Characterization of PiCDPK1 Mediated Signaling Pathways Regulating Pollen Tube Tip Growth

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Production of seeds or fruits is the goal of most agricultural and horticultural practices. In most cases seed and fruit development requires fertilization of ovules by sperm delivered by pollen. In most flowering plants ovules are enclosed within maternal tissues. To traverse this barrier, pollen produce tubes that penetrate the female tissues by a process known as tip-growth. How this process is regulated is not well understood but is key to plant sexual reproduction and is a potential target for the genetic manipulation of fertilization and seed set.Calcium ions play an important regulatory role in tip-growth and a calcium-regulated enzyme (PiCDPK1), which controls pollen tube growth polarity, has been identified. This enzyme is a protein kinase which regulates downstream signaling components by adding phosphate groups to their protein backbones. The objectives of this project are to characterize two such downstream components using molecular genetic and biochemical approaches. Preliminary results suggest that the phosphorylated forms of these components can mediate the inhibition or enhancement of pollen tube growth. This possibility will be investigated in detail using transgenic approaches.This study will significantly enhance knowledge of signaling events in pollen tube growth and is expected to provide molecular tools with which this process can be manipulated. Furthermore, the results may have broader implications for plant cell signaling as calcium is involved in many aspects of plant growth and development.The proposed research will provide training for a post-doctoral, a graduate and several undergraduate students in a variety of cell and molecular biology techniques. Through summer internships, two high school students per year will gain valuable experience in state of the art molecular biology techniques.