Physiologische und molekularbiologische Ansätze zur Analyse der Funktion von Indol-3-buttersäure in der Entwicklung arbuskulärer Mykorrhizen

Abstract

Inoculation of maize with the AM fungus Glomus intraradices resulted in a distinct root phenotype with a significant increase in the percentage of lateral roots during early stages of colonization. Auxins are known to play a role in different developmental processes including fine root formation and are therefore suitable candidates for the regulation of AM symbiosis. The increase in lateral root development coincided with an increase in the levels of the auxin indole-3-butyric acid (fA). The phenotype of mycorrhizal maize roots could be mimicked by exogenously applied IBA to non-mycorrhizal roots. Addition of trifluoro-IBA (IFIBA), an inhibitor of IBA-induced root growth and lateral root induction, simultaneously with IBA resulted in a phenotype resembling that of untreated controls. In roots treated with TFIBA the inoculation with AM-fungi did not increase the formation of fine roots. The IFIBA-treatment also reduced endogenous free IBA and the percentage of colonization in mycorrhizal roots. Using activity screening and cDNA-AFLP analysis, we have started to isolate the gene for IBA synthetase and other genes differentially induced by IBA and AM.