Biochemistry and Molecular Biology
Penn State Science
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Teh-hui Kao

Teh-hui Kao

Main Content

  • Distinguished Professor of Biochemistry and Molecular Biology
333 South Frear Laboratory
University Park, PA 16802
Phone: (814) 863-1042

Research Interests

Biochemical and molecular bases of self/non-self recognition during plant reproduction

Graduate Programs


Research Summary

Mechanism of self/non-self recognition between pollen and pistil in self-incompatible plants

Self-incompatibility (SI) is a self/non-self recognition mechanism that allows the pistil of flowering plants to distinguish between self (genetically related) and non-self (genetically unrelated) pollen to prevent inbreeding and promote out-crossing.  We use Petunia inflata (a relative of garden petunia) as a model to study the SI mechanism possessed by three families of flowering plants.  Here, SI is controlled by the highly polymorphic S-locus.  If the S-haplotype of haploid pollen matches either S-haplotype of the diploid pistil, the pollen is recognized as self-pollen and the growth of self-pollen tubes in the style is inhibited.  If the S-haplotype of pollen is different from both S-haplotypes of the pistil, the pollen is recognized as non-self pollen and their tubes are allowed to grow down through the style to the ovary to effect fertilization.  We are interested in two fundamental questions: (i) How does a pistil distinguish between self and non-self pollen? (ii) How does the self and non-self recognition lead to growth arrest of self-pollen tubes in the style?  Over the past more than two decades of research, we have identified the S-RNase gene as the gene that controls pistil specificity (Lee et al., Nature 367: 560-563, 1994) and the PiSLF (P. inflata S-locus F-box) gene as the gene that is involved in controlling pollen specificity (Sijacic et al., Nature 429: 302-305, 2004).  We have proposed a protein-degradation model, which invokes specific degradation of non-self S-RNases mediated by an allelic variant of PiSLF in the cytoplasm of a pollen tube, to explain the biochemical basis of S-haplotype-specific inhibition of pollen tube growth.  A current focus is to use in vivo approaches to test this model.  The information gained will be valuable to understanding not only this SI system, but also many cellular and developmental processes in a variety of organisms in which regulation of protein degradation has been implicated.

Structure and function of cellulose synthase complex of a cellulose-synthesizing bacterium, Gluconacetobacter hansenii, and a model plant, Arabidopsis

We have recently initiated a new direction of research as part of the Center of Lignocellulose Structure and Formation (, an Energy Frontier Research Center funded by the Department of Energy.  We focus on one of the three basic questions the Center is seeking to address: how does the cellulose synthase complex produce the cellulose microfibril?   We are working closely with the lab of Dr. Ming Tien to use molecular and biochemical approaches to elucidate the structure and function of the proteins that compose cellulose synthase complex in both Gluconacetobacter hansenii and Arabidopsis. For example, in G. hansenii, we are interested in the identification of interacting partners of AcsAB, AcsC and AcsD involved in cellulose synthsis, and the expression of soluble portions of AcsAB for structural and biochemical studies.  It is hoped that the knowledge acquired from our study will allow for modifications to the complex and subsequent alterations of cellulose structure and crystallinity, facilitating the use of cellulosic biomass for fuel production.

chart describing the pollination process.
Figure 1: The pistil of a self-incompatible flowering plant can recognize pollen, which has landed on, or been brought to, its stigmatic surface as self-pollen or non-self pollen, based on whether the S-haplotype of the pollen is present or not present in the pistil.  For the pollinations depicted, S1 and S2 pollen are recognized as self pollen by the pistil of S1S2 genotype and the growth of their tubes is arrested in the upper segment of the style; S4 pollen is recognized as non-self pollen and its tube is allowed to grow down to the ovary to effect fertilization.  This reproductive trait allows flowering plants to prevent inbreeding and promote out-crossing.

Transforming Leaf strips from Petunia inflata.

Figure 2: Leaf strips of Petunia inflata are transformed with Agrobacterium tumefaciens carrying a transgene construct, and the transformed tissues are cultured for regeneration of transgenic plants.  The ability to introduce genes into transgenic P. inflata plants allows in vivo studies of the function and structure/function relationships of the genes involved in self-incompatibility.

Selected Publications

  • Li, S., Williams, J.S., Sun, P., Kao, T.-h. (2016). All 17 S-locus F-box proteins of S2- and S3-haplotypes of Petunia inflata are assembled into similar SCF complexes with specific function in self-incompatibility. Plant J. 87, 606-616.
  • McManus, J.B., Deng, Y., Nagachar, N., Kao, T.-h., Tien, M. (2015). AcsA-AcsB: The core of the cellulose synthase complex from Glucoacetobacter hansenii ATCC23769. Enzyme Microb Tech doi:10.1016/j.enzmictec.2015.08.015.
  • Sun, P., Li, S., Lu, D., Williams, J.S., Kao, T.-h. (2015). Pollen S-locus F-box proteins of Petunia involved in S-RNase-based self-incompatibility are themselves subject to ubiquitin-mediated degradation. Plant J. 83, 213-223.
  • Williams, J.S., Wu, L., Li, S., Sun, P., Kao, T.-h. (2015). Insight into S-RNase-based self-incompatibility in Petunia: recent findings and future directions. Front. Plant Sci. doi:10.3389/fpls.2015.00041.
  • Deng, Y., Nagachar, N., Fang, L., Luan, X., Catchmark, J.M., Tien, M., Kao, T.-h. (2015). Identification andcharacterization of two cellulose morphology mutants of Gluconacetobacter hansenii ATCC23769 producing cellulose with lower crystallinity. PLOS ONE DOI: 10.1371/journal.pone.0119504.
  • Sun, P., Williams, J.S., Li, S., Kao, T.-h. (2014). S-RNase-based self-incompatibility in Petunia: a complex non-self recognition system between pollen and pistil.  In “Sexual Reproduction in Animals and Plants” (Sawada H, Inoue N, Iwano M eds), pp 289-303, Springer Tokyo Heidelberg New York Dordrecht London.
  • Williams, J.S., Der, J.P., dePamphilis, C.W., Kao, T.-h. (2014). Transcriptome analysis reveals the same 17 S-locus F-box genes in two haplotypes of the self-incompatibility locus of Petunia inflata. Plant Cell 26, 2873-2888.
  • Li, S., Sun P, Williams, J.S., Kao, T.-h. (2014). Identification of the self-incompatibility locus F-box protein-containing complex in Petunia inflata. Plant Reprod. 27, 31-45.
  • Williams, J.S., Natale, C.A., Wang, N., Li, S., Brubaker, T.R, Sun, P., Kao, T.-h. (2014). Four previously identified Petunia inflata S-locus-F-box genes are involved in pollen specificity in self-incompatibility. Mol. Plant 7, 567-569.

