Identification of the Main Regulator Responsible for Synthesis of the Typical Yellow Pigment Produced by Trichoderma reesei

Abstract

The industrially used ascomycete Trichoderma reesei secretes a typical yellow pigment during cultivation, while other Trichoderma species do not. A comparative genomic analysis suggested that a putative secondary metabolism cluster, containing two polyketide-synthase encoding genes, is responsible for the yellow pigment synthesis. This cluster is conserved in a set of rather distantly related fungi, including Acremonium chrysogenum and Penicillium chrysogenum. In an attempt to silence the cluster in T. reesei, two genes of the cluster encoding transcription factors were individually deleted. For a complete genetic proof-of-function, the genes were reinserted into the genomes of the respective deletion strains. The deletion of the first transcription factor (termed yellow pigment regulator 1 [Ypr1]) resulted in the full abolishment of the yellow pigment formation and the expression of most genes of this cluster. A comparative high-pressure liquid chromatography (HPLC) analysis of supernatants of the ypr1 deletion and its parent strain suggested the presence of several yellow compounds in T. reesei that are all derived from the same cluster. A subsequent gas chromatography/mass spectrometry analysis strongly indicated the presence of sorbicillin in the major HPLC peak. The presence of the second transcription factor, termed yellow pigment regulator 2 (Ypr2), reduces the yellow pigment formation and the expression of most cluster genes, including the gene encoding the activator Ypr1.IMPORTANCE Trichoderma reesei is used for industry-scale production of carbohydrate-active enzymes. During growth, it secretes a typical yellow pigment. This is not favorable for industrial enzyme production because it makes the downstream process more complicated and thus increases operating costs. In this study, we demonstrate which regulators influence the synthesis of the yellow pigment. Based on these data, we also provide indication as to which genes are under the control of these regulators and are finally responsible for the biosynthesis of the yellow pigment. These genes are organized in a cluster that is also found in other industrially relevant fungi, such as the two antibiotic producers Penicillium chrysogenum and Acremonium chrysogenum. The targeted manipulation of a secondary metabolism cluster is an important option for any biotechnologically applied microorganism.

Enhancing peptaibols production in the biocontrol fungus Trichoderma longibrachiatum SMF2 by elimination of a putative glucose sensor

“…In addition to tlx1 and tlx2 , the upregulated geneset includes two putative PKS encoding genes, one putative NRPS encoding gene, one putative hybrid PKS/NRPS encoding gene, and one putative terpenoid synthase encoding gene. Of particular note, two genes (SMF2FGGW_102078 and SMF2FGGW_102079) encoding putative PKSs that are close homologues of SOR1 and SOR2, two PKSs responsible for the synthesis of yellow pigment in T. reesei (Derntl et al, ; Derntl, Rassinger, Srebotnik, Mach, & Mach‐Aigner, ), show dramatic decreased expression in the Δ Tlstp1 strain, which is in accordance with the remarkable reduction of yellow pigment in the culture supernatant of Δ Tlstp1 (Figure S3). In addition to these two genes, another two genes encoding a putative PKS and a putative NRPS with unknown products are also downregulated in the absence of Tl STP1.…”

Transcription factor Xpp1 is a switch between primary and secondary fungal metabolism

“…The industrially used, cellulase-producing fungus T. reesei secretes a typical yellow pigment on a range of carbon sources (35)(36)(37). The pigment is a mixture of different sorbicillin derivatives, of which biosynthesis results from a gene cluster that is present in a range of not closely related ascomycetes (38,39). However, in a previous study, we cultivated an xpp1 deletion strain and its parent strain on carboxymethylcellulose (CMC) to determine the expression levels of cellulases (33).…”

“…To learn whether Xpp1 regulates the expression of the sorbicillin cluster genes, we compared the expression of Yellow pigment regulator 1 (Ypr1), the main regulator of the cluster (39), in the xpp1 deletion strain with its parent strain. The elevated ypr1 transcript levels in the xpp1 deletion strain (Fig.…”

“…‡ Homolog of P. chrysogenum SorB, which is involved in sorbicillin biosynthesis (38,39). § Homolog of P. chrysogenum SorA, which is essential for sorbicillin biosynthesis (38,39). 73621 from the sorbicillin cluster were increased in the xpp1 deletion compared with the parent strain (Fig.…”

“…The expression levels of the gene coding for PKS (35). ‡ Homolog of P. chrysogenum SorB, which is involved in sorbicillin biosynthesis (38,39). § Homolog of P. chrysogenum SorA, which is essential for sorbicillin biosynthesis (38,39).…”