The major olive pollen allergen (Ole e I) shows both gametophytic and sporophytic expression during anther development, and its synthesis and storagetakes place in the RER

The distribution of Ole e I (the major olive pollen allergen) and its trans cripts was investigated in the anther from premeiotic stages until the dehi scent pollen stage. Crude protein extracts were analyzed by immunoblotting and probed with a monoclonal antibody to Ole e I. The protein, with three v ariants, was found to accumulate from the early microspore stage onwards. I n addition to the previously reported localization of the protein, Ole e I has been immunolocalized for the first time within the pollen wall and in t he tapetum, Reverse transcription-polymerase chain reaction analysis using specific oligonucleotides and RNA extracted from whole anthers revealed tha t the Ole e I gene is expressed from the late tetrad stage onwards. No expr ession was found in control tissues such as petals, roots or leaves. Light microscopy in situ hybridization on developing flower buds and dehiscent po llen confirmed the transcripts to be present in both the microspores and th e sporophytic tissue (tapetum). Labeling was found primarily in the tapetum , reaching the highest concentration in the cytoplasm of the developing and mature pollen, once tapetum started to degenerate. In situ hybridization a t the transmission electron microscope level showed the transcripts to accu mulate on ribosomes of the rough endoplasmic reticulum, These studies, toge ther with others carried out previously by us, indicated that both synthesi s and storage of Ole e I take place in the endoplasmic reticulum, coinciden tally with the conspicuous changes suffered by this membrane system during pollen development. This process is most likely controlled at the transcrip tional level, The localization of the protein in the pollen ectexine bring new insights into the function of the allergen, which are discussed.