Hepler wins national award for plant discoveries

Plant cell biologist Peter Hepler has been honored by the American Society of Plant Biologists (ASPB) with an award for excellence in research, education, outreach and service. Hepler''s studies have advanced knowledge of the structure and dynamics of the plant cytoskeleton and calcium signaling processes in dividing and growing plant cells.

Hepler will receive the Charles Reid Barnes Life Membership Award, the society''s oldest, established in 1925, to be formally awarded at the ASPB''s annual conference in August in Minneapolis.

Hepler''s many contributions include "providing the first evidence of the interaction between microtubules and cellulose deposition, establishing the cross-bridging between microtubules and the mitotic spindle and demonstrating the connection between pulsed calcium ion signaling and tip growth of pollen of tubes," the society says.

Using a couple of different imaging methods, Hepler and colleagues explore the processes of cell division and cell growth not only to understand them but to provide visual presentations of them. Thus, they have filmed details of plant reproduction at the cellular level to discover and illustrate the secrets of pollen tube growth as it occurs.

Pollen tube tips are among the fastest growing tissues known, traveling about 100 to 500 nanometers per second, about 50 times faster than the growth rate of animal nerve cells and believed to be near the upper limit of cell growth. The tubes carry plant sperm through the pistil to fertilize the egg, which forms an embryo plus its food supply, the endosperm. The first pollen tube to get to the egg passes its DNA on to the next generation, in accord with the rules of evolutionary selection.

Over several years, Hepler and colleagues have pieced together how a specialized oscillatory growth pattern in pollen tube tips involves secretion of new cell wall materials from the pollen tube''s internal vesicles. They reported a breakthrough discovery last year, in fact, providing support for the idea that pectin deposits are forced into the wall matrix by turgor pressure, allowing the tip to extend and the tube to grow.

"We think our observations support the idea that cell wall yielding depends upon insertion of new building materials, the pectins, into the existing matrix, which is enough to weaken existing cell wall bonds and allow it to stretch but not break. It''s like a controlled dam break until the tip reaches the egg. In other words, it''s going to break and is designed to break, but not too soon," Hepler explains.

Understanding the mechanics of pollen tube tip growth is important because it''s part of plant fertilization necessary for the development of all fruits, nuts, grains, rice, corn, wheat and other crops on which we depend for food.

Hepler was elected as a Fellow of the American Association for the Advancement of Science in 2010 for his contributions as "one of the most influential plant cell biologists, who has continuously and continues to achieve breakthroughs that have guided research directions of numerous plant scientists."