Progress 08/01/06 to 07/31/08
Outputs
OUTPUTS: The results of this project have been presented in poster form at the Maize Genetics Conference, 2007 and 2008, and at Cornell Postdoc Research Day, 2007. International maize breeders and researchers, as well as scientists in related crops like sorghum, wheat and rice attend the Maize Genetics Conference. Cornell University sponsors a Postdoc Research Day that allows postdocs from the Ithaca and New York City campuses to present their research to each other and the rest of the Ithaca-based scientific community. I also presented a poster with my latest findings at the USDA Projects Director meeting in Washington, DC in April, 2008. Several talks on the results have been given on the Cornell Ithaca campus including talks to the Grass Genetics group and the Replication, Recombination and Repair group. Also, an invited talk on this work was presented at the Postdoc Research Day, 2008. The Grass Genetics group is a collection of Ithaca-based labs that meet bimonthly for talks regarding cutting edge research in grass crops. The Replication, Recombination and Repair group is made up of labs researching chromosome replication, recombination and repair in many different model systems and include members from Microbiology, the Vet school, Plant Breeding, and Molecular Genetics departments. PARTICIPANTS: Moira Sheehan, Project Director Ju-Kyung Yu, PhD., Syngenta Seeds, Inc., Partner Organization providing in-kind support for pam1 mapping. Paul Altendorf, Syngenta Seeds, Inc., Partner Organization providing in-kind support for pam1 mapping. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: I was unable to implement my last objective regarding the formation of the telomere bouquet in Tripsacum andersonii due to its infrequent flowering habit.
Impacts
During the course of this research project I have had several changes in knowledge regarding the pam1 mutation. The link between time of flowering and the severity of the pam1 mutation was seen again in a second field nursery, leading me to believe it is genetically, rather than environmentally, controlled. I have, with the help of collaborators at Syngenta, generated 138 new lightscanner markers for the fine mapping of in bin 1.05, which was just completed. Since my development of a living cell protocol for multiphoton microscopy, I have discovered and characterize wild-type movements in several meiotic stages. Although preliminary, it appears that pam1 chromosomes have severely dampened movement compared to wild-type plants. Several changes in actions were taken based on what I learned while working with the pam1 mutant. We had begun prior to termination of this grant to employ newly available transgenic lines for Histone and tubulin-b to monitor cellular dynamics in our multiphoton live imaging system.
Publications
- Sheehan, M.J., Altendorf, P., Yu, J.K., Golubovskaya, I.N., and Pawlowski, W.P. 2008. Dissecting the formation and function of the meiotic telomere bouquet using the plural abnormalities of meiosis1 (pam1) mutant of maize. USDA Awardees Meeting: Genes to Products: Bethesda, MD, USA. April 2008.
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Progress 08/01/06 to 07/31/07
Outputs
OUTPUTS: The results of this project have been presented in poster form at the Maize Genetics Conference, 2007 and at Cornell Postdoc Research Day, 2007. A poster with new results will be presented at the Maize Genetics Conference, 2008 in February. International maize breeders and researchers, as well as scientists in related crops like sorghum, wheat and rice attend the Maize Genetics Conference. Cornell University sponsors a Postdoc Research Day that allows postdocs from the Ithaca and New York City campuses to present their research to each other and the rest of the Ithaca-based scientific community. I plan to present again at both of these events this year. I will also be presenting my findings at the USDA Projects Director meeting in Washington, DC. Several talks on the results have been given on the Cornell Ithaca campus including talks to the Grass Genetics group and the Replication, Recombination and Repair group. The Grass Genetics group is a collection of Ithaca-based labs
that meet bimonthly for talks regarding cutting edge research in grass crops. The Replication, Recombination and Repair group is made up of labs researching replication, recombination and repair in many different model systems and include members from Microbiology, the Vet school, Plant Breeding and Molecular Genetics departments.
PARTICIPANTS: Moira Sheehan, Project Director Syngenta Seeds, Inc., Partner Organization providing in-kind support for pam1 mapping. Brandon Lemesh, Undergraduate Intern
TARGET AUDIENCES: Target audiences include maize biologists and breeders, as well as researchers in genetics and meiosis. Undergraduate and high school students receive mentoring via internships and independent research projects.
PROJECT MODIFICATIONS: I have experienced some delay in implementing my last objective regarding the formation of the telomere bouquet in Tripsacum andersonii due to its infrequent flowering habit. I am working to resolve this issue by using different photoperiods in order to induce flowering more frequently. Another unforeseen delay was the insufficient amount of genetic material (germplasm) to start with. This has been fully rectified and is no longer an issue. The last delay involves the FISH-Immunocolocalization. This anticipated an immunolocalization antibody for MLH1 that was delayed in it production and testing.
Impacts
During the course of this research project I have had several changes in knowledge regarding the pam1 mutation. Homozygous mutant pam1 plants have a distinct tassel and anther phenotype, allowing for easy visual identification. In addition, I have also found a link between time of flowering and the severity of the pam1 mutation. I have been able to utilize three different single copy probes, previously used only in 2-D microscopy, for assessment of pairing and meiotic progression in 3-D microscopy in maize meiotic mutants. I have, with the help of collaborators at Syngenta, mapped pam1 to a set of markers in bin 1.05. Several changes in actions were taken based on what I learned while working with the pam1 mutant. The phytochrome A1 and phytochrome A2 genes were too similar to make a unique probe for each one. A new strategy to detect ectopic paring was devised. A phytochrome B cDNA will be used to make a single probe that recognizes both phytochrome B1 (on bin 1.03)
and phytochrome B2 (on bin 9.06). To distinguish the chromosomes, this probe will be used in conjunction with the P1 gene also located at 1.03. We had planned on using time point collection to monitor meiotic progression in lieu of a live cell imaging system. However, we have made great progress in visualizing nuclear dynamics in living meiocytes using Two-Photon microscopy, minimizing our need for time point sampling. Based on our success at narrowing down the location of pam1, I have produced a large mapping population of 1250 plants for the purpose of cloning.
Publications
- Ronceret, A, Sheehan, M.J. and Pawlowski, W.P. 2007. Chromosome dynamics in meiosis. Chapter 6 in D.P.S. Verma and Z. Hong (eds.) Plant Cell Monographs (9): Cell Division Control in Plants. Springer-Verlag Berlin Heidelberg, Heidelberg, Germany, p. 103-124.
- Pawlowski, W.P., Sheehan, M.J., and Ronceret, A. 2007. In the beginning: the initiation of meiosis. BioEssays 29:511-514.
- Sheehan, M.J., Golubovskaya, I.N., and Pawlowski, W.P. 2007. Using the maize plural abnormalities of meiosis1 (pam1) mutant to dissect the role of the telomere bouquet in pairing and recombination. 49th Annual Maize Genetics Conference Program and Abstract Book, St. Charles, Illinois, USA (P-63)
- Sheehan, M.J., Altendorf, P., Yu, J.K., Golubovskaya, I.N., and Pawlowski, W.P. 2008. Dissecting the formation and function of the meiotic telomere bouquet using the plural abnormalities of meiosis1 (pam1) mutant of maize. 50th Annual Maize Genetics Conference Program and Abstract Book, Washington, DC, USA. Februrary 2008.
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