ORCID Profile
0000-0003-2863-4139
Current Organisation
University of Tasmania
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Publisher: Wiley
Date: 28-01-2010
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 07-2008
Publisher: Springer Science and Business Media LLC
Date: 26-09-2012
DOI: 10.1007/S00425-012-1761-4
Abstract: In most oxygenic phototrophs, including cyanobacteria, two independent enzymes catalyze the reduction of protochlorophyllide to chlorophyllide, which is the penultimate step in chlorophyll (Chl) biosynthesis. One is light-dependent NADPH:protochlorophyllide oxidoreductase (LPOR) and the second type is dark-operative protochlorophyllide oxidoreductase (DPOR). To clarify the roles of both enzymes, we assessed synthesis and accumulation of Chl-binding proteins in mutants of cyanobacterium Synechocystis PCC 6803 that either completely lack LPOR or possess low levels of the active enzyme due to its ectopic regulatable expression. The LPOR-less mutant grew photoautotrophically in moderate light and contained a maximum of 20 % of the wild-type (WT) Chl level. Both Photosystem II (PSII) and Photosystem I (PSI) were reduced to the same degree. Accumulation of PSII was mostly limited by the synthesis of antennae CP43 and especially CP47 as indicated by the accumulation of reaction center assembly complexes. The phenotype of the LPOR-less mutant was comparable to the strain lacking DPOR that also contained <25 % of the wild-type level of PSII and PSI when cultivated under light-activated heterotrophic growth conditions. However, in the latter case, we detected no reaction center assembly complexes, indicating that synthesis was almost completely inhibited for all Chl-proteins, including the D1 and D2 proteins.
Publisher: Oxford University Press (OUP)
Date: 15-11-2011
Abstract: We have investigated the location of the Psb27 protein and its role in photosystem (PS) II biogenesis in the cyanobacterium Synechocystis sp. PCC 6803. Native gel electrophoresis revealed that Psb27 was present mainly in monomeric PSII core complexes but also in smaller amounts in dimeric PSII core complexes, in large PSII supercomplexes, and in the unassembled protein fraction. We conclude from analysis of assembly mutants and isolated histidine-tagged PSII subcomplexes that Psb27 associates with the “unassembled” CP43 complex, as well as with larger complexes containing CP43, possibly in the vicinity of the large lumenal loop connecting transmembrane helices 5 and 6 of CP43. A functional role for Psb27 in the biogenesis of CP43 is supported by the decreased accumulation and enhanced fragmentation of unassembled CP43 after inactivation of the psb27 gene in a mutant lacking CP47. Unexpectedly, in strains unable to assemble PSII, a small amount of Psb27 comigrated with monomeric and trimeric PSI complexes upon native gel electrophoresis, and Psb27 could be copurified with histidine-tagged PSI isolated from the wild type. Yeast two-hybrid assays suggested an interaction of Psb27 with the PsaB protein of PSI. Pull-down experiments also supported an interaction between CP43 and PSI. Deletion of psb27 did not have drastic effects on PSII assembly and repair but did compromise short-term acclimation to high light. The tentative interaction of Psb27 and CP43 with PSI raises the possibility that PSI might play a previously unrecognized role in the biogenesis/repair of PSII.
Publisher: Cold Spring Harbor Laboratory
Date: 10-2023
Publisher: Oxford University Press (OUP)
Date: 04-10-2012
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 08-2012
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.PROTIS.2006.02.005
Abstract: Apicomplexan parasites represent one of the most important groups of parasitic unicellular eukaryotes comprising such important human parasites such as Plasmodium spp. and Toxoplasma gondii. Apicomplexan radiation as well as their adaptation to the parasitic style of life took place before the era of vertebrates. Thus, invertebrates were the first hosts of apicomplexan parasites that switched to vertebrates later in evolution. Despite this fact, apicomplexan parasites of invertebrates, with the exception of gregarines, have so far been ignored in phylogenetic studies. To address this issue, we sequenced the nuclear SSU rRNA genes from the homoxenous apicomplexan parasites of insects Adelina grylli and Adelina dimidiata, and the heteroxenous Aggregata octopiana and Aggregata eberthii that are transmitted between cephalopods and crustaceans, and used them for phylogenetic reconstructions. The position of the adelinids as a sister group to Hepatozoon spp. within the suborder Adeleorina was stable regardless of the phylogenetic method used. In contrast, both members of the genus Aggregata possess highly ergent SSU rRNA genes with an unusual nucleotide composition. Because of this, they form the longest branches in the tree and their position is variable. However, the genus Aggregata branches together with adelinids and hepatozoons in most of the analyses, although their position within the scope of this cluster is unstable.
Publisher: Frontiers Media SA
Date: 12-05-2016
Publisher: Wiley
Date: 04-2016
Abstract: Non-photochemical quenching (NPQ) is a photoprotective mechanism in light-harvesting antennae. NPQ is triggered by chloroplast thylakoid lumen acidification and is accompanied by violaxanthin de-epoxidation to zeaxanthin, which further stimulates NPQ. In the present study, we show that violaxanthin can act in the opposite direction to zeaxanthin because an increase in the concentration of violaxanthin reduced NPQ in the light-harvesting antennae of Chromera velia. The correlation overlapped with a similar relationship between violaxanthin and NPQ as observed in isolated higher plant light-harvesting complex II. The data suggest that violaxanthin in C. velia can act as an inhibitor of NPQ, indicating that violaxanthin has to be removed from the vicinity of the protein to reach maximal NPQ.
Publisher: Oxford University Press (OUP)
Date: 12-08-2015
DOI: 10.1104/PP.15.01150
Location: Czechia
No related grants have been discovered for Jana Talbot.