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

Virus-Induced Gene Silencing in Diverse Maize Lines Using the Brome Mosaic Virus-based silencing vector

Virus-induced gene silencing (VIGS) is a widely used tool for gene function studies in many plant species, though its use in cereals has been limited. In addition, within cereal species the varieties that best respond during VIGS screens are often not known. Using a Brome mosaic virus (BMV) vector designed to silence the maize phytoene desaturase (PDS) gene, a genetically diverse set of maize inbred lines was screened for development of gene silencing after inoculation of seeds through the novel use of a vascular puncture inoculation technique. In addition to Va35, which previously was shown to support silencing, maize lines NC300, Ki11, Oh7b, M162W and CML52 displayed significant visible photobleaching when challenged with the BMV-PDS. In these plants, targeted PDS mRNA expression was decreased 50-80% relative to levels in plants that were inoculated with BMV containing a fragment of the GUS gene or were mock-inoculated

Professional Development and the Informal Curriculum in End-of-Life Care

Although professionalism has emerged as a key competency for today’s physicians, there exists little insight into how best to teach medical students the relevant skills or instill in them the commitment required to practice according to the highest professional standards. Ten UCSF medical students were interviewed at three time points (second, third, and fourth years of school). Interviews focused on students’ learning and development regarding end-of-life care (EOLC). Students described varying steps in their professional development from their second to fourth years of school, including feeling confused about the definition of professionalism and integrating their personal and professional identities. In addition to professional development, four other themes contributed to the development of medical student understanding of how to provide EOLC as a professional: (1) curricular discordance, (2) role models, (3) the tightrope between trained versus human reactions, and (4) ethical dilemmas. These five themes represent dilemmas that students often learned how to respond to over the course of school. Professional development in EOLC required the acquisition of skills necessary to balance the tension between and navigate conflicting messages present in medical student training

Identification and characterization of a plastid-localized Arabidopsis glyoxylate reductase isoform: comparison with a cytosolic isoform and implications for cellular redox homeostasis and aldehyde detoxification

Enzymes that reduce the aldehyde chemical grouping (i.e. H-C=O) to its corresponding alcohol could be crucial in maintaining plant health. Recently, recombinant expression of a cytosolic enzyme from Arabidopsis thaliana (L.) Heynh (designated as glyoxylate reductase 1 or AtGR1) revealed that it effectively catalyses the in vitro reduction of both glyoxylate and succinic semialdehyde (SSA). In this paper, web-based bioinformatics tools revealed a second putative GR cDNA (GenBank Accession No. AAP42747; designated herein as AtGR2) that is 57% identical on an amino acid basis to GR1. Sequence encoding a putative targeting signal (N-terminal 43 amino acids) was deleted from the full-length GR2 cDNA and the resulting truncated gene was co-expressed with the molecular chaperones GroES/EL in Escherichia coli, enabling production and purification of soluble recombinant protein. Kinetic analysis revealed that recombinant GR2 catalysed the conversion of glyoxylate to glycolate (Km glyoxylate=34 μM), and SSA to γ-hydroxybutyrate (Km SSA=8.96 mM) via an essentially irreversible, NADPH-based mechanism. GR2 had a 350-fold higher preference for glyoxylate than SSA, based on the performance constants (kcat/Km). Fluorescence microscopic analysis of tobacco (Nicotiana tabacum L.) suspension cells transiently transformed with GR1 linked to the green fluorescent protein (GFP) revealed that GR1 was localized to the cytosol, whereas GR2-GFP was localized to plastids via targeting information contained within its N-terminal 45 amino acids. The identification and characterization of distinct plastidial and cytosolic glyoxylate reductase isoforms is discussed with respect to aldehyde detoxification and the plant stress response

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