Figure 4.

Induced Coexpression of clp1 and rbf1 Results in Reduced rbf1-Dependent Filament Formation and Repression of the a Mating-Type Genes.

(A) Strains UKH156 (a1 Δb::P_nar1:rbf1) and UKH164 (a1 Δb::P_nar1:rbf1; P_crg1:clp1) were grown in nitrate minimal medium supplemented with glucose (clp1 not expressed) or arabinose (clp1 expressed) as sole the carbon source. In UKH156, the nitrate-induced expression of rbf1 leads to filament formation; the arabinose-induced coexpression of clp1 in UKH164 results in reduced filament formation.

(B) Quantification of filament formation in strains UKH156 and UKH164 12 h after induction of rbf1 with or without clp1 as shown in (A). N = number of cells counted.

(C) qRT-PCR analysis of mfa1 and pra1 gene expression in response to rbf1 or clp1 induction. Strains UKH156 and UKH164 and, as a control, JB1 (a1 Δb) were grown for 12 h in nitrate minimal medium supplemented with arabinose. Shown are the mean values of two technical replicates. The experiment was repeated twice with similar results. Actin and eIF2b were used for normalization. Error bars represent the sd. Expression was calculated relative to the lowest expression value.