Molecular genetic analysis of LORELEI function in inducing the arrest of pollen tube growth in the Arabidopsis female gametophyte

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The seeds we depend on for our food are products of double fertilization. This essential process in plant reproduction requires delivery of sperm cells by the pollen tube to the egg and central cells of the embryo sac (female gametophyte). Although double fertilization was discovered more than a century ago, the controlling molecular mechanisms and genes remain poorly understood. We identified the Arabidopsis LORELEI (LRE) gene as critically important for an early step in reproduction. In lre mutants, pollen tubes do not arrest growth in the female gametophyte prior to releasing the sperm cells and consequently fail to complete double fertilization. We found that LRE encodes a putative membrane-anchored glycosylphosphatidylinositol (GPI)-anchored protein and is, therefore, an excellent candidate for mediating some aspects of signaling between the pollen tube and the female gametophyte. In this current project, molecular, genetic, and cell biological experiments will be conducted to elucidate the role of LORELEI protein in inducing pollen tube growth arrest in Arabidopsis female gametophytes. Specifically, we will determine the subcellular localization of LORELEI protein in the synergid cell and whether the LORELEI GPI anchor in is essential for its function in the synergid cell. The mechanism of LORELEI function in inducing the arrest of pollen tube growth will also be examined, and additional genes that function with LORELEI in this important signaling event will be identified.A comprehensive molecular understanding of seed formation may help generate tools to manipulate plant reproduction and increase seed yield. Consequently, this project could have a major impact since seeds are a source of staple food, fiber, nutrition, industrial products and biofuels. Additionally, this project will also have a major human resource impact. Undergraduate students will carry out some experiments and two post doctoral fellows and a research technician will be trained in experimental procedures, data analysis, and scientific data presentation.