ABSTRACT
Silene latifolia is a model species for the study of sex determination in plants. Not only is S. latifolia dioecious, but sex is determined by loci located on morphologically distinct chromosomes. Male plants have 22 autosomes and a pair of sex chromosomes, X and Y. Female plants have 22 autosomes and two X-chromosomes. Although most higher plant species are hermaphroditic, approximately 11% have single sex flowers and 4% are dioecious (Dellaporta and Calderon-Urrea, 1993). However, dimorphic sex chromosomes have only been shown to be sex-determining in a small number of species. Single sex flowers are considered a modern evolutionary development. For example, most dioecious species still possess rudimentary stamens in female flowers and a rudimentary gynoecium in male flowers. Furthermore, only one plant family (Cannabidaceae), and very few genera, are entirely dioecious and those species which are dioecious, are scattered amongst many families and genera, and have many close relatives which are hermaphroditic. The molecular mechanism by which sex chromosomes determine sex in a dioecious plant species such as S. latifolia is not yet understood although a number of laboratories are making progress in this area. In this chapter we describe the isolation and characterization of male sex-specific sequences from S. latifolia and their similarity to comparable sequences from other plant species.
