Photochemical efficiency of photosystem II,photon yield of O2 evolution,photosynthetic capacity,and carotenoid composition during the midday depression of net CO2 uptake in Arbutus unedo growing in Portugal

During the midday depression of net CO₂ exchange in the mediterranean sclerophyllous shrub Arbutus unedo, examined in the field in Portugal during August of 1987, several parameters indicative of photosynthetic competence were strongly and reversibly affected. These were the photochemical efficiency of photosystem (PS) II, measured as the ratio of variable to maximum chlorophyll fluorescence, as well as the photon yield and the capacity of photosynthetic O₂ evolution at 10% CO₂, of which the apparent photon yield of O₂ evolution was most depressed. Furthermore, there was a strong and reversible increase in the content of the carotenoid zeaxanthin in the leaves that occurred at the expense of both violaxanthin and -carotene. Diurnal changes in fluorescence characteristics were interpreted to indicate three concurrent effects on the photochemical system. First, an increase in the rate of radiationless energy dissipation in the antenna chlorophyll, reflected by changes in 77K fluorescence of PSII and PSI as well as in chlorophyll a fluorescence at ambient temperature. Second, a state shift characterized by an increase in the proportion of energy distributed to PSI as reflected by changes in PSI fluorescence. Third, an effect lowering the photon yield of O₂ evolution and PSII fluorescence at ambient temperature without affecting PSII fluorescence at 77K which would be expected from a decrease in the activity of the water splitting enzyme system, i.e. a donor side limitation.Abbreviations and symbols c_i concentration of CO₂ within the leaf - F_o instantaneous fluorescence emission - F_M maximum fluorescence emission - F_v variable fluorescence emission - PFD photon flux density (400–700 nm) - PSI, II photosystem I, II - T_L leaf temperature     

Expression of the landomycin biosynthetic gene cluster in a PKS mutant of Streptomyces fradiae is dependent on the coexpression of a putative transcriptional activator gene

The formation of landomycin A or one of its derivatives (5,6-anhydrolandomycin A) in a heterologous strain has never been achieved. It has now been made possible by the coexpression of a cosmid containing all biosynthetic genes necessary to produce landomycin A together with a pathway-specific regulatory gene. As host we used a polyketide synthase-defective mutant strain of Streptomyces fradiae Tü2717 which is not able to produce urdamycin A. Our results indicate that four glycosyltransferases are responsible for the formation of the hexasaccharide side chain of landomycin A.     

Genomic Organization and Developmental Fate of Adjacent Repeated Sequences in a Foldback DNA Clone of Tetrahymena thermophila

DNA sequence elimination and rearrangement occurs during the development of somatic cell lineages of eukaryotes and was first discovered over a century ago. However, the significance and mechanism of chromatin elimination are not understood. DNA elimination also occurs during the development of the somatic macronucleus from the germinal micronucleus in unicellular ciliated protozoa such as Tetrahymena thermophila. In this study foldback DNA from the micronucleus was used as a probe to isolate ten clones. All of those tested (4/4) contained sequences that were repetitive in the micronucleus and rearranged in the macronucleus. The presence of inverted repeated sequences was clearly demonstrated in one of them by electron microscopy. DNA sequence analysis showed that the left portion of this clone contains three tandem, directly repeated copies of a 340-bp sequence, a 120-bp portion of which appears in inverted orientation at a 1.6-kb distance. This clone, pTtFB1, was subjected to a detailed analysis of its developmental fate. Subregions were subcloned and used as probes against Southern blots of micronuclear and macronuclear DNA. We found that all subregions defined repeated sequence families in the micronuclear genome. A minimum of four different families was defined, two of which are retained in the macronucleus and two of which are completely eliminated. The inverted repeat family is retained with little rearrangement. Two of the families, defined by subregions that do not contain parts of the inverted repeat, one in the "loop" and one in the "right flanking region," are totally eliminated during macronuclear development--and contain open reading frames. A fourth family occurs in the "loop" region and is rearranged extensively during development. The two gene families that are eliminated are stable in the micronuclear genome but are not clustered together as evidenced by experiments in which DNAs from nullisomic strains are used to map family members to specific micronuclear chromosomes. The inverted repeat family is also stable in the micronuclear genome and is dispersed among several chromosomes. The significance of retained inverted repeats to the process of elimination is discussed.     

