Molecular cloning of a genomic DNA encoding the potato beta-1,3-glucanase

A genomic clone for potato beta-1,3-glucanase was isolated to study the reg ulatory expression mechanism of the plant gene. A genomic library was const ructed with total DNA isolated from potato (Solanum tuberosum L. cv. Sumi) leaves. The genomic library was screened by plaque hybridization using the cDNA clone for tobacco beta-1,3-glucanase as a probe. The genomic clone, la mbda Glc1, for beta-1,3-glucanase was isolated from the library mapped by r estriction analysis using Southern hybridization. The Southern blot analysi s showed that a 2.3kb fragment contained the coding region for beta-1,3-glu canase. The structure of the genomic clone was determined by nucleotide seq uencing, which, together with RNA mapping with nuclease S1, showed that the cloned beta-1,S-glucanase gene (lambda GluB3) was a genomic counterpart of the beta-1,3-glucanase gene (GluB3) from a different potato cultivar (S. t uberosum L. cv. Datura) and consisted of two exons and one intron encoding a protein of 315 amino acid residues. The major transcription initiation si te of lambda GluB3 was determined by primer extension and it appeared to be at 27bp upstream of the translation initiation site. The canonical TATA bo x and AGC-enhancer elements were found in the promoter region of lambda Glu B3 and sequence comparison revealed that the relevant promoter region of la mbda GluB3 was more similar to that of tobacco than that of rice or barley.