Figure 1
Identification of NCU00988 as a candidate D-galacturonic acid (D-GalA) transporter. (A) Induction of selected transporter genes after transfer for 4 h to pectin versus sucrose. The log2-fold induction of seven major facilitator superfamily (MFS)-type transporters from the most pectin-specific co-expression cluster as determined by Cuffdiff [37] is shown. Data were calculated from independent triplicate cultures. (B) Relative expression levels of the top three pectin-induced transporter genes in N. crassa as determined by quantitative PCR. Sucrose pre-grown mycelia were transferred to Vogel’s medium with 2 μM D-GalA or w/o carbon source (no carbon). Samples were taken 4 h after transfer. Relative transcript quantities (RQ) are depicted where 1 represents the transcription level on medium w/o carbon source. Only NCU00988 showed a response to the presence of D-GalA. Bars represent standard deviations (n = 3). (C) Pectin consumption phenotype. The deletion strains of the top three pectin-responsive transporters were grown for 4 days on 1% pectin and the consumption of pectin followed over time by measuring the remaining substrate concentration in the culture supernatants by the phenol-sulfuric acid method. Data represent the mean of triplicates and are plotted relative to the values at day 1 (as 100%). Only the deletion strain for NCU00988 (black triangle) displayed a strong delay in pectin consumption. WT, wild-type.