MOLECULAR-GENETIC EVIDENCE FOR THE INVOLVEMENT OF A SPECIFIC POLYGALACTURONASE, P2C, IN THE INVASION AND SPREAD OF ASPERGILLUS-FLAVUS IN COTTON BOLLS

Isolates of Aspergillus flavus can be differentiated based on producti on of the polygalacturonase P2c. One group of isolates produces P2c, w hereas the other group does not. In general, the group that produces P 2c causes more damage and spreads to a greater extent in cotton bolls than those isolates that do not produce P2c. To determine whether P2c contributes to disease, the expression of PecA, the gene previously de termined to encode P2c, was genetically altered. Adding the pecA gene to a strain previously lacking the gene resulted in the ability to reu se significantly more damage to the intercarpellary membrane and the a bility spread to a greater extent within the adjacent locule compared to the abilities of a control transformant. Conversely, eliminating th e expression of pecA by targeted disruption caused a significant reduc tion in aggressiveness compared to that of a nondisrupted control tran sformant. These results provide direct evidence that P2c contributes t o the invasion and spread of A. flavus during infection of cotton boll s. However, other factors not evaluated in this study also contribute to aggressiveness.