Glycoproteins of sugarcane plants facilitate the infectivity of Ustilago scitaminea and Xanthomonas albilineans, two sugar- cane pathogens

Sugarcane plants produce heterofructans composed of homofructan domains consisting of β-1,2-fructofuranoside chains which intercalate variable-length segments of polygalactitol. Sometimes, these heterofructans appear as the glycosidic moiety of glycoproteins. They are produced as a response to mechanical injuries and pathogen infections. These glycoproteins act as a defense mechanism against smut (Ustilago scitaminea) by inducing homotypic adhesion and by inhibiting teliospore germination. When smut teliospores are cultured on glycoproteins produced by resistant cultivars of sugarcane plants, the actin capping, which occurs before teliospore germination, is efficiently inhibited. Then, cell polarization is not achieved and the growth of germinative tube is completely inhibited. However, inoculation of sensitive cultivars with smut teliospores induce glycoprotein fractions that promote teliospore polarity after binding to their cell wall ligand, and are different from those obtained from resistant plants.