Whole genome sequences of Japanese porcine species C rotaviruses reveal a high diversity of genotypes of individual genes and will contribute to a comprehensive, generally accepted classification system.

Porcine rotavirus C (RVC) is distributed throughout the world and is thought to be a pathogenic agent of diarrhea in piglets. Although, the VP7, VP4, and VP6 gene sequences of Japanese porcine RVCs are currently available, there is no whole-genome sequence data of Japanese RVC. Furthermore, only one to three sequences are available for porcine RVC VP1-VP3 and NSP1-NSP3 genes. Therefore, we determined nearly full-length whole-genome sequences of nine Japanese porcine RVCs from seven piglets with diarrhea and two healthy pigs and compared them with published RVC sequences from a database. The VP7 genes of two Japanese RVCs from healthy pigs were highly divergent from other known RVC strains and were provisionally classified as G12 and G13 based on the 86% nucleotide identity cut-off value. Pairwise sequence identity calculations and phylogenetic analyses revealed that candidate novel genotypes of porcine Japanese RVC were identified in the NSP1, NSP2 and NSP3 encoding genes, respectively. Furthermore, VP3 of Japanese porcine RVCs was shown to be closely related to human RVCs, suggesting a gene reassortment event between porcine and human RVCs and past interspecies transmission. The present study demonstrated that porcine RVCs show greater genetic diversity among strains than human and bovine RVCs.

Fine mapping and allelic dosage effect of Hwc1, a complementary hybrid weakness gene in rice.

Hybrid weakness is a reproductive barrier that is found in many plant species. In rice, the hybrid weakness caused by two complementary genes, Hwc1 and Hwc2, has been surveyed intensively. However, their gene products and the molecular mechanism that causes hybrid weakness have remained unknown. We performed linkage analyses of Hwc1, narrowed down the area of interest to 60 kb, and identified eight candidate genes. In the F(2) population, in which both Hwc1 and Hwc2 genes were segregated, plants were separable into four classes according to their respective phenotypes: severe type, semi-severe type, F(1) type, and normal type. Severe type plants show such severe symptoms that they could produce only tiny shoot-like structures; they were unable to generate roots. Genetic analyses using closely linked DNA markers of the two genes showed that the symptoms of the F(2) plants were explainable by the genotypes of Hwc1 and Hwc2. Weakness was observed in plants that have both Hwc1 and Hwc2. In Hwc1 homozygote, the symptoms worsened and severe type or semi-severe type plants appeared. Consequently, Hwc1 should have a gene dosage effect and be a semi-dominant gene. The dosage effect of Hwc2 was recognizable, but it was not so severe as that in Hwc1. These results are useful to elucidate the mechanism that causes the hybrid weakness phenomenon and the role of each causal gene in hybrid weakness.