Exploring the Diversity of Plant DNA Viruses and Their Satellites Using Vector-Enabled Metagenomics on Whiteflies

Current knowledge of plant virus diversity is biased towards agents of visible and economically important diseases. Less is known about viruses that have not caused major diseases in crops, or viruses from native vegetation, which are a reservoir of biodiversity that can contribute to viral emergence. Discovery of these plant viruses is hindered by the traditional approach of sampling individual symptomatic plants. Since many damaging plant viruses are transmitted by insect vectors, we have developed “vector-enabled metagenomics” (VEM) to investigate the diversity of plant viruses. VEM involves sampling of insect vectors (in this case, whiteflies) from plants, followed by purification of viral particles and metagenomic sequencing. The VEM approach exploits the natural ability of highly mobile adult whiteflies to integrate viruses from many plants over time and space, and leverages the capability of metagenomics for discovering novel viruses. This study utilized VEM to describe the DNA viral community from whiteflies (Bemisia tabaci) collected from two important agricultural regions in Florida, USA. VEM successfully characterized the active and abundant viruses that produce disease symptoms in crops, as well as the less abundant viruses infecting adjacent native vegetation. PCR assays designed from the metagenomic sequences enabled the complete sequencing of four novel begomovirus genome components, as well as the first discovery of plant virus satellites in North America. One of the novel begomoviruses was subsequently identified in symptomatic Chenopodium ambrosiodes from the same field site, validating VEM as an effective method for proactive monitoring of plant viruses without a priori knowledge of the pathogens. This study demonstrates the power of VEM for describing the circulating viral community in a given region, which will enhance our understanding of plant viral diversity, and facilitate emerging plant virus surveillance and management of viral diseases

Silverleaf Whitefly - Trichome Density Relationships on Selected Upland Cotton Cultivars

We studied silverleaf whitefly (SLW) and trichome density relationships on ten selected upland cotton cultivars: Deltapine #20B, 50B and 90B, NuCOTN 33B, Stoneville 474, Fibermax #819 and 832, Siokra L-23, and 89013-114 at Maricopa, in AZ, 1999. Whitefly and stellate trichome densities were counted on leaves on main stem leaf nodes #1, 3, 5 and 7 of each cultivar. Stoneville 474 had about 2-3 times more eggs, nymphs, and adults and also had 3-30 times more branched trichomes on abaxial leaf surfaces compared with the nine other cultivars. The top young leaves on node #1 had about 6 times more stellate trichomes compared with older leaves. However, the top young leaves also had reduced numbers of eggs and nymphs (23 and 1/cm2 of leaf disk, respectively) compared with older leaves. The results suggest that other factors, in addition to trichomes, at least for young terminal leaves, affect silverleaf whitefly population development

Silverleaf Whitefly Cotton Cultivator Preference

All of nine cotton cultivars tested were susceptible to silverleaf whitey, Bemisia argentifolii Bellows and Perring in Imperial valley, CA in 1995 and 1996. Using 4.1 adults per leaf turn as an insecticide- treatment action threshold, Deltapine (DPL) 5409 and 5415 required 5.5 applications of insecticide, DPL 50, 5461, and 5517 required 6 applications, DPL 5432 and 5690 required 65 applications, Louisiana (LA) 887 required 7 application, and Stoneville (ST) 474 required 7.5 applications. Results indicate the potential to reduce insecticide application by selecting appropriate cultivars that are commercially available

Silverleaf Whitefly Studies: Effects of Trichome Density and Leaf Shape

We examined nine upland cotton cultivars in 2000 to determine silverleaf whitefly (SLW)-cotton leaf trichome relationships. The hairy leaf cultivar Stoneville 474 had significantly higher numbers of SLW eggs, nymphs and adults compared to eight other smooth leaf cotton cultivars. The top young leaves on main stem terminals had fewer SLW eggs, nymphs and adults, but higher numbers of trichomes compared with older leaves. Among the eight smooth leaf cultivars, the four okra leaf cultivars as a group had fewer SLW eggs, nymphs and adults compared with the four normal leaf cultivars

Flagella-driven motility is a target of human Paneth cell defensin activity.

In the mammalian intestine, flagellar motility can provide microbes competitive advantage, but also threatens the spatial segregation established by the host at the epithelial surface. Unlike microbicidal defensins, previous studies indicated that the protective activities of human α-defensin 6 (HD6), a peptide secreted by Paneth cells of the small intestine, resides in its remarkable ability to bind microbial surface proteins and self-assemble into protective fibers and nets. Given its ability to bind flagellin, we proposed that HD6 might be an effective inhibitor of bacterial motility. Here, we utilized advanced automated live cell fluorescence imaging to assess the effects of HD6 on actively swimming Salmonella enterica in real time. We found that HD6 was able to effectively restrict flagellar motility of individual bacteria. Flagellin-specific antibody, a classic inhibitor of flagellar motility that utilizes a mechanism of agglutination, lost its activity at low bacterial densities, whereas HD6 activity was not diminished. A single amino acid variant of HD6 that was able to bind flagellin, but not self-assemble, lost ability to inhibit flagellar motility. Together, these results suggest a specialized role of HD6 self-assembly into polymers in targeting and restricting flagellar motility

High-density <i>S</i>. Typhimurium (1e8 CFU/ml) in buffer alone (tris-maleate pH 6.4), related to supplemental Fig 1.

High-density S. Typhimurium (1e8 CFU/ml) in buffer alone (tris-maleate pH 6.4), related to supplemental Fig 1.</p

Population Development of the Invasive Species Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) on four Eucalyptus Species of the Subgenus Symphyomyrtus

Thaumastocoris peregrinus Carpintero & Dellapé (Hemiptera:Thaumastocoridae) is a small sap-sucking insect that feeds on Eucalyptus L?Hér. leaves. Although it is native to Australia, it currently has a global distribution and it is considered as one of the big five pests of eucalypts around the world. We described the development of T. peregrinus population on four Eucalyptus species under the environmental conditions in Argentina. We also analyzed the use of yellow sticky traps as a monitoring method for this pest. The four Eucalyptus species were suitable for T. peregrinus. A cyclic pattern was observed in the development of the bronze bug population with an annual seasonal peak followed by a decrease in the abundance, reaching a minimum value during the unfavorable seasons. During the fall and winter seasons, epizootic events were registered in all the Eucalyptus species, caused by an entomopathogenic fungus. None of the meteorological variables had a clear influence neither on the bronze bug population nor with the occurrence of fungal infection. We found a significant relationship between the number of nymphs and adults of T. peregrinusin branches and the number of individuals caught in traps, suggesting that traps give actual information about the bronze bug abundance in the tree canopy.Fil: Cuello, Eliana Marina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Microbiología y Zoología Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Andorno, Andrea Verónica. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Hernández Guzmán, Claudia Marcela. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: López, Silvia Noemí. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Microbiología y Zoología Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin