Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis--a serious disease of orange trees. The genome comprises a 52.7% GC-rich 2,679,305-base-pair (bp) circular chromosome and two plasmids of 51,158 bp and 1,285 bp. We can assign putative functions to 47% of the 2,904 predicted coding regions. Efficient metabolic functions are predicted, with sugars as the principal energy and carbon source, supporting existence in the nutrient-poor xylem sap. The mechanisms associated with pathogenicity and virulence involve toxins, antibiotics and ion sequestration systems, as well as bacterium-bacterium and bacterium-host interactions mediated by a range of proteins. Orthologues of some of these proteins have only been identified in animal and human pathogens; their presence in X. fastidiosa indicates that the molecular basis for bacterial pathogenicity is both conserved and independent of host. At least 83 genes are bacteriophage-derived and include virulence-associated genes from other bacteria, providing direct evidence of phage-mediated horizontal gene transfer.
This study was developed to evaluate selection effects on gene frequencies in a synthetic beef cattle cross (5/8 Charolais, 3/ 8 Zebu) named Canchim. A sample of 154 Canchim animals, representing three generation classes, was analyzed for seven molecular markers. Thirty-six Charolais cattle were also studied for comparison. A highly significant variation (P < 0.01), with a linear increase of the allele coding for valine at position 127 of the growth hormone peptide, was observed through generations. This allele was found in the Charolais sample but is not observed in Brazilian Bos indicus breeds. Four alleles were found for a microsatellite in the 5' flanking region of insulin-like growth factor I gene in Canchim. Allele sizes ranged from 231 to 225 bp. There was a significant (P < 0.05) nonlinear increase in the 225-bp allele frequency. This allele was not observed in Charolais. Six alleles were observed for microsatellite CSFM50 in the Canchim population. A significant (P < 0.05) linear reduction of the 168-bp allele was observed over the generations. The hypothesis of preferential mating for growth hormone polymorphism was supported by Wright's F-statistics. Estimated F IS value for growth hormone was 0.59 (P < 0.01). These results suggest that selection influenced three out of seven loci analyzed. The simultaneous increases of a Bos taurus-specific growth hormone allele and a Bos indicus-specific insulin-like growth factor I allele indicate that phenotypic selection favored different regions of both genomes.
ABSTRACT:The Ibicenco rabbit (Conill Pages D'Eivissa) is a rare breed mainly located on Ibiza Island, in rural areas. Today breeders are looking for a sustainable use and alternative routes for profitability of the population to avoid its extinction. The breed presents some variety in coat colour (brown, black, orange, and grey), and breeders would like to maintain these characteristics. The objectives of this study were to develop a method to design matings in a population with unbalanced pedigree depth in a scenario of maintaining the variety of coat colours, and to analyze the genealogical information of the Ibicenco rabbit to ascertain the genetic structure of the population. Equivalent effective population size mating was developed as a useful parameter to design the mating in this particular scenario. Results obtained by the initial application showed that this population was properly managed for maintaining the maximum genetic variability. This mating method is recommended to manage the genetic variability of this small rabbit population in a scenario of partial permanent colour structure. For the pedigree analysis, a reference population formed by 143 animals available for reproduction was used. A demographic study, a probability gene origin analysis, computation of inbreeding and effective size, and an analysis of genetic structure were done. The generation interval was approximately one year (11.8 months). The average number of equivalent generations was 3.4. The effective numbers of founders and ancestors were 10 and 11, respectively, and the founder genome equivalent was 6. The average inbreeding was 10.8%, but the mean inbreeding seems to have stopped increasing as a consequence of deeper monitoring in the mating design. The realized effective size was 9.6 (via inbreeding) and 17.5 (via coancestry). Regarding the genetic structure, the orange and black groups are the most distant genetically while grey and blacks are closer.
Restriction fragment length polymorphism (RFLP) has been detected at the bovine kappa-casein locus. The polymorphism has been analyzed for its effects in cattle production, mostly for milk traits and even for maternal effect on pre-weaning weights. We used polymerase chain reaction -restriction fragment length polymorphism (PCR-RFLP) to genotype 408 Nellore animals for the non-silent mutation (Thr/Ile136 and Asp/Ala148) that characterizes the A and B variants of the polymorphism and compared expected progeny difference (EPD) for a maternal effect on 120 and 210 days weights and direct EPD for 120, 210, 450 and 550 day weight between AA and AB animals. The EPD values were obtained from the University of São Paulo (Brazil) Nellore Cattle Breeding Program, which evaluated 266,272 animals in 2001. Analysis of Variance was used to compare weight expected progeny differences (EPDs) between animals genotyped as AA and AB. The A allele frequency was 0.911. Although the AA animals had higher weight EPDs than AB animals the differences were not statistically significant (p > 0.05).
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