Intron-dependent accumulation of mRNA in Coriolus hirsutus of lignin peroxidase gene the product of which is involved in conversion/degradation of polychlorinated aromatic hydrocarbons

The homobasidiomycete Coriolus hirsutus coding sequences of a lignin peroxidase (LiP) gene (lip, containing six (I-VI) introns), a lip cDNA (lipc), and three lipc derivatives containing one (I), three (I-III), or five (I-V) introns were inserted into chromosome-integrating expression vector. These recombinant plasmids were introduced into C. hirustus monokaryotic strain. The transformant carrying the promoter-lipc-terminator cassette did not contain enough mRNA molecules to be detectable by Northern-blot analysis. On the other hand, all the transformants carrying cassettes of genomic lip and intron(s)-containing lipc sequences contained sufficient amounts of mRNAs to be easily detected by Northern-blot analysis. LiP activities in the culture supernatants of these transformants were found to be about five times as high as those of transformants carrying the lipc cassette (or no cassette). The culture supernatants of the transformants with high LiP activity showed remarkably high conversion activity toward pentachlorophenol (PCP) and degradation activity toward 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD). These results indicate that at least one intron (intron I) is required for accumulation of lip mRNA and its subsequent translational expression in C. hirsutus.