The goals of this research are the characterization of pollen specific genes and genes expressed in both pollen and in sporophytic tissues and an identification of cis-acting regulatory sequence elements and trans-acting regulatory factors and their genes. The immediate objectives of the proposed research are: (i) to completely sequence the coding and 5' and 3' flanking regions of two pollen specific genes and two genes that are expressed both in pollen and in vegetative tissue; (ii) to identify cis-acting regulatory elements required for pollen expression by the use of cloned genes and DNA footprinting following binding with nuclear proteins; (iii) to determine the developmental time course of activation of trans-acting nuclear factors; (iv) to determine the organization in the chromosome, of pollen and sporophyte expressed genes, and (v) to determine by in situ hybridization the sites of localization of specific mRNAs in the male gametophyte.%%% The male gametophyte (pollen grain-pollen tube) plays a very important part in the life cycle of flowering plants. It produces two sperm cells and transports them through the tissues of the style and into the embryo sac in the ovule in the immediate vicinity of the egg and central cell. In the double fertilization that follows, fusion of the sperm cells with the egg and central cell gives rise to the zygote and primary endosperm cell respectively. The embryo and endosperm of crop plants are of vital importance to the nutrition of humans and domesticated animals. The results of these studies could help us to better utilize pollen selection as a tool in plant breeding. The isolation and characterization of pollen specific promoters will be of value in plant biotechnology in the engineering of male sterile lines for the production of hybrid seed.***
