RESPONSE OF SYMBIOTIC ENDOMYCORRHIZAL FUNGI TO ESTROGENS AND ANTIESTROGENS

Plant flavonoids reported previously to act as molecular signals in th e arbuscular mycorrhizal (AM) symbiosis are known to bind to estrogen receptors and to exert Estrogenic effects on mammalian cells. To furth er investigate the estrogen-like properties of flavonoids the present study examined whether estrogen and antiestrogens have flavonoid-relat ed functions in AM fungi. Bioassays were performed in a monoaxenic sys tem with the AM fungi Gigaspora margarita and Glomus intraradices. The plant flavonoids quercetin and biochanin A stimulate hyphal growth of G. margarita and G, intraradices, respectively, The stimulatory activ ity of biochanin A studied at concentrations ranging from 0.01 to 10.0 mu M shows an estimated ECS, value of 3.26 mu M The present results s how that 17 beta-estradiol and biochanin A exert similar stimulatory e ffects in G, intraradices. The agonist effect of biochanin A was effic iently suppressed by the new antiestrogen EM-652, which is also consis tent with the possible presence of estrogen-binding sites in AM fungi.