MAJOR ALLERGEN PHL-P-VB IN TIMOTHY-GRASS IS A NOVEL POLLEN RNASE

A cDNA coding for the major group V allergen Phl p Vb was isolated fro m a timothy grass pollen cDNA library by immunoscreening with a specif ic monoclonal antibody. It was discovered for the first time that the recombinant Phl p Vb pollen allergen after expression and purification has ribonuclease activity. High homology of Phl p Vb to other group V allergens in grass pollen indicates similar function. By RNase activi ty gel of natural pollen extract of timothy grass and consecutive West ern blot analysis of the excised proteins, the RNase active bands were shown to be group V allergens. Additionally it was demonstrated that an homologous protein to Phl p Vb in the mother plant could be induced by salicylic acid. This indicates that group Vb allergens may be invo lved in host-pathogen interactions because in pollen they are quickly exported RNases and in the mother plant they depend on a hormone which is related to expression of plant resistance genes.