A novel tissue-specific plantain beta-1,3-glucanase gene that is regulated in response to infection by Fusarium oxysporum fsp. cubense

Abstract

A new full-length beta-1,3-glucanase cDNA, MpGlu, was isolated from a plantain (Musa paradisica) by the rapid amplification of cDNA ends (RACE) technique. Recombinant GST-MpGlu protein, expressed in E. coli, hydrolyzed (1-->3),(1-->6)-beta-glucan of Laminaria digitata and inhibited the growth of Fusarium oxysporum fsp. cubense (race 4) suggesting that it is a beta-1,3-glucanase. Southern blot analysis indicated that there is one copy of MpGlu in the plantain genome. MpGlu gene expression was detected in plantain leaves, peel, and pulp by RT-PCR. Northern blot analysis revealed that the expression of MpGlu was up-regulated by Fusarium infection. Subcellular localization analysis indicated that 28 residues at the N-terminal end are necessary for extracellular secretion, while 32 residues at the C-terminal end are necessary to target the protein into vacuoles.