MOLECULAR CHARACTERIZATION OF A CYTOKININ-INDUCIBLE PERIWINKLE PROTEIN SHOWING SEQUENCE HOMOLOGY WITH PATHOGENESIS-RELATED PROTEINS AND THEBET-V-1 ALLERGEN FAMILY

Cytokinin treatment of periwinkle callus cultures increased the accumu lation of a protein, designated T1, in two-dimensional separated prote in extracts. The first 30 NH2-terminal amino acids were determined by Edman degradation. and showed significant sequence homology with intra cellular pathogenesis-related (TPR) plant proteins and the Bet v 1 all ergen family. The deduced amino acid sequence of cDNAs coding for T1, isolated by RT-PCR and 5' RACE-PCR, exhibited an average sequence iden tity of 40% with both IPR and Bet v I-related allergens. T1 and all re lated proteins contained a p-loop motif typically found in nucleotide- binding proteins as the most conserved sequence feature. Northern blot analysis showed that cytokinin treatment of periwinkle callus induced T1 transcripts, whereas addition of 2,4-dichlorophenoxyacetic acid in hibited this accumulation. Hybridization of genomic periwinkle DNA wit h the T1 cDNA. suggested that the protein is encoded by a single-copy gene. Immunoblot studies with a panel of Bet v 1-specific antibodies a nd sera from Bet v 1 allergic individuals identified T1 as a protein t hat is immunologically distinct from the Bet v 1 allergen family and h as no allergenic properties.