Complexities and protein complexes in the antimycin A-sensitive pathway of cyclic electron flow in plants

22013 LEI 1openInternationalInternational coauthor/editorAntimycin A-sensitive cyclic electron flow (AA-sensitive CEF) was discovered by Arnon and co-workers more than 50 years ago and serves to recycle electrons from ferredoxin (Fd) to plastoquinone (PQ). A role in AA-sensitive CEF has been attributed to the two thylakoid proteins PGR5 and PGRL1 ever since their identification, but this assignment remains controversial. While current technical limitations have prevented unequivocal clarification of their precise function in CEF in vivo, recent biochemical experiments have implied that PGRL1/PGR5 complexes possess Fd-PQ reductase (FQR) activity in vitro. Consequently, PGRL1-PGR5 complexes in flowering plants appear to shuttle between photosystem I (PSI) and the cytochrome (Cyt) b6f complex, whereas in the green alga Chlamydomonas PGRL1 (but not PGR5) has been detected in a PSI-Cyt b6f supercomplex that has intrinsic CEF activityopenLeister, D.; Shikanai, T.Leister, D.M.; Shikanai, T

It’s Harder to Break a Relationship When you Commit Long

Past research has produced evidence that parsing commitments strengthen over the processing of additional linguistic elements that are consistent with the commitments and undoing strong commitments takes more time than undoing weak commitments. It remains unclear, however, whether this so-called digging-in effect is exclusively due to the length of an ambiguous region or at least partly to the extra cost of processing these additional phrases. The current study addressed this issue by testing Japanese relative clause structure, where lexical content and sentence meaning were controlled for. The results showed evidence for a digging-in effect reflecting the strengthened commitment to an incorrect analysis caused by the processing of additional adjuncts. Our study provides strong support for the dynamical, self-organizing models of sentence processing but poses a problem for other models including serial two-stage models as well as frequency-based probabilistic models such as the surprisal theory

Structure and biogenesis of the chloroplast NAD(P)H dehydrogenase complex

AbstractEleven genes (ndhA-ndhK) encoding proteins homologous to the subunits of bacterial and mitochondrial NADH dehydrogenase (complex I) were found in the plastid genome of most land plants. These genes encode subunits of the chloroplast NAD(P)H dehydrogenase (NDH) complex involved in photosystem I (PSI) cyclic electron transport and chlororespiration. Although the chloroplast NDH is believed to be closely and functionally related to the cyanobacterial NDH-1L complex, extensive proteomic, genetic and bioinformatic studies have discovered many novel subunits that are specific to higher plants. On the basis of extensive mutant characterization, the chloroplast NDH complex is divided into four parts, the A, B, membrane and lumen subcomplexes, of which subunits in the B and lumen subcomplexes are specific to higher plants. These results suggest that the structure of NDH has been drastically altered during the evolution of land plants. Furthermore, chloroplast NDH interacts with multiple copies of PSI to form the unique NDH–PSI supercomplex. Two minor light-harvesting-complex I (LHCI) proteins, Lhca5 and Lhca6, are required for the specific interaction between NDH and PSI. The evolution of chloroplast NDH in land plants may be required for development of the function of NDH to alleviate oxidative stress in chloroplasts. In this review, we summarize recent progress on the subunit composition and structure of the chloroplast NDH complex, as well as the information on some factors involved in its assembly. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts

FZL, a dynamin-like protein localized to curved grana edges, is required for efficient photosynthetic electron transfer in Arabidopsis

