Isolation and characterization of mutants of common ice plant deficient in crassulacean acid metabolism

Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that improves water use efficiency by shifting part or all of net atmospheric CO2 uptake to the night. Genetic dissection of regulatory and metabolic attributes of CAM has been limited by the difficulty of identifying a reliable phenotype for mutant screening. We developed a novel and simple colorimetric assay to measure leaf pH to screen fast neutron-mutagenized populations of common ice plant (Mesembryanthemum crystallinum), a facultative CAM species, to detect CAM-deficient mutants with limited nocturnal acidification. The isolated CAM-deficient mutants showed negligible net dark CO2 uptake compared with wild-type plants following the imposition of salinity stress. The mutants and wild-type plants accumulated nearly comparable levels of sodium in leaves, but the mutants grew more slowly than the wild-type plants. The mutants also had substantially reduced seed set and seed weight relative to wild type under salinity stress. Carbon-isotope ratios of seed collected from 4-month-old plants indicated that C3 photosynthesis made a greater contribution to seed production in mutants compared to wild type. The CAM-deficient mutants were deficient in leaf starch and lacked plastidic phosphoglucomutase, an enzyme critical for gluconeogenesis and starch formation, resulting in substrate limitation of nocturnal C4 acid formation. The restoration of nocturnal acidification by feeding detached leaves of salt-stressed mutants with glucose or sucrose supported this defect and served to illustrate the flexibility of CAM. The CAM-deficient mutants described here constitute important models for exploring regulatory features and metabolic consequences of CAM.     

Evolution of the Hemagglutinin Gene of the Influenza A(H1N1)pdm09 Virus in Morocco During Two Influenza Seasons 2009–2011

To study genetic evolution of Moroccan influenza A(H1N1)pdm09 virus strains, we conducted a molecular characterization of the hemagglutinin gene subunit 1 (HA1) of 36 influenza A(H1N1)pdm09 virus strains. The stains were collected from patients in Rabat and Casablanca during two influenza seasons 2009–2010 and 2010–2011. Nucleotide and amino acid sequences of 14 influenza A(H1N1)pdm09 virus strains from 2009 to 2010 were ~97 and 99 %, respectively, similar to the reference strain A/California/07/2009 (H1N1). Phylogenetic analysis of 22 influenza A(H1N1)pdm09 virus strains from 2010 to 2011 revealed a co-circulation of three well-described different genetic groups. Most important, none of the identified groups showed significant changes at the antigenic site of the virus HA1 subunit which may alter the efficacy of California/07/2009 (H1N1) vaccine.     

Molecular Diagnostic and Prognostic Subtyping of Gliomas in Tunisian Population

It has become increasingly evident that morphologically similar gliomas may have distinct clinical phenotypes arising from diverse genetic signatures. To date, glial tumours from the Tunisian population have not been investigated. To address this, we correlated the clinico-pathology with molecular data of 110 gliomas by a combination of HM450K array, MLPA and TMA-IHC. PTEN loss and EGFR amplification were distributed in different glioma histological groups. However, 1p19q co-deletion and KIAA1549:BRAF fusion were, respectively, restricted to Oligodendroglioma and Pilocytic Astrocytoma. CDKN2A loss and EGFR overexpression were more common within high-grade gliomas. Furthermore, survival statistical correlations led us to identify Glioblastoma (GB) prognosis subtypes. In fact, significant lower overall survival (OS) was detected within GB that overexpressed EGFR and Cox2. In addition, IDH1R132H mutation seemed to provide a markedly survival advantage. Interestingly, the association of IDHR132H mutation and EGFR normal status, as well as the association of differentiation markers, defined GB subtypes with good prognosis. By contrast, poor survival GB subtypes were defined by the combination of PTEN loss with PDGFRa expression and/or EGFR amplification. Additionally, GB presenting p53-negative staining associated with CDKN2A loss or p21 positivity represented a subtype with short survival. Thus, distinct molecular subtypes with individualised prognosis were identified. Interestingly, we found a unique histone mutation in a poor survival young adult GB case. This tumour exceptionally associated the H3F3A G34R mutation and MYCN amplification as well as 1p36 loss and 10q loss. Furthermore, by exhibiting a remarkable methylation profile, it emphasised the oncogenic power of G34R mutation connecting gliomagenesis and chromatin regulation.     

