Photo of Thomas Sims

Thomas Sims

associate professor, graduate adviser

Research Interests

My research combines molecular and classical genetics to investigate cell-cell interactions during the gametophytic self-incompatibility response of Petunia hybrida. Self-incompatibility, a genetic barrier to inbreeding in higher plants, represents a distinct case of cell-cell interaction that is amenable to molecular dissection. The essence of this barrier is the ability--mediated by the S, or self-incompatibility locus--to discriminate self pollen from non-self pollen. Pollen tubes expressing an S-allele recognition specificity identical to that expressed in the style cease growth in the upper third of the style, whereas pollen tubes lacking S-alleles in common with the style grow normally and effect fertilization. According to current models of gametophytic self-incompatibility, pollen tubes expressing (presumed) S-linked proteins are recognized as incompatible by stylar-expressed S-alleles. Following recognition, an inhibition response involving ribonuclease activity of the stylar-expressed S-RNase acts to retard further growth of incompatible pollen tubes. As yet, neither the molecular basis of S-allele recognition, nor the nature of developmental programming governing S-locus expression in pollen and styles is understood. The long term goal of our research is to understand the molecular basis for recognition events functioning in self-incompatibility. Our approach has been to clone S-locus genes encoding style and pollen recognition factors, then seek to understand how these factors interact.

Representative Publications

Thomas L. Sims, Avani Patel and Pratima Shrestha. (2010). Protein interactions and subcellular localization in S-RNase-based self-incompatibility. Biochemical Society Transactions 38 622-626 (refereed).

L. Zhao, J. Huang, H. Zhao, Q. Li, T. L. Sims, and Y. Xue (2010). “The Skp1-like Protein SSK1 is Required for Cross-pollen Compatibility in S-RNase-Based Self-Incompatibility”, Plant Journal 65 52-63 (refereed).

T.L. Sims & T.P. Robbins (2009) Gametophytic Self-Incompatibility in Petunia", in Petunia: Evolutionary, Developmental and Physiological Genetics, Tom Gerats and Judith Strommer, eds., Springer, NY, pp 85-106.

T.L. Sims. (2007) Mechanisms of S-RNase-based Self-Incompatiblity. CAB Reviews: Perspectives in
Agriculture, Veterinary Science, Nutrition and Natural Resources 2 No 058.

T. L. Sims (2005) Pollen recognition and rejection in different self-incompatibility systems. in Recent Research Developments in Plant Molecular Biology 2 31-62.

T.L. Sims and M. Ordanic. (2001) Identification of a S-Ribonuclease binding protein in Petunia hybrida. Plant Molecular Biology 47 771-783.

W.S. Grayburn and T.L. Sims (1998) "Anchored Oligo dT primers for automated dye terminator DNA sequencing" Biotechniques 25 340-346.

K.R. Clark, J.J. Okuley and T.L. Sims (1995) "Complete nucleotide sequence of the S1-RNase gene of Petunia hybrida" Plant Physiology 107 307-308.

Sims T.L. (1994) Molecular genetics of gametophytic self-incompatibility in Petunia hybrida. In: Genetic control of self-incompatibility and reproductive development in flowering plants. EG Williams, AE Clarke, and RB Knox, eds. Kluwer Academic Publishers, Dordrecht. pp 19-41. 

Clark KR and Sims TL (1994) The S-ribonuclease gene of Petunia hybrida is expressed in nonstylar tissue, including immature anthers. Plant Physiology 106: 25-36. 

Sims TL (1993) Genetic Regulation of Self-Incompatibility. CRC Critical Reviews in Plant Sciences 12: 129-167 

Clark KR, Okuley JJ, Collins PD and Sims TL (1990) Sequence variability and developmental expression of S-alleles in self-incompatible and pseudo-self-compatible petunia. The Plant Cell 2: 815-826


Curriculum Vitae


NIH-NRSA Postdoctoral Fellow (Robert B. Goldberg Lab) UCLA, 1982-1985

Ph.D. 1981, University of Oregon 

B.S. 1975, University of Wisconsin, Madison

Fields of Interest: Molecular genetics of plant reproduction; self-incompatibility; molecular biology


Thomas L. Sims
Office: MO. 325D, MO 453
Dept. Biological Sciences
Northern Illinois University 
DeKalb, IL 60115-2861