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About Marian R Goldsmith

We are developing genetic and genomic resources for Lepidoptera (moths and butterflies). Our main focus is constructing molecular linkage maps for the domesticated silkworm, Bombyx mori, the central model for lepidopteran genetics and genomics. Silkworm linkage maps are composed of a variety of molecular markers which can be amplified by PCR, including RAPDs, microsatellites, STSs, and CAPS, as well as RFLPs and SNPs. The linkage maps have many applications, including cloning silkworm mutations of interest and analyzing quantitative traits (or QTL) for silk production, such as body size, cocoon shell weight, and timing of metamorphosis. We are engaged in both kinds of studies, as well as in developing anchor loci for comparative genome analysis.
A second project is construction of large-fragment DNA or Bacterial Artificial Chromosome (BAC) libraries for other model lepidopterans, notably the tobacco hornworm, Manduca sexta, the mimetic butterfly, Heliconius erato, and the agricultural pest, Heliothis virescens. BACs are used for cloning and analyzing full-length genes and their regulatory sequences. They are also used for constructing large-scale physical maps which can be integrated with genetic maps to aid in assembling whole genome shotgun sequences and for positional or map-based cloning of genes or mutations known only by their biological or phenotypic effects. The use of fluorescently-tagged BACs as probes for direct visualization of genes on chromosomes, or BAC-FISH (Fluorescence In Situ Hybridization), has led to a renaissance in lepidopteran cytogenetics, enabling rapid construction of physical maps for species such as the tobacco hornworm for which no genetic maps are available.
A relatively recent use of molecular genetic and BAC-FISH maps is to explore the extent of “synteny,” or conserved chromosome relationships among Lepidoptera. Early ancestors of moths and butterflies are estimated to be at least 100 million years old, leaving ample time for changes in chromosome organization. Finding a high level of synteny would enable investigators to use the well-established silkworm maps to pinpoint where to look for genes or mutations of interest in less well-characterized species, facilitating many kinds of studies. One that we are engaged in is mapping a mutation we found in silkworm with colleagues in Japan that confers resistance to Bt toxin, a class of insecticidal proteins produced by the bacterium, Bacillus thuringiensis, during sporulation. Crops genetically engineered to express Bt toxins are widely planted, presenting substantial risks for pests to evolve resistance in the field. If synteny is extensive among Lepidoptera, then identifying Bt-resistance gene(s) in silkworm could significantly speed up identification of similar mutations in pests, enabling new ways to monitor the rise of resistance in pests eating Bt-crops and, potentially, leading to the development of better Bt-based insecticides.


Present Faculty Member, University of Rhode Island


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