Characterization of a β-1,3-glucanase from citrus fruit as related to chilling-induced injury and ethylene production

We report the identification of a full-length cDNA encoding an acidic class III β-1,3-glucanase (CrGlcQ) from the flavedo of the chilling-sensitive ‘Fortune’ mandarin. By using heterologous expression of the CrGlcQ cDNA in Escherichia coli, we showed that it encoded a protein with glucanase but not antifreeze activity. Accumulation of the CrGlcQ mRNA appears to be linked to chilling-induced damage occurring during holding of fruit at a chilling temperature (2 °C). The CrGlcQ transcript was also up-regulated by mechanical wounding and by exogenous ethylene at low temperature, which reduced chilling injury (CI). This result suggests that the CrglcQ gene may play a role in reducing chilling-induced peel damage in citrus fruit. Furthermore, the induction of this gene in wounded fruit appears to be dependent on ethylene but also on an ethylene-independent signal associated with mechanical damage.