module100ul1 kit0.1 mg1 module0.2 mg100ug

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#34831107   2021/10/26 To Up

Identification of a Novel Mutation Exacerbated the PSI Photoinhibition in / Mutants; Caution for Overestimation of the Phenotypes in Arabidopsis Mutant.

PSI photoinhibition is usually avoided through P700 oxidation. Without this protective mechanism, excess light represents a potentially lethal threat to plants. PGR5 is suggested to be a major component of cyclic electron transport around PSI and is important for P700 oxidation in angiosperms. The known Arabidopsis PGR5 deficient mutant, , is incapable of P700 oxidation regulation and has been used in numerous photosynthetic studies. However, here it was revealed that was a double mutant with exaggerated PSI photoinhibition. significantly reduced growth compared to the newly isolated PGR5 deficient mutant, . The introduction of PGR5 into restored P700 oxidation regulation, but remained a pale-green phenotype, indicating that had additional mutations. Both and tended to cause PSI photoinhibition by excess light, but exhibited an enhanced reduction in PSI activity. Introducing AT2G17240, a candidate gene for the second mutation into restored the pale-green phenotype and partially restored PSI activity. Furthermore, a deficient mutant of PGRL1 complexing with PGR5 significantly reduced PSI activity in the double-deficient mutant with AT2G17240. From these results, we concluded that AT2G17240, named PSI photoprotection 1 (PTP1), played a role in PSI photoprotection, especially in PGR5/PGRL1 deficient mutants.
Shinya Wada, Katsumi Amako, Chikahiro Miyake

2008 related Products with: Identification of a Novel Mutation Exacerbated the PSI Photoinhibition in / Mutants; Caution for Overestimation of the Phenotypes in Arabidopsis Mutant.

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#34829660   2021/11/09 To Up

Current Knowledge on Mechanisms Preventing Photosynthesis Redox Imbalance in Plants.

Photosynthesis includes a set of redox reactions that are the source of reducing power and energy for the assimilation of inorganic carbon, nitrogen and sulphur, thus generating organic compounds, and oxygen, which supports life on Earth. As sessile organisms, plants have to face continuous changes in environmental conditions and need to adjust the photosynthetic electron transport to prevent the accumulation of damaging oxygen by-products. The balance between photosynthetic cyclic and linear electron flows allows for the maintenance of a proper NADPH/ATP ratio that is adapted to the plant's needs. In addition, different mechanisms to dissipate excess energy operate in plants to protect and optimise photosynthesis under adverse conditions. Recent reports show an important role of redox-based dithiol-disulphide interchanges, mediated both by classical and atypical chloroplast thioredoxins (TRXs), in the control of these photoprotective mechanisms. Moreover, membrane-anchored TRX-like proteins, such as HCF164, which transfer electrons from stromal TRXs to the thylakoid lumen, play a key role in the regulation of lumenal targets depending on the stromal redox poise. Interestingly, not all photoprotective players were reported to be under the control of TRXs. In this review, we discuss recent findings regarding the mechanisms that allow an appropriate electron flux to avoid the detrimental consequences of photosynthesis redox imbalances.
María-Cruz González, Francisco Javier Cejudo, Mariam Sahrawy, Antonio Jesús Serrato

2989 related Products with: Current Knowledge on Mechanisms Preventing Photosynthesis Redox Imbalance in Plants.

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#34792607   2021/11/18 To Up

PTOX-dependent safety valve does not oxidize P700 during photosynthetic induction in the pgr5 mutant.

