Isolation and sequencing of an endopolygalacturonase gene in Trichoderma virens

Fungi belonging to the genus Trichoderma are ubiquitous organisms commonly present in the soil. They play an important role in biological control thanks to their advantageous ecological and physiological properties: a good environmental fitness and a high antagonistic ability against soil microorganisms. The latter include the ability to exploit competitively many different nutritional sources and mycoparasitism. Trichoderma spp. produce a large array of antibiotics and degrading enzymes allowing them to inhibit or to parasitize other fungi, including plant pathogens. Recently some new features of these fungi have been described: Trichoderma isolates are able to establish a symbiotic-like association with plants by colonizing their roots, so promoting plant growth and inducing localized and systemic resistance towards several phytopathogenic fungi. In order to effectively colonize roots and to exploit dead plant material in the rhizosphere, plant cell wall degrading enzymes, such as endopolygalacturonases (endo-PG), are critical. The aim of this study was to isolate and to sequence a gene coding for endopolygalacturonase in Trichoderma. A small genic region has been identified by PCR with degenerate primers in a T. virens isolate (I10) and it has been extended on both sides by TAIL-PCR. A genomic region 2647 bp long has been cloned and its sequence has been determined. Sequence analysis by BLAST programs confirmed its endoPG nature. Alignments with all fungal endoPG genes available in databases allowed the identification of the full T. virens coding sequence, with an extra stretch on both sides: 1185 bp in 5’, 84 bp in 3’ flanking the coding region. Endo-PG sequences are not available in databases for species belonging to this genus, therefore this is the first full endoPG gene sequence in a Trichoderma species. The complete endo-PG sequence from T. virens can be a starting-point for a number of purposes including the study of the nature of the symbiotic relationship between Trichoderma and plants and could open new perspectives for exploiting Trichoderma as an inducer of plant resistance.