9632016 Hobbie The plant hormone auxin plays an important role in virtually all aspects of plant growth and development, including formation of shoots and roots and responses to gravity and light. Auxin affects these processes through regulation of cell elongation, cell division, and cell differentiation. However, exactly what auxin does and how it does it at the molecular level are still poorly understood. Only a few genes that act in the auxin response pathway have been identified. This research is designed to increase our knowledge of the function and mechanism of action of auxin by means of characterization and anlysis of two Arabidopsis mutants with defects in a previously-unknown gene called AXR6. Heterozygous axr6 mutants are auxin-resistant, dwarf, and bushy, consistent with a general reduction in auxin sensitivity. Homozygous axr6 plants show a novel phenotype for an auxin-related mutant: they arrest growth as young seedlings, with defects in both shoots and roots. These preliminary observations of the mutants' phenotype suggest that AXR6 is an essential gene involved in auxin response and regulation of development. This research should bring us closer to a complete understanding of plant physiology and development at the molecular level, and especially of the role of auxin. Such an understanding is fundamentally important, and should also enhance our ability to regulate plant development in desirable ways.
