Mutant identification and characterization of the laccase gene family in Arabidopsis

Laccases, EC 1.10.3.2 or p-diphenol:dioxygen oxidoreductases, are multi-copper containing glycoproteins. Despite many years of research, genetic evidence for the roles of laccases in plants is mostly lacking. In this study, a reverse genetics approach was taken to identify T-DNA insertional mutants (the SALK collection) available for genes in the Arabidopsis laccase family. Twenty true null mutants were confirmed for 12 laccase genes of the 17 total laccase genes (AtLAC1 to AtLAC17) in the family. By examining the mutants identified, it was found that four mutants, representing mutations in three laccase genes, showed altered phenotypes. Mutants for AtLAC2, lac2, showed compromised root elongation under PEG-induced dehydration conditions; lac8 flowered earlier than wild-type plants, and lac15 showed an altered seed colour. The diverse phenotypes suggest that laccases perform different functions in plants and are not as genetically redundant as previously thought. These mutants will prove to be valuable resources for understanding laccase functions in vivo.