The immunolocalization of nuclear antigens during the pollen developmental program and the induction of pollen embryogenesis.

The immunolocalization of nuclear antigens, combined with cytochemical procedures as well as in situ hybridization and recent in situ molecular methods, has been applied at different steps of pollen development to characterize the functional organization of the nucleus during the formation of the male gametophyte in an agronomically interesting plant, Capsicum annuum L. Pollen embryogenesis has been induced in pepper and the first stages of the process have been studied at the cellular level. Low temperature processing methods including cryosections and Lowicryl sections were very convenient for performing the various in situ techniques used in the pollen grains. Different molecular probes for localizing DNA, RNA, snRNPs, specific nucleolar proteins, various rRNA species, and DNA/RNA hybrids provided positive results in the pollen nuclei. The data obtained, and the changes observed in the organization of the nuclear compartments during pollen development, are related to the variations in gene activity undergone by the male gametophyte. The methodology used is proposed as a very convenient approach to localize molecules and events involved in the nuclear function in both gametophytic and sporophytic pollen development.