Judith K Brown

PMID: 12074729;Abstract:

During the 1990s, an epidemic of cassava mosaic virus disease caused major losses to cassava production in Uganda. Two factors associated with the epidemic were the occurrence of a novel recombinant begomovirus, EACMV-Ug, and unusually high populations of the whitefly vector, Bemisia tabaci. Here we present molecular evidence for the occurrence of two cassava-colonizing B. tabaci genotype clusters, Ug1 and Ug2, one of which, Ug2, can be consistently associated with the CMD epidemic in Uganda at the time of collection in 1997. By contrast, a second genotype cluster, Ug1, only occurred 'at' or 'ahead of' the epidemic 'front', sometimes in mixtures with Ug2. Comparison of mitochondrial cytochrome oxidase I gene sequences for Ug1 and Ug2 and well-studied B. tabaci reference populations indicated that the two Ugandan populations exhibited ≅ 8% divergence, suggesting they represent distinct sub-Saharan African lineages. Neither Ugandan genotype cluster was identified as the widely distributed, polyphagous, and highly fecund B biotype of Old World origin, with which they both diverged by ≅ 8%. Within genotype cluster divergence of Ug1 at 0.61±0.1% was twice that of Ug2 at 0.35±0.1%. Mismatch analysis suggested that Ug2 has undergone a recent population expansion and may be of non-Ugandan origin, whereas Ug1 has diverged more slowly, and is likely to be an indigenous genotype cluster.

Abstract:

Whiteflies (suborder Sternorrhyncha, family Aleyrodidae) are known to harbor prokaryotic symbionts, some of which are vital and provide specific nutritional needs, while others are transient or nonessential, that can either be beneficial or deleterious in the long-term. However, the extent to which diverse bacterial symbionts are associated with populations of the same species of whitefly that colonize herbaceous plants in diverse habitats, and their particular influence on the evolution of the whitefly host, are not well studied. Here, the composition and diversity of prokaryotic symbionts associated with biotypes or haplotypes of the whitefly Bemisia tabaci Gennadius were examined for collections from representative host plants and different geographical locations worldwide. The eubacterial 16S ribosomal DNA (rDNA) and Wolbachia-specific 16S rDNA genes for endosymbionts were obtained by polymerase chain reaction (PCR) amplification. Amplification and comparison of 16S rDNA sequences revealed that a primary-like symbiont was associated with all whitefly collections examined. However, the endosymbiont 16S rDNA phylogeny was not strictly concordant with the phylogeographically informative cytochrome oxidase I tree for the respective whitefly host. Secondary symbiont sequences for 13 of 20 whitefly populations clustered with Arsenophonus spp. and aphid T-type bacteria, which both belong to the Enterobacteriaceae. PCR and sequencing of Wolbachia-specific 16S rDNA revealed that at least 33% of B. tabaci populations harbored Wolbachia.

PMID: 23749046;Abstract:

The complete genome sequence of a monopartite begomovirus isolate infecting Creek Premna (Premna serratifolia L.) plants that exhibited leaf curl, vein swelling, and enation symptoms in Nha Trang, Vietnam, was cloned and sequenced. It comprises 2,753 nucleotides (JQ793786) and has a typical organization of begomoviruses DNA-A with AV1 and AV2 open reading frames (ORFs) in the viral-sense strand and AC1, AC2, AC3, AC4 and AC5 ORFs in the complementary-sense strand. The full-length genome sequence of the isolate (clone VN7) shared the highest level of nucleotide sequence identity (83 %) with the isolate IN:Pusa:Tb:10 of tobacco leaf curl Pusa virus (HQ180391). The phylogenetic relationship of VN7 to other begomoviruses was also investigated. VN7 grouped most closely with a clade containing begomoviruses from China, India and Japan. According to the current taxonomic criteria for the genus Begomovirus, family Geminiviridae, the isolate VN7 represents a new species, herein named "Premna leaf curl virus" (PrLCV). © 2013 Springer-Verlag Wien.

PMID: 17638064;Abstract:

Sida acuta and Corchorus siliquosus plants showing yellow mosaic and yellow vein symptoms, respectively, were collected in the Yucatan Peninsula, Mexico. Total DNA was isolated from both plant species and used for the amplification, cloning, and sequencing of the Begomovirus genome. Nucleotide comparison of the complete DNA-A component isolated from S. acuta and C. siliquosus confirmed the presence of two distinct begomoviruses species. Based on phenotypic symptoms observed in infected field plants, the names Sida yellow mosaic Yucatan virus (SiYMYuV) and Corchorus yellow vein Yucatan virus (CoYVYuV) were proposed. The SiYMYuV DNA-A shared the highest nucleotide identity (86%) with the Okra yellow mosaic Mexico virus (OkYMMV). The complete DNA-B component shared the highest nucleotide identity (80%) with CoYVYuV. The CoYVYuV DNA-A shared the highest nucleotide identity (84%) with SiYMYuV. The 166-nt common region (CR) sequence for the DNA-A and DNA-B components of SiYMYuV shared a high nucleotide identity of 99%, and the 151 nt of CoYVYuV CR shared 95% of nucleotide identity. The organization and the iterated sequence of the putative AC1 binding site (located within the common region) of both isolates, were similar to that of the begomoviruses of the Western Hemisphere. Phylogenetic analyses placed the DNA-A and DNA-B of SiYMYuV and CoYVYuV in the clade containing the Abutilon mosaic virus (AbMV). © 2007 Springer Science+Business Media, LLC.