An anther- and petal-specific gene SlMF1 is a multicopy gene with homologous sequences on sex chromosomes.

A male flower-specific gene SlMF1 was isolated from male flower buds of the dioecious plant Silene latifolia. SlMF1 is expressed in all the floral meristems at the very early stage of development in both male and female flower buds. At the mature stage of development in male flower buds, SlMF1 transcripts were specifically accumulated in pollen mother cells, tapetal cells, and the developing tips of petals. Genomic Southern hybridization revealed that SlMF1 was a multicopy gene with a Y chromosome-linked homologous sequence. PCR analyses with flow-sorted chromosomes showed that SlMF1 was localized on both autosomes and the X chromosome.

Genetic and functional analysis of DD44, a sex-linked gene from the dioecious plant Silene latifolia, provides clues to early events in sex chromosome evolution.

Silene latifolia is a dioecious plant with heteromorphic sex chromosomes. The sex chromosomes of S. latifolia provide an opportunity to study the early events in sex chromosome evolution because of their relatively recent emergence. In this article, we present the genetic and physical mapping, expression analysis, and molecular evolutionary analysis of a sex-linked gene from S. latifolia, DD44 (Differential Display 44). DD44 is homologous to the oligomycin sensitivity-conferring protein, an essential component of the mitochondrial ATP synthase, and is ubiquitously expressed in both sexes. We have been able to genetically map DD44 to a region of the Y chromosome that is genetically linked to the carpel-suppressing locus. Although we have physically mapped DD44 to the distal end of the long arm of the X chromosome using fluorescence in situ hybridization (FISH), DD44 maps to the opposite arm of the Y chromosome as determined by our genetic map. These data suggest that chromosomal rearrangements have occurred on the Y chromosome, which may have contributed to the genetic isolation of the Y chromosome. We discuss the implications of these results with respect to the structural and functional evolution of the S. latifolia Y chromosome.

Mapping of sex determination loci on the white campion (Silene latifolia) Y chromosome using amplified fragment length polymorphism.

S. latifolia is a dioecious plant with morphologically distinct sex chromosomes. To genetically map the sex determination loci on the male-specific Y chromosome, we identified X-ray-induced sex determination mutants that had lost male traits. We used male-specific AFLP markers to characterize the extent of deletions in the Y chromosomes of the mutants. We then compared overlapping deletions to predict the order of the AFLP markers and to locate the mutated sex-determining genes. We found three regions on the Y chromosome where frequent deletions were significantly associated with loss of male traits. One was associated with hermaphroditic mutants. A second was associated with asexual mutants that lack genes needed for early stamen development and a third was associated with asexual mutants that lack genes for late stages of stamen development. Our observations confirmed a classical genetic prediction that S. latifolia has three dispersed male-determining loci on the Y chromosome, one for carpel suppression, one for early stamen development, and another for late stamen development. This AFLP map provides a framework for locating genes on the Y chromosome and for characterizing deletions on the Y chromosomes of potentially interesting mutants.

Silver enhances stamen development in female white campion (Silene latifolia [Caryophyllaceae]).

Sex expression in the dioecious plant white campion (Silene latifolia Poiret subsp. alba) appears to be insensitive to exogenous applications of auxins, cytokinins, gibberellic acid, and ethylene; however, silver thiosulfate (Ag(2)S(2)O(3)), an ethylene inhibitor, enhanced stamen development in female white campion. In wild-type females, stamen development is arrested before the microspore mother cells are formed. In contrast, stamens of Ag(2)S(2)O(3)-treated females completed meiosis and produced microspores. Stamen development for these females was incomplete, however, and pollen did not mature. Ag(2)S(2)O(3) stimulated stamen development to the same extent in asexual white campion mutants that retained a Y chromosome but had lost Y-linked genes needed for early stages of stamen development. Although Ag(2)S(2)O(3) can inhibit ethylene signaling, the enhancement of stamen development in female white campion cannot be explained as a loss of ethylene response because no other ethylene inhibitor tested (1-methylcyclopropene, trans-cyclooctene, aminoethoxyvinylglycine, and cobalt chloride) caused stamens to develop in female plants. In addition, application of other metal ions could not enhance stamen development. Therefore, the effect we observed on female white campion was specifically caused by silver ions but not by their action on ethylene signaling.