Functional and structural characterization of domain truncated violaxanthin de‐epoxidase

Hallin, Erik I.; Guo, Kuo; Åkerlund, Hans Erik

doi:10.1111/ppl.12428

Cited by 5 publications

(3 citation statements)

References 26 publications

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“…Ascorbate is a reductant for violaxanthin deepoxidase in vascular plants (Saga et al, 2010; Hallin et al, 2016), but is not required for green algal-type violaxanthin deepoxidases (Li et al, 2016; Vidal-Meireles et al, 2020). Instead, Asc mitigates an oxidative stress-related qI component of non-photochemical quenching (NPQ) and, therefore, NPQ is increased upon Asc-deficiency in C. reinhardtii (Vidal-Meireles et al, 2020).…”

Section: Resultsmentioning

confidence: 99%

The chloroplastic phosphate transporter CrPHT4-7 supports phosphate homeostasis and photosynthesis in Chlamydomonas

Tóth,

Kuntam,

Ferenczi

et al. 2023

Preprint

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In eukaryotic cells, phosphorus is assimilated and utilized primarily as phosphate (Pi). Pi homeostasis is mediated by transporters that have not yet been adequately characterized in green algae. This study reports on CrPHT4-7 fromChlamydomonas reinhardtii, a member of the PHT4 transporter family, which exhibits remarkable similarity to AtPHT4;4 fromArabidopsis thaliana, a chloroplastic ascorbate transporter. Using fluorescent protein tagging we show that CrPHT4-7 resides in the chloroplast envelope membrane.Crpht4-7mutants, generated by the CRISPR/Cas12a-mediated single-strand templated repair, show retarded growth especially in high light, enhanced sensitivity to phosphorus limitation, reduced ATP level, strong ascorbate accumulation and diminished non-photochemical quenching in high light. Conversely, CrPHT4-7 overexpressing lines exhibit enhanced biomass accumulation under high light conditions in comparison with the wild-type strain. Expressing CrPHT4-7 in a yeast strain lacking Pi transporters substantially recovered its slow growth phenotype demonstrating that it transports Pi. Even though CrPHT4-7 shows a high degree of similarity to AtPHT4;4, it does not display any significant ascorbate transport activity in yeast or intact algal cells. Thus, the results demonstrate that CrPHT4-7 functions as a chloroplastic Pi transporter essential for maintaining Pi homeostasis and photosynthesis inChlamydomonas reinhardtii.One-sentence summaryWe demonstrate that the CrPHT4-7 transporter ofChlamydomonas reinhardtiiis located in the chloroplast envelope membrane and contributes to maintaining phosphate homeostasis and photosynthesis.

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Section: Resultsmentioning

confidence: 99%

The chloroplastic phosphate transporter CrPHT4-7 supports phosphate homeostasis and photosynthesis in Chlamydomonas

Tóth,

Kuntam,

Ferenczi

et al. 2023

Preprint

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“…2). Asc is required for violaxanthin de-epoxidase activity (Bratt et al, 1995; Saga et al, 2010; Hallin et al, 2016); accordingly, Asc-deficiency diminishes NPQ, particularly in HL (Fig. 1) and the de-epoxidation index was approximately 50% lower in the vtc2-4 mutant than in Col-0 in HL (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Asc may also donate electrons to PSII and photosystem I (PSI) in bundle sheath cells with a very low oxygen-evolving capacity (Ivanov et al, 2001; Ivanov et al, 2007). In vascular plants, Asc acts as a cofactor of violaxanthin de-epoxidase, thereby playing an essential role in the process of non-photochemical quenching (NPQ) allowing the dissipation of excess energy as heat (Bratt et al, 1995; Müller-Moulé et al, 2002; Saga et al, 2010; Hallin et al, 2016). On the other hand, Asc-deficiency does not limit NPQ in Chlamydomonas reinhardtii , as it is not required as a co-factor for algal-type violaxanthin de-epoxidase (Li et al, 2016; Vidal-Meireles et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Chloroplastic ascorbate acts as a regulatory hub in plant metabolism regardless of oxidative stress

Tóth,

Tengölics,

Aarabi

et al. 2024

Preprint

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Ascorbate is a major plant metabolite that plays crucial roles in various processes, from reactive oxygen scavenging to epigenetic regulation. However, to what extent and how ascorbate modulates metabolism is largely unknown. To address this, we investigated the consequences of chloroplastic and total cellular ascorbate-deficiencies by studying chloroplastic ascorbate-transporter pht4;4 mutant lines, and the ascorbate-deficient vtc2-4 mutant of Arabidopsis thaliana. Under regular growth conditions, both ascorbate-deficiencies caused minor alterations in photosynthesis, with no apparent signs of oxidative damage. In contrast, metabolomics analysis revealed a global and largely overlapping metabolome rewiring in both ascorbate-deficiencies, suggesting that chloroplastic ascorbate modulates plant metabolism. We observed significant alterations in amino acid metabolism, particularly in arginine metabolism, activation of nucleotide salvage pathways, and changes in secondary metabolism. In addition, proteome-wide analysis of thermostability revealed that ascorbate may interact with enzymes involved in arginine metabolism, the Calvin-Benson cycle, and several photosynthetic electron transport components. Overall, our results suggest that, independently of oxidative stress, chloroplastic ascorbate interconnects and coordinates diverse metabolic pathways in vascular plants and thus acts as a regulatory hub.

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Molecular studies on structural changes and oligomerisation of violaxanthin de-epoxidase associated with the pH-dependent activation

et al. 2016

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Violaxanthin de-epoxidase (VDE) is a conditionally soluble enzyme located in the thylakoid lumen and catalyses the conversion of violaxanthin to antheraxanthin and zeaxanthin, which are located in the thylakoid membrane. These reactions occur when the plant or algae are exposed to saturating light and the zeaxanthin formed is involved in the process of non-photochemical quenching that protects the photosynthetic machinery during stress. Oversaturation by light results in a reduction of the pH inside the thylakoids, which in turn activates VDE and the de-epoxidation of violaxanthin. To elucidate the structural events responsible for the pH-dependent activation of VDE, full length and truncated forms of VDE were studied at different pH using circular dichroism (CD) spectroscopy, crosslinking and small angle X-ray scattering (SAXS). CD spectroscopy showed the formation of α-helical coiled-coil structure, localised in the C-terminal domain. Chemical crosslinking of VDE showed that oligomers were formed at low pH, and suggested that the position of the N-terminal domain is located near the opening of lipocalin-like barrel, where violaxanthin has been predicted to bind. SAXS was used to generate models of monomeric VDE at high pH and also a presumably dimeric structure of VDE at low pH. For the dimer, the best fit suggests that the interaction is dominated by one of the domains, preferably the C-terminal domain due to the lost ability to oligomerise at low pH, shown in earlier studies, and the predicted formation of coiled-coil structure.

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Functional and structural characterization of domain truncated violaxanthin de‐epoxidase

Cited by 5 publications

References 26 publications

The chloroplastic phosphate transporter CrPHT4-7 supports phosphate homeostasis and photosynthesis in Chlamydomonas

The chloroplastic phosphate transporter CrPHT4-7 supports phosphate homeostasis and photosynthesis in Chlamydomonas

Chloroplastic ascorbate acts as a regulatory hub in plant metabolism regardless of oxidative stress

Molecular studies on structural changes and oligomerisation of violaxanthin de-epoxidase associated with the pH-dependent activation

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