Fig. 5.

Schematic visualization of the four main evolutionary scenarios postulated to affect the evolution of PCWDEs in plant pathogenic fungi (yellow circles). Different hosts are represented by different leaf shapes. Different symbols indicate PCWDEs belonging to the same gene family and colors represent different alleles (protein variants) of a specific gene. 1) Life cycle specialization: Members of the same gene family are preferentially expressed at different stages of the pathogen life cycle. 2) Host adaptation: Purifying selection for different protein variants of the same gene on different hosts. 3) Host evasion: Recognition of a specific protein (blue) by the host and subsequent diversifying selection on the same protein to evade recognition. 4) Conserved substrate optimization: Purifying selection for the same optimized protein variant on different hosts.