Accumulation of Maize chlorotic dwarf virus proteins in its plant host and leafhopper vector

AbstractThe genome of Maize chlorotic dwarf virus (MCDV; genus Waikavirus; family Sequiviridae) consists of a monopartite positive-sense RNA genome encoding a single large polyprotein. Antibodies were produced to His-fusions of three undefined regions of the MCDV polyprotein: the N-terminus of the polyprotein (R78), a region between coat proteins (CPs) and the nucleotide-binding site (NBS) (R37), and a region between the NBS and a 3C-like protease (R69). The R78 antibodies react with proteins of 50 kDa (P50), 35 kDa (P35), and 25 kDa (P25) in virus preparations, and with P35 in plant extracts. In extracts of the leafhopper vector Graminella nigrifrons fed on MCDV-infected plants, the R78 antibodies reacted with P25 but not with P50 and P35. The R69 antibodies bound proteins of approximately 36 kDa (P36), 30 kDa (P30), and 26 kDa (P26) in virus preparations, and P36 and P26 in plant extracts. Antibodies to R37 reacted with a 26-kDa protein in purified virus preparations, but not in plant extracts. Neither the R69 nor the R37 antibodies bound any proteins in G. nigrifrons. Thus, in addition to the three CPs, cysteine protease and RNA-dependent RNA polymerase, the MCDV polyprotein is apparently post-transitionally cleaved into P50, P35, P25, P36, P30, and P26

Mapping QTL contributing to SCMV resistance in tropical maize.

Sugarcane mosaic virus (SCMV) has been increasing in importance as a maize disease in Brazil. In this study, we mapped and characterized quantitative trait loci (QTL) associated with resistance to SCMV in a maize population consisting of 150 F2:3 families from the cross between two tropical maize inbred lines, L520 (resistant) and L19 (susceptible). F2 individuals were genotyped with microsatellite (SSR) markers, and the derived F2:3 families were evaluated for their response to artificial inoculation with SCMV under field conditions at Sete Lagoas, MG, Brazil, in 2001 and 2005. Multiple interval mapping was used for QTL detection with a linkage map based on 19 SSR markers. Three QTLs for SCMV resistance were identified with two QTLs (Scm2a and Scm2b) clustered on chromosome 3, bin 3.04, and one QTL (Scm1) on chromosome 6, bin 6.01, explaining 13.34, 41.85 and 7.66% of the phenotypic variation for SCMV resistance, respectively

The Capsid Protein of \u3ci\u3eTurnip Crinkle Virus\u3c/i\u3e Overcomes Two Separate Defense Barriers to Facilitate Systemic Movement of the Virus in \u3ci\u3eArabidopsis\u3c/i\u3e

The capsid protein (CP) of Turnip crinkle virus (TCV) is a multifunctional protein needed for virus assembly, suppression of RNA silencing-based antiviral defense, and long-distance movement in infected plants. In this report, we have examined genetic requirements for the different functions of TCV CP and evaluated the interdependence of these functions. A series of TCV mutants containing alterations in the CP coding region were generated. These alterations range from single-amino-acid substitutions and domain truncations to knockouts of CP translation. The latter category also contained two constructs in which the CP coding region was replaced by either the cDNA of a silencing suppressor of a different virus or that of green fluorescent protein. These mutants were used to infect Arabidopsis plants with diminished antiviral silencing capability (dcl2 dcl3 dcl4 plants). There was a strong correlation between the ability of mutants to reach systemic leaves and the silencing suppressor activity of mutant CP. Virus particles were not essential for entry of the viral genome into vascular bundles in the inoculated leaves in the absence of antiviral silencing. However, virus particles were necessary for egress of the viral genome from the vasculature of systemic leaves. Our experiments demonstrate that TCV CP not only allows the viral genome to access the systemic movement channel through silencing suppression but also ensures its smooth egress by way of assembled virus particles. These results illustrate that efficient long-distance movement of TCV requires both functions afforded by the CP

The Capsid Protein of \u3ci\u3eTurnip Crinkle Virus\u3c/i\u3e Overcomes Two Separate Defense Barriers to Facilitate Systemic Movement of the Virus in \u3ci\u3eArabidopsis\u3c/i\u3e

The capsid protein (CP) of Turnip crinkle virus (TCV) is a multifunctional protein needed for virus assembly, suppression of RNA silencing-based antiviral defense, and long-distance movement in infected plants. In this report, we have examined genetic requirements for the different functions of TCV CP and evaluated the interdependence of these functions. A series of TCV mutants containing alterations in the CP coding region were generated. These alterations range from single-amino-acid substitutions and domain truncations to knockouts of CP translation. The latter category also contained two constructs in which the CP coding region was replaced by either the cDNA of a silencing suppressor of a different virus or that of green fluorescent protein. These mutants were used to infect Arabidopsis plants with diminished antiviral silencing capability (dcl2 dcl3 dcl4 plants). There was a strong correlation between the ability of mutants to reach systemic leaves and the silencing suppressor activity of mutant CP. Virus particles were not essential for entry of the viral genome into vascular bundles in the inoculated leaves in the absence of antiviral silencing. However, virus particles were necessary for egress of the viral genome from the vasculature of systemic leaves. Our experiments demonstrate that TCV CP not only allows the viral genome to access the systemic movement channel through silencing suppression but also ensures its smooth egress by way of assembled virus particles. These results illustrate that efficient long-distance movement of TCV requires both functions afforded by the CP

