Meiosis and meiotic recombination in plants
CALS Impact Statement
My lab studies meiosis in plants, particularly pairing of homologous chromosomes and meiotic recombination. Our main goal is to understand the mechanisms regulating these processes at the molecular level. The springboard to this research is the poor homologous synapsis 1 (phs1) gene in maize that I recently cloned. phs1 is required for proper pairing of homologous chromosomes in meiosis. To better understand the role of the PHS1 protein, we are: (1) characterizing the protein itself (behavior during meiosis, functions of conserved domains, and role in regulating the progression of meiotic recombination), and (2) identifying other meiotic proteins that interact with PHS1. In a separate study, we identified two meiotic mutants in maize, desynapticCS (dsyCS) and segregationII (segII), which may represent genes involved in the same step of chromosome pairing as phs1. We are characterizing these mutants and started cloning the corresponding genes. We are also initiating studies on how the telomere clustering (formation of "the bouquet") during meiotic prophase and chromatin structure impact homologous chromosome pairing.
Meiosis is essential for accurate transmission of genetic material from parents to the progeny and for genetic recombination, which is a source of genetic variation. Consequently, it is one of the most fundamental processes in all sexually reproducing organisms. While much is known about the mechanisms of meiotic recombination and chromosome synapsis, homologous chromosome pairing remains the least understood process in meiosis. This research will lead to the identification of gene networks that regulate homology recognition and chromosome pairing. Many proteins are predicted to act in meiosis. Some are unique to meiosis, whereas others are also involved in other cellular processes, such as DNA damage repair and genome maintenance. Consequently, studying meiosis provides insights into the molecular control of many basic cellular processes. Studying meiosis in plants will contribute to the development of methods for homologous gene replacement and improved genetic transformation, allowing manipulation of meiotic recombination levels, and acquiring apomixis (embryo development without fertilization). Understanding the mechanisms of meiosis is a central problem of medical genetics because meiotic errors in humans result in infertility and formation of aneuploid gametes. Aneuploidy is the primary genetic cause of pregnancy loss and the most common cause of mental retardation if the fetus survives to term.
As a postdoctoral researcher, I have cloned and characterized the poor homologous synapsis1 (phs1) gene in maize, which is a key regulator of chromosome homology recognition and pairing in meiosis. This gene is required for promoting pairing between homologous chromosomes and for coordination of meiotic recombination, pairing, and synapsis. Mutants in the phs1 gene show severe defects in both meiotic recombination and chromosome pairing. More recently, my research group at Cornell University has identified two more maize mutants, which exhibit high frequencies of non-homologous chromosome associations that replace homologous pairing, phenotypes very similar to that of the phs1 mutant. We postulate that these three mutants define a novel class of meiotic genes required for proper homology recognition and homologous pairing. During the past year we made a substantial progress towards generating tools that we will need to study the interactions between the genes involved in chromosome pairing and to identify more that function in this process. We generated segregating maize population for cloning the dsyCS and segII genes. We also worked on producing transgenic maize plants expressing a tagged version of the PHS1 protein that will be used to identify proteins that interact with PHS1.
This is a basic research project, which is still in its infancy. Consequently, it is still too early to see any specific impact of this research on society or economy. However, we expect that in the long run this research will contribute to development of new methods for plant breeding and biotechnology and benefit US and agriculture. As research on meiosis in model systems is and will continue to be transferable to humans, we also foresee that our findings may contribute to development of new methods to diagnose and treat reproductive disorders in humans, such as infertility.