Reciprocal regulation of protein synthesis and carbon metabolism for thylakoid membrane biogenesis

Metabolic control of gene expression coordinates the levels of specific gene products to meet cellular demand for their activities. This control can be exerted by metabolites acting as regulatory signals and/or a class of metabolic enzymes with dual functions as regulators of gene expression. However, little is known about how metabolic signals affect the balance between enzymatic and regulatory roles of these dual functional proteins. We previously described the RNA binding activity of a 63 kDa chloroplast protein from Chlamydomonas reinhardtii, which has been implicated in expression of the psbA mRNA, encoding the D1 protein of photosystem II. Here, we identify this factor as dihydrolipoamide acetyltransferase (DLA2), a subunit of the chloroplast pyruvate dehydrogenase complex (cpPDC), which is known to provide acetyl-CoA for fatty acid synthesis. Analyses of RNAi lines revealed that DLA2 is involved in the synthesis of both D1 and acetyl-CoA. Gel filtration analyses demonstrated an RNP complex containing DLA2 and the chloroplast psbA mRNA specifically in cells metabolizing acetate. An intrinsic RNA binding activity of DLA2 was confirmed by in vitro RNA binding assays. Results of fluorescence microscopy and subcellular fractionation experiments support a role of DLA2 in acetate-dependent localization of the psbA mRNA to a translation zone within the chloroplast. Reciprocally, the activity of the cpPDC was specifically affected by binding of psbA mRNA. Beyond that, in silico analysis and in vitro RNA binding studies using recombinant proteins support the possibility that RNA binding is an ancient feature of dihydrolipoamide acetyltransferases. Our results suggest a regulatory function of DLA2 in response to growth on reduced carbon energy sources. This raises the intriguing possibility that this regulation functions to coordinate the synthesis of lipids and proteins for the biogenesis of photosynthetic membranes

Biogenic membranes of the chloroplast in Chlamydomonas reinhardtii

The polypeptide subunits of the photosynthetic electron transport complexes in plants and algae are encoded by two genomes. Nuclear genome-encoded subunits are synthesized in the cytoplasm by 80S ribosomes, imported across the chloroplast envelope, and assembled with the subunits that are encoded by the plastid genome. Plastid genome-encoded subunits are synthesized by 70S chloroplast ribosomes directly into membranes that are widely believed to belong to the photosynthetic thylakoid vesicles. However, in situ evidence suggested that subunits of photosystem II are synthesized in specific regions within the chloroplast and cytoplasm of Chlamydomonas. Our results provide biochemical and in situ evidence of biogenic membranes that are localized to these translation zones. A “chloroplast translation membrane” is bound by the translation machinery and appears to be privileged for the synthesis of polypeptides encoded by the plastid genome. Membrane domains of the chloroplast envelope are located adjacent to the cytoplasmic translation zone and enriched in the translocons of the outer and inner chloroplast envelope membranes protein import complexes, suggesting a coordination of protein synthesis and import. Our findings contribute to a current realization that biogenic processes are compartmentalized within organelles and bacteria

Child labor and conflict: evidence from Afghanistan

We study the impact of conflict on both the extensive and the intensive margin of child labor in Afghanistan. We identify and test two main mechanisms. First, if conflict reduces a household income through a decline in parent's compensations, child labor may insure against the decrease in consumption (extensive margin). Second, a child may work longer hours if the marginal benefits of working under conflict is greater than its marginal cost, which may depend on the relative compensations between adults and children, and on the alternative activities (e.g. schooling). Using detailed conflict data from the Afghan War Diary we identify the effect of conflict relying on a shift-share IV strategy. We find that conflict increases the probability that girls work, but reduces the number of hours worked. Our results suggest that this is due to a decrease in household income and an increase in the relative compensations of adults

