Influenza NA and PB1 Gene Segments Interact during the Formation of Viral Progeny: Localization of the Binding Region within the PB1 Gene

The influenza A virus genome comprises eight negative-sense viral RNAs (vRNAs) that form individual ribonucleoprotein (RNP) complexes. In order to incorporate a complete set of each of these vRNAs, the virus uses a selective packaging mechanism that facilitates co-packaging of specific gene segments but whose molecular basis is still not fully understood. Recently, we used a competitive transfection model where plasmids encoding the A/Puerto Rico/8/34 (PR8) and A/Udorn/307/72 (Udorn) PB1 gene segments were competed to show that the Udorn PB1 gene segment is preferentially co-packaged into progeny virions with the Udorn NA gene segment. Here we created chimeric PB1 genes combining both Udorn and PR8 PB1 sequences to further define the location within the Udorn PB1 gene that drives co-segregation of these genes and show that nucleotides 1776–2070 of the PB1 gene are crucial for preferential selection. In vitro assays examining specific interactions between Udorn NA vRNA and purified vRNAs transcribed from chimeric PB1 genes also supported the importance of this region in the PB1-NA interaction. Hence, this work identifies an association between viral genes that are co-selected during packaging. It also reveals a region potentially important in the RNP-RNP interactions within the supramolecular complex that is predicted to form prior to budding to allow one of each segment to be packaged in the viral progeny. Our study lays the foundation to understand the co-selection of specific genes, which may be critical to the emergence of new viruses with pandemic potential

Utilização do 'não tecido' de polipropileno como proteção da cultura de alface durante o inverno de Ponta Grossa - PR Use of non woven polypropylene protection under lettuce crop during winter season in Ponta Grossa, Brazil

O experimento foi realizado na UEPG, Ponta Grossa, PR. Estudou-se o efeito da proteção com 'não tecido' de polipropileno sobre o desenvolvimento, a qualidade e a produção de três cultivares de alface, transplantadas no inverno de 1998. O delineamento experimental foi inteiramente casualizado, distribuído segundo esquema fatorial 3x2 (cultivares x sistema de cultivo), com 5 repetições. As cultivares utilizadas foram Tainá, Elisa e Verônica, cultivadas sob a proteção do 'não tecido' de polipropileno (PP) e em ambiente natural (AN). O uso do 'não tecido' como proteção de plantas de alface resultou em maior peso de matéria fresca de cabeça para todas as cultivares estudadas quando comparado ao AN. Verificou-se, para as cultivares Tainá e Verônica, incremento do índice de área foliar, com conseqüente aumento da biomassa das plantas produzidas sob o 'não tecido'. A cultivar Elisa apresentou limbo foliar com aspecto de estiolamento, perdendo a turgidez rapidamente após a colheita. Possivelmente, os níveis de radiação sob PP foram inferiores ao ponto de saturação fotossintética para a cv. Elisa. Recomenda-se o uso do 'não tecido' para as cultivares Verônica e Tainá, no inverno, para a região de Ponta Grossa, por apresentarem cabeças com ótima qualidade e peso comercial.<br>A field experiment was carried out in ''Capão da Onça'' School Farm, at the Universidade Estadual de Ponta Grossa in Brazil. The effect of the protection of an spunbonded polypropylene non woven fabric on the development, quality and yield of three lettuce cultivars, transplanted during the winter of 1998 was studied. The experimental design was of complete randomized blocks, displayed in a factorial scheme 3x2 (cultivars x crop system), with five replications. The cultivars were Tainá, Elisa and Verônica growing under non woven polypropylene protection (PP) and environmental conditions (EC). Greater head fresh weight was observed on woven protected plants. Increased leaf area index (LAI) was observed for 'Tainá' and 'Verônica', with consequent increase of biomass in row cover plants. 'Elisa' showed etiolate leafs, that lost rapidly the turgidity after harvesting. It is possible that the radiation levels under PP were bellow of the saturated photosynthetic point for cv. Elisa. The use the non woven protection for cv. Verônica and cv. Tainá, during winter season of Ponta Grossa's region is recommended, due to the fact that these plants presented heads with excellent quality and commercial weight