Transcriptional repression distinguishes somatic from germ cell lineages in a plant.

In flowering plants, the male germline begins with an asymmetric division, after which one of the resulting cells, the generative cell, divides symmetrically to produce two sperm cells. We show here that the male germline is initiated by transcriptional control. We identify GRSF, germline-restrictive silencing factor, from the lily. GRSF is ubiquitous in nongerm cells and is absent from male germ cells. GRSF recognizes silencer sequences in promoters of genes specific to the germline, stably repressing these genes in cells that are not destined to become germ cells.