Crown-gall-resistant transgenic apple trees that Silence Agrobacterium tumefaciens oncogenes

• Published in: Molecular breeding 2003-11, Vol.12 (4), p.283-295
• Main Authors: J. Viss, Walter, Pitrak, Jennifer, Humann, Jodi, Cook, Mike, Driver, John, Walt Ream, and
• Format: Article
• Language: English
• Subjects: aaM gene; Agrobacterium tumefaciens; Apples; Biosynthesis; Crown gall; Cytokinins; Deactivation; Double-stranded RNA; Fruit trees; Gall; Gene expression; Gene sequencing; Genomes; iaa gene; iaaH gene; iaaM gene; Inactivation; ipt gene; Malus; Molecular biology; Oncogenes; Orchards; phytohormones; Plant bacterial diseases; Plant biology; Plant cells; Plant hormones; Roots; Transgenes; Trees; Tumors; Vineyards
• ISSN: 1380-3743; 1572-9788
• DOI: 10.1023/B:MOLB.0000006805.76717.08

Crown gall disease is an economically significant problem in fruit and nut orchards, vineyards, and nurseries worldwide. Tumors on stems and leaves result from excessive production of the phytohormones auxin and cytokinin in plant cells genetically transformed by Agrobacterium tumefaciens. High phytohormone levels result from expression of three oncogenes transferred stably into the plant genome from A. tumefaciens: iaaM, iaaH, and ipt. The iaaM and iaaH oncogenes direct auxin biosynthesis, and the ipt oncogene causes cytokinin production. In contrast to other tissues, roots do not respond to high cytokinin levels, and auxin overproduction is sufficient to cause tumor growth on roots. Inactivation of iaaM abolished gall formation on apple tree roots. Transgenes designed to express double-stranded RNA from iaaM and ipt sequences prevented crown gall disease on roots of transgenic apple trees.