FIG 4 .

A derived, high-frequency nonsynonymous variant in pp4 is associated with the expression level of a novel putative ammonium sensor. (A) The top panel shows an amino acid alignment of a region of the putative protein phosphatase PP4, in which the major allele among Louisiana strains of N. crassa (N_crassa_LA) encodes a glycine at residue 177, whereas the major allele among Caribbean isolates (N_crassa_CARIB) and the sequence in other Sordariomycetes encodes an aspartate. The inset shows allele frequencies of the aspartate and glycine alleles in the Louisiana and Caribbean N. crassa populations. (B) Each column reports the expression of Nc_nmr6 (NCU00789) across Louisiana N. crassa strains harboring the indicated allele at the PP4 variant in panel A. The Nc_nmr6 expression level associated at modest significance with the pp4 genotype across Louisiana strains (nominal P = 0.0001; Benjamini-Hochberg-corrected P = 0.12). Symbols are as in Fig. 2.