Tracking Proteins in Recombination Nodules During Synapsis

Colorado State University, Fort Collins CO

Investigators

Abstract

The research plan is to use light and electron microscopic immunolocalization of conserved recombination proteins to integrate more fully the molecular aspects of genetic recombination with the cytological structures of early recombination nodules (ENs), late recombination nodules (LNs) and synaptonemal complexes. Tomato is the optimum choice for this study for a number of reasons, including its excellent cytology, the extensive information available on tomato ENs and LNs, and the fact that antibodies are already available for a number of tomato recombination proteins. The three specific objectives for this research are: 1) To determine the pattern of immunolabeling of recombination proteins in recombination nodules throughout synapsis using both light and electron microscopy. This aspect of the research will include detailed EM observations of labeled and unlabeled ENs including their relationship to each other, to synaptic initiation sites and synaptic forks, and to LNs. 2) To test the hypothesis that ENs differ in protein composition and function during synapsis. This may be related to current evidence that a subset of ENs become LNs and/or that there is more than one pathway for genetic recombination. And 3) to test the hypothesis that there are a defined number of ENs (gene conversions) between LNs (crossovers). This hypothesis has been proposed as a possible mechanism to account for genetic interference. This research will provide an important step in our understanding of RN components in relation to synapsis, crossing over, and genetic interference. In addition, this work will help us evaluate conserved aspects of the meiotic pathway as well as identify features that may be specific to plants. More broadly, elucidating these features in tomato, a crop plant, may help with practical issues such as changing recombination rates and/or aiding transfer of desirable "wild" alleles to domesticated species in plant breeding programs. Because meiotic recombination is highly conserved, the results of this study will be generally applicable to other plants of economic importance, such as maize and rice. An important element of this work will be the training and education of several undergraduate students as well as a graduate student.