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.