Determination of the primary sequence of the duck αD globin mRNA and comparison of all adult duck and chick globin mRNA sequences

The nucleotide sequence of the duck α^D globin mRNA was determined. Its main feature is an exceptionally short 3′ non-coding segment of only 46 nucleotides, placed after the coding sequence of 141 codons. The last of the 6 adult globin mRNA of duck and chicken being thus sequenced, a comparison of all their features has become possible. Comparing the duck α^D mRNA to the related sequence in the chicken, we found greater homology than comparing it to the linked α^A globin sequence in the same species. Extensive homology can be found for a same globin chain α^A, α^D or β in between different avian species including also the goose and the ostrich; the avian α globin chains show a lower degree of sequence conservation in between species than the β chains. In contrast, within one species the three globin sequences have further diverged. The divergence between the α^A and α^D globin within a same species point to individual functional specificity and hence independent evolution and suggest that a mechanism of ‘gene conversion’ did not operate in between the avian α globin genes. Two segments of the amino acid sequence which we named ‘A^α’ and ‘B^α’ remain homologous in all avian α globins; two other regions ‘A^β’ and ‘B^β’ are identical in between the β globins. Segment A is placed at the 5′ end of exon II, and segment B at the 3′ end of the same exon; some amino acids in those segments are involved in the Heme binding site. Being almost identical in all know mammalian and avian globins of the α respectively the β type, regions A and B seem to represent the best conserved sequences in adult globin mRNA maintained during the divergence of species.     

Characterization of a nontoxic pyomelanin pigment produced by the yeast Yarrowia lipolytica

In this study, we report on the ability of the yeast Yarrowia lipolytica W29 to produce an extracellular melanin-like brown pigment at high yield (0.5 mg/ml) in culture medium supplemented with L-tyrosine. This pigment has been characterized as pyomelanin and its synthesis was found to occur by the so-called HGA-melanin pathway. The purified pyomelanin was found embedded with antioxidant properties as it exhibited a radical scavenging activity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC₅₀ of 230 μg/ml. It was also characterized as noncytotoxic toward two mammalian cell lines, namely the mouse fibroblast NIH3T3 and human keratinocytes HaCaT. When blended with different commercial sunscreens, the purified pyomelanin increased significantly the sun protection factor (SPF) value, highlighting its potential utilization as UV-filter in cosmetic preparations.     

Cadmium effects on growth and mineral nutrition of two halophytes: Sesuvium portulacastrum and Mesembryanthemum crystallinum

Growth, cadmium accumulation and potassium and calcium status were studied in two halophytes from Aizoaceae family: Sesuvium portulacastrum and Mesembryanthemum crystallinum. After multiplication, the seedlings were cultivated on nutrient solution supplemented with NaCl (100mM) and CdCl2 (0, 50, 100, 200 and 300 microM). After 1 month of treatment, plants were harvested and the dry weight, as well as the Cd, K and Ca concentrations in tissues were determined. Results showed that S. portulacastrum, a perennial halophyte with slow growth, is significantly more tolerant to Cd than M. crystallinum, an annual plant. Cd severely inhibited Mesembryanthemum growth even at the lowest Cd concentration in culture medium (50 microM), and did not modify significantly that of Sesuvium. For both halophytes, Cd accumulation was significantly higher in the roots than in the shoots. However, Cd concentration reached 350-700 microg g(-1) DM in the shoots, values characteristic of Cd hyperaccumulator plants. The addition of Cd in the culture medium led to a disturbance of Ca and especially K nutrition, suggesting the possibility to improve plant growth and Cd phytoextraction of both halophytes by increasing nutrient availability in the culture medium.