NEW IN-SITU APPROACHES TO STUDY THE INDUCTION OF POLLEN EMBRYOGENESISIN CAPSICUM-ANNUUM-L

The induction of pollen embryogenesis in Capsicum annuum L. has been s tudied at the cellular level using various in situ approaches with sev eral molecular probes for DNA, RNA and proteins, The late vacuolated m icrospore and the young bicellular pollen grain are stages of gametoph ytic development in which embryogenesis can be induced, Our results sh ow that the late vacuolated microspore stage is most responsive to emb ryogenesis induction, The proliferating cell nuclear antigen (PCNA) ha s been immunolocalized at the electron microscopy level, in order to m ap replication sites in relation to the fine structure of chromatin, I t shows different patterns of labeling at both developmental stages st udied, revealing that the late vacuolated microspore is in a period of replication, Other in situ studies have been performed to characteriz e the state of nuclear activity at the specific developmental stages i n which the embryogenic induction can occur, The modern in situ termin al-deoxy-nucleotidyl transferase (TdT) reaction for DNA, the immunoloc alization of various nuclear antigens (as snRNPs, fibrillarin, RNA) an d the ultrastructural in situ hybridization using 18S and 25S ribosoma l probes provided valuable data about the specific features displayed by the functional nuclear compartments of the microspore, and the youn g vegetative and generative cells, They are related not only to the st ate of gene activity but also with probably the ability to switch to t he sporophytic pathway at specific developmental times of their gameto phytic program.