SIX1 and infection: This region contains SIX14, SIX1, SIX2, SIX3, SIX5 and SIX13. We conclude that, although all SIX genes are highly expressed during infection (van der Does et al., 2016) and the corresponding Six proteins are abundant in the xylem sap of infected tomato plants (Schmidt et al., 2013), only a subset of these proteins are required for virulence.