The chromosomes of higher organisms contain centromeres -- highly specialized regions that are essential for chromosome inheritance during cell division. Through the assembly of a unique structure, the kinetochore, centromeres form attachments to the spindle fibers and direct chromosomes to each daughter cell. Centromeres undergo dramatic changes in morphology through the cell cycle, alternating between an extended conformation during cell growth and a condensed form incorporating millions of base pairs during mitosis and meiosis. Despite their fundamental role in chromosome inheritance, the DNA sequences that are necessary for centromere function are understood only in single-celled organisms, such as the yeast Saccharomyces cerevisiae. The long term goal of this research is to identify and characterize the DNA sequences required for centromere functions in plants.
To dissect the function of centromeric DNA sequences, two plant species will be examined --Arabidopsis thaliana and Chlamydomonas reinhardtii. Importantly, the unique genetic properties of these plants make it feasible to precisely delineate chromosomal regions that have centromere activity. The complete DNA sequence of all five Arabidopsis centromere regions will be obtained, and the key centromere elements will be identified by using genetic techniques that monitor their function. Comparisons ofArabidopsis centromere sequences with each other will allow evolutionarily conserved domains to be identified. In addition, comparisons with centromere sequences from Chlamydomonas will reveal critical components that are broadly shared among many plant species. By combining a genetic and evolutionary approach, these studies represent a unique opportunity to describe the chromosomal elements that are critical for partitioning genetic material in many multicellular organisms.
The information obtained from this work will form a foundation for the understanding of the fundamental controls that regulate chromosome distribution, the assembly of specific chromosome structures through the cell cycle, and the binding of unique proteins near the centromere. Moreover, the work will tremendously improve genetic technology in plants, including crop species. The centromeres identified in this study will enable the construction of artificial chromosomes, making it possible to move genes in and out of cells more easily and to control the context and level of gene expression. Thus, this system provides an opportunity to impact biotechnology broadly while investigating a fundamentally important biological process.
