PECTATE LYASE OF COLLETOTRICHUM-GLOEOSPORIOIDES ATTACKING AVOCADO FRUITS - CDNA CLONING AND INVOLVEMENT IN PATHOGENICITY

Polyclonal antibodies were used to study the secretion of a pectate ly ase (PL) during infection of avocado fruits by Colletotrichum gloeospo rioides. Pectate lyase was detected in decayed fruit tissue 5 days aft er fruit inoculation, concomitantly with the decrease of the preformed antifungal 1-acetoxy- 2-hydroxy-4-oxo-12,15-heneicosa diene to subfun gitoxic concentrations. A higher amount of the enzyme was detected in the leading edge of the decayed lesion than in the already decayed tis sue. As a first stage to determine the relation between PLs from C. gl oeosporiodes attacking avocado and PLs from Colletotrichum strains att acking other fruits, a cDNA encoding PL of C. gloeosporioides was clon ed and sequenced. The cloned DNA showed high homology to known pels fr om fungi, bacteria and plants. The pel gene of C. gloeosporioides hybr idized to single genomic restriction fragments from C. gloeosporioides isolated from mango and papaya fruits and Colletotrichum musae from b anana fruit. Western blot analysis of culture fluids from these pathog ens revealed one band of 38-41 kDa that specifically cross-reacted wit h antibodies raised against the pectate lyase from C. gloeosporioides isolated from avocado. Pectate lyase antibodies had no effect on spore germination, germ tube elongation or appressoria formation. However, when conidia were mixed with the antibodies prior to inoculation, symp tom development was inhibited on avocado, mango and banana fruits. The se results suggest the presence of a similar PL in Colletotrichum stra ins attacking avocado, mango, papaya and banana. The detection and inh ibition of fungal development by PL antibodies suggest the importance of this enzyme during C. gloeosporioides attack in fruits. (C) 1997 Ac ademic Press Limited.