EAGER: DNA demethylation in maize pollen gene regulation

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Pollen is made of two cell types, sperm cells and pollen vegetative cells, each with different sets of active genes. Pollen vegetative cells carry the sperm cells inside them on their journey first through the air and then through the female reproductive structure to fuse with eggs and make seeds. During this process, the pollen vegetative cells use a large number of genes to grow and develop and to protect their cargo of sperm cells. Robust pollen that can survive adverse environmental conditions is essential for high yield in crops like corn (maize). Especially in regard to heat tolerance, pollen is an important consideration in crop improvement. Recent discoveries have revealed that enzymes called DNA glycosylases, which change the structure of DNA, are important for activating genes in pollen vegetative cells. This project aims to investigate the function of these enzymes in corn pollen. The results will yield new knowledge about pollen genetics and new tools for putting that knowledge to use in plant reproduction.DNA methylation generally represses repetitive DNA. In certain situations, however, DNA methylation can regulate developmental gene expression. In plants, DNA glycosylases remove methylation and can mediate epigenetic inheritance. The goal of this project is to identify both genes and intergenic regions of the genome that are targeted for demethylation and to determine the functional significance of demethylation in pollen. This will involve a novel approach to determine the effects of demethylation on gene expression at single-cell resolution in mixed populations of normal and glycosylase-defective pollen. The capstone of the project will be testing the potential of engineering glycosylases to demethylate specific genetic elements. This will be an initial step toward a larger goal of creating experimental resources for studying the consequences of methylation as well as for epigenetically controlling gene expression in pollen, with potential for heritability into the next generation.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.