Characterization of a Family of Putative Effectors from Magnaporthe oryzae

A novel 21-member gene family encoding secreted cysteine-rich proteins was identified in genome sequences of the rice blast fungus, Magnaporthe oryzae (Pyricularia oryzae).  The allelic diversity of gene family members from rice-infecting isolates is low in terms of amino acid substitutions. However, null alleles for most gene family members do occur within these populations (absence, frame-shift, pre-mature stop codons).  This suggests that selection for loss-of-function is occurring within this gene family. Most of the gene family members are expressed during infection of rice. Preliminary localization of GFP fusions suggests that different gene family members have different localization patterns, indicating specialization of the functions of the gene family members. The gene family is not present in other fungal species except for monocot-infecting isolates of Colletotrichum.  Thus, homologs of these genes are present only in fungi that are monocot-infecting foliar pathogens that produce melanized appressoria for plant penetration.