Analysis of members of the Silene latifolia Cys2/His2 zinc-finger transcription factor family during dioecious flower development and in a novel stamen-defective mutant ssf1.

Sex determination in dioecious Silene latifolia Poir. is governed by the inheritance of heteromorphic sex chromosomes. In male plants the Y chromosome influences two aspects of male organogenesis, the continued differentiation of stamen primordia and male fertility, and one aspect of female organogenesis, the arrest of development of the pistil. S. latifolia is susceptible to infection by the parasitic smut fungus Ustilago violacea, which induces stamen development in genetically female plants. Here we describe the identification and characterisation of a novel male mutant, short stamen filaments 1 (ssf1), defective in stamen differentiation. Although several independent studies have identified genes expressed during sex-determination in S. latifolia, analyses suggest that none of these encode regulatory proteins involved in the control of sex determination. We therefore isolated six S. latifolia cDNAs encoding members of a family of transcriptional regulators, the ZPT-type Cys2/His2 zinc-finger proteins that had previously shown to be co-ordinately regulated during stamen development in Petunia x hybrida hort. Vilm.-Andr. We have analysed the genomic organisation of these genes in male and female plants and their expression dynamics in male and female plants, in smut-infected female plants and in the ssf1 mutant. Our studies reveal expression patterns during development of the androecium that suggest a possible role for SlZPT2-1 in filament elongation and SlZPT4-1 in aspects of male fertility during stamen differentiation.