Project description:Colletotrichum gloeosporioides, a widely distributed economically important agent in postharvest fruit disease thrives by massive secretion of ammonia to alkalize its environment and activate its pathogenicity genes. We sequenced the C. gloeosporioides transcriptomes of WT and a M-bM-^HM-^FpacC mutant, a major gene regulator under changing pH, under pH 7.0 in order to examine pacC regulation. Transcriptome analysis of the M-bM-^HM-^FpacC strain showed that 468 and 458 genes were up or down regulated, respectively. Both the up and down regulated genes were clustered into similar functions including: transporters to maintain cellular homeostasis, cell wall degrading enzymes to optimize pathogenicity and GATA-like transcription factors. Suggesting that activation of pacC under alkaline condition regulates genes expression to fit their optimal PKa. The transcript level predictions were verified by growth in different pH and fruit infection. Further analyses showed pacC binding sites were over-represented in the promoters of the pacC up-regulated genes but not in the promoters of the down-regulated genes, where instead, GATA-like binding sites were prominent. Evolutionary conservation of pacC control was sought by examining the gene orthologs in 5 fungal genomes whose members display contrasting alkaline or acidifying pathogenicity strategies. The results showed that irrespective of pathogen colonization strategy, only orthologs of up-regulated genes showed over-representation of pacC binding sites. Significantly, the down regulated orthologs revealed cross-genome over-representation of GATA transcription factor binding sites. Thus, pacC is a phylogenetically conserved fungal mechanism exerting dual pH control for maintaining homeostasis and pathogenicity in changing environments. Examination of C. gloeosporioides WT and a M-bM-^HM-^FpacC mutant grown under pH 7.0
