Search for flavor-changing neutral currents and lepton-family-number violation in two-body D0 decays

Results of a search for the three neutral charm decays, D0 -> mu e, D0 -> mu mu, and D0 -> e e, are presented. This study was based on data collected in Experiment 789 at the Fermi National Accelerator Laboratory using 800 GeV/c proton-Au and proton-Be interactions. No evidence is found for any of the decays. Upper limits on the branching ratios, at the 90% confidence level, are obtained.Comment: 28 pages, 18 figures. Submitted to Physical Review

Silencing of Vlaro2 for chorismate synthase revealed that the phytopathogen Verticillium longisporum induces the cross-pathway control in the xylem

The first leaky auxotrophic mutant for aromatic amino acids of the near-diploid fungal plant pathogen Verticillium longisporum (VL) has been generated. VL enters its host Brassica napus through the roots and colonizes the xylem vessels. The xylem contains little nutrients including low concentrations of amino acids. We isolated the gene Vlaro2 encoding chorismate synthase by complementation of the corresponding yeast mutant strain. Chorismate synthase produces the first branch point intermediate of aromatic amino acid biosynthesis. A novel RNA-mediated gene silencing method reduced gene expression of both isogenes by 80% and resulted in a bradytrophic mutant, which is a leaky auxotroph due to impaired expression of chorismate synthase. In contrast to the wild type, silencing resulted in increased expression of the cross-pathway regulatory gene VlcpcA (similar to cpcA/GCN4) during saprotrophic life. The mutant fungus is still able to infect the host plant B. napus and the model Arabidopsis thaliana with reduced efficiency. VlcpcA expression is increased in planta in the mutant and the wild-type fungus. We assume that xylem colonization requires induction of the cross-pathway control, presumably because the fungus has to overcome imbalanced amino acid supply in the xylem

Preliminary results from Fermilab E789

Fermilab experiment 789 studies low-multiplicity decays of neutral D and B mesons in a high-rate fixed-target environment. Preliminary results from the 1991 run are presented

Detection of the nondefoliating pathotype of Verticillium dahliae in infected olive plants by nested PCR

11 páginas, 4 figurasAn increasing incidence and distribution of verticillium wilt has occurred in the last few years in newly established olive orchards in southern Spain. This spread of the disease may result from use of Verticillium dahliae-infected planting material. The early in planta detection of the pathogen would aid the implementation of certification schemes for pathogen-free planting material. In this work, a nested polymerase chain reaction (PCR) method was developed for the in planta detection of the nondefoliating (ND) V. dahliae pathotype, aimed especially at nurseryproduced olive plants. For this purpose, specific primers were designed from the sequence of a 1958-bp random amplified polymorphic DNA (RAPD) marker of ND V. dahliae, and a procedure for the extraction of PCR-quality total genomic DNA from infected root and stem tissues of young olive plants was tested and further optimized. Nested PCR assays detected ND V. dahliae in 4- to 14-month-old artificially infected plants of three olive cultivars. The ND-specific PCR product was not amplified from total genomic DNA extracted from olive plants infected with the defoliating V. dahliae pathotype. Detection of the ND pathotype was effective from the very earliest moments following artificial inoculation of olive plants with a V. dahliae conidial suspension. Also, detection was achieved in inoculated, though symptomless, olive plants as well as in plants that were symptomatic but became symptomless by 217 days after inoculation.Comisión Interministerial de Ciencia y Tecnología (CICYT), España. 1FD97-0763-C03-01; Comunidad Europea, contrato no. QLK5-CT1999-01523.Peer reviewe

Variabilidade de Xanthomonas malvacearum (E. F. Smith) Dowson, no estado de São Paulo

No presente trabalho foi determinada a variabilidade de X. malvacearum, em condições de casa de vegetação, baseando-se na reação dos hospedeiros diferenciais para raças fisiológicas do patógeno. A técnica de inoculação empregada foi a de riscos feitos na página inferior das folhas e para avaliação dos sintomas foi adotada uma escala que variou de 1 a 5. Foi detectada a ocorrência das raças fisiológicas 3, 8 e 10. A linhagem do algodoeiro IAC RM3-4133 71/523 foi resistente à raça fisiológica 3, enquanto que as linhagens (Acala x Nu.16) 71/213 e IAC 12-2 71/170 foram resistentes às raças 3, 8 e 10.The variability of X. malvacearum was studied under greenhouse conditions with isolates obtained from the principal cotton growing regions of the State of São Paulo. The isolates were introduced into the tissues by scratching the under side of the leaves with a bamboo pick previously dipped in a bacterial suspension. For the evaluation of the symptoms a scale based on five infection types was used. As a result of these tests, the isolates were grouped into three races of X. malvacearum respectively races 3,8 and 10. The IAC RM3 71/523 line showed resistence to race 3, while (Acala x Nu-16) 71/213 and IAC 12-2 71/170 lines showed resistence to races 3,8 and 10. The susceptible cotton varieties IAC RM3, IAC 13-1 and IAC 12-2, cultivated in São Paulo State, reacted equally to the three races mentioned