Plastid terminal oxidase (PTOX) accepts electrons from plastoquinol to reduce molecular oxygen to water. We introduced the gene encoding Chlamydomonas reinhardtii (Cr)PTOX2 into the Arabidopsis (Arabidopsis thaliana) wild type (WT) and proton gradient regulation5 (pgr5) mutant defective in cyclic electron transport around photosystem I (PSI). Accumulation of CrPTOX2 only mildly affected photosynthetic electron transport in the WT background during steady-state photosynthesis but partly complemented the induction of nonphotochemical quenching (NPQ) in the pgr5 background. During the induction of photosynthesis by actinic light (AL) of 130 µmol photons m-2 s-1, the high level of PSII yield (Y(II)) was induced immediately after the onset of AL in WT plants accumulating CrPTOX2. NPQ was more rapidly induced in the transgenic plants than in WT plants. P700 was also oxidized immediately after the onset of AL. Although CrPTOX2 does not directly induce a proton concentration gradient (ΔpH) across the thylakoid membrane, the coupled reaction of PSII generated ΔpH to induce NPQ and the downregulation of the cytochrome b6f complex. Rapid induction of Y(II) and NPQ was also observed in the pgr5 plants accumulating CrPTOX2. In contrast to the WT background, P700 was not oxidized in the pgr5 background. Although the thylakoid lumen was acidified by CrPTOX2, PGR5 was essential for oxidizing P700. In addition to acidification of the thylakoid lumen to downregulate the cytochrome b6f complex (donor-side regulation), PGR5 may be required for draining electrons from PSI by transferring them to the plastoquinone pool. We propose a reevaluation of the contribution of this acceptor-side regulation by PGR5 in the photoprotection of PSI.
Qi Zhou, Caijuan Wang, Hiroshi Yamamoto, Toshiharu Shikanai

2375 related Products with: PTOX-dependent safety valve does not oxidize P700 during photosynthetic induction in the pgr5 mutant.

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#34712896   2021/10/20 To Up

Comparative proteomics of thylakoids from grown in laboratory and field conditions.

Compared to controlled laboratory conditions, plant growth in the field is rarely optimal since it is frequently challenged by large fluctuations in light and temperature which lower the efficiency of photosynthesis and lead to photo-oxidative stress. Plants grown under natural conditions therefore place an increased onus on the regulatory mechanisms that protect and repair the delicate photosynthetic machinery. Yet, the exact changes in thylakoid proteome composition which allow plants to acclimate to the natural environment remain largely unexplored. Here, we use quantitative label-free proteomics to demonstrate that field-grown Arabidopsis plants incorporate aspects of both the low and high light acclimation strategies previously observed in laboratory-grown plants. Field plants showed increases in the relative abundance of ATP synthase, cytochrome , ferredoxin-NADP reductases (FNR1 and FNR2) and their membrane tethers TIC62 and TROL, thylakoid architecture proteins CURT1A, CURT1B, RIQ1, and RIQ2, the minor monomeric antenna complex CP29.3, rapidly-relaxing non-photochemical quenching (qE)-related proteins PSBS and VDE, the photosystem II (PSII) repair machinery and the cyclic electron transfer complexes NDH, PGRL1B, and PGR5, in addition to decreases in the amounts of LHCII trimers composed of LHCB1.1, LHCB1.2, LHCB1.4, and LHCB2 proteins and CP29.2, all features typical of a laboratory high light acclimation response. Conversely, field plants also showed increases in the abundance of light harvesting proteins LHCB1.3 and CP29.1, zeaxanthin epoxidase (ZEP) and the slowly-relaxing non-photochemical quenching (qI)-related protein LCNP, changes previously associated with a laboratory low light acclimation response. Field plants also showed distinct changes to the proteome including the appearance of stress-related proteins ELIP1 and ELIP2 and changes to proteins that are largely invariant under laboratory conditions such as state transition related proteins STN7 and TAP38. We discuss the significance of these alterations in the thylakoid proteome considering the unique set of challenges faced by plants growing under natural conditions.
Sarah E Flannery, Federica Pastorelli, William H J Wood, C Neil Hunter, Mark J Dickman, Philip J Jackson, Matthew P Johnson

2945 related Products with: Comparative proteomics of thylakoids from grown in laboratory and field conditions.

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#34650584   2021/09/28 To Up

The Complementary Roles of Chloroplast Cyclic Electron Transport and Mitochondrial Alternative Oxidase to Ensure Photosynthetic Performance.

