INTERACTION BETWEEN THE PHYTOTOXIN DOTHISTROMIN AND PINUS-RADIATA EMBRYOS

Dothistromin (DOTH) is a fungal toxin occurring in Pinus radiata needl es infected with Dothistroma pini. Dose-dependent toxicity of DOTH tow ard both I! radiata mature seed embryos and meristematic leaf callus w as observed. DOTH effected 50 and 100% inhibition of embryo and leaf c allus growth after absorbing 3 and 13 nmol of DOTH per g of tissue, re spectively. DOTH-binding sites were localized, using immunohistology f or light and electron microscopy, within small vesicles in the embryos . A 40-kDa peptide was identified in the particulate fraction of matur e embryo extracts that reacted specifically with a DOTH-mouse albumin conjugate.