Collaborative Research: Mechanisms of pollen-specific phospholipases in maize haploid production

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Sexual reproduction mixes the genetic materials from two parents, which is the driving force for natural selections and a basis for plant breeding improvements. However, the cellular and molecular mechanisms that ensure the transfer of the genetic information from each parent to the next generation are largely unknown. This project addresses how specific enzymes that cleave phospholipids, which are building blocks of cell membranes, such as those of sperm and egg cells, affect the sperm genome transfer in maize seed production. Genetic defects in those enzymes lead to some embryos without the sperm genome, producing maternal haploids with genetic information only from the egg. This study will investigate how those enzymes affect membrane lipid changes and how the lipid changes lead to haploid formation. Thus, findings from this project will advance the fundamental, mechanistic understanding of sperm genome stability and haploid seed production with potential applications to crop improvement, such as haploid induction technology to enhance crop breeding and production for food, feed, fuel, and industrial feedstocks. This project will have additional broader impacts on science, education, and society by providing opportunities for training of students and postdoctoral researchers and serving as a platform to broaden participation of underrepresented groups in research. The research materials, including various maize lines, will be distributed to community and the results and large datasets will be disseminated to enhance science and education through lectures and seminars, in classroom teaching, at national and international meetings, and through timely publications in peer-reviewed journals.The goal of this project is to elucidate how two pollen-specific phospholipases, pPLAIIφ and PLD3, are involved in sperm genome transmission and haploid seed production in cereal crops. The research tests the hypotheses that loss of the pPLAIIφ and PLD3 activities perturbs lipid homeostasis, membrane structures, and sperm-egg membrane fusion during fertilization, leading to haploid induction and decreased seed production. The supporting objectives are to: 1) determine the role of pPLAIIφ and PLD3 catalytic activities in haploid and seed production, 2) characterize the effect of the phospholipases on pollen and sperm membrane lipid homeostasis, and 3) measure lipid dynamics and effects on sperm-egg fusion. The results will advance the understanding of sperm genome stability and sexual reproduction and have the potential to identify chemical and molecular modifiers applicable to enhance haploid induction for crop improvement.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.