The alternative oxidase pathway is involved in optimizing photosynthesis in Medicago truncatula infected by Fusarium oxysporum and Rhizoctonia solani

Phytopathogen infection alters primary metabolism status and plant development. The alternative oxidase (AOX) has been hypothesized to increase under pathogen attack preventing reductions, thus optimizing photosynthesis and growth. In this study, two genotypes of Medicago truncatula, one relatively resistant (Jemalong A17) and one susceptible (TN1.11), were infected with Fusarium oxysporum and Rhizoctonia solani. The in vivo foliar respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) were measured using the oxygen isotope fractionation. Gas exchange and photosynthesis-related parameters were measured and calculated together with antioxidant enzymes activities and organic acids contents. Our results show that the in vivo activity of AOX (v_alt) plays a role under fungal infection. When infected with R. solani, the increase of v_alt in A17 was concomitant to an increase in net assimilation, in mesophyll conductance, to an improvement in the maximum velocity of Rubisco carboxylation and to unchanged malate content. However, under F. oxysporum infection, the induced v_alt was accompanied by an enhancement in the antioxidant enzymes, superoxide dismutase (SOD; EC1.15.1.1), catalase (CAT; EC1.11.1.6) and guaiacol peroxidase (GPX; EC1.11.1.7), activities and to an unchanged tricarboxylic acid cycle intermediates. These results provide new insight into the role of the in vivo activity of AOX in coordinating primary metabolism interactions that, partly, modulate the relative resistance of M. truncatula to diseases caused by soil-borne pathogenic fungi.     

Secreted recombinant P53 protein from Pichia pastoris is a useful antigen for detection of serum p53: autoantibody in patients with advanced colorectal adenocarcinoma

The detection of P53 alteration by serological method is easier to perform, does not require tumor tissues and is of interest for patients monitoring. In this study, we described the development of a home made ELISA test based on recombinant human P53 protein produced in Pichia pastoris and used as antigen for the detection of serum p53-Abs in colorectal carcinoma patients. The human P53 was secreted as a His-tagged protein by recombinant KM71 strain (Kα21) via the peptide signal α of the Saccharomyces cerevisiae mating type gene. The recombinant P53-His was able to detect p53-Abs in 23.4 % of patients. Serum p53-Abs correlated significantly with surgical treatment (P = 0.007), relapse during follow-up (P = 0.036), depth of invasion (P = 0.036) and the level of CA19-9 (P = 0.034). Survival analysis showed that patients negative for serum p53-Abs exhibited a prolonged disease free survival period (P log rank = 0.012). In conclusion, the secreted recombinant human P53-His produced in P. pastoris seems to be a useful antigen for detection of serum p53 Abs in patients with colorectal carcinoma.     

The Cu/Zn superoxide dismutase +35A/C (rs2234694) variant correlates with altered levels of protein carbonyls and glutathione and associates with severity of COPD in a Tunisian population

Chronic obstructive pulmonary disease (COPD) is a major cause of mortality that has been associated with inflammation and oxidative stress. The purpose of the present case–control study was to determine the relationships between oxidative stress-related genetic variants and the risk and severity of COPD, as well as, the influence of these variants on inflammatory and oxidative stress parameters. Genotyping of superoxide dismutase 1 (SOD1) + 35 A/C (rs2234694), catalase [A-21T (rs7943316), C-262T (rs1001179)] and glutathione peroxidase 1 (reduced glutathione (GSH)-Px1) 198Pro/Leu (rs1050450) was carried out in 143 patients with COPD and 216 healthy controls using PCR-RFLP. Serum levels of IL-6 and TNF-α were determined by enzyme-linked immunosorbent assays (ELISA), while the levels of reduced GSH, total antioxidant status (TAS), H₂O₂, lipid peroxides (TBARS) and protein carbonyls (PCs) were determined using spectrophotometric methods. We also evaluated the activities of GSH-Px, catalase, and superoxide dismutase (SOD) in both plasma and erythrocytes. We did not observe significant differences in the genotype and allele frequencies of chosen variants between COPD patients and healthy controls. A significant correlation was retrieved between the SOD1?+?35A/C variant and disease severity (odds ratios (OR) = 0.15, p?=?0.04). In addition, patients having the +35AC genotype presented increased plasma levels of GSH and a reduced level of PCs (p?=?0.03, p?=?0.04, respectively). The present data highlighted the important role of antioxidant enzymes and their genetic variants in the oxidative stress-mediated pathogenesis and progression of COPD.     