  • Sun, P., Kao, T.-h. (2013). Self-incompatibility in Petunia inflata: the relationship between a self-incompatibility locus F-box protein and its non-self S-RNases. Plant Cell 25, 470-485.

  • Guo, J., Catchmark, J.M., Mohamed, M.N.A., Benesi, A.J., Tien, M., Kao, T.-h., Watts, H.D., Kubicki, J.D. (2013). Identification and characterization of a cellulose binding heptapeptide revealed by phage display. Biomacromolecules 14, 1795-1805.

  • Deng, Y., Nagachar, N., Xiao, C., Tien, M., Kao, T.-h. (2013). Identification and characterization of non-cellulose-producing mutants of Gluconacetobacter hansenii generated by Tn5 transposon mutagenesis. J Bacteriol. 195, 5072-5083.

  • Wang, N., Kao, T-h (2012). Self-incompatibility: a self/non-self recognition mechanism employing S-locus F-box proteins and S-RNase to prevent inbreeding. WIREs Dev Biol 1:267-275, doi: 10.1002/wdev.10.
  • Iyer, PR, Liu, Y-A, Deng, Y., McManus, JB, Kao, T-h, Tien, M. (2012). Processing of cellulose synthase (AcsAB) from Gluconacetobacter hansenii 23769. ABB 10.1016/
  • Meng, X., Hua, Z., Sun, P., Kao, T-H (2011). The amino terminal F-box domain of Petunia inflata S-locus F-box protein is involved in self-incompatibility mechanism. AoB Plaints doi:10.1093/aodpla/plr016.
  • Fields, A.M., Wang, N., Hua, Z., Meng, X. and Kao, T.-h. (2010). Functional characterization of two chimeric proteins between a Petunia inflata S-locus F-box protein, PiSLF2, and a PiSLF-like protein, PiSLFLb-S2. Plant Mol. Biol. 74, 279-292.
  • Iyer, P.R., Geib, S.M., Catchmark, J., Kao, T.-h. and Tien M (2010). Genome sequence of a cellulose producing bacterium, Gluconacetobacter hansenii ATCC 23769. J. Bacteriol. 192, 4256-4257.
  • Meng, X., Hua, Z., Wang, N., Fields, A.M., Dowd, P.E. and Kao, T.-h. (2009). Ectopic expression of S-RNase of Petunia inflata in pollen results in its sequestration and non-cytotoxic function. Sex. Plant Reprod. 22, 263-275.
  • Hua, Z., Fields, A. and Kao, T.-h. (2008). Biochemical models for S-RNase-based self-incompatibility. Mol. Plant. 1, 575-585.
  • Hua, Z. and Kao, T.-h. (2008). Identification of major lysine residues of S3-RNase of Petunia inflata involved in ubiquitin-26S proteasome-mediated degradation in vitro. Plant J. 54, 1094-1104.
  • Hua, Z., Meng, X., Kao, T.-h. (2007). Comparison of Petunia inflata S-locus F-box protein (Pi SLF) and Pi SLF-like proteins reveals its unique function in S-RNase-based self-incompatibility. Plant Cell 19, 3593-3609.
  • Kokubun, H., Nakano, M., Tsukamoto, T., Watanabe, H., Hashimoto, G., Marchesi, E., Bullrich, L., Basualdo, I. L., Kao, T.-h. and Ando, T. (2006). Distribution of self-compatible and self-incompatible populations of Petunia axillaris (Solanaceae) outside Uruguay. J. Plant Res. 119, 419-430.
  • Skirpan, A.L., Dowd, P. E., Sijacic, P., Jaworski, C. J., Gilroy, S. and Kao, T.-h. (2006). Isolation and characterization of PiORP1, a Petunia oxysterol-binding-protein related protein involved in receptor-kinase mediated signaling in pollen, and analysis of the ORP gene family in Arabidopsis. Plant Mol. Biol. 61, 553-565.
  • Dowd, P. E., Coursol, S., Skirpan A. L., Kao, T.-h. and Gilroy, S. (2006). Petunia phospholipase C1 is involved in pollen tube growth. Plant Cell 18, 1438-1453.
  • Hua, Z. and Kao, T.-h. (2006). Identification and characterization of components of a putative PiSLF-containing E3 ligase complex involved in S-RNase-based self-incompatibility. Plant Cell 18, 2531-2553.