A novel glycine-rich/hydrophobic 16 kDa polypeptide gene from tobacco: Similarity to proline-rich protein genes and its wound-inducible and developmentally regulated expression

We have isolated a cDNA clone, NT16, encoding a novel glycine-rich/hydrophobic protein from tobacco crown gall tumor tissues, which was induced by the T-DNA genes of Agrobacterium tumefaciens. The accumulation of NT16 transcripts was high in unorganized callus as well as in shoot-forming calli. In normal tobacco plants, the transcript levels were high in roots, and low in stems, whereas virtually no transcript accumulation was found in flowers or leaves. In leaves, however, NT16 transcript accumulation was induced by mechanical wounding. These results show that NT16 expression is developmentally regulated and induced by wound-stress conditions. Sequence analysis suggests that NT16 encodes a putative 16 kDa polypeptide that is apparently composed of 3 structural domains: two hydrophobic regions separated by a glycine-rich region. The NT16 polypeptide displays similarity to a number of proteins in its hydrophobic domains, but is unique in its glycine-rich domain which, in the corresponding domains of the homologous proteins, are mostly proline-rich. Since both glycine-rich and proline-rich proteins are generally reported to be mostly cell wall proteins, the NT16 gene may be involved in shoot and root formation and in wound-healing process by modifying cell wall composition.