Backbone-free transformation of barrel medic (Medicago truncatula) with a Medicago-derived transfer DNA

In the present work, Agrobacterium tumefaciens-mediated genetic transformation of the model legume Medicago truncatula Gaertn. (barrel medic) was carried out using the pSIM843 vector that contains a Medicago-derived transfer DNA, delineated by a 25-bp sequence homologous to bacterial T-DNA borders. The transfer DNA contains an expression cassette for the nptII (neomycin phosphotransferase) gene and is flanked by an expression cassette for the backbone integration marker gene ipt (isopentenyl transferase). Our results demonstrate that the Medicago-derived RB-like elements efficiently support DNA mobilization from A. tumefaciens to M. truncatula. Kanamycin-resistant shoots with normal phenotype and ipt-shooty lines were recovered at a frequency of 11.7 and 7.8%, respectively. Polymerase chain reaction (PCR) analyses demonstrated that 44.4% of the independent transgenic lines were backbone-free and evidenced the occurrence of backbone-transfer events.     

Dispersal of the Cotton Boll Weevil (Coleoptera: Curculionidae) in South America: Evidence of RAPD Analysis

RAPD technique provides useful information on the geographic origin and dispersal of the boll weevil Anthonomus grandis in South America. Nine populations from Argentina, Brazil, Paraguay, Mexico and USA were analyzed. Weevils were captured on native plants (Misiones province, Argentina) and on cotton cultures, except the sample from the United States (USDA laboratory-reared colony). A sample of the ‘Peruvian square weevil’, A. vestitus, from Ecuador, was included in the analysis in order to compare interspecific variation. The four primers used in the analysis revealed 41 ‘anonymous loci’. The neighbor-joining tree based on Nei's distances and values of Nm (migrants per generation), indicate that genetic similarity between samples from Tecomán (Mexico) and Puerto Iguazú (Argentina), is higher than among remaining South American populations. This result supports an hypothesis of natural occurrence of the boll weevil in South America, prior to extensive cotton cultivation. Population outbreaks of the species would be associated with increase of agricultural lands. This revised version was published online in August 2006 with corrections to the Cover Date.     

Quantitative Detection of Epstein-Barr Virus DNA in Cerebrospinal Fluid and Blood Samples of Patients with Relapsing-Remitting Multiple Sclerosis

The presence of Epstein-Barr Virus (EBV) DNA in cerebrospinal fluid (CSF) and peripheral blood (PB) samples collected from 55 patients with clinical and radiologically-active relapsing-remitting MS (RRMS) and 51 subjects with other neurological diseases was determined using standardized commercially available kits for viral nucleic acid extraction and quantitative EBV DNA detection. Both cell-free and cell-associated CSF and PB fractions were analyzed, to distinguish latent from lytic EBV infection. EBV DNA was detected in 5.5% and 18.2% of cell-free and cell-associated CSF fractions of patients with RRMS as compared to 7.8% and 7.8% of controls; plasma and peripheral blood mononuclear cells (PBMC) positivity rates were 7.3% and 47.3% versus 5.8% and 31.4%, respectively. No significant difference in median EBV viral loads of positive samples was found between RRMS and control patients in all tested samples. Absence of statistically significant differences in EBV positivity rates between RRMS and control patients, despite the use of highly sensitive standardized methods, points to the lack of association between EBV and MS disease activity.     

The finding of eggs of Diphyllobothrium in human coprolites (4,100-1,950 B.C.) from northern Chile

Twenty six coprolites from an archaeological site in the province of Iquique, northern Chile, were examined for parasites. Coprolites were found in two excavation units, I and II (Tiliviche site), dated respectively at 5,900 B.C. to 4,110 B.C. and 4,110 B.C. to 1,950 B.C., and identified as of human origin. Only at the unit II coprolites containing helminth eggs identified as Diphyllobothrium pacificum were found. The presence of this tapeworm, a parasite of the American Sea Lion, in human coprolites, points to a diet which included marine fishes and provides information on the antiquity of infection by Diphyllobothrium pacificum. It is interesting to note that Baer (1969) suggests the presence of this tapeworm in pre-Columbian populations when diagnosing the first human cases in today's population in Peru.     

The nature of the last universal ancestor and the root of the tree of life, still open questions.

The nature of the last universal ancestor to all extent cellular organisms and the rooting of the universal tree of life are fundamental questions which can now be addressed by molecular evolutionists. Several scenarios have been proposed during the last years, based on the phylogenies of ribosomal RNA and of duplicated proteins, which suggest that the last universal ancestor was either an RNA progenote or an hyperthermophilic prokaryote. We discuss these hypotheses in the light of new data on the evolution of DNA metabolizing enzymes and of contradictions between different protein phylogenies. We conclude that the last universal ancestor was a member of the DNA world already containing several DNA polymerases and DNA topoisomerases. Furthermore, we criticize current data which suggest that the rooting of the universal tree of life is located in the eubacterial branch and we conclude that both rooting the universal tree and the nature of the last universal ancestor are still open questions.