Dr. Frank Howarth and Dr. Fred Stone

 

   

 

Phylogeny of Parasitic Angiosperms and Evolution of a Group I intron in the COXI gene of angiosperms

Since 1996 I have been collaborating with Dr. Claude dePamphilis at Pennsylvania State University on determining a global phylogeny of angiosperms based on the COX I mitochondrial gene, which can be used for phylogenetic analysis of all angiosperms, including those that lack chloroplast genes customarily used for phylogenetic analysis. I am currently studying a unique group I intron found rarely in other angiosperms but found in virtually every parasitic lineage studied. This work should not only elucidate the phylogeny of these plants but also should lead to an understanding of horizontal transfer of the intron to these plants.


 

Work in Progress

  • dePamphilis, C. W., Croom, H. B., Young, N. D., Elisens, W. J., Wolfe, A. D., Bowe, L.M., Moore, A. G., and Turner, J. H., Molecular Evolution of COXI , a plant mitochondrial gene: RNA editing, processed paralogy, and a preliminary phylogeny of diverse flowering plants, (In preparation for Proc. Natl. Acad. Sci USA)
  • Croom, H. B., Turner, J. H.,, Smith R. A., and dePamphilis, C. W. Parasitic angiosperms all have a novel Group I intron in the COX I gene of mitochondrial DNA. (In preparation for Nature)
  • Croom, H. B. and dePamphilis, C. W. The Group I intron of the COXI mitochondrial gene of Cuscuta spp. is unique among parasitic angiosperms and suggests multiple origins of the intron. (In preparation for Molecular Biology and Evolution)


Posters

  • dePamphilis, C. W., Barkman, T. J., Bowe, L. M., Croom, H. B., Elisens, W. J. Moore, A. G., Wolfe, A. D., Young, N. D. McNeal, J. R, Coat, G., Phylogeny of seed plants based on mitochondrial COXI and ATPA DNA sequences, International Botanical Congress, August 1999, St. Louis, MO.
  • McNeal, J. R, Croom, H. B, and dePamphilis, C. W., Molecular phylogenetics and COXI intron hypervariability in the genus Cuscuta, International Botanical Congress, August 1999, St. Louis, MO.
  • Barkman, T. J., Croom, H. B., Young, N. D., McNeal, J. R., Coat, G., Steiner, K., and dePamphilis, C. W., Multiple origins of parasitism in angiosperms inferred with mitochondrial COXI & ATPA DNA sequences, International Botanical Congress, August 1999, St. Louis, MO.

Pattern and Process of Speciation in Hawaiian Spiders in the Genus Tetragnatha

Since 1988 I have been collaborating with Dr. Rosemary Gillespie at the University of Hawaii-Manoa on the evolution of tetragnathid spiders which have undergone dramatic radiation into new species found only in Hawaii. Dr. Gillespie conducts field studies and alpha taxonomy on the sixty-odd species she has discovered, and I sequence their DNA in order to understand the pattern and process of evolution of the group since its first introduction to the islands millions of years ago. My current work on this group centers on outgroup analysis in order to understand better the number of natural introductions to the islands. We hope that such knowledge will better enable conservation of these highly endangered and unique species.


Publications

  • Gillespie, R.G., Croom, H.B. and Hasty, G. L., Phylogenetic relationships and adaptive shifts among major clades of Tetragnatha spiders (Araneae: Tetragnathidae) in Hawaii. Pacific Science 51, 380-394, 1997.
  • Gillespie, R. G. and Croom, H. B., Pattern and process in speciation: A comparative approach using a Hawaiian spider radiation, in Patterns of Speciation and Biogeography of Hawaiian Biota, Wagner, W. L. and Funk, V. A., eds. Smithsonian Press, 1995.Review
  • Gillespie, R. G., Croom, H. B., and Palumbi, S. R., Multiple Origins of a Spider Radiation in Hawaii, Proc. Natl. Acad. Sci. USA 91, 2290-94, 1994. Abstract
  • Croom, H. B., Gillespie, R. G., and Palumbi, S. R., Mitochondrial DNA sequences coding for a portion of the RNA of the small mitochondrial subunit of Tetragnatha mandibulata and Tetragnatha hawaiiensis (Araneae, Tetragnathidae), J. Arachnology 19, 210-214, 1991

