Ym. Chen et Rn. Strange, PRODUCTION OF A PROTEINACEOUS PHYTOTOXIN BY ASCOCHYTA-RABIEI GROWN INEXPRESSED CHICKPEA SAP, Plant Pathology, 43(2), 1994, pp. 321-327
Production of the solanapyrone toxins by Ascochyta rabiei is nutrient
dependent. When grown on a medium consisting entirely of expressed sap
from the aerial parts of young chickpea plants (PSM), only low concen
trations of the solanapyrones were produced (<24 mu M). However, toxic
ity of 4-day-old culture filtrates to isolated cells of chickpea leafl
ets was comparable with that obtained from 12-day-old culture filtrate
s on Czapek Dox nutrients supplemented with chickpea seed extract or c
ations-media that are conducive to solanapyrone production. The additi
onal toxic component which peaked at 4 days in culture was heat labile
, losing about 50% of its activity on boiling for 10 min. Affinity for
solid-phase extraction media, precipitation with ammonium sulphate an
d acetone, ionization properties and UV absorption characteristics sug
gested that the toxin was a polypeptide. The toxin was purified by sol
id-phase extraction, acetone precipitation and high performance liquid
chromatography (HPLC) on a C2 column. Hydrolysis of the purified toxi
n yielded 14 amino acids, and calculation of the numbers of residues o
f each amino acid suggested a molecular mass of 7,551 Da. A band corre
sponding to this molecular mass was present on SDS-PAGE gels. However,
both the native peptide and its hydrolysate contained a compound that
reacted with p-anisaldehyde suggesting the possibility of a glycosidi
c moiety.