Molecular characterization and differential expression of β-1,3-glucanase during ripening in banana fruit in response to ethylene, auxin, ABA, wounding, cold and light-dark cycles

β-1,3-Glucanases (E. C. 3.2.1.39) are widely distributed enzyme among bacteria, fungi, and higher plants. Analyses of accumulation levels of β-1,3-glucanase protein in various tissues in banana have clearly indicated abundance of β-1,3-glucanase protein accumulation in ripe pulp tissue. After cloning of β-1,3-glucanase from banana pulp (cultivar Cavendish), we have carried out an in silico analysis to investigate the sequential, structural, and phylogenetic characteristics of the putative banana β-1,3-glucanase protein. As like other ripening specific genes, β-1,3-glucanase is regulated in response to a wide variety of factors. Therefore, we have analyzed the transcript accumulation pattern and protein levels of β-1,3-glucanase in response to ethylene, auxin, ABA, wounding and, low temperature in preclimacteric banana fruit. Expression profile analyses have indicated that whereas exogenous application of ethylene strongly stimulated β-1,3-glucanase transcript accumulation, ABA partially induced the expression of the gene. On the other hand, wound treatment did not induce β-1,3-glucanase expression. Conversely, auxin and cold treatment negatively regulated β-1,3-glucanase gene expression and thus inhibited glucanase activity. In addition, β-1,3-glucanase transcript level was markedly decreased by constant exposure to white light. Protein level and enzymatic activity of β-1,3-glucanase were substantially increased with considerable decrease in fruit firmness by ethylene treatment and reduced exposure to white light conditions as compared with other treatments. Together, the overall study of β-1,3-glucanase expression pattern, glucanase activity, and changes in fruit firmness during ripening in various conditions suggest the possible physiological function of β-1,3-glucanase in fruit pulp softening. © 2010 Springer-Verlag.