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Testing a Role for Rop9 GTPase in Maize Pollen Tube Growth

Testing a Role for Rop9 GTPase in Maize Pollen Tube Growth. Lauren A. Osborn Dr. John Fowler Botany and Plant Pathology Summer 2005. Pollen Tube Growth. Pollination and pollen tube growth is essential fertilization seed production in plants

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Testing a Role for Rop9 GTPase in Maize Pollen Tube Growth

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  1. Testing a Role for Rop9 GTPase in Maize Pollen Tube Growth Lauren A. Osborn Dr. John Fowler Botany and Plant Pathology Summer 2005

  2. Pollen Tube Growth • Pollination and pollen tube growth is essential • fertilization • seed production in plants • Two phases for pollen tube growth in Maize • Germination • Growth in the silk Pollen Tubes Germination

  3. Corn Life Cycle Pollen Grains Silk and Egg Mature Adult Fertilization Seedlings Seed

  4. Rop Genes • Nine different Rop genes in maize • ROP GTPases are proteins that act as a signaling molecule (example: pollen tube growth) • Rop2 mutant pollen has a reduced ability to fertilize

  5. My Research: Rop9 gene ATG

  6. Unusual Inheritance • Previous analysis on a Rop9 mutant corn ear had more wild type kernels • Also the kernels were distributed with more mutants at the top

  7. m + + + Less mutants expected if mutation affects pollen

  8. Hypothesis • Rop9 affects pollen tube growth in silk • Mutant pollen at a disadvantage competing with wild type to fertilize

  9. Predictions • Pollen tubes from Rop9 mutant pollen grains will grow more slowly • If pollen tube growth is affected Rop9 mutants would have a disadvantage at reaching kernels at the bottom of the ear Short silks Long Silks

  10. Experiments • There are two ways to test for the role of Rop9 in pollen tube growth • Indirectly and Directly

  11. The Indirect Test • Test through genotyping kernels by PCR • Test top and bottom of maize ears • Genotype kernels at top and bottom Top Rop9 Wild typeband Bottom Rop9 Mutant bands

  12. Rop9 Result Totals Wild Type vs. Mutant Ear 1 Ear 2 Ear 4 Ear 5 Ear 3 m1 m6

  13. Ear 1 Ear 2 Ear 4 Ear 5 Ear 3 m1 m6 Results do not confirm top and bottom prediction

  14. The Direct Test • Use fresh pollen • Microscope imaging to observing pollen tube growth • See directly whether mutant pollen grains germinate or grow pollen tubes more slowly than wild-type pollen grains

  15. Pollen Germination on Media Light: wild type Dark: mutant

  16. Results from Direct Test I Percent Germination

  17. Results from Direct Test II Pollen Tube Length 1 Hour

  18. Summary • Rop9 has an effect on pollen’s ability to carry out fertilization • However my results do not confirm a role for Rop9 in pollen tube growth

  19. Future Research • Initial hypothesis: Pollen Tube Growth • Possibly may have an effect on late events • Fertilization?

  20. Acknowledgements • Ernest and Pauline Jaworski Fund • Howard Hughes Medical Institute • Dr. Kevin Ahern • Dr. John Fowler • Zuzana Vejlupkova • Rex Cole • Kirsten Carol • Darin Olson

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