Complete DNA sequence and analysis of a mitochondrial plasmid in the mycoparasitic Trichoderma harzianum strain T95

Abstract

A circular plasmid called pThr1, with a monomer size of 2.6 kb, was identified in the mitochondria of a Trichoderma harzianum isolate. Hybridization studies using cloned plasmids revealed no DNA sequence similarity between the plasmid and the mitochondrial genome of the isolate. The complete sequence of the plasmid was determined, and the sequence analysis revealed that it contained a single long open reading frame of 1818 bp. Sequence comparisons indicated that the derived amino acid sequence of the ORF exhibited similarity to the reverse transcriptases of the circular Mauriceville and Varkud retroplasmids of Neurospora spp. and the linear pFOXC2 and pFOXC3 retroplasmids of Fusarium oxysporum strains. In the regions of homology all of the seven conserved amino acid blocks characteristic of RTs could be found.