Co-Authors:
Clark, E., Department of Plant Genetics, ARO, Volcani Center, Bet Dagan, Israel, Department of Plant Pathology, 147 Hilgard Hall, University of California, Berkeley
Manulis, S., Department of Plant Genetics, ARO, Volcani Center, Bet Dagan, Israel
Ophir, Y., Department of Plant Genetics, ARO, Volcani Center, Bet Dagan, Israel
Barash, I., Department of Plant Genetics, ARO, Volcani Center, Bet Dagan, Israel, Department of Botany, Tel Aviv University, Tel Aviv, Israel
Gafni, Y., Department of Plant Genetics, ARO, Volcani Center, Bet Dagan, Israel
Abstract:
Erwinia herbicola pv. gypsophilae induces galls on its host, Gypsophila paniculata. A 16-kb DNA fragment derived from a 78-Md native plasmid with homology to the iaa operon of Pseudomonas syringae pv. savaslanoi was isolated from an EMBL3 library of E. h. gypsophilae, strain PD713, DNA. A 7.5-kb £coRI fragment was subcloned into pUCI 18 to generate pEGlOI. Escherichia coli DH5o cells transformed with pEGIOI produced indole-3-acetic acid (IAA) when cultured in medium supplemented with i.-tryptophan (TRP). Pcrmcabilized, transformed cells direct the synthesis of IAA from indolc-3-acetamide (IAM). The IAA biosynlhetic capability was localized to a 4.0-kb ///ndIII-£coRI fragment through subcloning and insertional inactivation. The IAA biosynlhetic genes of E. h. gypsophilae were designated iaaM and iaaH because of their structural and functional similarity to the iaaM and iaaH of P. s. savaslanoi, which encode tryptophan-2-monooxygenase and indoleacetamide hydrolase, respectively. Insertional mutations were generated in £. h. gypsophilae iaaM and iaaH. Marker-exchange mutants of E. h. gypsophilae, generated using insertionally inactivated constructs, produced the same amount of IAA in culture as the wild type. The marker-exchange mutants, which exhibited either reduction or elimination of iaaH activity, induced smaller galls than did unmodified E. h. gypsophilae.