Induction of micronuclei by Zearalenone in Vero monkey kidney cells and in bone marrow cells of mice: protective effect of Vitamin E

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin mainly produced by Fusarium graminaerum, found as a world-wide contaminant mainly of corn and wheat. Previous studies have demonstrated that among several other effects on animals and humans, ZEN also displays hepatotoxicity, immunotoxicity and nephrotoxicity. ZEN is mainly known as a hormonal disrupter due to its estrogenic activities and consequent toxicity for reproduction. Furthermore, mutagenic and genotoxic proprieties of ZEN were disclosed recently, the molecular mechanisms of which are not yet well understood. In the present study, the genotoxic potential of ZEN was evaluated using genotoxicity tests: the 'cytokinesis block micronucleus assay' in Vero monkey kidney cells and the 'in vivo mouse bone marrow micronucleus assay'. In cultured cells treated with 5, 10 and 20 microM ZEN, the frequency of binucleated micronucleated cells (BNMN) was assessed in 1000 binucleated cells and in mice given oral doses of 10, 20 and 40 mg/kg bw, the frequency of polychromatic erythrocytes micronucleated (PCEMN) in bone marrow cells was assessed in 2000 polychromatic erythrocytes (PCE). The potential prevention of ZEN-induced effects by 25 microM Vitamin E (Vit E) was also evaluated.In vivo, doses of 10, 20 and 40 mg/kg bw ZEN representing, respectively 2, 4 and 8% of the LD50 (LD50 of ZEN in mice is 500 mg/kg bw), were administered to animals either with or without pre-treatment with Vit E (216.6 mg/kg bw) in order to evaluate its preventive potential.ZEN was found to induce micronuclei (MN) in a dose-dependent manner in cultured Vero cells as well as in mouse bone marrow cells. The present data emphasise the likely clastogenic pathway among the molecular mechanisms that underlay the ZEN-induced genotoxicity. Vit E was found to prevent partially-from 30 to 50%-these toxic effects, most likely acting either as a structural analogue of ZEN or as an antioxidant.     

Mutation Spectrum of RB1 Gene in Unilateral Retinoblastoma Cases from Tunisia and Correlations with Clinical Features

Retinoblastoma, an embryonic neoplasm of retinal origin, is the most common primary intraocular malignancy in children. Somatic inactivation of both alleles of the RB1 tumor suppressor gene in a retinal progenitor cell through diverse mechanisms including genetic and epigenetic modifications, is the crucial event in initiation of tumorigenesis in most cases of isolated unilateral retinoblastoma. We analyzed DNA from tumor tissue and from peripheral blood to determine the RB1 mutation status and seek correlations with clinical features of 37 unrelated cases of Tunisian origin with sporadic retinoblastoma. All cases were unilateral except one who presented with bilateral disease, in whom no germline coding sequence alteration was identified. A multi-step mutation scanning protocol identified bi-allelic inactivation of RB1 gene in 30 (81%) of the samples tested. A total of 7 novel mutations were identified. There were three tumors without any detectable mutation while a subset contained multiple mutations in RB1 gene. The latter group included tumors collected after treatment with chemotherapy. There were seven individuals with germline mutations and all presented with advanced stage of tumor. There was no difference in age of onset of RB based on the germline mutation status. Thus 20% of the individuals with sporadic unilateral RB in this series carried germline mutations and indicate the importance of genetic testing all children with sporadic retinoblastoma. These findings help to characterize the spectrum of mutations present in the Tunisian population and can improve genetic diagnosis of retinoblastoma.     

Association Between Haptoglobin 2-2 Genotype and Coronary Artery Disease and Its Severity in a Tunisian Population

Haptoglobin (Hp) polymorphism generates three common human genotypes (Hp1-1, Hp2-1, and Hp2-2), having functional differences, related to the risk of development of cardiovascular diseases. These functions are a consequence of hemoglobin binding that leads to the synthesis of an antioxidant like ferritin. We explored the association of Hp polymorphism with significant coronary stenosis (SCS) and its severity within 400 Tunisian patients, using genotyping, biochemical parameters, and the Gensini score. After adjustments for age and gender, Hp2-2 was associated with the highest ferritin but the lowest Hp concentrations. After adjustments for confounding parameters, the OR of SCS associated with Hp2-2 was 1.74 (95% CI 1.18–2.58; p = 0.005). This effect was enhanced within diabetics (OR 1.90, 95% CI 1.11–3.24; p = 0.018), obese subjects (OR 1.98, 95% CI 1.10–4.86; p = 0.034), and smokers (OR 4.17, 95% CI 1.54–1.29; p = 0.005). The Hp2-2 genotype is associated with an increase in SCS especially in diabetics, the obese, and smokers.     

