Joseph P. Ogas

Active Mentor - currently hosting PULSe students for laboratory rotations and recruiting PULSe students into the laboratory; serves on preliminary exam committees

Current Research Interests:

We are interested in characterizing the factors and mechanisms that govern the flexible nature of plant cell identity. To accomplish this goal, we are utilizing a mutant of Arabidopsis thaliana, pickle (pkl), in which the primary root differentiates improperly and expresses embryonic characteristics after germination. Expression of the pickle root phenotype is dependent on gibberellin (GA), a plant growth regulator known to promote such diverse processes as germination, cell elongation, and initiation of flowering. We have cloned PKL, and it codes for a predicted CHD3-chromatin remodeling factor. CHD3 proteins from Xenopus and human cell lines have been shown to associate with histone deacetylase indicating that they may act as negative regulators of transcription. Consistent with such a role for PKL in Arabidopsis, we have shown that LEC1, a promoter of embryonic identity, is derepressed in germinating pkl seedlings.

Based on the phenotype of the pkl mutant and the function of proteins that are similar to PKL, our working model is that PKL regulates the transcription of genes in response to GA. Specifically, we propose that PKL establishes transcriptional repression of embryonic genes during germination by altering the structure of chromatin. This model will be tested by the following experimental strategies: examination of the expression of PKL, identification of genes that exhibit PKL-dependent transcription by microarray analysis, analysis of the promoters of those genes, identification of proteins that interact with PKL, and genetic screens for mutations that affect the phenotype of pkl plants.

Selected Publications:

Muir WM, Romero-Severson J, Rider SD, Simons A, and Ogas J (2006). Application of One Sided t-tests and a Generalized Experiment Wise Error Rate to High-Density Oligonucleotide Microarray Experiments: An Example Using Arabidopsis. J Data Sci 4:323

Li H-C, Chuang K., Henderson JT, Rider Jr SD, Bai Y, Zhang H, Fountain M, Gerber J, and Ogas J (2005). PICKLE acts during germination to repress expression of embryonic traits. Plant Journal 44:1010.

Rider SD, Hemm MR, Hostetler HA, Li H.-C., Chapple C, and Ogas J (2004). Metabolic profiling of the Arabidopsis pkl mutant reveals selective derepression of embryonic traits. Planta 219:489-99.

Hemm MR, Rider SD, Ogas J, Murry DJ, and Chapple C (2004). Light induces phenylpropanoid metabolism in Arabidopsis roots. Plant J. 38:765-78.

Henderson JT, Li H-C, Rider SD, Mordhorst AP, Cheng JC, Romero-Severson J, Cheng J-C, Robey J, Sung ZR, de Vries SC, and Ogas J (2004). PICKLE plays a role in GA-dependent responses and acts throughout the plant to repress expression of embryonic traits. Plant Physiol 134:995-1005.

Rider SDR, Henderson JT, Jerome RE, Edenberg HJ, Romero-Severson J, and Ogas J (2003). Coordinate repression of regulators of embryonic identity by PICKLE during germination of Arabidopsis. Plant J. 35:33-43

Ogas J, Kaufmann S, Henderson J, and Somerville C (1999). PICKLE is a CHD3 chromatin-remodeling factor that regulates the transition from embryonic to vegetative development in Arabidopsis. Proc. Natl. Acad. Sci. USA 96:13839-13844.

Ogas J, Cheng J-C, Sung ZR, and Somerville C (1997). Cellular differentiation regulated by gibberellin in the Arabidopsis thaliana pickle mutant. Science 277:91-94.