Molecular evidence that the asexual industrial fungus Trichoderma reesei is a clonal derivative of the ascomycete Hypocrea jecorina.

Abstract

The relationship of the important cellulase producing asexual fungus Trichoderma reesei to its putative teleomorphic (sexual) ancestor Hypocrea jecorina and other species of the Trichoderma sect. Longibrachiatum was studied by PCR-fingerprinting and sequence analyses of the nuclear ribosomal DNA region containing the internal transcribed spacers (ITS-1 and ITS-2) and the 5.8S rRNA gene. The differences in the corresponding ITS sequences allowed a grouping ofanamorphic (asexual) species of Trichoderma sect. Longibrachiatum into Trichoderma longibrachiatum, Trichoderma pseudokoningii, and Trichoderma reesei. The sexual species Hypocrea schweinitzii and H. jecorina were also clearly separated from each other. H. jecorina and T. reesei exhibited identical sequences, suggesting close relatedness or even species identity. Intraspecific and interspecific variation in the PCR-fingerprinting patterns supported the differentiation of species based on ITS sequences, the grouping of the strains, and the assignment of these strains to individual species. The variations between T. reesei and H. jecorina were at the same order of magnitude as found between all strains ofH.jecorina, but much lower than the observed interspecific variations. Identical ITS sequences and the high similarity of PCRfingerprinting patterns indicate a very close relationship between T. reesei and H. jecorina, whereas differences of the ITS sequences and the PCR-fingerprinting patterns show a clear phylogenetic distance between T. reesei/H. jecorina and T. longibrachiatum. T. reesei is considered to be an asexual, clonal line derived from a population of the tropical ascomycete H. jecorina.Trichoderma reesei is an asexually reproducing filamentous fungus. Isolated in the Solomon Islands during World War II from cotton canvas, the species is unique because it is known only from a single isolate (QM6a). This isolate is renowned for its high ability to produce cellulases and it is the sole progenitor of the many mutants currently in use (1). T reesei is not known to undergo recombination through meiosis. Many deuteromycetes are permanently sexually incompetent (2, 3) and possibly clonal derivatives of life cycles that once included a meiosis, some aspect of an outcrossing mating system having been perturbed. Because Trichoderma is a genus of special economic interest-individual species are used in biological control (4, 5), in the production of cellulolytic and other hydrolytic enzymes (6, 7), and in antibiotics (8)-the identification of a teleomorph (sexual state) would be useful. The ability to recover meiotic progeny would provide a means to study biological properties using classical genetics, an approach that has proven invaluable in the study of the molecular biology of Neurospora crassa and Aspergillus nidulans (9). Further, teleomorphs are powerful predictors of taxonomic relationships, and related species can be expected to possess similar biological abilities. The question thus arises whether T. reesei, and many other fungi of economic i...

Examination of Trichoderma phylogenies derived from ribosomal DNA sequence data

“…Further to this, Muthumeenakshi et al (1998) recently proposed that their Th1 isolates corresponded to the neotype T. harzianum strain, based on ITS1 sequence similarity. With respect to the other species investigated, T. atroviride M1057, OG3, TTS, M1037, HPP1, TBHPP7, D and D74 all shared 100 % ITS sequence similarity with three other T. atroviride isolates (GenBank X93948, X9394, Z48817), three isolates referred to as T. harzianum\atroviride (Kuhls et al, 1996) and a biocontrol T. harzianum strain LC1 (Schlick et al, 1994). Of these, the T. harzianum isolates have since been reidentified as T. atroviride (W. Gams, pers.…”

Aspartyl protease from Trichoderma harzianum CECT 2413: cloning and characterization The GenBank/EMBL/DDBJ accession number for the sequence reported in this paper is AJ276388.

“…Other bands that hybridized weakly indicated variable degrees of sequence conservation. These sequences were present both among genes of various Trichoderma species, including Hypocrea jecorina, the sexual form of T. reesei (Kuhls et al, 1996) and among other genes (probably proteaseencoding genes) present in T. harzianum CECT 2413. (Fig.…”

Phosphorylation Positively Regulates DNA Binding of the Carbon Catabolite Repressor Cre1 of Hypocrea jecorina(Trichoderma reesei)

“…Trichoderma reesei, the anamorph of the ascomycete H. jecorina (25), is an industrially important producer of cellulases and hemicellulases and Cre1-dependent carbon catabolite repression has been demonstrated for some of these genes (26 -28). Using H. jecorina as a model for Cre1 regulation, we will show in this paper that Cre1 is indeed a phosphoprotein, but that both the kinase phosphorylating H. jecorina Cre1, as well as the effect of phosphorylation, are different from that known for S. cerevisiae.…”