EXPRESSION OF BET-V-1, THE MAJOR BIRCH POLLEN ALLERGEN, DURING ANTHERDEVELOPMENT - AN IN-SITU HYBRIDIZATION STUDY

Bet v 1 proteins, a group of isoforms that constitute the major pollen allergen of the white birch (Betula verrucosa), are encoded by a comp lex multigene family which also includes a subset of genes transcripti onally activated in cell suspension cultures in the presence of microb ial pathogens. We have investigated the temporal and spatial expressio n patterns of Bet v 1 genes during development of male birch infloresc ences. Western and Northern analysis indicated that the expression of Bet v 1 isoallergens is regulated at the transcriptional level and act ivated only during the late phases of anther maturation, so that high levels of these proteins accumulate in mature pollen. In situ hybridiz ation experiments, carried out with sections of male inflorescences is olated at defined developmental stages, showed that Bet v 1 genes are specifically expressed in late bicellular and mature pollen, but no tr anscripts were detected in sporophytic anther tissues of any developme ntal stage. These data suggest a possible role of Bet v 1 proteins dur ing pollen germination on the stigma, protecting the female reproducti ve tissues from infection by pathogens.