Browsing by Author "Du, Min"

Now showing 1 - 4 of 4
  • Thumbnail Image
    A greenhouse screening method for resistance to gray leaf spot in maize
    Du, Min (Virginia Tech, 1993-05-15)
    Gray leaf spot (GLS) disease of maize (Zea mays L.), caused by the fungus Cercospora zeae-maydis, causes significant corn yield losses in Virginia and other mid-Atlantic states. A new greenhouse assay method with filter paper discs of C. zeaemaydis mycelia has been developed to evaluate corn germplasm for resistance to GLS. Mycelial inoculum obtained from cultures of mycelia in liquid malt media was pipetted at 100 ul samples onto each filter paper disc which was then adhered to the lower leaf surface by transparent tape. The inoculated corn seedlings were placed in a moist plastic chamber with high relative humidity provided by a humidifier. The first macroscopic symptoms induced by this inoculation method appeared 3 days after inoculation. This new inoculation method with mycelial discs was used on five corn genotypes (VA14, B68, PA875 , B73, and M017) to screen resistance to GLS disease. With this inoculation method, resistant and susceptible inbreds were easily differentiated based on lesion type. Resistant inbreds including VA14, B68, and P A875 were characterized by water-soaked appearance or small chlorotic flecks while susceptible inbreds like B73 and M017 were characterized by more extensive necrosis. Necrotic area under the mycelial disc was a good indicator for disease severity. However, the percent leaf area under discs affected by mycelia which reflected the total host responses was not appropriate to indicate disease severity. The effects of plant physiological factors on the expression of resistance to GLS was also investigated. Placing mycelial discs on lower leaf surfaces induced more responses than placing on upper leaf surfaces. Inoculation of lower older leaves induced more severe lesions than inoculation of upper leaves. The effect of cercosporin was investigated by inoculating corn seedlings with cercosporin-producing mycelia and with non-cercosporin containing mycelia. The former induced much more severe host response than the latter. Conidiation of C. zeae-maydis was examined with the mycelial inoculation method in the greenhouse. Conidiophores were found emerging from stomata as early as 15 days after inoculation in B73 and M017 and limited only to necrotic tissue. No conidiation was observed in resistant genotypes VA14, B68 and PA875.
  • Thumbnail Image
    Lipid metabolism, adipocyte depot physiology and utilization of meat animals as experimental models for metabolic research.
    Dodson, Michael V.; Hausman, Gary J.; Guan, Leluo; Du, Min; Rasmussen, Theodore P.; Poulos, Sylvia P.; Mir, Priya; Bergen, Werner G.; Fernyhough, Melinda E.; McFarland, Douglas C.; Rhoads, Robert P.; Soret, Beatrice; Reecy, James M.; Velleman, Sandra G.; Jiang, Zhihua (2010-11-22)
    Meat animals are unique as experimental models for both lipid metabolism and adipocyte studies because of their direct economic value for animal production. This paper discusses the principles that regulate adipogenesis in major meat animals (beef cattle, dairy cattle, and pigs), the definition of adipose depot-specific regulation of lipid metabolism or adipogenesis, and introduces the potential value of these animals as models for metabolic research including mammary biology and the ontogeny of fatty livers.
  • Thumbnail Image
    PCR-based cloning, characterization, and stress-induced expression of chitinase genes in Kentucky bluegrass (Poa pratensis L.)
    Du, Min (Virginia Tech, 1996-07-05)
    Chitinase is an enzyme that catalyzes the hydrolysis of chitin, an essential component of the cell walls of many fungi. Plant chitinases have been implicated in plant defense against pathogens. In plants, chitinase often exists as isoforms and three classes of chitinases have been proposed. In this study, isolation, characterization and expression of chitinase genes in Kentucky bluegrass (Poa pratensis L.) were studied. With primers designed from conserved regions of chitinase genes from other plant species, a 710 bp fragment (CH710) containing a partial chitinase gene sequence was amplified from Kentucky bluegrass by PCR. Using cassette ligation mediated PCR, we amplified four 5’ and five 3’ unknown sequences flanking CH710. The sequence information of these flanking fragments led us to the amplification of three genomic sequences from Kentucky bluegrass by PCR, KBCH1, KBCH2 and KBCH3, which contain full coding regions of chitinase genes. The chitinase genes carrying KBCH1, KBCH2 and KBCH3 were designated as chi1, chi2 and chi3, respectively. Southern blot hybridization indicated the presence of more than seven chitinase genes in the Kentucky bluegrass genome. Chi1 and chi2 each contain an open reading frame with no introns, encoding polypeptides of 340 and 320 amino acids, respectively. Both CHI1 and CHI2, the predicted proteins encoded by chi7 and chi2, are class I chitinases and share 94% amino acid identity. CHI1 has a short C-terminal extension, implicating that this protein may be a vacuolar protein. Although chi3 has high sequence similarity to chi7 and chi2, the potential open reading frame of chi3 is interrupted by a translation termination codon at the 51st amino acid indicating that it does not encode a functional chitinase. In this study, the expression of chitinase genes in Kentucky bluegrass under various stress conditions was also investigated. RNA blot hybridization showed that stresses such as cold, heat, salicylic acid and ethephon all induced an increased accumulation of chitinase MRNA in Kentucky bluegrass leaves with ethephon leading to the highest induction. After ethephon treatment, the accumulation of chitinase transcripts at a high level was observed from 2 days to 5 days. The expression of two individual chitinase genes, chi1 and chi2, was shown to be stimulated, while being coordinately regulated, by ethephon.
  • Thumbnail Image
    Skeletal muscle stem cells from animals I. Basic cell biology.
    Dodson, Michael V.; Hausman, Gary J.; Guan, Leluo; Du, Min; Rasmussen, Theodore P.; Poulos, Sylvia P.; Mir, Priya; Bergen, Werner G.; Fernyhough, Melinda E.; McFarland, Douglas C.; Rhoads, Robert P.; Soret, Beatrice; Reecy, James M.; Velleman, Sandra G.; Jiang, Zhihua (2010-08-31)
    Skeletal muscle stem cells from food-producing animals are of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding of muscle stem cell biology and function is essential for developing technologies and strategies to augment the metabolic efficiency and muscle hypertrophy of growing animals potentially leading to greater efficiency and reduced environmental impacts of animal production, while concomitantly improving product uniformity and consumer acceptance and enjoyment of muscle foods.