FALL 2013 SEMINARS
All seminars are in DSB 130 at 11:20 AM unless otherwise noted
Sept. 3 – Chris Herlihy, MTSU (tenure and promotion seminar)
Sept. 17 – Mary Farone, MTSU (tenure and promotion seminar)
Sept. 19 – Matt Klukowski, MTSU (tenure and promotion seminar)
Sept. 24 – Rob Brucker, Vanderbilt University
Oct. 8 – Kirk Zigler, University of the South
Oct. 22 - Wail El-rafai, Vanderbilt University
Oct. 24 – Elliot Altman, MTSU
Oct. 29 – Rob McFeeters, University of Alabama, Huntsville
Nov. 5 – Joel Harp, Vanderbilt University
Nov. 12 – Ken Spitze, Indiana University
Nov. 19 – Joey Shaw, Department of Biological and Environmental Sciences, University
of Tennessee, Chattanooga
Nov. 21 - Jeff Leblond, Department of Biology, MTSU
Nov. 26 – Manoj Khadka, MTSU
Comparative study of sterol and galactolipid compositions in the recently identified
chromerids, Chromera velia and Vitrella brassicaformis
The phylum Chromerida consists of two species, Chromera velia and Vitrella brassicaformis,
that are close photosynthetic relatives of obligately parasitic, nonphotosynthetic
apicomplexan parasites such as Plasmodium and Toxoplasma. In this presentation, I
will discuss the sterol and galactolipid compositions of those two species, as determined
by a variety of mass spectrometry techniques, and will present a chemotaxonomic inference
between them and the presumed plastid ancestor (i.e. red algae) of chromerids in general.
In addition, I will present RNA seq data that identifies key sterol and galactolipid
Sterols are ringed lipid that play a role in maintaining membrane fluidity. We have
found that C. velia possesses two primary sterols, 24-ethylcholesta-5,22E-dien-3β-ol,
and 24-ethylcholest-5-en-3β-ol, along with 3 minor sterols, whereas V. brassicaformis
produces only 24R-ethylcholest-5-en-3β-ol as primary sterol along with an unknown
C27 sterol as minor sterol. RNA seq analysis has shown that the sterol biosynthesis
in both chromerids occurs through the non-mevalonate pathway, which is common to the
apicomplexan parasite Plasmodium, cyanobacteria, the red alga Cyanidioschyzon merolae,
and several chlorophytes.
The galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol
(DGDG) are generally the major plastid structural lipids in all photosynthetic organisms.
These galactolipids play important roles in organization of the thylakoid membrane,
and maintenance of photosynthetic ability of the photosystem I and II complexes in
the chloroplast. V. brassicaformis primarily contained C20/C14 (sn-1/sn-2 regiochemistry),
C20/C16 and C20/C18 fatty acid components attached to the glycerol moieties of MGDG
and DGDG; these forms of MGDG and DGDG are different and structurally more diverse
than the previously identified C20/C20 forms that compose nearly the entirety of C.
velia's MGDG and DGDG.
These biochemical differences in sterol and galactolipid profiles are consistent with
previously observed ultrastructural and pigmentation differences between V. brassicaformis
and C. velia. Though the plastids of C. velia and V. brassicaformis seem to be originated
from a red algal ancestry, the galactolipid diversity indicates possible differences
in galactolipid biosynthesis. Thus, I will present hypotheses for how other aspects
of the galactolipid biosynthesis pathways, namely fatty acid elongation and desaturation,
in the two organisms must differ prior to the addition of galactose to form MGDG and
Dec. 3 - John Niedzwiecki, Belmont University
Comparative landscape genetics of Darwin's finches
The role of gene flow gene flow and local adaptation in speciation remain controversial.
The adaptive radiation of Darwin's finches is a model of both the roll of genetic
isolation and ecological factors in speciation. Microsatellite loci are used to estimate
migration rates of Darwin's finches across species and across the archipelago. Migration
rates for each species are estimated, and the ecological and geographic factors which
affect successful immigration/emigration are tested using multiple regression models.
Isolation by distance does not seem to play a significant role in restricting gene
glow, but other geographic factors may.