Effect of cDNA fragments in different length derived from Potato Virus Y coat protein gene on the induction of RNA-mediated virus resistance

We have reported that cDNA derived from entire coat protein (CP) gene of potato virus Y (PVY) could induce resistance to PVY infection in transgenic tobacco plants, and the resistance was further demonstrated to be RNA-mediated rather than coat protein-mediated. In this study, we cloned cDNA fragments of 202 bp, 417 bp, and 603 bp in length derived from the 3′ end of the PVY CP gene, and the cDNA fragments were introduced into tobacco (var. NC89) plants via Agrobacterium-mediated transformation system. The results of resistance assay showed that the CP cDNA fragments of 417 bp and 603 bp could confer resistance of the trans-genic plants to PVY infection, but the fragment of 202 bp in length could not. Molecular analysis revealed that the resistance was RNA-mediated, which is believed to be a result of post-transcriptional gene silencing. The results indicate that the length of cDNA fragments needed for resistance induction was located somewhere between 202 bp and 417 bp from the 3′ end of PVY CP gene.

植物抗病毒基因工程研究进展

为了得到抗病毒的寄主植物,很多学者进行了大量研究,形成了许多行之有效的抗病毒育种策略。利用来源于病毒自身基因的一些抗病毒策略(Pathogen-derived resistance,PDR),如病毒外壳蛋白基因,复制酶基因,反义RNA、移动蛋白基因等,均可以获得一些抗病毒植物。近年来,对RNA介导的抗病毒策略机制进行了深入研究。基因沉默的发现使得人们对植物和病毒的相互关系有了一个新的认识。转录后基因沉默(Post-transcriptional gene silencing,PT-GS)现象是植物抵御病毒入侵,保持自身基因组完整性的一种防御机制。对于PTGS产生的机理,已经提出不少模型,但是都未能较全面地解释基因沉默中出现的各种实验现象。对转录后基因沉默的特点、发生机理和作为抗病毒防卫机制,在改良植物抗病性方面的应用和进展进行了综述。