Copper induces transcription of BcLCC2 laccase gene in phytopathogenic fungus, Botrytis cinerea

Laccases are one of many groups of inducible enzymes produced by the filamentous fungus, Botrytis cinerea during colonisation of host plant tissues. While the processes involved in laccase induction are not fully understood, Cupric ions (e.g. CuSO(4)) and gallic acid (GA) have been reported as laccase inducers. This study investigates laccases activities and the expression of three laccase genes (BcLCC1, BcLCC2, BcLCC3) in three B. cinerea isolates grown in laccase-inducing medium (LIM) supplemented with CuSO(4) and GA. Laccase activity in culture filtrates with CuSO(4) increased after 48 h of growth in LIM at 24°C. The induction of BcLCC2 transcription was greatest at a concentration of 0.6 mM CuSO(4), concentrations greater than 0.6 mM inhibited fungal growth. In contrast, no laccase induction was observed in the presence of GA. Liquid chromatography-mass spectroscopy (NanoLC ESI MS/MS) analysis confirmed the presence of a 63.4 kDa protein, the BcLCC2 isoform in the culture filtrate with 0.6 mM CuSO(4). Analysis of mRNA transcripts further showed BcLCC3 was also inducible and the expression of BcLCC2 and BcLCC3 was isolate-dependent. In conclusion, CuSO(4) induces a 63.4 kDa laccase in B. cinerea by induced transcription of the BcLCC2 gene.