Nucleotide binding site (NBS)-leucine-rich repeat (LRR) genes belong to the largest class of disease-resistance gene super groups in plants, and their intra- or interspecies nucleotide variations have been studied extensively to understand their evolution and function. However, little is known about the evolutionary patterns of their copy numbers in related species. Here, 129, 245, 239 and 508 NBSs were identified in maize, sorghum, brachypodium and rice, respectively, suggesting considerable variations of these genes. Based on phylogenetic relationships from a total of 496 ancestral branches of grass NBS families, three gene number variation patterns were categorized: conserved, sharing two or more species, and species-specific. Notably, the species-specific NBS branches are dominant (71.6%), while there is only a small percentage (3.83%) of conserved families. In contrast, the conserved families are dominant in 51 randomly selected house-keeping genes (96.1%). The opposite patterns between NBS and the other gene groups suggest that natural selection is responsible for the drastic number variation of NBS genes. The rapid expansion and/or contraction may be a fundamentally important strategy for a species to adapt to the quickly changing species-specific pathogen spectrum. In addition, the small proportion of conserved NBSs suggests that the loss of NBSs may be a general tendency in grass species.

Further research is required to elucidate whether gemycircularviruses can infect humans or are indicative of contamination occurring during phlebotomy, plasma pool processing, or ongoing donor fungal infections.

BackgroundSeveral animal species can reportedly act as reservoirs for Hepatitis E virus (HEV), a zoonotic pathogen. HEV and antibody to the virus have been detected in a variety of animals including rodents. Pig and rat models for HEV have been established for HEV, but a nude mouse has not yet been developed.MethodsBalb/c nude mice were inoculated with swine HEV, both orally and via intravenous injection to insure infection. Negative control and experimental contact-exposed groups of mice were also included in the study. The liver, spleen, kidney, jejunum, ileum, cecum and colon of each mouse from all three groups were collected for reverse transcription nested polymerase chain reaction (RT-nPCR) detection, indirect immunofluorescence observation and histopathologic examination. The sera from nude mice were tested for anti-HEV IgG by enzyme linked immunosorbent assay (ELISA). Activities of liver enzymes, including alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), as well as total bilirubin (TBIL) were also measured in the sera of the nude mice.ResultsHEV antigens and HEV RNA were detected in liver, spleen, kidney, jejunum, ileum and colon both by indirect immunofluorescence and by RT-nPCR in all of the inoculated and in one of the contact-exposed nude mice. Histopathological changes were observed in the liver and spleen of these mice. Infected mice showed increased levels of AST, ALP, and anti-HEV IgG in sera. The livers of contact-exposed mice showed obvious histopathological damage.ConclusionNude mice could be readily infected by HEV isolated from pigs. The nude mouse may therefore be a useful animal model for studying the pathogenesis of HEV.