转不可翻译PVY^N CP基因烟草的抗病性分析

THE VIRAL RESISTANCE OF TRANSGENIC TOBACCO PLANTS CONTAINING UNTRANSLATABLE PVY ~N COAT PROTEIN GENE

我们曾报道表达不可翻译PVY^N CP基因的转基因烟草抗病性是由RNA介导的,其抗病性类似于转录后的基因沉默(PTGS)。本研究以这类不同抗性的Tn代转基因烟草植株为材料,对自交后的T1代转基因植株的遗传和抗病性进行了分析,并选取部分T_1代抗病株系自交留种。对T_2代RNA介导抗病性转基因植株进行了分子分析和一系列抗病性研究。结果表明,含1-2个转基因拷贝的T_0代感病植株,在T_1代中的Km抗性分离符合单位点插入的3∶1的遗传规律;含3个或3个以上转基因拷贝的T_0代中抗或高抗植株,在T_1代中的Km抗性分离符合多位点插入的15∶1或63∶1的遗传规律。大多数T_1、T_2代转基因植株的抗病性与转基因拷贝数成正相关,转基因在T_1、T_2代植株中能够转录表达,且转基因植株之间转基因mRNA在细胞质中的积累水平与转基因植株的抗病性成负相关。转基因植株的抗病性能够在T_1、T_2代中遗传,且T_2代转基因植株的抗病性具有以下特征:1)既抗病毒粒体又抗病毒RNA的侵染,且这种抗病性不受接种物剂量的影响;2)抗病谱较窄,只对PVY的某些株系具有高度抗病性;3)与传毒方式无关,既抗摩擦接种又抗带毒蚜虫接种;4)与植株的发育阶段没有关系。

In previous study, we have proved that the resistance of the transgenic tobacco plants containing untranslatable PVYN CP gene was mediated by PVYN CP transgene RNAs, and the resistance mechanism was similar to PTGS. In this paper, TO progeny transgenic lines with different resistant levels were selected to further study the transgene inheritance and resistant stability of transgenic plants. Results showed that TO progeny susceptible lines, which contained 1-2 transgene copies, displayed a 3:1 segregation ratio in T1 progeny lines; TO progeny middle resistant lines, which contained 3-4 transgene copies, revealed a 15:1 segergation ratio in T1 progeny lines; T0 progeny highly resistant lines, which contained 5 - 7 transgene copies, followed 15:1 or 63:1 segregation pattern in T1 progeny lines. Southern blot analysis revealed the resistance in most T1 and T2 progeny transgenic lines was related to copy numbers of the transgene. Northern blot analysis indicated that PVYN CP trans-genes were expressed at transcription level in most T1 and T2 progeny transgenic lines, and the trans-gene mRNA accumulation in cytoplasm varied among transgenic lines. There was an inverse correlation between transgene transcript accumulation and virus resistance. Resistance of transgenic lines was inheritable over at least two generations, and the resistance of T2 progeny transgenic lines, which containing untranslatable PVYN CP gene, was (1) not overcome by PVYN particle or PVYN RNA; (2) independent of inoculum levels; (3) resistant to either aphid or mechanically transmitted PVYN; (4) not dependent on plant development stages; (5) PVY-specific (i. e. , broad-spectrum resistance was not observed).