Genetic diversity and population structure of Tunisian wild Kermes oak (Quercus coccifera L.): Assessment by ISSR molecular markers and implication for conservation

Molecular Biology Reports - In Tunisia, Kermes oak (Quercus coccifera L.) populations are severely destroyed due to deforestation. Nowadays, no preservation programs are attempted, yet, to conserve...     

Polymorphisms in the RANTES gene increase susceptibility to active tuberculosis in Tunisia

RANTES plays a pivotal role in attracting and activating various leukocyte populations that control Mycobacterium tuberculosis infection. The present study investigated the relationship between the RANTES polymorphisms (-28C/G; rs2280788, and -403G/A; rs2107538) and susceptibility to active tuberculosis (TB) in Tunisian populations. A total of 168 patients with pulmonary TB (pTB), 55 with extrapulmonary TB (epTB), and 150 control subjects were studied. Genotype analyses were carried out using polymerase chain reaction-restriction fragment length polymorphism method. We found that the -28 GG genotype was significantly associated with susceptibility to pTB (odds ratio [OR]=11.19; 95% confidence intervals [CI], 5.14-25; P corrected for the number of genotypes [Pc]=10(-8)) and epTB (OR=11.67; 95% CI, 4.74-29.33; Pc=10(-8)). However, the -28 CC genotype was found to be significantly associated with resistance to pTB (OR=0.08; 95% CI, 0.04-0.16; Pc=10(-8)) and epTB development (OR=0.11; 95% CI, 0.05-0.27; Pc=10(-8)). -403A allele was associated with increased risk development of epTB (OR=2.21; 95% CI, 1.18-4.14; p=0.007). G-G and A-C haplotypes and the AG/GC diplotype were associated with increase susceptibility to pTB (OR=7.88, 95% CI, 5.38-11.55; Pc=3.10(-8); OR=2.32, 95% CI, 1.32-4.11; Pc=3.10(-3); OR=13.26, 95% CI, 6.06-29.89; Pc=3.10(-8); respectively) and epTB (OR=6.64, 95% CI, 4-11.05; Pc=3.10(-8); OR=2.6, 95% CI, 1.26-5.35; Pc=12.10(-3); OR=11.26, 95% CI, 4.44-29.28; Pc=3.10(-8); respectively). Collectively, our findings suggested an association of the RANTES -28C/G and -403G/A functional polymorphisms with susceptibility to Mycobacterium tuberculosis infection in Tunisian populations.     

Lyme borreliosis situation in North Africa

Many epidemiological studies were conducted for studying Lyme borreliosis (LB) which represents a new global public health problem. It is now the most common vector-borne disease in Europe and North America. The causative agent Borrelia burgdorferi sl is a bacterial species complex comprising 12 delineated and named species. In North Africa, few studies based on clinical and serological features, have suggested that LB could occur. Indeed, recent studies conducted in Tunisia, Algeria and Morocco have showm that Ixodes ricinus is present in cooler and humid area of these regions. These studies also revealed that this species is a vector of B. burgdorferi sl with high prevalence of infection. Using IFI and PCR tests, the mean rate of Borrelia-infection ranged from 50 to 60% in I. ricinus adult collected in Tunisia and Morocco and from 30 to 40% in nymphs; in contrast, the prevalence in larvae is less than 2.5%. Several strains of B. burgdorfer were isolated from adult and nymph I ricinus collected in Tunisia and Morocco. The identification of these strains and DNAs directly extracted from Ixodes was done by PCR-RFLP and sequence analysis. The results showed that B. lusitaniae (genotypes Poti B2 and Poti B3) is the predominant species circulating in I. ricinus in Tunisia and Morocco, B. garinii and B. burgdorferi ss and B lusitaniae were also present but very rare. These results provide the evidence for the existence of B. burgdorferi sl in North Africa; however, the impact of LB in the human population seem to be negligible and the seroprevalence of Borrelia in forest workers (considered as population at high risk) in Tunisia is less than 4%.