Presently I'm involved with three on-going research projects and another
project is awaiting an interested graduate student:
(1) The first research project involves participation of undergraduate
students entirely. I recruit those students that are majoring in biology
who have an interest in research. These students get credit in Biology
Problems (BIOL 4861).
Plants are known to produce chemicals that affect the growth of
insects. In numerous instances, these naturally occurring chemicals have
deleterious effects on the insects. Over the last 15 years or so,
scientists have been working earnestly to identify plants that produce
such compounds, to separate and isolate these toxic molecules, and to
identify the exact molecular structure of these compounds.
A collaborative effort has been established with Dr. Manfred Reinecke
(Dept of Chemistry, Texas Christian University) to address these goals.
Our role at TSU is to assay insects against various plant extracts Dr.
Reinecke's lab has prepared. The students prepare an artificial diet for
lepidopteran insects, specifically Trichoplusia ni (cabbage looper). The
students include in the diet extracts of different plants. After a
specified period of time students weigh the larvae, analyze
the data, and identify extracts that have toxic
compounds. Students who have been involved in this project include
Malinda Walter (Summer 1997), Tom Parish, (Summer 1998), Lori Acosta (Fall
2000), and Jana Caldwell (Spring 2002).
We have identified several plants that have toxic effects on insects.
A search of the literature has revealed that many of these plants have not
been previously identified as harboring molecules with insecticidal
effects. A manuscript is in preparation.
(2) Another research project is funded by The Robert A. Welch
Foundation through a Departmental Research Grant and involves
undergraduate chemistry students via the course Chemistry Problems (CHEM
4861). Trypsin inhibitors are compounds produced by plants and are known to inhibit the
growth of herbivorous insects. These compounds are found in
large quantities in legumes. A native legume is our source of tissue for
the isolation of this type of insecticidal molecule. Students work under
my guidance to develop an isolation scheme to purify this molecule. After
the molecule has been purified, students characterize
its chemical and physical properties. Students Brian Kanz, Zachary House,
Corrie Williams, Melissa Cather, and Lin Winton have worked on this
project. This work was presented at the 34th Annual
Meeting of the Dallas-Fort Worth Section of the American Chemical Society
held at Tarleton State University in April, 2001.
(3) The third on-going research project has involved graduate and
undergraduate students to identify drought resistant genes in crop plants that are
agriculturally important to central Texas and native Texas plants. This
project has been funded by the Amy Shelton McNutt Charitable Trust
($27,000) with matching funds from TSU, and recently by TSU's Organized
Research Committee ($11,995). Jennifer Jurney, Nathan Leslie, Angela
Roberson, Kashandra Smith, and Shyam Shridhar have all been involved in
developing this project to its current status. By using the polymerase chain
reaction (PCR), students have identified potential drought-tolerant
genes in peanuts, little bluestem, side oats gramma, buffalo grass, and
bermuda grass. A manuscript has been submitted to the Texas Journal of
Science outlining our results with peanuts, and Mr. Shridhar has presented
his results at the 105th Annual Meeting of the Texas Academy of Science,
February 28-March 2, 2002. Mr. Shridhar gains graduate credit in Thesis
(BIOL 5883).
(4) The last project is another approach to control insect pests
and addresses a genetic question. Plants produce toxic
proteins in response to pathogen attack. The gene that we use for this
project is composed of three regions. One region is to direct the nascent
protein to its proper cellular location, known as a leader sequence. The
middle region codes for the toxic portion. The last region is
hypothesized to neutralize the toxicity of the second region so the plant
cell that translated it can survive. There is very little evidence to
support this hypothesis.
One goal of this project is to express the various portions and
combinations of this gene, purify the polypeptides, and inject them into
insect larvae. This will determine which region(s) and combinations of
the gene has the most toxicity towards insect pests, and if the
hypothesized neutralizing region can render the toxic polypeptide
non-toxic.
The next goal will then be to clone DNA sequences of the most
toxic region(s) into a baculovirus. Baculoviruses infect only
arthropods, almost entirely lepidopterans. These viruses can be used in
an agricultural setting but they are slow to kill. By incorporating a
toxic protein in the genome of the baculovirus the insect should be killed
faster. There is some indication from other research groups and other
toxic proteins that this approach can be successful. Hopefully, baculoviruses containing our
selected gene will kill insects faster than wild-type baculoviruses.
This project has been supported by the TSU Organized Research
Committee and has seen the graduation of Jeff Brady and Tony Reeves with
Master's degrees. Both of them are now at Texas A&M University working on
their PhD.