Linear mitochondrial plasmids of Fusarium oxysporum contain genes with sequence similarity to genes encoding a reverse transcriptase from Neurospora spp

Abstract

Two linear mitochondrial plasmids called pFOXC1 and pFOXC2 from the fungus Fusarium oxysporum were previously described. DNA sequence comparisons indicated that the derived amino acid sequences of both plasmids exhibit similarity to the reverse transcriptase of the Mauriceville and Varkud plasmids of Neurospora spp. The derived amino acid sequence of pFOXC2 has 51% similarity and 32% identity to the Neurospora reverse transcriptase; sequence similarity was greatest for seven blocks of amino acids that are conserved in reverse transcriptases from a wide range of biological sources. Northern analysis suggests that full-length RNAs corresponding to the plasmids are found in representative isolates.

Expression and localization of the linear DNA plasmid-encoded protein (RS224) inRhizoctonia solaniAG2-2

“…Reverse transcriptase activity was assayed by incorporation of [α‐ 32 P]dTTP into trichloroacetic acid‐precipitable material, as described previously [3]; however, putative reverse transcriptase activity is not present in mitochondrial lysates from R. solani isolate H‐16 (unpublished data). In contrast, two linear mitochondrial plasmids (pFOXC2 and pFOXC3) of the plant‐pathogenic fungus F. oxysporum contain a single, long ORF that encodes a protein of 527 amino acids, and that is highly conserved between the two plasmids [10,17]. This ORF contains conserved amino acid sequence blocks (I–VII) characteristic of retroviral and other reverse transcriptases [11]; and pFOXC2 and pFOXC3 encode an 81‐kDa protein that has reverse transcriptase activity [17].…”