Photosynthetic electron transfer and its regulation processes take place on thylakoid membranes, and the thylakoid of vascular plants exhibits particularly intricate structure consisting of stacked grana and flat stroma lamellae. It is known that several membrane remodeling proteins contribute to maintain the thylakoid structure, and one putative example is FUZZY ONION LIKE (FZL). In this study, we re-evaluated the controversial function of FZL in thylakoid membrane remodeling and in photosynthesis. We investigated the sub-membrane localization of FZL and found that it is enriched on curved grana edges of thylakoid membranes, consistent with the previously proposed model that FZL mediates fusion of grana and stroma lamellae at the interfaces. The mature fzl thylakoid morphology characterized with the staggered and less connected grana seems to agree with this model as well. In the photosynthetic analysis, the fzl knockout mutants in Arabidopsis displayed reduced electron flow, likely resulting in higher oxidative levels of Photosystem I (PSI) and smaller proton motive force (pmf). However, nonphotochemical quenching (NPQ) of chlorophyll fluorescence was excessively enhanced considering the pmf levels in fzl, and we found that introducing kea3-1 mutation, lowering pH in thylakoid lumen, synergistically reinforced the photosynthetic disorder in the fzl mutant background. We also showed that state transitions normally occurred in fzl, and that they were not involved in the photosynthetic disorders in fzl. We discuss the possible mechanisms by which the altered thylakoid morphology in fzl leads to the photosynthetic modifications

Bone marrow necrosis related to paracoccidioidomycosis: the first eight cases identified at autopsy

To report the first eight bone marrow necrosis (BMN) cases related to paracoccidioidomycosis (PCM) from patient autopsies with well-documented bone marrow (BM) histology and cytology.A retrospective evaluation was performed on BM specimens from eight autopsied patients from Botucatu University Hospital with PCM-related BMN. Relevant BMN literature was searched and analysed.All eight patients had acute PCM. Six had histological only (biopsies) and two cytological only (smears) specimens. Five biopsy specimens revealed severe and one mild coagulation patterned necrotic areas. Five had osteonecrosis. The cytological specimens also showed typical BMN patterns. Paracoccidioides brasiliensis yeast forms were visible within necrotic areas in all cases

Preventive effect of fermented brown rice and rice bran on spontaneous type 1 diabetes in NOD female mice

Consumption of brown rice and rice bran fermented with Aspergillus oryzae (FBRA) suppresses spontaneously occurring diabetes in female NOD mouse. While control diet-fed mice showed glucosuria and hyperglycemia at around 20 week of age and the ratio reached to 57% at 30 weeks of age, the ratio did not increase in the 0.5% FBRA-containing diet-fed group. The FBRA-fed group at 30 weeks of age kept higher ratio of intact islets and showed significantly lower insulitis score compared to the control diet group, with dose-dependency from 0.25% to 0.5% dietary concentration of FBRA. The percentage of diabetic mice was significantly lower at 24 weeks of age as compared to the control group (p = 0.01, log rank test). These results indicate that the suppressive effects of dietary administration of 0.5% FBRA in delaying the spontaneous onset of diabetes in NOD mice is probably achieved by maintaining the number of intact islets

A Cyan Fluorescent Reporter Expressed from the Chloroplast Genome of Marchantia polymorpha.

Recently, the liverwort Marchantia polymorpha has received increasing attention as a basal plant model for multicellular studies. Its ease of handling, well-characterized plastome and proven protocols for biolistic plastid transformation qualify M. polymorpha as an attractive platform to study the evolution of chloroplasts during the transition from water to land. In addition, chloroplasts of M. polymorpha provide a convenient test-bed for the characterization of genetic elements involved in plastid gene expression due to the absence of mechanisms for RNA editing. While reporter genes have proven valuable to the qualitative and quantitative study of gene expression in chloroplasts, expression of green fluorescent protein (GFP) in chloroplasts of M. polymorpha has proven problematic. We report the design of a codon-optimized gfp varian, mturq2cp, which allowed successful expression of a cyan fluorescent protein under control of the tobacco psbA promoter from the chloroplast genome of M. polymorpha. We demonstrate the utility of mturq2cp in (i) early screening for transplastomic events following biolistic transformation of M. polymorpha spores; (ii) visualization of stromules as elements of plastid structure in Marchantia; and (iii) quantitative microscopy for the analysis of promoter activity