Submitted to: Molecular and General Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 1998
Publication Date: N/A
Interpretive Summary: Fruit growth and ripening are controlled be the interaction of several signaling compounds (plant hormones), the most important of which are auxin and ethylene. Reduction in auxin levels toward the end of fruit growth results in a rapid rate of the biochemical processes known as ripening. In order to develop the technology to alter auxin levels in fruit, the gene for a bacterial enzyme that releases free auxin from bound forms was cloned and the gene put into another bacterium that then acquired the new activity. These findings will be important for the development of improved genetic traits for the production of tomato fruit with better ripening and postharvest qualities. These results will be useful to plant biochemists, plant breeders and molecular biologist interested in improving the quality and ripening characteristics of tomato and to consumers interested in the potential for obtaining variety improvements.
Technical Abstract: A 5.5 kb DNA fragment containing the indole-3-acetyl-aspartic acid (IAA-asp) hydrolase gene (iaaspH) was isolated from Enterobacter agglomerans strain GK12 using a hybridization probe based on the protein's N-terminal amino acid sequence. The DNA sequence of a 2.4 kb region of this fragment was determined and revealed a 1311 nucleotide open reading frame large enough to encode the 45 kDa IAA-hydrolase. A 1.5 kb DNA fragment containing iaaspH was sub cloned into the E. coli expression plasmid pTTQ8. Extracts from IPTG-induced Escherichia coli cultures containing the pTTQ8-iaaspH recombinant plasmid showed IAA-asp hydrolase levels 5-10-fold higher than those from E. agglomerans extracts. Homology searches reveled that the IAA-asp hydrolase was similar to a variety of amidohydrolases. In addition, IAA-asp hydrolase had a 70 percent amino acid identity to a hypothetical thermostable carboxypeptidase of E. coli.