Posters

  • Gillespie, R. G., Croom, H. B. and Hasty, G. L, Radiation and phylogeny of tetragnathid spiders(Araneae) in Hawaii, International Congress of Entomology, Symposium on ‘The Legacy of R.C.L. Perkins’, August 1996, Florence, Italy.
  • Gillespie, R. G. and Croom, H. B., Pattern and process in speciation: A comparative approach using a Hawaiian spider radiation, American Institute of Biological Sciences annual meeting, August 1992, Honolulu, HI.
  • Croom, H. B. and Gillespie, R. G., DNA sequences reveal three major clades of endemic Hawaiian spiders in the genus Tetragnatha, American Arachnological Society annual meeting, June 1991 Oxford, MS.
  • Croom, H. B., Gillespie, R. G.. and Palumbi, S. R., Mitochondrial DNA sequences suggest that Hawaiian spiders in the genus Tetragnatha fall into three major clades, Society for the Study of Evolution annual meeting, July 1991, Hilo, HI.
  • Gillespie, R. G., Palumbi, S. R., and Croom, H. B., Adaptive radiation in the spider genus Tetragnatha in Hawaii, Fourth International Congress of Systematic and Evolutionary Biology, July 1990, College Park, MD

Cytoskeletal proteins and genes

This work continues my interest in self-assembling cellular organelles, begun in graduate studies on the ribosomes of E. coli. It centers on two cytoskeletal proteins: microtubules from rat hrain and an axonemal protein from Chlamydomonas. The neurotubule work focuses on the effects of removing guanine nucleotides on the stability of tubulin in vitro, and the axonemal work focuses on elucidation of an axonemal protein-coding gene that is expressed after shearing flagella from the algae.

Publications

  • Schloss, J. and Croom, H. B., Normal Chlamydomonas nuclear gene structure on linkage group XIX, J. Cell Sci. 100, 877-881, 1991 .Abstract
  • Croom, H. B., Correia, J. J., and Williams, R. C., Jr., The effects of elevated pH and high salt concentrations on tubulin, Archives Biochem. Biophys. 249, 397-406, 1986. Abstract
  • Croom, H. B., Correia, J. J., Baty, L. T., and Williams, R. C., Jr., Release of exchangeably-bound guanine nucleotides from tubulin in a magnesium-free buffer, Biochemistry 24, 768-775, Abstract
    1985

Posters

  • .Schloss, J. A. and Croom, H. B., Structure and expression of a gene on Chlamydomonas linkage group XIX , The American Society for Cell Biology annual meeting, December 1991, Boston, MA.
  • Baty, L. T., Correia, J. J., Croom, H. B., and Williams, R. C., Jr., Guanine nucleotide exchange by tubulin, The American Biophysical Society meetings, February 1985, Baltimore, MD.
  • Baty, L. T., Correia, J. J., Croom, H. B., and Williams, R. C., Jr., Guanine nucleotide binding to tubulin, The American Society for Cell Biology annual meeting, November 1984, Kansas City, MO.

Research with Students, Scientific Sewanee, and Honors Theses

This work has been conducted by my students during Biology 444: Independent Study and/or during summer internships at the University of the South. Some of it has been presented at national and regional meetings, some has been presented at Scientific Sewanee at the University of the South, and some has been submitted for graduation with honors in biology from the University of the South. The honors papers are available in the Archives of duPont Library, Sewanee, TN.

Posters with Students at National and Regional Meetings

  • Keefer, Christopher J. and Croom, Henrietta B. A morphological and molecular study of speciaiton in cave spiders (Araneae: Nesticidae: Nesticus) of the Southern Cumberland Plateau. Tennessee Academy of Science, April 1994.
  • Thompson, Amy and Croom, Henrietta B. Three DNA Sequencing Templates of a Portion of Mitochondrial 16S Ribosomal DNA Used to Generate a Preliminary Phylogeny for Four Hawaiian Species of the Genus Tetragnatha (Araneae, Tetragnathidae), Tennessee Academy of Science, April 1994.
  • McDonald, W. H. and Croom, H. B., Multiple introductions of a single spider genus to the Hawaiian Islands, Society for the Study of Evolution annual meeting, June 1993, Snowbird, UT.
  • McDonald, W. H. Croom, Henrietta, and Toll, Ronald, Analyzing and Sequencing of Cephalopod mtDNA for use in Phylogenetic Analysis, Tennessee Academy of Science, April 1993

 

 

 

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