The chloroplast protein CPSAR1, dually localized in the stroma and the inner envelope membrane,is involved in thylakoid biogenesis

Thylakoid biogenesis is a crucial step for plant development involving the combined action of many cellular actors. CPSAR1 is shown here to be required for the normal organization of mature thylakoid stacks, and ultimately for embryo development. CPSAR1 is a chloroplast protein that has a dual localization in the stroma and the inner envelope membrane, according to microscopy studies and subfractionation analysis. CPSAR1 is close to the Obg nucleotide binding protein subfamily and displays GTPase activity, as demonstrated by in vitro assays. Disruption of the CPSAR1 gene via T‐DNA insertion results in the arrest of embryo development. In addition, transmission electron microscopy analysis indicates that mutant embryos are unable to develop thylakoid membranes, and remain white. Unstacked membrane structures resembling single lamellae accumulate in the stroma, and do not assemble into mature thylakoid stacks. CPSAR1 RNA interference induces partially developed thylakoids leading to pale‐green embryos. Altogether, the presented data demonstrate that CPSAR1 is a protein essential for the formation of normal thylakoid membranes, and suggest a possible involvement in the initiation of vesicles from the inner envelope membrane for the transfer of lipids to the thylakoids.     

A Major Determinant for Binding and Aminoacylation of tRNA in Cytoplasmic Alanyl-tRNA Synthetase Is Mutated in Dominant Axonal Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth disease (CMT) is the most common cause of inherited peripheral neuropathy, with an estimated frequency of 1/2500. We studied a large family with 17 patients affected by the axonal form of CMT (CMT2). Analysis of the 15 genes or loci known to date was negative. Genome-wide genotyping identified a CMT2 locus in 16q21-q23 between D16S3050 and D16S3106. The maximum two-point LOD score was 4.77 at θ = 0 for marker D16S3050. Sequencing of candidate genes identified a unique mutation, c.986G>A (p.Arg329His), affecting a totally conserved amino acid in the helical domain of cytoplasmic alanyl-tRNA synthetase (AlaRS). A second family with the same mutation and a different founder was then identified in a cohort of 91 CMT2 families. Although mislocation of mutant Arg329His-AlaRS in axons remains to be evaluated, experimental data point mostly to a quantitative reduction in tRNA^Ala aminoacylation. Aminoacylation and editing functions closely cooperate in AlaRS, and Arg329His mutation could also lead to qualitative errors participating in neurodegeneration. Our report documents in 18 patients the deleterious impact of a mutation in human cytoplasmic AlaRS and broadens the spectrum of defects found in tRNA synthetases. Patients present with sensory-motor distal degeneration secondary to predominant axonal neuropathy, slight demyelination, and no atypical or additional CNS features.     

Increasing cell biomass in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> increases recombinant protein yield: the use of a respiratory strain as a microbial cell factory

Background  

Recombinant protein production is universally employed as a solution to obtain the milligram to gram quantities of a given protein required for applications as diverse as structural genomics and biopharmaceutical manufacture. Yeast is a well-established recombinant host cell for these purposes. In this study we wanted to investigate whether our respiratory Saccharomyces cerevisiae strain, TM6*, could be used to enhance the productivity of recombinant proteins over that obtained from corresponding wild type, respiro-fermentative strains when cultured under the same laboratory conditions.     

Estimating amplification efficiency improves multiplex real-time PCR quantification of Bacillus licheniformis and Bacillus subtilis spores in animal feed

A multiplex real-time PCR assay was developed for absolute quantification in animal feed of Bacillus subtilis CH201 and Bacillus licheniformis CH200 spores, which constitute the viable component of the microbial growth promoter, BioPlus 2B. Spores were lysed using a bead-beating protocol. DNA was extracted and purified from the lysates with the Qiagen DNeasy Plant Kit. Two standard curves for absolute quantification were made and tested. Standard curve-1 was made from feed samples spiked with BioPlus 2B, while standard curve-2 was made from serially diluted DNA extracted from BioPlus 2B powder. Feed samples supplemented with BioPlus 2B were quantified using both standard curves. The detection limit of the assay was 10(4) CFU g(-1) of feed. The amplification efficiency (Eff) of each PCR was determined using the LinRegPCR software and Eff differences between individual samples and standards were corrected for. When compared to plate counts, standard curve-1 slightly under-estimated the number of spores (mean=-2.47% of plate counts). A spore density-dependent Eff was found, and Eff for standard curve-1 could not be determined. Standard curve-2 over-estimated spore numbers when not corrected for individual Eff (mean=+5.46% of plate counts). Standard curve-2 Eff was independent (Eff(mean)=1.96) of spore density. The assay quantified the numbers of spores in feed samples very similar to plate counts (mean=+0.47% of plate counts), when standard curve-2 was used and individual Eff was accounted for.     

Angiotensin II type 1 receptor blockade attenuates TGF-beta-induced failure of muscle regeneration in multiple myopathic states

Skeletal muscle has the ability to achieve rapid repair in response to injury or disease. Many individuals with Marfan syndrome (MFS), caused by a deficiency of extracellular fibrillin-1, exhibit myopathy and often are unable to increase muscle mass despite physical exercise. Evidence suggests that selected manifestations of MFS reflect excessive signaling by transforming growth factor (TGF)-beta (refs. 2,3). TGF-beta is a known inhibitor of terminal differentiation of cultured myoblasts; however, the functional contribution of TGF-beta signaling to disease pathogenesis in various inherited myopathic states in vivo remains unknown. Here we show that increased TGF-beta activity leads to failed muscle regeneration in fibrillin-1-deficient mice. Systemic antagonism of TGF-beta through administration of TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor blocker losartan normalizes muscle architecture, repair and function in vivo. Moreover, we show TGF-beta-induced failure of muscle regeneration and a similar therapeutic response in a dystrophin-deficient mouse model of Duchenne muscular dystrophy.