Catharina Coenen   Research Interests

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Auxin Action: Growth, Gravitropism & Genetics

The plant hormone auxin controls virtually every aspect of plant growth and development.  I study the action mechanism of auxin by analyzing growth responses, morphogenesis, and gene expression in auxin-resistant mutants of tobacco and tomato.

	How do plants know which way's up? The redistribution of auxin to the lower side of horizontally placed stems or roots causes a bending reaction, which allows roots to grow into the soil and stems to grow upright. I study gravity responses of roots and shoots as they relate to the perception and action of auxin.
	How does auxin turn on genes? Auxin causes growth responses, such as gravitropism, by activating the transcription of a specific set of auxin-responsive genes. Auxin-responsive reporter gene constructs allow me to monitor auxin effects on gene expression by color reactions or light emission in transgenic seedlings.
	How is the auxin signal perceived and transmitted? Mutations that abolish auxin responses likely affect genes that are needed for an auxin signaling pathway. Mutant plants that carry such mutations can be isolated because they are resistant to growth inhibiting concentrations of auxin. I characterize growth, auxin responses, and gene expression in auxin resistant tobacco and tomato plants to uncover connections between different auxin response pathways during development.

Description of student summer project on plant peroxidases funded by AAS/Merck.

Research Articles

Coenen C, Christian M, Lüthen H, Lomax TL (2003) Cytokinin antagonizes auxin action through inhibiting a subset of DGT-dependent, primary auxin responses in tomato (Lycopersicon esculentum). Plant Physiology 131, 1692-1704

Coenen C, Bierfreund N, Lüthen H, and Neuhaus G (2002) Developmental Regulation of Proton ATPase-dependent Auxin Responses in the diageotropica Mutant of Tomato (Lycopersicon esculentum Mill.). Physiologia Plantarum 114, 461-471

Coenen C, Lomax T (1998) The DIAGEOTROPICA gene differentially affects auxin and cytokinin responses throughout development in tomato (Lycopersicon esculentum Mill.). Plant Physiology 117, 63-72

Coenen C, Lomax T (1997) Auxin-cytokinin interactions in higher plants: Old problems and new tools. Trends in Plant Science 2, 325-363

Lomax TL, Coenen C, Gaiser JC, Hopkins R, Rayle DL, Rice MS (1993) Auxin perception and the regulation of tomato growth and development. In: Molecular Biology of Tomato, pp. 129-138, Yoder, J. (ed.), Technomic Publishing Co. Lancaster, PA, USA

Conference Abstracts and Presentations

Coenen C, Gutierrez L*, Nardozzi K*, Richards B (2003) Auxin Responses and Anatomy in Roots of the R15 Mutant of Nicotiana plumbaginifolia. Poster presentation at Recent Advances in Plant Signal Transduction, the 67th Annual Meeting of the Northeast Section of the American Society of Plant Biologists, held at Bucknell University, in Lewisburg, PA.

Carpenter S* and McCartney NB* (Coenen C) (2002) Nicotine levels increase in Nicotiana sylvestris exposed to artificially damaged conspecifics. Poster presentation by Sara Carpenter at national conference of the American Society for Plant Biology, Plant Biology 2002, Denver, CO.

Coenen C and Kleinschmidt A (2001) Investigative lab in molecular biology: Expression of plant peroxidase isoenzymes. Poster presentation at Plant Biology 2001, an international conference of the American Society of Plant Biologists , Providence, RI.

Coenen C, Borowski S, Neuhaus G (2000) The R15 mutant of Nicotiana plumbaginifolia shows defects in gravitropism and altered expression from auxin-inducible promoters. Poster presentation at Plant Signaling 2000, at The Pennsylvania State University, University Park, PA.

Coenen C, Kleinschmidt A (2000) Investigative lab in molecular biology: Expression of plant peroxidase isoenzymes. Poster presentation at the 8th National Conference of the Council on Undergraduate Research, Wooster, OH.

Coenen C, Bierfreund N, Neuhaus G (1999) Brassinolide, Cytokinin, and the DIAGEOTROPICA gene product control auxin-stimulated proton secretion. Poster presentation at the Keystone Conference on Intersections and Interactions in Plant Signal Transduction, Coeur d'Alene, ID.

Coenen C, Lomax TL (1995) The tomato gene DIAGEOTROPICA affects responses to both auxin and cytokinin. Selected for presentation to the International Plant Growth Regulator Society, Minneapolis, MN.

Coenen C, Lomax TL (1995) Cytokinin-treated tomato plants show morphological traits of the auxin-insensitive diageotropica mutant. Journal of Cellular Biochemistry, Suppl. 19C, J5 404.

Lomax TL, Coenen C, Kim K (1995) Auxin redistribution and gravitropism: support for the Cholodny-Went theory and regulation by cytokinin. Journal of Cellular Biochemistry, Suppl. 19C.

Coenen C, Lomax TL (1995) The diageotropica mutant affects responses involving both auxin and cytokinin. Northwest Regional Developmental Biology Conference, Friday Harbour, WA.

Coenen C, Lomax TL (1994) Phenocopy of the auxin-insensitive diageotropica mutant of tomato by cytokinin application. Plant Physiology 105 (1), p. 140.

* denotes Allegheny student co-authors