XVI International Botanical Congess

The nuclei of male gametes of flowering plants have highly condensed chromatin, as do the nuclei of animal sperm. We have detected four kinds of specific or highly concentrated histone variants (p35, p22.5, p21, p18.5) in the isolated generative nuclei of Lilium longiflorum. Immunofluorescence staining using specific antisera clearly demonstrated that these histone variants were specific to male gametic (generative and sperm) nuclei in pollen grains and pollen tubes of L. longiflorum. Because the deduced amino acid sequences of the cDNAs of these histone variants showed some homology to somatic histones H1, H2B, H3 and H2A, respectively, they were designated gH1, gH2B, gH3 and gH2A. They are assumed to be related to the condensation of chromatin of the male gametic nuclei. Therefore, their function is now being investigated by gene transfer experiments.