Chloroplasts use light energy and a linear electron transport (LET) pathway for the coupled generation of NADPH and ATP. It is widely accepted that the production ratio of ATP to NADPH is usually less than required to fulfill the energetic needs of the chloroplast. Left uncorrected, this would quickly result in an over-reduction of the stromal pyridine nucleotide pool (i.e., high NADPH/NADP ratio) and under-energization of the stromal adenine nucleotide pool (i.e., low ATP/ADP ratio). These imbalances could cause metabolic bottlenecks, as well as increased generation of damaging reactive oxygen species. Chloroplast cyclic electron transport (CET) and the chloroplast malate valve could each act to prevent stromal over-reduction, albeit in distinct ways. CET avoids the NADPH production associated with LET, while the malate valve consumes the NADPH associated with LET. CET could operate by one of two different pathways, depending upon the chloroplast ATP demand. The NADH dehydrogenase-like pathway yields a higher ATP return per electron flux than the pathway involving PROTON GRADIENT REGULATION5 (PGR5) and PGR5-LIKE PHOTOSYNTHETIC PHENOTYPE1 (PGRL1). Similarly, the malate valve could couple with one of two different mitochondrial electron transport pathways, depending upon the cytosolic ATP demand. The cytochrome pathway yields a higher ATP return per electron flux than the alternative oxidase (AOX) pathway. In both and , PGR5/PGRL1 pathway mutants have increased amounts of AOX, suggesting complementary roles for these two lesser-ATP yielding mechanisms of preventing stromal over-reduction. These two pathways may become most relevant under environmental stress conditions that lower the ATP demands for carbon fixation and carbohydrate export.
Avesh Chadee, Nicole A Alber, Keshav Dahal, Greg C Vanlerberghe

2597 related Products with: The Complementary Roles of Chloroplast Cyclic Electron Transport and Mitochondrial Alternative Oxidase to Ensure Photosynthetic Performance.

96T5x96 well plate 100ul1x96 well plate200 units25 mg

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#34623443   2021/10/08 To Up

Maintaining the Chloroplast Redox Balance Through the PGR5-Dependent Pathway and the Trx System is Required for Light-Dependent Activation of Photosynthetic Reactions.

Light-dependent activation of chloroplast enzymes is required for the rapid induction of photosynthesis after a shift from dark to light. The thioredoxin (Trx) system plays a central role in this process. In chloroplasts, the Trx system consists of two pathways: the ferredoxin (Fd)/Trx pathway and the NADPH-Trx reductase C (NTRC) pathway. In Arabidopsis (Arabidopsis thaliana) mutants defective in either pathway, photoreduction of thiol enzymes was impaired, resulting in decreased carbon fixation. The close relationship between the Fd/Trx pathway and PROTON GRADIENT REGULATION 5 (PGR5)-dependent photosystem I cyclic electron transport (PSI CET) in the induction of photosynthesis was recently elucidated. However, how the PGR5-dependent pathway is involved in the NTRC pathway is unclear, although NTRC has been suggested to physically interact with PGR5. In this study, we analyzed Arabidopsis mutants lacking either the PGR5 or the NADH dehydrogenase-like (NDH)-dependent PSI CET pathway in the ntrc mutant background. The ntrc pgr5 double mutant suppressed both the growth defects and the high non-photochemical quenching (NPQ) phenotype of the ntrc mutant when grown under long-day conditions. By contrast, inactivation of NDH activity with the chlororespiratory reduction 2-2 (crr2-2) mutant failed to suppress either phenotype. We discovered that the phenotypic rescue of ntrc by pgr5 is caused by the partial restoration of Trx-dependent reduction of thiol enzymes during the induction of photosynthesis. These results suggest that electron partitioning to the PGR5-dependent pathway and the Trx system needs to be properly regulated for activation of the Calvin-Benson-Bassham cycle enzymes during the induction of photosynthesis.
Yuki Okegawa, Natsuki Tsuda, Wataru Sakamoto, Ken Motohashi

1513 related Products with: Maintaining the Chloroplast Redox Balance Through the PGR5-Dependent Pathway and the Trx System is Required for Light-Dependent Activation of Photosynthetic Reactions.

1100ug Lyophilized100.1 mg100 IU100ug Lyophilized100ug Lyophilized500 Units

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#34530327   2021/09/13 To Up

Thioredoxin-like protein CDSP32 alleviates Cd-induced photosynthetic inhibition in tobacco leaves by regulating cyclic electron flow and excess energy dissipation.