A multiparallel bioreactor for the cultivation of mammalian cells in a 3D‐ceramic matrix

For adherently growing cells, cultivation is limited by the provided growth surface. Excellent surface‐to‐volume ratios are found in highly porous matrices, which have to face the challenge of nutrient supply inside the matrices' caverns. Therefore, perfusion strategies are recommended which often have to deal with the need of developing an encompassing bioreactor periphery. We present a modular bioreactor system based on a porous ceramic matrix that enables the supply of cells with oxygen and nutrients by perfusion. The present version of the reactor system focuses on simple testing of various inoculation and operation modes. Moreover, it can be used to efficiently test different foam structures. Protocols are given to set‐up the system together with handling procedures for long‐time cultivation of a CHO cell line. Experimental results confirm vital growth of cells inside the matrices' caverns. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Clinical and molecular genetic features of ARC syndrome

Arthrogryposis, renal dysfunction and cholestasis (ARC) syndrome (MIM 208085) is an autosomal recessive multisystem disorder that may be associated with germline VPS33B mutations. VPS33B is involved in regulation of vesicular membrane fusion by interacting with SNARE proteins, and evidence of abnormal polarised membrane protein trafficking has been reported in ARC patients. We characterised clinical and molecular features of ARC syndrome in order to identify potential genotype-phenotype correlations. The clinical phenotype of 62 ARC syndrome patients was analysed. In addition to classical features described previously, all patients had severe failure to thrive, which was not adequately explained by the degree of liver disease and 10% had structural cardiac defects. Almost half of the patients who underwent diagnostic organ biopsy (7/16) developed life-threatening haemorrhage. We found that most patients (9/11) who suffered severe haemorrhage (7 post biopsy and 4 spontaneous) had normal platelet count and morphology. Germline VPS33B mutations were detected in 28/35 families (48/62 individuals) with ARC syndrome. Several mutations were restricted to specific ethnic groups. Thus p.Arg438X mutation was common in the UK Pakistani families and haplotyping was consistent with a founder mutation with the most recent common ancestor 900–1,000 years ago. Heterozygosity was found in the VPS33B locus in some cases of ARC providing the first evidence of a possible second ARC syndrome gene. In conclusion we state that molecular diagnosis is possible for most children in whom ARC syndrome is suspected and VPS33B mutation analysis should replace organ biopsy as a first line diagnostic test for ARC syndrome.     

Whole-Exome Sequencing Identifies LRIT3 Mutations as a Cause of Autosomal-Recessive Complete Congenital Stationary Night Blindness

Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous retinal disorder. Two forms can be distinguished clinically: complete CSNB (cCSNB) and incomplete CSNB. Individuals with cCSNB have visual impairment under low-light conditions and show a characteristic electroretinogram (ERG). The b-wave amplitude is severely reduced in the dark-adapted state of the ERG, representing abnormal function of ON bipolar cells. Furthermore, individuals with cCSNB can show other ocular features such as nystagmus, myopia, and strabismus and can have reduced visual acuity and abnormalities of the cone ERG waveform. The mode of inheritance of this form can be X-linked or autosomal recessive, and the dysfunction of four genes (NYX, GRM6, TRPM1, and GPR179) has been described so far. Whole-exome sequencing in one simplex cCSNB case lacking mutations in the known genes led to the identification of a missense mutation (c.983G>A [p.Cys328Tyr]) and a nonsense mutation (c.1318C>T [p.Arg440^∗]) in LRIT3, encoding leucine-rich-repeat (LRR), immunoglobulin-like, and transmembrane-domain 3 (LRIT3). Subsequent Sanger sequencing of 89 individuals with CSNB identified another cCSNB case harboring a nonsense mutation (c.1151C>G [p.Ser384^∗]) and a deletion predicted to lead to a premature stop codon (c.1538_1539del [p.Ser513Cysfs^∗59]) in the same gene. Human LRIT3 antibody staining revealed in the outer plexiform layer of the human retina a punctate-labeling pattern resembling the dendritic tips of bipolar cells; similar patterns have been observed for other proteins implicated in cCSNB. The exact role of this LRR protein in cCSNB remains to be elucidated.     

Two models for assessing the prey mass of European ungulates from wolf scats

Among the prey of wolfCanis lupus Linnaeus, 1758, in many European regions, roe deerCapreolus capreolus, red deer Cervuselaphus and wild boarSus scrofa are of primary significance. Up to now, these species were not represented in models which allow an estimation of the consumed biomass on the basis of wolf scats. To develop such formulae for roe deer, red deer and wild boar, we fed these species to 5 captive adult wolves of European origin. In 10 feeding trials, the wolves were fed 10 prey, whose body mass ranged from 15.3 to 118.5 kg. We related the body mass of the prey in accordance with Weaver (1993) to one collectable scat (Model l:y=0.00554+0.00457x) and, as it is difficult to define one unit scat, we alternatively related it to one meter length of scats (Model 2:y=0.141+0.0487x). The Model 1 equation differed from both of Weaver’s (1993) regressions, which he had calculated on the basis of his own feeding trials and on the basis of the summarised data of Floydet al. (1978), Traves (1983) and Weaver (1993). Applying an equation gained through the European ungulates resulted in lower estimates of prey mass. Model 1 and Model 2 estimates were comparable in size.