Expression of a Bet v 1 homologue gene encoding a PR 10 protein in birch roots: induction by auxin and localization of the transcripts by in situ hybridization

In birch roots (Betula pendula Roth), two members of the Bet v 1 gene famil y which encode PR 10 proteins have previously been characterized. One of th ese members, named Bet v 1-sc1, is significantly induced in response to bio tic or abiotic factors. We have analysed the expression of Bet v 1-sc1 in b irch roots treated either with 1 muM indole-3-acetic acid (IAA) or 1 muM ki netin using reverse transcription-polymerase chain reaction (RT-PCR), north ern blotting and competitive PCR. High accumulation of the Bet v 1-sc1 tran scripts was recorded only after auxin application, while kinetin had no eff ect. By in situ hybridization, we have investigated the localization of Bet v 1-sc1 mRNA in birch roots after induction of the gene by root treatment with 1 muM IAA. Using root tip sections, we showed that Bet v 1-sc1 is sign ificantly expressed in the apical meristem and the procambium. In sections taken in the zone producing lateral roots, the presence of Bet v 1-sc1 was found at sites of emerging secondary root primordia. This first report of l ocalization of Bet v 1-sc1 expression suggests that this gene could be invo lved in the processes leading to lateral root initiation.