Herbert Newby McCoy Award

2011 McCoy Award Recipient

Clint Chapple
Distinguished Professor in the Department of Biochemistry

Clint Chapple has long been fascinated by the compounds that plants produce and the diverse catalytic repertoire that is required to make them. Armed with training in the fundamentals of plant form and function that he gained through his B.Sc. and M.Sc. in botany at the University of Guelph, he continued at the same institution to earn a Ph.D. in chemistry with Dr. Brian Ellis studying the biosynthesis of glucosinolates, compounds that give mustard, horseradish and wasabi their characteristic flavors. Interested in how he could use genetics and the emerging model plant Arabidopsis thaliana to gain a better understanding of plant biochemistry, he moved on to a postdoctoral position with Dr. Chris Somerville at the Michigan State University Department of Energy Plant Research Laboratory in 1990.

A Distinguished Professor in the Department of Biochemistry, where he has been a faculty member since 1993, Dr. Chapple’s research now focuses on the analysis and manipulation of metabolic pathways in plants, with particular emphasis on Arabidopsis, using the tools of biochemistry, molecular biology and genetics. Dr. Chapple has received $8.7 million for his research program at Purdue University. He has published 57 papers and 17 reviews and book chapters and has given over 70 invited lectures at conferences and other universities. He was recognized as a Purdue University Faculty Scholar in 1999, won the Purdue University Agricultural Research Award in 2001 and the 2006-07 Richard L. Kohls Outstanding Undergraduate Teacher Award in the College of Agriculture. In 2002, he was named a Fellow of the American Association for the Advancement of Science. He has trained 13 graduate students, 11 postdoctoral fellows and takes particular pride in having given research experiences to over 40 Purdue undergraduates.

LECTURE ABSTRACT

Increasing awareness of the impact of global greenhouse gas emissions,dwindling petroleum reserves and concerns with regard to energy security have led to a dramatic increase in interest in the development of renewable, cellulose-based sources of biofuels. Lignin stands as a significant barrier to this goal because it interferes with the conversion of lignocellulosic biomass to fermentable sugars. Efforts aimed at decreasing lignin deposition show promise for improving biomass conversion efficiency, but considering that lignin is essential to plant viability, it is clear that novel approaches to the modification of lignin will be required to make efficient cellulose-based biofuel production a reality. One solution with significant promise takes advantage of the ability of the lignin biosynthetic machinery to accommodate a wide variety of input monomers, opening the door to the production of “designer lignins” that could support plant growth but be more readily removed post-harvest.

RESEARCH ACCOMPLISHMENTS

Many metabolites found in plants are generated via the phenylpropanoid pathway and it is now known that many of these molecules play important roles in plant defense responses or absorb potentially damaging UV-B light. The pathway also generates the building blocks of lignin, a major component of the cell wall of vascular plants, which rigidifies plant tissues and enables water-conducting cells to withstand the tension generated during transpiration. From a human perspective, lignin has long been recognized for its negative impact on forage quality, paper manufacturing and more recently, cellulosic biofuel production. The analysis of the phenylpropanoid pathway in Arabidopsis using the tools of biochemistry, molecular biology and genetics is the focus of our laboratory.

Over the past 18 years, we have characterized mutants that are defective in the synthesis of sinapoylmalate, one of the major soluble phenylpropanoid secondary metabolites in Arabidopsis. In wild type, sinapoylmalate is accumulated in the upper leaf epidermis where it functions to absorb the UV light that accompanies the photosynthetically active wavelengths of light that plants depend upon. The character of this blue-fluorescent secondary metabolite can be exploited as a rapid method for isolating mutants defective in genes encoding enzymes or regulatory factors of the phenylpropanoid pathway. Mutants that lack sinapoylmalate can be readily identified by their red chlorophyll fluorescence under UV light among a population of blue f luorescent wild-type plants. Using this mutant screen, we have isolated a variety of mutants that have enabled us to clone genes of the phenylpropanoid pathway that have not previously been characterized. Surprisingly, these efforts have revealed that the phenylpropanoid pathway had been incorrectly drawn in textbooks for decades.