研究了Cre/loxP系统在转化细胞水平上删除转基因水稻中抗性标记基因的可行性和效率。采用农杆菌介导法将Cre/loxP标记基因剪切系统载体pNCG导入水稻细胞，用G418筛选法获得水稻抗性愈伤组织后，在组织培养不同阶段的培养基中添加25 μmol/L雌激素进行Cre基因的诱导表达和标记基因的剪切，PCR检测T0植株中标记基因nptⅡ、重组酶基因Cre和目标基因gusA的整合情况。将扩增结果为gusA（+）/nptⅡ（-）/Cre（-）的转基因植株统计为标记基因剪切成功的植株。结果表明，在抗性愈伤组织培养的预分化前、预分化和分化阶段添加雌激素诱导表达重组酶Cre均能成功切除标记基因序列，标记基因剪切成功率为6.82%~46.43%。在预分化前采用液体培养基添加雌激素诱导处理愈伤组织3 d，T0植株中标记基因的剪切效率高达173.33%，主要原因是雌激素处理提高了愈伤组织绿苗分化率。直接在分化培养基中添加雌激素诱导处理,T0植株中标记基因剪切成功率达46.43%，剪切效率（144.44%）也较高。表明雌激素诱导的Cre/loxP系统能在水稻抗性愈伤组织水平上实现对标记基因序列高效快速删除。
The feasibility and the efficiency of excision of marker genes in transgenic rice were studied at transformed cell level by using the Cre/loxP system. The vector pNCG including estrogeninduced Cre/loxP marker gene excision system was introduced to rice cell via Agrobacteriummediated transformation. After the resistant calli were screened out under G418 selection， the Cre gene expression was induced to excise the marker gene by adding 25 μmol/L estrogen to the medium at different stages of tissue culture. The integration of marker gene nptⅡ, recombinase gene Cre and target gene gusA in regenerated transgenic rice plants was analyzed by PCR. The plantlet of gusA（+）/nptⅡ（-）/Cre（-） in PCR test were calculated as transgenic plants with excision successful. Results showed that marker gene sequences could be excised successfully by estrogen induction at three tissue culture stages including before predifferentiation, predifferentiation and differentiation. The frequency of marker gene excision ranged from 6.82% to 46.43%. When transformed calli were treated by estrogen in liquid medium for 3 d before predifferentiation，the efficiency of marker gene excision in T0 transgenic rice plants was as high as 173.33%, mainly because the estrogen treatment improved the green plant regeneration frequency of calli. When estrogen was directly added to differentiation medium for induction treatment, the frequency of marker gene excision in T0 transgenic rice plants was 46.43% with a higher efficiency of marker gene excision （144.44%）. The results confirmed that marker gene sequences in transgenic rice plants could be excised efficiently and quickly by using the Cre/loxP system under estrogeninduced treatment at resistant calli level.
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