TY - JOUR
T1 - Resistance of gibberellin-treated persimmon fruit to Alternaria alternata arises from the reduced ability of the fungus to produce endo-1,4-β-glucanase
AU - Eshel, D.
AU - Ben-Arie, R.
AU - Dinoor, A.
AU - Prusky, D.
PY - 2000
Y1 - 2000
N2 - Black-spot symptoms, caused by Alternaria alternata, developed in persimmon fruits during prolonged storage at -1°C. A preharvest treatment with gibberellic acid (GA3) extended the storage life of the fruit by delaying both black-spot development and fruit softening. Conversely, treatment of persimmon fruits with paclobutrazol (PBZ), an inhibitor of gibberellin (GA) synthesis, enhanced black-spot development and fruit softening during storage. Production of endo-1,4-β-glucanase (EC 3.2.1.4, EG) by A. alternata in culture and in the presence of cell walls from PBZ-treated fruits as the carbon source, was enhanced by 150% over production in the presence of cell walls from control fruits, whereas endoglucanase (EG) production in the presence of cell walls from GA3-treated fruits was reduced by 49% relative to controls. To determine the importance of EG in symptom development, A. alternata EG was purified from a culture-inducing medium. It had a molecular mass of 41 kDa, its optimal pH and temperature for activity were 5.5 and 47°C, respectively, and the pI was 4.3. Its K(m) and V(max) were 0.43 mg ml-4 and 18 μmol reducing groups minute per milligrams of protein, respectively. The internal sequence of a 21-mer amino acid peptide from the purified EG showed 62% similarity and 38% identity to the EG-1 of Trichoderma reesei and of T. longibrachiatum. Purified EG induced black-spot symptoms on the fruit, similar to those caused by A. alternata, whereas boiled enzyme caused only pricking signs. Our results suggest that the black-spot symptoms caused by A. alternata, in persimmon, are related to the ability of the fungus to produce EG in developing lesions.
AB - Black-spot symptoms, caused by Alternaria alternata, developed in persimmon fruits during prolonged storage at -1°C. A preharvest treatment with gibberellic acid (GA3) extended the storage life of the fruit by delaying both black-spot development and fruit softening. Conversely, treatment of persimmon fruits with paclobutrazol (PBZ), an inhibitor of gibberellin (GA) synthesis, enhanced black-spot development and fruit softening during storage. Production of endo-1,4-β-glucanase (EC 3.2.1.4, EG) by A. alternata in culture and in the presence of cell walls from PBZ-treated fruits as the carbon source, was enhanced by 150% over production in the presence of cell walls from control fruits, whereas endoglucanase (EG) production in the presence of cell walls from GA3-treated fruits was reduced by 49% relative to controls. To determine the importance of EG in symptom development, A. alternata EG was purified from a culture-inducing medium. It had a molecular mass of 41 kDa, its optimal pH and temperature for activity were 5.5 and 47°C, respectively, and the pI was 4.3. Its K(m) and V(max) were 0.43 mg ml-4 and 18 μmol reducing groups minute per milligrams of protein, respectively. The internal sequence of a 21-mer amino acid peptide from the purified EG showed 62% similarity and 38% identity to the EG-1 of Trichoderma reesei and of T. longibrachiatum. Purified EG induced black-spot symptoms on the fruit, similar to those caused by A. alternata, whereas boiled enzyme caused only pricking signs. Our results suggest that the black-spot symptoms caused by A. alternata, in persimmon, are related to the ability of the fungus to produce EG in developing lesions.
KW - Postharvest diseases
KW - Quiescent infection
UR - http://www.scopus.com/inward/record.url?scp=0033745283&partnerID=8YFLogxK
U2 - 10.1094/PHYTO.2000.90.11.1256
DO - 10.1094/PHYTO.2000.90.11.1256
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AN - SCOPUS:0033745283
SN - 0031-949X
VL - 90
SP - 1256
EP - 1262
JO - Phytopathology
JF - Phytopathology
IS - 11
ER -