Peter Klock Hepler HonFRMS (born 1936) is the Constantine J. Gilgut and Ray Ethan Torrey Professor Emeritus in the Biology Department of the University of Massachusetts at Amherst who is notable for his work on elucidating the roles of calcium, membranes and the cytoskeleton in plant cell development and cell motility.
Personal life Peter Klock Hepler was born on October 29, 1936, in Dover, New Hampshire, to Jesse Raymond Hepler and Rebecca Orpha Peterson Hepler. He married Margaret (Peggy) Dennison Hunt on March 7, 1964. They have three children: Sarah, Anna and Lukas. Peter and Peggy have six grandchildren: Finn, Leif, Louisa (Lulu), Jesse, Marit, and Haakon. In an interview published in the Newsletter of the American Society of Plant Biologists, Hepler was asked, "What is your most treasured possession?" He answered, "My family; but I don't possess them." Peter and Peggy Hepler live on a farm in Pelham, Massachusetts that was established in 1740 and is now a part of the Kestrel Land Trust.
University life Peter Hepler graduated from Dover High School in 1954. He received his B.S. in chemistry from the University of New Hampshire in 1958 and earned his Ph.D. in plant cell biology from University of Wisconsin in 1964, studying the role of cortical microtubules in plant cell development with Eldon H. Newcomb. After receiving his Ph.D., Hepler served at the Walter Reed Army Institute of Research until 1966, studying malarial parasites. Hepler then returned to the University of Wisconsin for a postdoctoral fellowship and then became a postdoctoral fellow with Keith Porter at Harvard University from 1966 to 1967, where he continued his investigation of microtubules, focusing on their role in the mitotic apparatus and the phragmoplast of the endosperm cells of Haemanthus Katharinae. After being an assistant professor at Stanford University, Hepler joined the faculty in the Botany Department at the University of Massachusetts at Amherst. He was an associate professor from 1977 to 1980, a professor from 1980 to 1989, and became the Ray Ethan Torrey Professor in 1989 and the Constantine J. Gilgut Professor in 1998. Hepler retired from the Biology Department as the Constantine J. Gilgut and Ray Ethan Torrey Professor Emeritus, although he continues to do research. Hepler spent many summers teaching and doing research at the Marine Biological Laboratory at Woods Hole, Massachusetts. Hepler also participated in a multiyear international collaboration with Brian E. S. Gunning. Hepler was an associate editor of Protoplasma from 1994 to 2001 and associate editor of Plant Physiology from 1998 to 2000. He has been on the editorial boards of the Annual Review Plant Physiology, Plant and Cell Physiology, the Journal of Submicroscopic Cytology, Cell Motility and the Cytoskeleton, and BioEssays.
Research Hepler's scientific method is to know thoroughly the classical botanical literature and then develop or apply modern physico-chemical techniques to answer salient and extensive biological questions using plants that are well-suited to answer those questions. In so doing, Hepler opened whole areas of research. Hepler did pioneering work in showing the relationship of the microscopic elements of the cytoskeleton to the macroscopic properties of plant growth, development and function. He also did pioneering work on plasmodesmata, stomatal function, the role of calcium in plant development and in the development of techniques useful for answering questions using light and electron microscopy. Hepler's scientific publications with Barry A. Palevitz are notable for quoting Woody Allen and Yogi Berra. Hepler described his realization of the influence a review he and Palevitz wrote on microtubules and microfilaments "to introduce new thoughts and promising avenues for future research" had with his characteristic self-deprecating sense of humor: "I became aware that the review was being read widely one summer (1979) while working in the library at the Marine Biological Laboratory. I turned to the library's volume of the Annual Review of Plant Physiology that contained our paper and when I put the volume down, it literally fell open at our article; worn edges on the pages and the penciled corrections of all the misspellings and punctuation errors indicated that the chapter had been thoroughly perused." Hepler, along with Ledbetter and Porter, is considered to be a co-discoverer of microtubules.
Microtubules and cell shape In late 1962 and early 1963, Hepler tested the newly developed procedure using a glutaraldehyde pre-fix followed by an osmium post-fix to study plant cell structure using an electron microscope. Building on the earlier work by Sinnott and Bloch, who had shown that wounding the existing tracheary elements in a Coleus stem induced neighboring parenchyma cells to differentiate into new tracheary elements, Hepler showed that cytoplasmic microtubules were localized specifically in the cortical cytoplasm immediately over the bands of new secondary wall thickenings. Moreover, Hepler discovered that the microtubules were oriented parallel to the cellulose microfibrils of the newly formed secondary wall thickenings. This work, along with the studies of Ledbetter and Porter and Green established the importance of cortical microtubules in controlling the alignment of cellulose microfibrils in the cell wall. Further work with Barry Palevitz showed that microtubules were involved in orienting the cellulose microfibrils in the walls of guard cells in a pattern of radial micellation that is necessary for stomatal function. Hepler, along with the husband and wife team of Dale Callaham and Sue Lancelle, developed a method to achieve rapid freeze fixation of particularly small plant cells that showed that cortical microtubules are closely associated with one another, actin microfilaments, the endoplasmic reticulum and the plasma membrane.
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