| As even the most casual of gardeners will notice, plants respond to changes of environment. Leaves and stems grow toward light, roots toward darkness. Changes of temperature and the availability of nutrients likewise trigger developmental changes. It has long been known that auxin, a plant hormone, is an important mediator, regulating almost all qualities of plant growth -- stature, shoot and root architecture, shoot strength, seed and fruit size, ripening, and aging. Although the chemical structure of auxin has also been known for nearly 70 years, the genetic pathway by which it is synthesized has remained elusive.
New research by Anna Hull (GRS’02), a doctoral student in the laboratory of John Celenza, assistant biology professor, and collaborators from the Salk Institute and the University of Massachusetts, Amherst, has shed new light on this process.
Hull and her colleagues, working with the model plant species Arabidopsis thaliana, identified two cytochrome P450 enzymes, encoded by two genes they had previously identified in the species, and demonstrated the critical role they play in auxin synthesis. To do this they engineered Arabidopsis mutants, some of which produced an abundance of the enzymes and others that were unable to produce the enzymes. The mutant plants produced more auxin in the first group and reduced amounts of auxin in the second. Significantly, the mutant plants showed developmental changes consistent with the changes in auxin, indicating that by modulating auxin production, plant development can be modulated.
Since all higher plants share a close evolutionary link, this new piece in the auxin puzzle has relevance to other, more agriculturally important, plants.
This research was published in the December 1, 2002, issue of the journal Genes & Development. Other BU authors include Neeru R. Gupta (CAS’00, MED’04), who did her honors thesis in Celenza’s lab funded in part by grants from the Howard Hughes Medical Institute and BU’s Undergraduate Research Opportunities Program, and Kendrick A. Goss (GRS’03). Hull received the biology department’s 2002 Belamarich Award for outstanding thesis for this work. Celenza and his colleague Jennifer Normanly of UMass-Amherst recently received USDA funding to continue the investigation. |
