Isolation of a cDNA encoding a 31-kDa, pathogenesis-related 5/thaumatin-like (PR5/TL) protein abundantly expressed in apple fruit (Malus domestica cv. Fuji)

A fruit-specific and pathogenesis-related 5/thaumatin-like (PR5/TL), 31-kDa protein was isolated by 2D-PAGE from fully-grown apples (Malus domestica c v. Fuji) and named Mdt11 (Malus domestica thaumatin-like protein 1). Using the N-terminal sequence of the protein, the full-length cDNA encoding Mdt11 was isolated. The cDNA clone (Mdt11) consists of 944 bp with an open readi ng frame (ORF) of 744 bp encoding a protein of 247 amino acids. The deduced amino acid sequence of Mdt11 shows high similarity to the sequences of PR5 /TL proteins. Mdt11 is a slightly acidic protein with a putative signal pep tide and a putative N-glycosylation site, and lacks a C-terminal extension. This suggests that Mdt11 is an apoplastic glycoprotein. Results of norther n blotting indicated that expressions of Mdt11 are developmentally regulate d. Southern blot analysis showed that Mdt11 may be present as a single copy , and there exist other genes closely related to Mdt11 in the apple genome.