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A search for factors influencing etioplast-chloroplast transition.

ABSTRACT: Chloroplast biogenesis in angiosperm plants requires the light-dependent transition from an etioplast stage. A key factor in this process is NADPH:protochlorophyllide oxidoreductase A (PORA), which catalyzes the light-dependent reduction of protochlorophyllide to chlorophyllide. In a recent study the chloroplast outer envelope channel OEP16 was described to be involved in etioplast to chloroplast transition by forming the translocation pore for the precursor protein of PORA [Pollmann et al. (2007) Proc Natl Acad Sci USA 104:2019-2023]. This hypothesis was based on the finding that a single OEP16.1 knockout mutant in Arabidopsis thaliana was severely affected during seedling de-etiolation and PORA protein was absent in etioplasts. In contrast, in our study the identical T-DNA insertion line greened normally and showed normal etioplast to chloroplast transition, and mature PORA was present in etioplasts [Philippar et al. (2007) Proc Natl Acad Sci USA 104:678-683]. To address these conflicting results regarding the function of OEP16.1 for PORA import, we analyzed several lines segregating from the original OEP16.1 T-DNA insertion line. Thereby we can unequivocally show that the loss of OEP16.1 neither correlates with impaired PORA import nor causes the observed de-etiolation phenotype. Furthermore, we found that the mutant line contains at least 2 additional T-DNA insertions in the genes for the extracellular polygalacturonase converter AroGP1 and the plastid-localized chorismate mutase CM1. However, detailed examination of the de-etiolation phenotype and a genomewide transcriptional analysis revealed no direct influence of these genes on etioplast to chloroplast transition in Arabidopsis cotyledons.

SUBMITTER: Pudelski B

PROVIDER: S-EPMC2715521 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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A search for factors influencing etioplast-chloroplast transition.

Pudelski Birgit B Soll Jürgen J Philippar Katrin K

Proceedings of the National Academy of Sciences of the United States of America 20090630 29

Chloroplast biogenesis in angiosperm plants requires the light-dependent transition from an etioplast stage. A key factor in this process is NADPH:protochlorophyllide oxidoreductase A (PORA), which catalyzes the light-dependent reduction of protochlorophyllide to chlorophyllide. In a recent study the chloroplast outer envelope channel OEP16 was described to be involved in etioplast to chloroplast transition by forming the translocation pore for the precursor protein of PORA [Pollmann et al. (200 ...[more]

PMID: 19567834

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Project description:BackgroundAntiretroviral medicines (ARVs) are one of the most costly parts of HIV/AIDS treatment. Many countries are struggling to provide universal access to ARVs for all people living with HIV and AIDS. Although substantial price reductions of ARVs have occurred, especially between 2002 and 2008, achieving sustainable access for the next several decades remains a major challenge for most low- and middle-income countries. The objectives of the present study were twofold: first, to analyze global ARV prices between 2005 and 2008 and associated factors, particularly procurement methods and key donor policies on ARV procurement efficiency; second, to discuss the options of procurement processes and policies that should be considered when implementing or reforming access to ARV programs.MethodsAn ARV-medicines price-analysis was carried out using the Global Price Reporting Mechanism from the World Health Organization. For a selection of 12 ARVs, global median prices and price variation were calculated. Linear regression models for each ARV were used to identify factors that were associated with lower procurement prices. Logistic regression models were used to identify the characteristics of those countries which procure below the highest and lowest direct manufactured costs.ResultsThree key factors appear to have an influence on a country's ARV prices: (a) whether the product is generic or not; (b) the socioeconomic status of the country; (c) whether the country is a member of the Clinton HIV/AIDS Initiative. Factors which did not influence procurement below the highest direct manufactured costs were HIV prevalence, procurement volume, whether the country belongs to the least developed countries or a focus country of the United States President's Emergency Plan For AIDS Relief.ConclusionOne of the principal mechanisms that can help to lower prices for ARV over the next several decades is increasing procurement efficiency. Benchmarking prices could be one useful tool to achieve this.

Dataset Information

A search for factors influencing etioplast-chloroplast transition.

Publications

A search for factors influencing etioplast-chloroplast transition.

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