Defensive glycoproteins from sugarcane plants induce hemotaxis, cytoaglutination and death of smut teliospores

Abstract

Sugarcane produces and secretes high molecular mass glycoproteins (HMMG) in response to pathogenic infections, wounds or several types of stress. The teliospores of the pathogenic filamentous fungus Sporisorium scitamineum produces smut disease in non-resistant varieties of sugarcane. Two HMMG from smut-resistant varieties of sugarcane promote teliospore chemotaxis and agglutination, respectively. However, HMMG from by non-resistant varieties do not promote teliospore aggregation. Agglutination is a lectin-dependent response from the HMMG endowed with arginase activity that also inhibits teliospore germination. Conversely, dispersal of teliospore aggregates and loss of chemotaxis are induced by other glycoproteins from resistant cultivars after prolonged contact with the chemoattractant. This is accompanied by disassembly of the cell wall protoplast leakage, which is caused by hydrolytic enzymes, such as chitinase and β-1,4- and β-1,3-glucanases. In this report, we describe agglutination as a “bait and kill” mechanism that congregates as many pathogenic organisms in a specific region to be killed by the action of a second, concerted hydrolytic switch.