We have identified a cellular factor that interacts with the virus genome-linked proteins (VPgs) of a diverse range of potyviruses. The factor, called Potyvirus VPg-interacting protein (PVIP), is a plant-specific protein with homologues in all the species examined, i.e., pea, Arabidopsis thaliana, and Nicotiana benthamiana. The sequence of PVIP does not identify a specific function, although the existence of a "PHD finger" domain may implicate the protein in transcriptional control through chromatin remodeling. Deletion analysis using the yeast two-hybrid system showed that the determinants of the interaction lay close to the N terminus of VPg; indeed, the N-terminal 16 amino acids were shown to be both necessary and sufficient for the interaction with at least one PVIP protein. From a sequence comparison of different potyvirus VPg proteins, a specific amino acid at position 12 was directly implicated in the interaction. This part of VPg is distinct from regions associated with other functional roles of VPg. Through mutation of Turnip mosaic virus (TuMV) at VPg position 12, we showed that the interaction with PVIP affected systemic symptoms in infected plants. This resulted from reduced cell-to-cell and systemic movement more than reduced virus replication, as visualized by comparing green fluorescent protein-tagged wild-type and mutant viruses. Furthermore, by using RNA interference of PVIP in Arabidopsis, we showed that reduced expression of PVIP genes reduced susceptibility to TuMV infection. We conclude that PVIP functions as an ancillary factor to support potyvirus movement in plants.The Potyvirus group is the major genus of the family Potyviridae. Potyviruses infect a broad range of monocot and dicot plants and can be responsible for severe damage to crops. Despite the economic importance of potyviruses, relatively little is understood about the detailed molecular interactions that occur in infected tissues that lead to the exploitation of cellular machinery and the accumulation of high virus titers. Notably, only the translation factors eIF4E (28, 30) and eIF(iso)4E (14, 15) have been identified as susceptibility factors supporting virus replication in potyvirus hosts. These proteins have been identified variously through mutational analysis of model host plants, such as Arabidopsis thaliana (hereafter referred to as Arabidopsis) (14), and through protein-protein interaction studies, initially in Saccharomyces cerevisiae (15,30). We have also applied the latter approach to identify host proteins that interact with the potyvirus genome-linked protein, VPg.VPg forms a covalent linkage to the 5Ј end of the viral RNA and is one of the diagnostic features of the picornavirus supergroup, which includes the family Potyviridae (13). For potyviruses, it is one of 10 mature proteins that are proteolytic products of the primary translated protein product encoded by the viral RNA (6, 27). VPg is a multifunctional protein with several suggested roles in the viral infection cycle. It may act as a primer for RNA replica...

Seventy-eight cattle samples from three Creole Caribbean islands and one Brazilian breed were analyzed for sequence variation in the hypervariable segment of the mitochondrial DNA control region. Seventy-three samples displayed Bos taurus haplotypes, and five samples exhibited haplotypes that were of Bos indicus ancestry. Phylogenetic analysis revealed that all sampled B. taurus sequences fell into two distinct clusters with separate African and European origins. European sequences were encountered in each population; however, the distribution of African haplotypes was uneven, with the highest proportion of African influence found in the Guadeloupe Creole. The reduced levels of African haplotypic variation within the Caribbean and Brazilian are consistent with prior founder effects. Additionally, genetic variation at three microsatellite loci illustrated African influence uniquely in the Guadeloupe Creole. Collectively, the data suggest that this African influence is, at least in part, attributable to the historical importation of African cattle to the Americas. Furthermore, alleles of B. indicus ancestry were detected at appreciable frequencies in all Caribbean Creole populations and may reflect zebu introgressions from either West Africa or the Indian subcontinent.

Polyacrylamide gel electrophoresis (PAGE) of isoenzymes of chromosomal origin, and plasmid profile analyses, were used to investigate genetic variation within and between natural populations of Rhizobium leguminosarum biovar trifolii from diverse sources. PAGE showed that, within the biovar in general, relatively few alleles existed for the enzyme loci studied. There was a strong genetic disequilibrium between loci, suggesting that chromosomal recombination is rare. Both PAGE and plasmid profile analysis revealed differences in the degree of strain polymorphism at the sites examined. At sites which were acidic, improved (by liming) and neutral, strain variation was found to be low, intermediate and high, respectively.