IN-SITU CHARACTERIZATION OF THE LATE VACUOLATE MICROSPORE AS A CONVENIENT STAGE TO INDUCE EMBRYOGENESIS IN CAPSICUM

Pollen embryogenesis has been induced in Capsicum annuum L., selecting the late vacuolate microspore as the suitable developmental stage for the induction. Various modem in situ methods including cytochemistry, immunocytochemistry, and in situ hybridization have been used to characterize the functional organization of the microspore nucleus at this specific stage of development in which the change to the sporophytic program can be induced. The results on the chromatin pattern, interchromatin structures and nucleolar subcompartments reveal a transcriptionally very active nucleus in the late vacuolate microspore and define characteristic cellular features of this specific period. The first stages of the microspore derived embryos have also been studied identifying the main ultrastructural features exhibited by the nuclei of two-cell and multicellular pollen grains. The approach used, providing information on the subcellular location and expression time of key molecules involved in gene expression, presents a high potential for studying the complex process of pollen embryogenesis induction.