ITO Kumiko Tohoku University, Faculty of Agriculture, Research Assistant, 農学部, 教務職員 (10228603)
KARASAWA Akira Tohoku University, Faculty of Agriculture, Research Associate, 農学部, 助手 (90204651)
HASHIBA Teruyoshi Tohoku University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (20189476)
|Budget Amount *help
¥7,400,000 (Direct Cost : ¥7,400,000)
Fiscal Year 1996 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1995 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1994 : ¥5,500,000 (Direct Cost : ¥5,500,000)
This experiment was carried out to confirm whether or not the mammalian inteferon (IFN) system-like metabolism are induced in virus infected plants. Although the extracts from necrotic local lesion-formed leaves on cucumber mosaico virus (CMV)-infected cowpea and tobacc mosaic virus (TMV)-infected N-gene-carrying tobacco were analyzed by Western blotting with antisera of mammalian alpha, beta and gamma interferons, any positive signals were not detected. To examine the occurrence of the 2,5-oligoadenylate synthetase (2,5-AS) and protein kinase (PX) induced in animal cells by IFN in these infected plants, the extracts from the plants were analyzed by Northern hybridization using mammalian 2,5-AS and PK cDNAs as probes. 2,5-AS and PK mRNAa were not detected in the extracts. The 2,5 AS activity was also examined using the sensitive radioimmune assay, but no significant activity was observed. From the rusults, it was concluded that the mammalian interferon-like metabolic system was absent in plants. A human 2,5-AS cDNA was introduced into tobacco (Nicotiana tabacum cv. Samsun NN) plants by Agrobacterium-mediated transformation. The transgenic plants expressed the 2,5-AS mRNA,but not the 2,5-AS protein. While the transgenic plants showed resistance to CMV and TMV.The resistance is probably induced by co-suppression between 2,5-AS mRNA and virus RNA.On the other hand, the transgenic tobacco plants introduced IFN-induced PK cDNA also showed resistance to both viruses. In this case, neither PK-mRNA nor PK were detected in the transgenic plants, suggesting the resistance caused by indirect mechanism for a foreign cDNA integration in to the host DNA.
As mentioned above, it was confirmed that INF-like metabolism was not present in plants, and that virus resistance in transgenic plants introduced IFN-related enzyme genes was resulted in different mechanism from IFN system.