Male gametic cell-specific expression of H2A and H3 histone genes.

Formation of the generative cell in flowering plants initiates the male spermatogenesis pathway which eventually culminates in the process of double fertilization. Little is known about the molecular mechanisms operative in the generative cell. Here, we report the isolation and characterization of cDNA clones encoding generative cell-specific histones, gcH2A and gcH3. In situ hybridization analysis revealed that both genes are activated after formation of the generative cell and accumulation of transcripts increases progressively during generative cell maturation. These results suggest that gcH2A and gcH3 mRNAs are products of transcriptional activation of the generative cell nucleus and thus provide the first evidence for male germ line cell-specific gene expression in flowering plants.