Molecular cloning, characterization and expression analysis of a pacC homolog in the mycoparasite Coniothyrium minitans

Abstract

Coniothyrium minitans is a mycoparasite and a promising biocontrol agent of Sclerotinia sclerotiorum, an omniovorous plant pathogenic fungus. Our previous studies indicate that mycoparasitism and antibiosis of C. minitans are greatly affected by ambient pH, implying that a pH-regulatory system may exist in C. minitans. In this study, we cloned a putative pH-responsive transcription factor gene, cmpacC, from strain Chy-1 of C. minitans. The full-length DNA sequence of cmpacC (GenBank Acc. No. FJ176399) has one open reading frame (ORF) and two introns. cmpacC putatively encodes a polypeptide with 596 amino acid residues (GenBank Acc. No. ACN43303). The sequence of this polypeptide has three conserved zinc finger domains. Meanwhile, a 2,740 bp-long 5′ flanking sequence of cmpacC was obtained. It contains five copies of PacC binding sequences (5′-GCCAAG-3′). Real-time RT-PCR analysis indicated that with the increase of ambient pH from 3 to 8, expression of cmpacC, as well as the chitinase gene (cmch1) and the β-1,3-glucanase gene (cmg1), increased consistently in C. minitans. Cloning of cmpacC from C. minitans suggests that the conserved pH-dependent signaling pathway might exist in C. minitans. It provides a clue for further deciphering of the pH-regulatory mechanism responsible for the pH-associated interaction between C. minitans and S. sclerotiorum.