Cloning and characterization of bgn16p'3, coding for a o-1,6-glucanase expressed during Trichoderma harzianum mycoparasitism

摘要

To clone and characterize the gene coding for BGN16p"3, a o-1,6-glucanase putatively implicated in mycoparasitism by Trichoderma harzianum, a biocontrol agent used against plant pathogenic fungi. Using degenerate primed PCR and cDNA library screening, we have cloned the cDNA coding BGN16p"3. bgn16p"3 showed a significant sequence identity (50%) to bgn16p"1; however, they both have low identity to the previously cloned bgn16p"2, allowing the identification of amino acid sequences putatively involved in the common catalytic activity of the three proteins. bgn16p"3 is a single-copy gene and highly homologous sequences are present in all tested Trichoderma species. bgn16p"3 expression pattern is analysed by Northern blot, finding that it is expressed during the interaction of T. harzianum CECT 2413 with Botrytis cinerea, supporting the implication of the enzyme in the mycoparasitic process. The cloned bgn16p"3 completes the knowledge on the o-1,6-glucanase isozyme system from T. harzianum CECT 2413. A highly homologous gene is present in all analysed Trichoderma strains. bgn16p"3 is expressed under few specific conditions, including the mycoparasitic process. This study contributes to the knowledge of o-1,6-glucanases. It implicates this group of enzymes in the mycoparasitism by some biocontrol agents such as T. harzianum.