.: Department of Biology: Tom McKnight

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Tom McKnight received his B.S. degree in Microbiology and Ph.D. in Molecular and Population Genetics from the University of Georgia, and did postdoctoral research at Atlantic Richfield's Plant Cell Research Institute. He is a Professor and Associate Head in the Department of Biology and a member of the interdepartmental faculties of Genetics, Plant Physiology and Molecular and Cell Biology. Dr. McKnight teaches molecular cell biology and microbiology at the undergraduate level, and plant molecular biology and plant cell biology at the graduate level.

Tom McKnight

Tom McKnight
Professor and Assocociate Head

3258 TAMU
College Station, TX 77843-3258

Office:
Biological Sciences Building East
Room 202C
Butler Hall
Room 100B
979-845-3896

Lab:
Biological Sciences Building East
Room 206
979-845-6749

Fax: 979-845-2891
Email: mcknight@mail.bio.tamu.edu

Plant Molecular and Cell Biology

My lab is currently investigating mechanisms that regulate telomerase activity in plants. We previously showed that the pattern of telomerase expression in plants is remarkably similar to the pattern seen in humans, despite fundamental differences in development between plants and animals. Telomerase is abundantly expressed in reproductive organs but is undetectable in most vegetative organs (Fitzgerald et al., 1996). Additionally, telomerase can be induced in leaves and other vegetative organs by exposure to exogenous auxin.

To isolate genes that regulate telomerase, we screened a large population of activation tagged lines of Arabidopsis thaliana, and found that several lines that ectopically express telomerase in leaves. The first line we characterized over-expressed a gene encoding a small zinc finger transcription factor we designated TELOMERASE ACTIVATOR 1 (Ren et al., 2004). This factor does not bind to the promoter for TERT, which encodes the catalytically active subunit of telomerase. Instead, it binds to and activates transcription of BT2, a gene encoding a component of a ubiquitin ligase (Ren et al., 2007). Our working model is that the BT2 ubiquitin ligase marks a telomerase repressor for destruction, thereby allowing expression of telomerase. Efforts in the lab are currently focused on identifying the presumed telomerase repressor protein and other proteins that interact with BT2.

Ren, S., Boedeker, A., Rathore, K., and McKnight, T.D. 2007. Regulation of telomerase in Arabidopsis by AtBT2, an apparent target of the TAC1 transcription factor. Plant Cell 19, 23-31.

Lu, H., Gorman, E., and McKnight, T.D. 2005. Molecular Characterization of two anthranilate synthase alpha subunit genes in Camptotheca acuminata. Planta 221;352-360.

Ren, S., Johnston,J.S., Shippen, D. E., and McKnight, T.D. 2004. TELOMERASE ACTIVATOR1 induces telomerase activity and potentiates responses to auxin in Arabidopsis. Plant Cell 16; 2910-2922.

McKnight, T.D. and Shippen, D.E. 2004. Historical Perspective: Plant Telomere Biology. Plant Cell 16; 794-803.

McKnight, T.D., Riha, K., and Shippen, D.E. 2002. Telomeres, telomerase, and stability of the plant genome. Plant Mol. Biol. 48; 331-337.

Riha, K., McKnight,T.D., Griffing, L.R., and Shippen, D.E. 2001. Living with genome instability: plant responses to telomere dysfunction. Science 291; 1797-1800.

Fitzgerald, M.S., Shakirov, E.V., Hood, E.E., McKnight, T.D., and Shippen, D.E. 2001. Different modes of de novo telomere formation by plant telomerases. Plant J. 26; 77-88.

Riha, K., McKnight, T.D., Fajkus, J., Vyskot, B., and Shippen, D.E. 2000. Asymmetric distribution of G-overhangs on plant telomeres. Plant J. 23; 633-641.

Hanson, R.E., Islam-Faridi, M.N., Crane, C.F., Zwick, M.S., Czeschin, D.G., Wendel, J.F., McKnight, T.D., Price, H.J., and Stelly, D.M. 2000. Ty1-copia retrotransposon behavior in a polyploid and its putative diploid ancestors. Chromosome Res. 8; 73-76.

Hanson, R.E., X.P. Zhao, M.N. Islam-Faridi, A.H. Paterson, M.S. Zwick, C.F. Crane, T.D. McKnight, D.M. Stelly, and H.J. Price. Evolution of interspersed repetitive elements in Gossypium (Malvaceae). Am. J. Bot. 85:1364-1368.

Lu, H. and T.D. McKnight. 1999. Tissue specific expression of the beta subunit of tryptophan synthase in Camptotheca acuminata, an indole alkaloid producing plant. Plant Physiol. 120: 43-52.

Shippen, D.E. and T.D. McKnight. 1998. Telomeres, Telomerase and Plant Development. Trends in Plant Sciences 3:126-130.

Fitzgerald, M.S., T.D. McKnight, and D.E. Shippen. 1996. Characterization and developmental patterns of telomerase expression in plants. Proc. Natl. Acad. Sci. USA. 93: 14422-14427.

Hanson, R.E., M.N. Islam-Faridi, E.A. Percival, D.F. Crane, Y. Ji, T.D. McKnight, D.M. Stelly, and H.J. Price. 1996. Distribution of 5S and 18S-28S rDNA loci in a tetraploid cotton (Gossypium hirsutum L.) and its putative diploid ancestors. Chromosoma. 105: 55-61.