ADDRESS
Department of Botany
University of Texas at Austin
Austin, TX 78713-7640
Phone: (512) 471-3364
Email: ims1030@utxvms.cc.utexas.edu
POSITIONS HELD
Lecturer
Department of Botany, The University of Texas at
Austin.
August 1996 to present
Research Associate
Department of Botany, The University of Texas at
Austin.
April 1991 to present
Go-Principal investigator
(USDA grants)
Department of Botany, The University of Texas at
Austin
September 1992 to present
Post-Doctoral Associate
Department of Botany, The University of Texas at
Austin
January 1986 to March 1991
EDUCATION
Ph. D. (Life Sciences)
1984
Jawaharlal Nehru University, New Delhi, India
Thesis: Studies on the uptake and integration of
foreign DNA in plant cells.
M. Sc. (Genetics)
1978
G. B. Pant University of Agriculture and Technology,
Pantnagar, India
OGPA 4.859/5.000 (87.8%)
Subjects: Genetics, Biochemistry and Microbiology
Thesis: Studies on intranuclear distribution of
chiasmata in Secale cereale
B. Sc. (Honours)
1974
G. B. Pant University of Agriculture and Technology,
Pantnagar, India
OGPA 4.855/5.000 (87. 1 %)
Subjects: Agriculture and Animal Husbandry
AWARDS
1979-83
Council of Scientific and Industrial Research Fellowship
1974-76
Indian Council of Agricultural Research Fellowship
1971-74
Indira Gandhi Agricultural Scholarship
PROFESSIONAL DEVELOPMENT
American Association
for the Advancement of Science
American Society
for Microbiology
GRANTS
1. R. Malcolm Brown, Jr. and Inder M. Saxena. USDA
Grant. Genetic analysis of cellulose biosynthesis in Acetobacter xylinum.
9/1/96-8/31/98.
2. R. Malcolm Brown, Jr. and Inder M. Saxena.
USDA Grant. Molecular analysis of cellulose biosynthesis in Acetobacter
xylinum. 9/1/93-8/31/95.
3. R. Malcolm Brown, Jr. and Inder M. Saxena. USDA
Grant. Molecular analysis of cellulose biosynthesis in Acetobacter xylinum.
9/1/92-8/31/93.
PATENTS
1. Saxena, I. M., F. C. Lin, and R. M. Brown, Jr.
1995. Recombinant Cellulose Synthase. (U.S.Patent application). UTSB#564.
2. Saxena, I. M., E. M. Roberts, and R. M. Brown,
Jr. 1990. Modification of cellulose normally synthesized by cellulose-producing
microorganisms. U.S.Patent 4,950,597.
PUBLICATIONS
1. Saxena, 1. M., and R. M. Brown, Jr.
1997. Identification of cellulose synthase(s) in higher plants: Sequence
analysis of processive B-glycosyltransferases with the common motif "D,
D, D35Q(R,Q)XRW". Cellulose (in press)
2. Brown, R. M., Jr., Saxena, I. M., and Kudlicka,
K. 1996. Cellulose biosynthesis in higher plants. Trends in plant science
1: 149-156
3. Saxena, I. M., and R. M. Brown, Jr. 1995. Identification
of a second cellulose synthase gene (acsAll) in Acetobacter xylinum.
J. Bacteriol. 177: 5276- 5283.
4. Saxena, I. M., R. M. Brown, Jr., M. Fevre, R.
A. Geremia, and B. Henrissat. 1995. Multidomain architecture of glycosyl
transferases: Implications for mechanism of action. J. Bacteriol. 177:1419-1424.
5. Saxena, I. M., K. Kudlicka, K. Okuda, and R. M.
Brown, Jr. 1994. Characterization of genes in the cellulose-synthesizing
operon lacs operon) of Acetobacter xylinum: Implications for cellulose
crystallization. J. Bacteriol. 176:
5735-5752.
6. Saxena, I. M., F. C. Lin, and R. M. Brown, Jr.
1991. Identification of a new gene in an operon for cellulose biosynthesis
in Acetobacter xylinum. Plant Mol Biol. 16: 947-954.
7. Saxena, I. M., F. C. Lin and R. M. Brown,
Jr. 1990. Cloning and sequencing of the cellulose synthase catalytic subunit
gene of Acetobacter xylinum. Plant Mol Biol. 15: 673-683.
8. Saxena, I. M., and R. M. Brown, Jr. 1989.
Cellulose biosynthesis in Acetobacter xylinum: A genetic approach.
In : Schuerch, C. (ed) Cellulose and Wood - Chemistry and Technology, pp
537-557. John Wiley and Sons, New York.
9. Roberts, E., I. M. Saxena, and R. M. Brown,
Jr. 1989a. Biosynthesis of cellulose II. In : Schuerch, C. (ed) Cellulose
and Wood - Chemistry and Technology, pp 689-704. John Wiley and Sons, New
York.
10. Roberts, E., I. M. Saxena, and R. M. Brown, Jr.
1989b. Does cellulose II occur in nature? In : Bailey, G. W. (ed) Proceedings
of the 47th Annual Meeting of the Electron Microscopy Society of America,
pp 780-781.
