Meiosis and recombination in plants.

Date: 

2007

Summary: 

My lab studies meiosis in plants. We are particularly interested in pairing of homologous chromosomes and meiotic recombination. Our goal is to understand the mechanisms regulating these processes at the molecular level. The springboard to our research on homologous chromosome pairing is the poor homologous synapsis 1 (phs1) gene in maize that I cloned in 2004. phs1 is required for proper pairing of homologous chromosomes. We have recently discovered that this gene functions in a novel pathway that regulates pairing by affecting the dynamics of chromosomes and the entire nucleus at the early stages of meiosis. We are also studying two other meiotic genes in maize, desynapticCS (dsyCS) and segregationII (segII), which may be involved in the same step of chromosome pairing as phs1. We are cloning these two genes and characterizing their function.. In addition, we are investigating studying telomere clustering during meiotic prophase impacts chromosome pairing. To understand the genetic regulation of meiotic recombination, we initiated a project to survey the diversity in the rates of meiotic recombination in maize. Evidence exists that substantial genetically controlled within-species variation in meiotic recombination rates exists in this species. We want to survey this variation and identify its sources. The long-term goal of this project is to identify QTLs that regulate meiotic recombination rates in maize and other crops.

Issue: 

Meiosis is essential for accurate transmission of genetic material from parents to the progeny. Consequently, it is one of the most fundamental processes in all sexually reproducing organisms. Our research on the mechanisms that regulate homologous chromosome pairing and meiotic recombination will lead to identification and characterization of gene networks that regulate these processes. 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 has profound practical application because meiosis and meiotic recombination are the main sources of genetic diversity in plants, which is the basis of plant breeding. Meiosis research in plants will also 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.

Response: 

To understand the mechanisms of homologous chromosome pairing, we identified a group of three genes in maize, phs1, dsyCS, and segII, which define a novel class of meiotic genes required for proper chromosome homology recognition and homologous pairing. During the past year we discovered that phs1 regulates chromosome pairing by a novel pathway affecting the dynamic motility of chromosomes and the entire nucleus during the early stages of meiosis. We developed a new live imaging technique using mulitphoton microscopy to visualize chromosome dynamics in meiotic prophase. We also used cytological tools to characterize the function of the dsyCS and segII genes. We are pursuing cloning of these two genes. In addition, we are studying the pam1 gene in maize, which is required for telomere clustering in early meiosis in maize. This process has been studied in yeast, but is very poorly understood in higher eukaryotres, including plants. In collaboration with Syngenta Seeds, we are positionally cloning pam1. In 2007, we generated, screened, and genotyped a large cloning population segregating for a pam1 mutation. We expect completing cloning the gene in spring of 2008. In collaboration with Ed Buckler and Elisabeth Esch, we developed a method to map quantitative trait loci (QTL) regulating genome-wide recombination frequencies. This method will enable breeders to create hyper-recombinogenic lines to help overcome limited recombination that hampers breeding progress.

Impact: 

This is a basic research project. Consequently, it is still too early to see a 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 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.

Submitted by: 

  • Pawlowski, Wojtek P

Researchers involved: 

  • Ronceret, Arnaud
  • Bozza, Christopher
  • Sheehan, Moira
  • Sidhu, Gagan
  • Zhao, Junliang
  • Eliasinski, Patricia
  • Lemesh, Brendon

Organizations involved: 

  • PURDUE UNIVERSITY

International focus: 

  • United States of America
  • France
  • Germany
  • Israel

United States focus: 

  • New York