Thioredoxin-like protein CDSP32 (Trx CDSP32), a thioredoxin-like (Trx-like) protein located in the chloroplast, can regulate photosynthesis and the redox state of plants under stress. In order to examine the role of Trx CDSP32 in the photosynthetic apparatus of plants exposed to cadmium (Cd), the effects of Trx CDSP32 on photosynthetic function and photoprotection in tobacco leaves under Cd exposure were studied using a proteomics approach with wild-type (WT) and Trx CDSP32 overexpression (OE) tobacco plants. Cd exposure reduced stomatal conductance, blocked PSII photosynthetic electron transport, and inhibited carbon assimilation. Increased water use efficiency (WUE), cyclic electron flow (CEF) of the proton gradient regulation 5 pathway (PGR5-CEF), and regulated energy dissipation [Y(NPQ)] are important mechanisms of Cd adaptation. However, CEF of the NAD(P)H dehydrogenase pathway (NDH-CEF) was inhibited by Cd exposure. Relative to control conditions, the expression levels of violaxanthin de-epoxidase (VDE) and photosystem II 22 kDa protein (PsbS) in OE leaves were significantly increased under Cd exposure, but those in WT leaves did not change significantly. Moreover, the expression of zeaxanthin epoxidase (ZE) under Cd exposure was significantly higher than that in WT leaves. Thus, Trx CDSP32 increased Y(NPQ) and alleviated PSII photoinhibition under Cd exposure. Trx CDSP32 not only increased PGR5-like protein 1A and 1B expression, but also alleviated the down-regulation of NAD(P)H-quinone oxidoreductase subunits induced by Cd exposure. Thus, Trx CDSP32 promotes CEF in Cd-exposed tobacco leaves. Thus, Trx CDSP32 alleviates the Cd-induced photoinhibition in tobacco leaves by regulating two photoprotective mechanisms: CEF and xanthophyll cycle-dependent energy dissipation.
Huihui Zhang, Xiaoqian Liu, Hongbo Zhang, Yue Wang, Tong Li, Yanhui Che, Jiechen Wang, Dandan Guo, Guangyu Sun, Xin Li

1568 related Products with: Thioredoxin-like protein CDSP32 alleviates Cd-induced photosynthetic inhibition in tobacco leaves by regulating cyclic electron flow and excess energy dissipation.

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#34305990   2021/07/07 To Up

The Physiological Functionality of PGR5/PGRL1-Dependent Cyclic Electron Transport in Sustaining Photosynthesis.

The cyclic electron transport (CET), after the linear electron transport (LET), is another important electron transport pathway during the light reactions of photosynthesis. The proton gradient regulation 5 (PGR5)/PRG5-like photosynthetic phenotype 1 (PGRL1) and the NADH dehydrogenase-like complex pathways are linked to the CET. Recently, the regulation of CET around photosystem I (PSI) has been recognized as crucial for photosynthesis and plant growth. Here, we summarized the main biochemical processes of the PGR5/PGRL1-dependent CET pathway and its physiological significance in protecting the photosystem II and PSI, ATP/NADPH ratio maintenance, and regulating the transitions between LET and CET in order to optimize photosynthesis when encountering unfavorable conditions. A better understanding of the PGR5/PGRL1-mediated CET during photosynthesis might provide novel strategies for improving crop yield in a world facing more extreme weather events with multiple stresses affecting the plants.
Mingzhu Ma, Yifei Liu, Chunming Bai, Yunhong Yang, Zhiyu Sun, Xinyue Liu, Siwei Zhang, Xiaori Han, Jean Wan Hong Yong

1644 related Products with: The Physiological Functionality of PGR5/PGRL1-Dependent Cyclic Electron Transport in Sustaining Photosynthesis.

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#34273632   2021/07/15 To Up

Corrigendum to "Thin cell layer cultures of Chlamydomonas reinhardtii L159I-N230Y, pgrl1 and pgr5 mutants perform enhanced hydrogen production at sunlight intensity" [Bioresour. Technol. 333 (2021) 125217].


Valéria Nagy, Anna Podmaniczki, André Vidal-Meireles, Soujanya Kuntam, Éva Herman, László Kovács, Dávid Tóth, Alberto Scoma, Szilvia Z Tóth

2622 related Products with: Corrigendum to "Thin cell layer cultures of Chlamydomonas reinhardtii L159I-N230Y, pgrl1 and pgr5 mutants perform enhanced hydrogen production at sunlight intensity" [Bioresour. Technol. 333 (2021) 125217].

100 reactions20 ul5ug20 ul50 ul50 µg100 extractions1.00 flask20 ul50 ul50 ul

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