Characterization of interfamilial somatic hybrids between 5-methyltryptophan-resistant (5MT-resistant) rice (Oryza sativa L.) and 5MT-sensitive carrot (Daucus carota L.) ; expression of resistance to 5MT by the somatic hybrids

Kisaka, H.; Kisaka, M.; Kameya, T.

Breeding Science 46(3): 221-226, 285


ISSN/ISBN: 1344-7610
Accession: 002775732

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The production of the asymmetric hybrid plants between 5MT-resistant O. sativa and 5MT-sensitive D. carota was reported previously. Although morphology of the somatic hybrid plants closely resembled that of the parental carrot plants, all of the somatic hybrids were resistant to 5MT. Here, the expression of resistance to 5MT in cells of these somatic hybrids is investigated. The calli induced from hybrid plants and their parents grew in a medium that contained a high concentration of 5MT when those calli were supplied with anthranilic acid or tryptophan. However, chorismic acid was not effective in reducing the inhibition of cell growth by 5MT. The activities of anthranilate synthase and tryptophan synthetase of cells of the somatic hybrids and 5MT-resistant O. sativa were about 5 times and 2 times as high as those of cells of 5MT-sensitive D. carota, respectively. These results indicated that anthranilate synthase was involved in the mechanism of resistance to 5MT. However, anthranilate synthase activities of the somatic hybrids and 5MT-resistant O. sativa were quite sensitive to feedback inhibition by tryptophan, as was that of 5MT-sensitive D. carota. Northern hybridization using a gene for anthranilate synthase as a probe revealed that levels of expression of the gene in the somatic hybrids and 5MT-resistant O. sativa were higher than in 5MT-sensitive D. carota. Furthermore, the somatic hybrids contained the gene for anthranilate synthase that originated from 5MT-resistant O. sativa. These results suggested that the resistance to 5MT in cells of the somatic hybrids was transferred from 5MT-resistant O. sativa via cell fusion.