He focuses on one of the two phases to their life cycle. In the first phase, the sporophyte is the diploid generation—that is with two similar sets of chromosomes--that undergoes meiosis to produce cells called spores. Each spore divides forming a single set of chromosomes (haploid) --the gametophyte--which produces the sperm and egg cells.

Evans studies how the haploid genome is required for normal egg and sperm function. In flowering plants, the female gametophyte, called the embryo sac, consists of four cell types: the egg cell, the central cell, and two types of supporting cells. Two sperm cells from the male gametophyte—the pollen—fertilize the egg and central cells to produce the embryo and endosperm, respectively. The embryo and endosperm together make up the seed. The embryo develops into the new plant and the endosperm contains the nutritive material used by the embryo and seedling; it comprises the bulk of the grain weight in cereals such as wheat, rice, and maize.

Proper seed development depends on genes from the embryo and endosperm and from genes from the maternal embryo sac and sporophyte. Using maize, Evans is developing tools for identifying genes that are required for normal embryo sac development and function. He is also investigation the factors that prevent maize and it’s wild cousin teosinte from cross pollinating, and he is identifying  genes important for gametophyte function.

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