Isolation of genes from plant Y chromosomes.
Few plant species are dioecious and only a small fraction of these species are known to have sex chromosomes. Considerable efforts to isolate sex-linked genes from dioecious Silene latifolia (Caryophillaceae) have resulted in the isolation of surprisingly few sex-linked genes, suggesting that the methods used previously were not efficient in plants. This chapter analyzes the methods that have been and can be used for isolation of genes from plant sex chromosomes. The most successful method used for the isolation of Y-linked genes included the screening of a male complementary DNA (cDNA) library with the probe obtained by degenerate oligonucleotide-primed polymerase chain reaction (PCR) of the microdissected Y chromosomes. However, chromosome microdissection requires sophisticated equipment and is difficult to apply to species with cytologically indistinguishable sex chromosomes. Genome and cDNA library subtraction methods were surprisingly unsuccessful, probably because of low divergence between the homologous X- and Y-linked genes in plants. Segregation testing and genomics-based methods are increasingly popular and are the most promising approaches for isolation of multiple genes from plant sex chromosomes.