ID1 and infection: The role of modulating sugar metabolism/transport in infection is exemplified in that soluble sugar content of maize (Zea mays) leaves is greatly altered during infection by the biotrophic pathogen Ustilago maydis (Doehlemann et al., 2008; Horst et al., 2008) and maize mutants with defects in sugar accumulation (id1: indeterminate1; increased accumulation of sucrose) or starch metabolism (su1: sugary1; altered starch metabolism) display reduced susceptibility to U. maydis infection (Kretschmer et al., 2017).