11. Gupta, A., I. M. Saxena, S. K. Sopory, and S.
Guha-Mukherjee. 1983a. Regulation of nitrate-reductase synthesis during
early germination in seeds of barley (Hordeum vulgare). Journal of Experimental
Botany 34:34-46.
12. Gupta, A., S. Disa, I. M. Saxena, N. B. Sarin,
S. Guha-Mukherjee, and S. K. Sopory. 1983b. Role of nitrate in the induction
of nitrite-reductase activity during wheat seed germination. Journal of
Experimental Botany 34:396-404.
13. Ramaswamy, O., I. M. Saxena, S. Guha-Mukherjee,
and S. K. Sopory. 1983. Phytochrome regulation of nitrate-reductase in
wheat. Journal of Biosciences 5:63-70.
PAPERS SUBMITTED/IN PREPARATION FOR PUBLICATION
14. Saxena, I. M., and R. M. Brown, Jr. 1997. IS 1238: a new mobile insertion sequence element from Acetobacter xylinum.
RESEARCH EXPERIENCE
During my Ph.D program (1978-1984), I worked on the
genetic modification of higher plants. The transfer of foreign DNA to plant
cells was done using the Agrobacterium tumefaciens Ti-plasmid system,
and the direct uptake of DNA by plant
protoplasts. These studies involved the techniques of plant cell and
tissue culture, and DNA isolation and analysis from bothbacterial and plant
sources. In the same period, I was also involved in studies on nitrate
assimilation in higher plants (Gupta) et al., 1983a and 1983b; Ramaswamy
et al., 1983), and continued this work by analyzing nitrate reductase-deficient
mutants of Nicotiana tabacum till December 1985.
Since January 1986, 1 have been studying cellulose
biosynthesis in the bacterium Acetobacter xylinum (Saxena and Brown,
1989; Roberts at al., 1989a and 1989b). These studies led to the identification
of genes for cellulose biosynthesis for the first time from any organism
(Saxena et al., 1990 and 1991). During the same period, a group from
Cetus Corp. also identified a similar set of genes from A. xylinum.
The A. xylinum genes for cellulose biosynthesis were characterized
by isolation of insertion mutants (Saxena at al., 1994), and subsequently
a second gene encoding for cellulose synt~iase activity was described in
this bacterium (Saxena and Brown., 1995). Comparison of the A.
xylinum cellulose synthase sequence with other O- glycosyltransferases
using hydrophobic cluster analysis (HCA) led to the identification of conserved
domains in these proteins and the prediction of catalytic residues (Saxena
et al., 1995). Putative catalytic residues in the A. xylinum cellulose
synthase have been analyzed by site-directed mutagenesis (Saxena and Brown,
1997).
In the course of my research work, I have used a
variety of approaches and techniques to get an overall picture of the process
under investigation (Brown at al., 1996). As a result I have experience
of working in the broad areas of genetics, biochemistry, microbiology and
plant biology, utilizing techniques of cell and molecular biology for my
studies.
TEACHING AND TRAINING EXPERIENCE
1. Teaching Cell Biology (BOT 323K) to undergraduate
students at the University of Texas at Austin since August 1996.
2. Training undergraduate students (three, at present)
for research in molecular biology.
STATEMENT OF RESEARCH INTERESTS
Glycosyltransferases involved in the biosynthesis of oligosaccharide
and polysaccharide chains.
Glycosyltransferases are an important class of enzymes required for
the addition of sugars to a variety of biological molecules and leading
to the formation of glycolipids, glycoproteins, oligosaccharides, polysaccharides,
and other glycosylated compounds. The biological roles of glycosyl transfer
ranges from providing molecular specificity to elaborating cellular structure.
Glycosyltransferases required for the synthesis of oligosaccharide and
polysaccharide chains are processive enzymes that are involved in the synthesis
of signaling molecules (the 'nod' factor in Rhizobium sp. and a
chito- oligosaccharide in Xenopus laevis) and structural polysaccharides
(cellulose and chitin). However, these glycosyltransferases have been difficult
to study because they are membrane proteins and usually difficult to purify.
With cloning of the genes for cellulose synthases, chitin synthases, and
hyaluronan synthases, it became possible to analyze these glycosyltransferases
and identify regions on
these proteins that are involved in catalysis and processivity. I am
interested in identifying and characterizing the specific amino acid residues
involved in catalysis and in designing proteins that allow incorporation
of other sugars with the same or a different linkage in the oligolpolysaccharide
backbone. The characterization of the mechanism used for controlling chain
length will allow
synthesis of oligo/polysaccharide chains of desired length. A number
of these experiments will be done using the cellulose synthase genes from
bacteria as well as those from higher plants. I am also interested in determining
the structure of a glycosyltransferase, specifically cellulose synthase,
where the catalytic site is predicted to bind at least two sugar residues
in an orientation that allows these residues to be positioned 180" with
respect to each other in the polysaccharide backbone.