My long-term interest is elucidating genetic mechanisms controlling chromosome interactions in meiosis. To achieve this goal, our lab pursues two major research themes: (i) understanding the patterns of distribution of meiotic recombination events along chromosomes as well as the factors that control these patterns and (ii) elucidating factors that affect chromosome dynamics during early prophase of meiosis, particularly rapid chromosome movements that lead to homologous chromosome pairing. These basic research studies will provide a platform for investigations on how meiotic processes can be modified to improve plant breeding methods. Currently, the main projects in the lab currently are:
(1) Understanding Recombination in Maize (sponsored by NSF and BARD). Recombination is the main source of genetic variation in higher eukaryotes; it facilitates adaptation, purges deleterious mutations from genomes and populations, and is a major determinant of genome architecture. In addition, recombination is utilized as an unparalleled instrument of plant breeding. We generated the first map of sites where recombination is initiated in the genome of a plant (maize) by formation of double-strand breaks in chromosomal DNA. Few of these breaks are repaired to produce chromosomal arm exchanges (crossovers), leaving about one-fifth of maize genes in regions of highly reduced crossover rates. We found that specific chromatin features are the main factors deciding which recombination events become crossovers. Developing ways to increase crossovers in crossover-depressed regions will allow utilizing higher numbers of allele combinations in breeding programs, leading to more efficient breeding.
(2) Chromosome axis dynamics during meiotic recombination (sponsored by ERA-CAPS/NSF). As a part of an international group of plant scientists we study how chromosome reorganization in meiosis and chromosome dynamics affect recombination outcomes, i.e., how they contribute to meiotic crossovers being formed in specific chromosome locations. To address this question, we use several advanced microscopy methods, such as restorative deconvolution, multiphoton excitation, and structured illumination microscopy.
(3) Meiotic recombination and genome rearrangements in new polyploids. Polyploidization events have been frequent in plant evolution. Many plant species and most crops are polyploid. Most polyploidization events are followed by rapid and extensive genome rearrangement. The predominant mechanism of these rearrangements is illegitimate recombination (IR) taking place during meiosis. These changes can occur on a massive scale in the first few generations following a polyploidization event, but they are also thought to continue several million years thereafter. How meiotic recombination acts to restructure the genomes of newly created polyploids is not understood. We utilize knowledge of meiotic recombination in diploids to elucidate molecular mechanisms controlling genome restructuring in polyploids.
Outreach and Extension Focus
As part of our collaborative NSF-sponsored project, we jointly operate a Science Undergraduate Minority Mentoring Internship and Training (SUMMIT) program, which sponsors four 10-week internships for minority undergraduate students (http://summitprogram.cfans.umn.edu). The interns participate in research in the three laboratories involved in the project, at Cornell and the University of Minnesota. They also attend weekly seminars, discussions, and training sessions that cover such professional development topics as networking, resume/CV and personal statement preparation, elevator pitches, data presentation, and scientific writing.
I teach courses in genetics, including Advanced Plant Genetics (PLBRG6060), Problems in Genetics and Development (BIOMG7810), and Laboratory in Plant Molecular Biology (PLBIO6410).
- He, Y., Wang, M., Dukowic-Schulze, S., Zhou, A., Tiang, C. L., Shilo, S., Sidhu, G. K., Eichten, S., Bradbury, P., Springer, N. M., Buckler, E., Levy, A. A., Sun, Q., Pillardy, J., Kianian PMA,, Kianian, S. F., Chen, C., & Pawlowski, W. (2017). Genomic features shaping the landscape of meiotic double-strand-break hotspots in maize. Proceedings of the National Academy of Sciences of the United States of America. 114:12231-12236.
- Chen, L. Q., Luo, J. H., Cui, Z. H., Xue, M., Wang, L., Zhang, X. Y., Pawlowski, W., & He, Y. (2017). ATX3, ATX4, and ATX5 encode putative H3K4 methyltransferases and are critical for plant development. Plant Physiology. 174:1795-1806.
- Sidhu, G. K., Warzecha, T., & Pawlowski, W. (2017). Evolution of meiotic recombination genes in maize and teosinte. BMC Genomics. 18:106.
- He, Y., Wang, M., Qi, S., & Pawlowski, W. (2016). Mapping recombination initiation sites in maize using chromatin immunoprecipitation. Methods in Molecular Biology. 1429:177-88.
- Sidhu, G. K., Fang, C., Olson, M., Falque, M., Martin, O. C., & Pawlowski, W. (2015). Recombination patterns in maize reveal limits to crossover homeostasis. Proceedings of the National Academy of Sciences of the United States of America. 112:15982-7.
- Zhang , J., Pawlowski, W., & Han, F. (2013). Centromere pairing in early meiotic prophase requires active centromeres and precedes installation of the synaptonemal complex in maize. Plant Cell. 25:3900-3909.
- Sheehan, M. J., & Pawlowski, W. (2009). Live imaging of rapid chromosome movements in meiotic prophase I in maize. Proceedings of the National Academy of Sciences of the United States of America. 106:20989-94.
- Pawlowski, W., Wang, C. R., Golubovskaya, I. N., Szymaniak, J. M., Shi, L., Hamant, O., Zhu, T., Harper, L., Sheridan, W. F., & Cande, W. Z. (2009). Maize AMEIOTIC1 is essential for multiple early meiotic processes and likely required for the initiation of meiosis. Proceedings of the National Academy of Sciences of the United States of America. 106:3603-3608.
- Ronceret, A., Doutriaux , M., Golubovskaya, I. N., & Pawlowski, W. (2009). PHS1 regulates meiotic recombination and homologous chromosome pairing by controlling the transport of RAD50 to the nucleus. Proceedings of the National Academy of Sciences of the United States of America. 106:20121-6.
- Pawlowski, W., Golubovskaya, I. N., Timofeeva, L., Meeley, R. B., Sheridan, W. F., & Cande, W. Z. (2004). Coordination of meiotic recombination, pairing, and synapsis by PHS1. Science. 303:89-92.