Professor of Botany

Purdue University
Botany and Plant Pathology, Lilly Hall
915 West State Street
West Lafayette, IN 47907-2054

Office:  WSLR B022
Phone:  (765) 494-9902
FAX:      (765) 494-5896
E-mail:   

Area: Plant Hormones - Biochemical and molecular studies on the biosynthesis and metabolism of natural plant hormones such as gibberellins and abscisic acid.

Dr. Coolbaugh is currently on a phased retirement program and has discontinued his active research and direct supervision of graduate students.  He is working part time on teaching and directing the Purdue Summer Research Opportunity Program.

Background

Ph.D., Oregon State University, Plant Physiology

Coolbaugh is a member of the Society of Sigma Xi, Phi Kappa Phi, and Gamma Sigma Delta. He is one of the organizers for the International Symposia on Cytochromes P450 and a host for the annual Midwest Cytochromes P450 Symposium which is held on the Purdue campus. He teaches Introductory Plant Science and serves as an undergraduate and graduate advisor. He was department head from 1987 to 1997.

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Research Interests

In our laboratory we study plant growth substances and herbicides which affect plant growth. Gibberellins are natural plan hormones. They stimulate seed germination, stem elongation, flower initiation, and seed growth. Understanding how and where these hormones are formed in the plant has been our goal for several years. We have isolated some of the enzymes involved in production of gibberellins and demonstrated that their activities change in certain tissues throughout development.

Some of the key enzymes in the gibberellin biosynthetic pathway belong to the superfamily of oxidative enzymes known as cytochromes P450. One of our recent research projects has led to the determination that one of the plant P450s is localized in the outer envelope membrane of chloroplasts (see the figure below). We are currently investigating how the enzyme can function in such an unusual location.

In addition to the enzymes involved in hormone metabolism, we are also interested in those that metabolize herbicides and fungicides, and the cell biology of these processes. These studies involve the combined use of biochemistry, genetics, and plant molecular biology.

Insertion of CYP86B1 into chloroplastic membranes is both specific and sensitive to protease digestion. [35S]-Labeled- (a) CYP86B1, (b) CYP73A5 (an ER localized protein) and (c) pSS were incubated with pea chloroplasts in the absence of ATP (a) or in the presence of 4 mM ATP (b and c) for 30 min. After import, chloroplasts were incubated with (+) or without (-) Thermolysin (Th.) for 30 min at 4°C in the dark. Protease reactions were quenched with EDTA and chloroplast fractions were isolated and analyzed.

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Assistantships and Positions

Please contact me directly for information on assistantships and openings in my program. Follow these links for general information on graduate programs or employment announcements.

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Selected Publications

Al-Nimri, Laila F., and Ronald C. Coolbaugh. 1991. Cell-free conversion of 1'-deoxy-2H-ABA to 2H-ABA in extracts of Cercospora rosicola. J. Plant Growth Regulation. 9: 221-225.

Hasebroek, J.P. & R.C. Coolbaugh, 1991. Separation of light-induced [14C]ent-kaurene metabolsim and light -induced germination in Grand Rapids lettuce seeds. Plant Physiol. 96: 837-842.

Jennings, J.C., R.C. Coolbaugh, D.A. Nakata, and C.A. West. 1993. Characterization and solubilization of kaurenoic acid hydroxylase from Gibberella fujikuroi. Plant Physiol. 101: 925-930.

Jennings, J.C. J.A. Banks, and R.C. Coolbaugh. 1996. Subtractive hybridization between cDNAs from untreated and AMO-1618-treated cultures of Gibberella fujikuroi. Plant and Cell Physiol. 37: 847-854.

Watson, C, J Froehlich, C Josefsson, C Chapple, F Durst, I Benveniste, R Coolbaugh. 2001. Localization of CYP86B1 in outer envelope of chloroplasts. Plant and Cell Physiol. 42:873-878.

Lo, S.C.C., R.C. Coolbaugh, and R.L. Nicholson. 2002. Molecular characterization and in silico expression analysis of a cholcone synthase gene family in Sorghum bicolor. Physiol, Molec Plant Path. (in press)

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Web Links of Interest

• Plant P450s - Oxidative metabolism related to plant protection and growth
• The Midwest Cytochromes P450 Symposium
• The MARC/AIM Summer Research Program