Lignocellulose affects Mn2+ regulation of peroxidase transcript levels in solid-state cultures of Pleurotus ostreatus

Abstract

The effect of Mn2+ amendment on peroxidase gene expression was studied during Pleurotus ostreatus growth on cotton stalks. Four peroxidase-encoding genes were expressed differentially and in a manner different from that observed in defined media. Mn2+ affects mnp3 expression even 2 h after its addition to the cultures, suggesting a direct effect of the metal ion on expression.

FIG. 1.

The effect of Mn²⁺ amendment (73 ppm) on peroxidase gene expression of P. ostreatus grown under SSF conditions on cotton stalks. Gene expression was determined by relative RT-PCR utilizing specific primer sets for each gene. β-Tubulin gene expression was used as an internal control. Amplicons with increasing amounts (1-, 1.3-, and 1.5-fold amounts of RNA in panels a, b, and c, respectively) of mRNA template per gram of substrate, established on the basis of the linear range of the β-tubulin amplicon produced (see reference 9), are shown.

FIG. 2.

P. ostreatus mnp gene expression, 2 h after addition of Mn²⁺ (23 ppm in 1% Tween 20) to a 7-day-old culture grown on cotton stalks. Gene expression was determined using relative RT-PCR and specific primer sets for each gene as explained in the Fig. 1 legend. Since the same pattern of linear range was observed, only one RNA concentration is presented. β-Tubulin gene expression was used as an internal control. (A) Nonamended control; (B) 1% Tween 20 control; (C) Mn²⁺ amendment (23 ppm).