Primary structure of a hormonally regulated β-glucanase of Nicotiana plumbaginifolia

A cDNA clone for a hormonally regulated β-glucanase from Nicotiana plumbaginifoliahas been isolated by using an oligodeoxynucleotide probe, synthesized to match the previously determined N-tenninal amino acid sequence. The cDNA has the complete sequence of the mature protein and contains at least part of a hydrophobic signal peptide. At the amino acid level, the β-glucanase of N. plumbaginifoliais 73% homologous to a β(l,3)-glucanase from tobacco and 52% homologous to a β(1,3;1,4)-glucanase from barley. Southern-blot analysis clearly demonstrated that N. plumbaginifoliacontains at least two related genes encoding β-glucanase. The extent of the complete signal peptide of the cloned β-glucanase was determined by sequencing part of the corresponding gene. Northern analysis showed that the expression of the β-glucanase gene is influenced by auxins and cytokinins.