Plant sex determination and sex chromosomes

Heredity (2002) 88, 94–101  2002 Nature Publishing Group All rights reserved 0018-067X/02 $25.00 www.nature.com/hdy

Plant sex determination and sex chromosomes
D Charlesworth
Institute of Cell, Animal and Population Biology, University of Edinburgh, Scotland, UK

Sex determination systems in plants have evolved many times from hermaphroditic ancestors (including monoecious plants with separate male and female flowers on the same individual), and sex chromosome systems have arisen several times in flowering plant evolution. Consistent with theoretical models for the evolutionary transition from hermaphroditism to monoecy, multiple sex determining genes are

involved, including male-sterility and female-sterility factors. The requirement that recombination should be rare between these different loci is probably the chief reason for the genetic degeneration of Y chromosomes. Theories for Y chromosome degeneration are reviewed in the light of recent results from genes on plant sex chromosomes. Heredity (2002) 88, 94–101. DOI: 10.1038/sj/hdy/6800016

Keywords: dioecy; sex linkage; Y chromosomes; Silene latifolia

Introduction: why are plant sex chromosomes of particular interest?
The genetic control of sex determination is becoming well understood in several animal systems, particularly Drosophila melanogaster, Caenorhabditis elegans and mammals. In plants, understanding the sex determination system is closely connected with understanding how separate sexes evolved, and current theoretical ideas about this also illuminate the evolution of sex chromosomes. Angiosperms are also of particular interest for empirical studies of sex chromosome evolution, because they probably evolved separate sexes repeatedly and relatively recently. Other plants, particularly Bryophytes (see Okada et al, 2001), also have interesting independently evolved sex chromosomes. In many sexually reproducing plant species (and some animals) all individuals are essentially alike in their