Maize chlorotic mottle virus exhibits low divergence between differentiated regional sub-populations.

Maize chlorotic mottle virus has been rapidly spreading around the globe over the past decade. The interactions of maize chlorotic mottle virus with Potyviridae viruses causes an aggressive synergistic viral condition - maize lethal necrosis, which can cause total yield loss. Maize production in sub-Saharan Africa, where it is the most important cereal, is threatened by the arrival of maize lethal necrosis. We obtained maize chlorotic mottle virus genome sequences from across East Africa and for the first time from Ecuador and Hawaii, and constructed a phylogeny which highlights the similarity of Chinese to African isolates, and Ecuadorian to Hawaiian isolates. We used a measure of clustering, the adjusted Rand index, to extract region-specific SNPs and coding variation that can be used for diagnostics. The population genetics analysis we performed shows that the majority of sequence diversity is partitioned between populations, with diversity extremely low within China and East Africa

A virulence activator of a surface attachment protein in Burkholderia pseudomallei acts as a global regulator of other membrane-associated virulence factors

Burkholderia pseudomallei (Bp), causing a highly fatal disease called melioidosis, is a facultative intracellular pathogen that attaches and invades a variety of cell types. We previously identified BP1026B_I0091 as a surface attachment protein (Sap1) and an essential virulence factor, contributing to Bp pathogenesis in vitro and in vivo. The expression of sap1 is regulated at different stages of Bp intracellular lifecycle by unidentified regulator(s). Here, we identified SapR (BP1026B_II1046) as a transcriptional regulator that activates sap1, using a high-throughput transposon mutagenesis screen in combination with Tn-Seq. Consistent with phenotypes of the Δsap1 mutant, the ΔsapR activator mutant exhibited a significant reduction in Bp attachment to the host cell, leading to subsequent decreased intracellular replication. RNA-Seq analysis further revealed that SapR regulates sap1. The regulation of sap1 by SapR was confirmed quantitatively by qRT-PCR, which also validated the RNA-Seq data. SapR globally regulates genes associated with the bacterial membrane in response to diverse environments, and some of the genes regulated by SapR are virulence factors that are required for Bp intracellular infection (e.g., type III and type VI secretion systems). This study has identified the complex SapR regulatory network and its importance as an activator of an essential Sap1 attachment factor

Infectious clones development and transmission biology of maize chlorotic mottle virus

M.S. University of Hawaii at Manoa 2013.Includes bibliographical references.Maize chlorotic mottle virus (MCMV) has become one of the most widespread corn viruses in the Hawaiian Islands. In the US Mainland, MCMV has been reported to be transmitted by chrysomelid beetles. However, none of these beetle species are established in Hawaii where the corn thrips, Frankliniella williamsi has been identified to be the main vector. In this research, I showed that thrips transmitted the virus with no evidence for latent periods. Both larvae and adults transmitted MCMV for up to 6 days after acquisition, with decreasing rates of transmission as time progressed. There was also no evidence that adult thrips that acquired the virus as larvae were competent vectors. Real-time RT-PCR assays showed that viral load was depleted from the vector's body after thrips had access to healthy plant tissue. Depletion of viral load was also observed when thrips matured from larvae to adults. Thrips were able to transmit MCMV after acquisition and inoculation access periods of 3 hours. In addition, I used an artificial feeding assay to feed thrips on purified MCMV or MCMV genomic RNA. Based on results achieved, I postulated that MCMV employs a capsid strategy for vector transmission. To further study the molecular determinants in MCMV transmission by vectors, I developed infectious clones of MCMV using a long RT-PCR assay. Taken altogether this research suggests that corn thrips transmit MCMV in a semi-persistent manner and that MCMV employs a capsid strategy for vector transmission

A first global phylogeny of<i>Maize chlorotic mottle virus</i>

ABSTRACT Maize chlorotic mottle virus has been rapidly spreading around the globe over the past decade. The interactions of Maize chlorotic mottle virus with potyviridae viruses causes an aggressive synergistic viral condition - maize lethal necrosis, which can cause total yield loss. Maize production in sub-Saharan Africa, where it is the most important cereal, is threatened by the arrival of maize lethal necrosis. We obtained Maize chlorotic mottle virus genome sequences from across East Africa and for the first time from Ecuador and Hawaii, and constructed a phylogeny which highlights the similarity of Chinese to African isolates, and Ecuadorian to Hawaiian isolates. We used a measure of clustering, the adjusted Rand index, to extract region-specific SNPs and coding variation that can be used for diagnostics. The population genetics analysis we performed shows that the majority of sequence diversity is partitioned between populations, with diversity extremely low within China and East Africa

The Burkholderia pseudomallei intracellular 'TRANSITome'

Prokaryotic cell transcriptomics has been limited to mixed or sub-population dynamics and individual cells within heterogeneous populations, which has hampered further understanding of spatiotemporal and stage-specific processes of prokaryotic cells within complex environments. Here we develop a 'TRANSITomic' approach to profile transcriptomes of single Burkholderia pseudomallei cells as they transit through host cell infection at defined stages, yielding pathophysiological insights. We find that B. pseudomallei transits through host cells during infection in three observable stages: vacuole entry; cytoplasmic escape and replication; and membrane protrusion, promoting cell-to-cell spread. The B. pseudomallei 'TRANSITome' reveals dynamic gene-expression flux during transit in host cells and identifies genes that are required for pathogenesis. We find several hypothetical proteins and assign them to virulence mechanisms, including attachment, cytoskeletal modulation, and autophagy evasion. The B. pseudomallei 'TRANSITome' provides prokaryotic single-cell transcriptomics information enabling high-resolution understanding of host-pathogen interactions