Analisa Pondasi Pile Raft Pada Tanah Lunak Dengan Plaxis 2d

Permasalahan penurunan menjadi salah satu masalah yang sering dihadapi para perencana pondasi bangunan dikarenakan oleh kondisi tanah yang lunak. Untuk mengatasi permasalahan yang ada, banyak perencana menggunakan pondasi raft atau pondasi rakit, karena dianggap mampu memberikan faktor keamanan yang memadai dalam menghadapi kegagalan daya dukung ultimate. Namun diperkirakan pondasi raft ini akan mengalami penurunan yang besar. Permasalahan tersebut mungkin dapat berkurang jika adanya penambahan pile pada pondasi raft sehingga menjadi pondasi pile raft. Dengan penambahan pile pada pondasi raft diharapkan perencanaannya mempertimbangkan segi ekonomis. Dengan menggunakan beban merata 6 t/m2, dilakukan penelitian pada pondasi pile raft dengan memvariasikan tebal raft yakni 80 cm, 100 cm, 120 cm dan 140 cm. Untuk panjang pile divariasikan dari panjang 5 m, 7 m, 9 m, 13 m dan 15 m. Analisis penurunan dilakukan dengan menggunakan software Plaxis 2D dan Metode Poulos. Hasil dari penelitian ini menunjukkan bahwa Penambahan jumlah pile pada pondasi raft menghasilkan profil penurunan yang berkurang namun pada suatu keadaan tertentu penambahan pile tidak memberikan kontribusi yang lebih signifikan. Begitupun dengan perhitungan Poulos, pada konfigurasi pile tertentu tidak memberi kontribusi lagi. Sehingga desain yang ekonomis pada penelitian ini adalah dengan menggunakan tebal raft 80 cm dengan panjang pile 13 m dan konfigurasi pile 7x7

Sub-cellular location of FtsH proteases in the cyanobacterium Synechocystis sp PCC 6803 suggests localised PSII repair zones in the thylakoid membranes

Marie Curie Initial Training Networks. Grant Number: FP7-PEOPLE-ITN-2008 Biotechnology and Biological Sciences Research Council. Grant Numbers: BB/G021856, BB/F020554/

Author response

Chloroplast function is orchestrated by the organelle's intricate architecture. By combining cryo-focused ion beam milling of vitreous Chlamydomonas cells with cryo-electron tomography, we acquired three-dimensional structures of the chloroplast in its native state within the cell. Chloroplast envelope inner membrane invaginations were frequently found in close association with thylakoid tips, and the tips of multiple thylakoid stacks converged at dynamic sites on the chloroplast envelope, implicating lipid transport in thylakoid biogenesis. Subtomogram averaging and nearest neighbor analysis revealed that RuBisCO complexes were hexagonally packed within the pyrenoid, with similar to 15 nm between their centers. Thylakoid stacks and the pyrenoid were connected by cylindrical pyrenoid tubules, physically bridging the sites of light-dependent photosynthesis and light-independent carbon fixation. Multiple parallel minitubules were bundled within each pyrenoid tubule, possibly serving as conduits for the targeted one-dimensional diffusion of small molecules such as ATP and sugars between the chloroplast stroma and the pyrenoid matrix

Photoactivation: The light-driven assembly of the water oxidation complex of Photosystem II

Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II. The assembly of the Mn4O5Ca requires light and involves a sequential process called photoactivation. This process harnesses the charge-separation of the photochemical reaction center and the coordination environment provided by the amino acid side chains of the protein to oxidize and organize the incoming manganese ions to form the oxo-bridged metal cluster capable of H2O-oxidation. Although most aspects of this assembly process remain poorly understood, recent advances in the elucidation of the crystal structure of the fully assembled cyanobacterial PSII complex help in the interpretation of the rich history of experiments designed to understand this process. Moreover, recent insights on the structure and stability of the constituent ions of the Mn4CaO5 cluster may guide future experiments. Here we consider the literature and suggest possible models of assembly including one involving single Mn2+ oxidation site for all Mn but requiring ion relocation.Peer reviewedMicrobiology and Molecular Genetic

Powered by my own energy: Bairro Solar EDP, your solar energy for the neighbourhood

The recent law decree 162/2019 opened the door to numerous opportunities within collective self-consumption projects in Portugal. The ever increasing need to adopt sustainable practices results in significant impacts and business opportunities that EDP Comercial maybenefit from. This study examines the best approach to introduce solar communities in the Portuguese market by exploring possible business models and developing a coherent marketing strategy. In order to provide a better answer to these questions, semi-structured interviews with 30 participants and a questionnaire with 201valid responses were conducted to gather insights and support the decisions