On the genome constitution and evolution of intermediate wheatgrass (Thinopyrum intermedium: Poaceae, Triticeae)

<p>Abstract</p> <p>Background</p> <p>The wheat tribe Triticeae (Poaceae) is a diverse group of grasses representing a textbook example of reticulate evolution. Apart from globally important grain crops, there are also wild grasses which are of great practical value. Allohexaploid intermediate wheatgrass, <it>Thinopyrum intermedium </it>(2n = 6x = 42), possesses many desirable agronomic traits that make it an invaluable source of genetic material useful in wheat improvement. Although the identification of its genomic components has been the object of considerable investigation, the complete genomic constitution and its potential variability are still being unravelled. To identify the genomic constitution of this allohexaploid, four accessions of intermediate wheatgrass from its native area were analysed by sequencing of chloroplast <it>trn</it>L-F and partial nuclear GBSSI, and genomic <it>in situ </it>hybridization.</p> <p>Results</p> <p>The results confirmed the allopolyploid origin of <it>Thinopyrum intermedium </it>and revealed new aspects in its genomic composition. Genomic heterogeneity suggests a more complex origin of the species than would be expected if it originated through allohexaploidy alone. While <it>Pseudoroegneria </it>is the most probable maternal parent of the accessions analysed, nuclear GBSSI sequences suggested the contribution of distinct lineages corresponding to the following present-day genera: <it>Pseudoroegneria</it>, <it>Dasypyrum</it>, <it>Taeniatherum</it>, <it>Aegilops </it>and <it>Thinopyrum</it>. Two subgenomes of the hexaploid have most probably been contributed by <it>Pseudoroegneria </it>and <it>Dasypyrum</it>, but the identity of the third subgenome remains unresolved satisfactorily. Possibly it is of hybridogenous origin, with contributions from <it>Thinopyrum </it>and <it>Aegilops</it>. Surprising diversity of GBSSI copies corresponding to a <it>Dasypyrum</it>-like progenitor indicates either multiple contributions from different sources close to <it>Dasypyrum </it>and maintenance of divergent copies or the presence of divergent paralogs, or a combination of both. <it>Taeniatherum</it>-like GBSSI copies are most probably pseudogenic, and the mode of their acquisition by <it>Th. intermedium </it>remains unclear.</p> <p>Conclusions</p> <p>Hybridization has played a key role in the evolution of the Triticeae. Transfer of genetic material via extensive interspecific hybridization and/or introgression could have enriched the species' gene pools significantly. We have shown that the genomic heterogeneity of intermediate wheatgrass is higher than has been previously assumed, which is of particular concern to wheat breeders, who frequently use it as a source of desirable traits in wheat improvement.</p

The Genetics and Genomics of Virus Resistance in Maize

Viruses cause significant diseases on maize worldwide. Intensive agronomic practices, changes in vector distribution, and the introduction of vectors and viruses into new areas can result in emerging disease problems. Because deployment of resistant hybrids and cultivars is considered to be both economically viable and environmentally sustainable, genes and quantitative trait loci for most economically important virus diseases have been identified. Examination of multiple studies indicates the importance of regions of maize chromosomes 2, 3, 6, and 10 in virus resistance. An understanding of the molecular basis of virus resistance in maize is beginning to emerge, and two genes conferring resistance to sugarcane mosaic virus, Scmv1 and Scmv2, have been cloned and characterized. Recent studies provide hints of other pathways and genes critical to virus resistance in maize, but further work is required to determine the roles of these in virus susceptibility and resistance. This research will be facilitated by rapidly advancing technologies for functional analysis of genes in maize

Response of Soybean Cultivars to \u3ci\u3eBean pod mottle virus\u3c/i\u3e Infection

Bean pod mottle virus (BPMV) has become increasingly common in soybean throughout the north-central region of the United States. Yield loss assessments on southern soybean germplasm have reported reductions ranging from 3 to 52%. Currently, no soybean cultivars have been identified with resistance to BPMV. The objective of this study was to determine the impact of BPMV infection on soybean cultivars representing a broad range of northern soybean germplasm by comparing inoculated and noninoculated soybean plants in paired row studies. In all, 30 and 24 cultivars were evaluated in Nebraska (NE) in which soybean plants were inoculated at the V3 to V4 growth stage. Eleven cultivars from public and breeding lines were inoculated at the VC and R5 to R6 growth stages in Ohio (OH). Disease severity, yield, and percent seed coat mottling were assessed at both locations, whereas protein and oil content also were assessed at NE. Yield and percent seed coat mottling was significantly reduced following inoculation at the VC (OH) and V3 to V4 (NE) growth stages. In addition, seed oil and protein composition were impacted in 1 of the 2 years of the study. This study demonstrates that substantial yield losses can occur in soybean due to BPMV infection. In addition, protein and oil may be affected depending on the environment during the production season