Research Summary

All organisms employ controls to ensure that their offspring inherit correct genetic material. DNA strands are partitioned with astonishing precision, providing gametes with an appropriate chromosome complement. In addition, sperm and egg cells exhibit remarkable selectivity, fusing only with appropriate gametes. We are addressing these questions in flowering plants, where the ability to use genetic, genomic, and evolutionary techniques is providing insight into the cellular events that contribute to species diversity. We have collected centromere sequences from several species closely related to Arabidopsis and are exploring their diversity and evolution. First, we analyzed satellite sequences, and found that they undergo rapid change in composition, yet their length remains unusually constant, pointing to a structural role. By comparing regions that flank the satellites, we found more dramatic change: the insertion of repetitive elements, as well as the appearance of novel non-coding DNA sequences, leads to rapid divergence. Our understanding of centromere sequences has made it possible to develop artificial chromosomes in plants, a technological breakthrough that enables direct investigation of centromere structure and function. Our investigations of fertilization in Arabidopsis focus on interactions between pollen and the stigma surface and on the subsequent growth of pollen tubes. We identified two protein families from the pollen surface, each encoded by a tandem gene array; these proteins exhibit an enhanced rate of evolution due to nucleotide divergence, insertions and deletions. We are also investigating the role of these proteins in pollen allergy, a disorder that affects nearly 20% of the US population. Our work on pollen tubes has shown an important role for gamma-amino butyric acid (GABA), a common neurotransmitter. Currently, we are using an in vitro assay to test the mechanisms behind signaling by GABA and other small molecules.

Selected Publications

S.E. Hall, S. Luo, A.E. Hall, and D. Preuss. (2005) Differential Rates of Local and Global Homogenization in Centromere Satellites from Arabidopsis Relatives. Genetics 170:1913-1927. (PubMed)

M.A. Johnson, K. von Besser, Q. Zhou, E. Smith, G. Aux, D. Patton, J. Levin, D. Preuss. (2004) Arabidopsis hapless Mutations Define Essential Gametophyte Functions. Genetics 168:971-82. (PubMed)

A. Fiebig, R. Kimport and D. Preuss. (2004) Comparisons of Pollen Coat Genes across Brassicaceae Species Reveal Rapid Evolution by Repeat Expansion and Diversification. Proc. Natl. Acad. Sci. 101: 3286-3291. (PubMed)

S. Luo, A.E. Hall, S.E. Hall, and D. Preuss. (2004) Whole-genome Fractionation Rapidly Purifies DNA from Centromeric Regions. Nature Methods 1: 67-71. (PubMed)

Palanivelu, R., Brass, L., Edlund, A. F. and Preuss, D. (2003). Pollen tube growth and guidance is regulated by POP2, an Arabidopsis gene that controls GABA levels. Cell 114: 47-59. (PubMed)