Engineered Resistance Against Papaya ringspot virus in Venezuelan Transgenic Papayas.

Local varieties of papaya grown in the Andean foothills of Mérida, Venezuela, were transformed independently with the coat protein (CP) gene from two different geographical Papaya ringspot virus (PRSV) isolates, designated VE and LA, via Agrobacterium tumefaciens. The CP genes of both PRSV isolates show 92 and 96% nucleotide and amino acid sequence similarity, respectively. Four PRSV-resistant R0 plants were intercrossed or selfed, and the progenies were tested for resistance against the homologous isolates VE and LA, and the heterologous isolates HA (Hawaii) and TH (Thailand) in greenhouse conditions. Resistance was affected by sequence similarity between the transgenes and the challenge viruses: resistance values were higher for plants challenged with the homologous isolates (92 to 100% similarity) than with the Hawaiian (94% similarity) and, lastly, Thailand isolates (88 to 89% similarity). Our results show that PRSV CP gene effectively protects local varieties of papaya against homologous and heterologous isolates of PRSV.

Adding value to cocoa (Theobroma cacao L.) germplasm information with domestication history and admixture mapping.

A sound understanding of crop history can provide the basis for deriving novel genetic information through admixture mapping. We confirmed this, by using characterization data from an international collection of cocoa, collected 25 years ago, and from a contemporary plantation. We focus on the trees derived from three centuries of admixture between Meso-American Criollo and South American Forastero genomes. In both cacao sets of individuals, linkage disequilibrium extended over long genetic distances along chromosome regions, as expected in populations derived from recent admixture. Based on loose genome scans, genomic regions involved in useful traits were identified. Fifteen genomic regions involved in seed and fruit weight variation were highlighted. They correspond to ten previously identified QTLs and five novel ones. Admixture mapping can help to add value to genetic resources and thus, help to encourage investment in their conservation.

Recombinantes estables entre el bacteriofago M13 y el plasmido pHR322 / Stable recombinants between the bacteriophage M13 and the plasmid PHR322

Se han aislado dos recombinantes entre el fago M13 y el plásmido pHR322, analizando el contenido plasmídico de una centena de clones obtenidos por transducción. El estudio de la estructura de los dos recombinates muestra que un fragmento del genoma de M13 ha sido integrado a pHR322. En los dos casos, ese fragmento contiene una parte de la región replicativa del fago y está insertado en el replicón de pHR322 o cerca del mismo. El hecho de que los replicones del fago y del plásmido parezcan estar involucrados en el evento de recombinación sugiere que el mismo es facilitado cuando la replicación comienza. En ningún caso ha sido posible aislar un recombinante llevando los genomas enteros de pHR322 y M13. Esto es debido, sin duda, a la inestabilidad de la molécula recombinante

Cloneo in vivo de genes de Escherichia coli K12 mediante recombinacion homologa / Cloning of gene of Escherichia coli K12 by means of homologue recombination

Plasmid pT153, a stable recombinant between pBR322 plasmid and M13 bacteriophage, and Tn10 transposon were employed for in vivo cloning of a chromosomal segment of Escherichia coli including the nar locus. The strategy consisted in creating an homology between pT153 and the E. coli chromosome, incorporating a Tn10 transposon close to the nar locus of a polA12 temperature-sensitive strain. The selection of clones carrying the plasmid into the chromosome was realized at 42 degrees C, with ampiciline, taken advantage that the replicon of pT153 requires the ADN Polymerase I for its functioning. The plasmid integrated in the polA12 strain has the opportunity of excising and carrying part of bacterial genome and autonomically replicating after a thermal change from 42 degrees C to 30 degrees C. The stable recombinant plasmids could be efficiently transduced with the M13 bacteriophage to a E. coli strain (delta narGHJI), obtaining Nit+ Apr transductant clones. The versatility of this method of E. coli gene cloning is the facility to create the homologue region anywhere in the bacterial genome and the efficient transduction of pT153 plasmid by M13 bacteriophage

Obtención de clones de Trypanosoma cruzi a partir de epimastigotes y tripomastigotes sanguícolas delgados y gruesos en diferentes medios agarizados / Attainment of clones of Trypanosoma cruzi from this and thick sanguicolous trypomastigotes in different agar medium

Trypanosoma cruzi (cepa EP) presenta crecimiento clonal cuando es incorporado dentro del agar al 0,7% y en superficie al 0,8%. Las colonias fueron obtenidas a partir de un solo parásito y en un tiempo relativamente corto. La eficiencia de plaqueo fue variable y dependía del tipo de medio agarizado. Se obtuvo un máximo de eficiencia para el agar/LIT-BHI al 0,7% y para el agar/LIT-BHI-Sangre al 0,8%. Los tripomastigotes sanguícolas, tanto delgados como gruesos, fueron capaces de generar colonias a partir de parásitos únicos, con una eficiencia de plaqueo de 100%, superiores al 80% correspondiente a los epimastigotes provenientes de medio LIT