pH effect on strain-specific transcriptomes of the take-all fungus

The soilborne fungus Gaeumannomyces graminis var. tritici (Ggt) causes the take-all disease on wheat roots. Ambient pH has been shown to be critical in different steps of Ggt life cycle such as survival in bulk soil, saprophytic growth, and pathogenicity on plants. There are however intra-specific variations and we previously found two types of Ggt strains that grow preferentially either at acidic pH or at neutral/alkaline pH; gene expression involved in pH-signal transduction pathway and pathogenesis was differentially regulated in two strains representative of these types. To go deeper in the description of the genetic pathways and the understanding of this adaptative mechanism, transcriptome sequencing was achieved on two strains (PG6 and PG38) which displayed opposite growth profiles in two pH conditions (acidic and neutral). PG6, growing better at acidic pH, overexpressed in this condition genes related to energy production and protein deubiquitination. In contrast, PG38, which grew better at neutral pH, overexpressed in this condition genes involved in fatty acids metabolism. This strain also expressed stress resistance mechanisms at both pH, to assert a convenient growth under various ambient pH conditions. These differences in metabolic pathway expression between strains at different pH might buffer the effect of field or soil variation in wheat fields, and explain the success of the pathogen.