Hexose Transporter Genes and the Origin of Land Plants

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9628869 GRAHAM Land plants, like animals, begin life by forming embryos. Land plant embryos, like many but not all animal embryos, develop while attached to a parent from which they obtain food, especially sugars. The genetic mechanisms associated with sugar transport are not well understood, especially in morphologically simple plants such as bryophytes (mosses, liverworts, hornworts), which have embryos, and charophycean green algae, which are closely related to mosses but do not have embryos. In this study, Linda Graham and Lee Wilcox will begin an evaluation of one set of genes, the hexose transporter gene family, that are involved in sugar transport in plants. They will obtain molecular sequence information from hexose transporter genes in charophycean green algae. They will use these sequences to construct phylogenetic trees, and compare these trees with others derived from sequences of different genes, and from the morphological and anatomical features of the plants, seeking additional support for the hypothesis that charophycean green algae and bryophytes are closely related. They will seek support for the hypothesis that sugar transport from parent plant to embryo is based in part upon hexose transporter gene products (i.e., proteins) that are derived from plants without embryos (charophycean green algae) but are specifically expressed at the junction between parent plant and developing embryo in bryophytes. The results should provide significant new information on the origin, early history, and development of the land plant embryo, one of the most fundamentally important events in the life history of land plants.