摘要
以用农杆菌介导法育成的日本晴等 3个品种 (系 )的转基因水稻为材料 ,对外源基因的分离情况进行了研究。这几份转基因水稻都携带串联排列的抗虫基因cry1Ab和报告基因gusA等基因。在自交后代中 ,cry1Ab和gusA协同分离 ,但阳性植株与阴性植株之比都显著小于 3∶1,阴性植株显著偏多。以杂合转基因植株 (gusA/ - )作母本植株 ,与常规品种 (- / - )杂交所得测交F1,阳性植株 (+/ - )和阴性植株 (- / - )的比例基本符合 1∶1。在反交时 ,阴性植株与阳性植株之比显著大于 1∶1的比例。比较日本晴转基因后代中gusA阳性株与阴性株的结实率发现 ,前者的结实率显著低于后者。综合上述结果可以看出 ,携带crylAb等转基因的花粉存在竞争劣势 ,可能是导致外源基因异常分离的主要原因。
The segregation mode of transgenes was investigated in the transgenic progenies of three rice varieties (lines) produced by Agrobacterium mediated transformation. The transgenic lines all contained the Bacillus thuringiensis cry1Ab gene, under the control of a maize ubiquitin promoter, and linked in tandem with gusA and hpt genes. PCR analysis showed the transgenes cry1Ab and gusA co segregated in all selfed and crossed progenies tested. Therefore, GUS bio assay of leaf or endosperm tissues was used to monitor transgene segregation in the experiment. It was found that the ratio of positive to negative plants was significantly smaller than 3∶1 in all heterozygous plants derived progenies, which implied the segregation biased from typical Mendelian mode for a single dominant gene. Less GUS positive plants, and consequently less homozygous transgenic lines than expected were recovered from the selfed progenies. Transgenic heterozygous plants (+/-) were crossed as female or male parent to conventional rice varieties (-/-), and the ratio of gusA positive (+/-) to negative (-/-) plants was investigated in test F 1 population. When used as female parent, the segregation fit to 1∶1, but significantly smaller than 1∶1 when used as male parent. The seed set of transgenic Nipponbare progeny was investigated individually for GUS positive and negative plants. It was found that the positive plants had an average seed set of 64.5%, significantly lower than that of negativeplants (77.9%). The biological and genetic basis of distorted segregation of transgenes was discussed and deduced on the basis of above results, and the authors are inclined to ascribe these phenomena to the poor competitive ability of pollens carrying transgenes.
基金
国家科技部转基因植物专项 (J2 0 0 0 B 0 0 9)
美国洛克菲勒基金 (RF990 0 1#3 74FS0 2 0 )
霍英东高校青年教师基金共同资助 ~~
