EXPRESSION OF ANIMAL INTERFERON(FN) SYSTEM-LIKE METABOLISM IN PLANTS AND MOLECULAR ANALYSIS OF ANTI-VIRAL MECHANISM IN TRANSGENIC PLANTS INTRODUCED INF-RELATING GENES.

本实验旨在证实病毒感染植物是否诱导哺乳动物干扰素（IFN）系统样代谢。对黄瓜花叶病毒（CMV）感染的豇豆和烟草花叶病毒（TMV）感染的n基因烟草的坏死局部病变叶片提取物进行Western blotting分析，均未检测到任何阳性信号。为检测IFN诱导动物细胞中2,5-寡聚腺苷酸合成酶（2,5- as）和蛋白激酶（PX）的发生情况，以哺乳动物2,5- as和PK cdna为探针，采用Northern杂交技术对植物提取物进行分析。提取物中未检测到2,5- as和PK mrna。使用灵敏的放射免疫试验也检测了2,5 AS的活性，但未观察到明显的活性。结果表明，植物中不存在哺乳动物干扰素样代谢系统。将人2,5- as cDNA导入烟草（Nicotiana tabacum cv.）。Samsun NN)植物的农杆菌介导转化。转基因植株表达2,5- as mRNA，但不表达2,5- as蛋白。而转基因植株对巨细胞病毒和TMV表现出抗性。抗性可能是由2,5- as mRNA与病毒RNA的共抑制引起的。另一方面，引入ifn诱导的PK cDNA的转基因烟草植株也表现出对这两种病毒的抗性。在这种情况下，在转基因植株中既没有检测到PK- mrna，也没有检测到PK，这表明外源cDNA整合到宿主DNA的间接机制引起了抗性。如上所述，证实植物中不存在干扰素样代谢，引入IFN相关酶基因的转基因植物产生病毒抗性的机制与IFN系统不同。

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.