Fu Jianmei, Liu Guoqiang, Liu Biao
Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing, China.
Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, China.
Front Plant Sci. 2021 Feb 11;12:608721. doi: 10.3389/fpls.2021.608721. eCollection 2021.
Genetic modifications in rice, which resulted in insect resistance, have been highly efficacious. However, they have also induced undesirable secondary phenotypes, such as delayed flowering. The molecular mechanisms associated with these unwanted effects remain unclear. Here, we showed that the flowering time for insect-resistant transgenic rice Huahui-1 (HH1) was delayed, compared with that for the parental rice Minghui-63 (MH63), cultivated on farmland and saline-alkaline soils. In contrast, the insect-resistant transgenic rice cultivars T1C-19 and MH63 had similar flowering times under the same conditions. We quantified the following: the expression of five major flowering genes in HH1, T1C-19, and MH63; florigen Hd3a protein expression levels in HH1 and MH63; interactions between Cry1Ab/c and the five main flowering proteins; and the effects of E3s ubiquitin ligase-mediated Cry1Ab/c expression on florigen Hd3a. Hd3a transcription was significantly lower in HH1 but not in T1C-19, compared with that in MH63. The results of yeast two-hybrid, complementary bimolecular fluorescence, and co-immunoprecipitation assays revealed that florigen Hd3a interacted with the exogenous Cry1Ab/c expressed in HH1 and not the exogenous Cry1C expressed in T1C-19. When Cry1Ab/c, Hd3a, and E3s fusion proteins were transiently co-expressed in tobacco cells, the Hd3a expression level was significantly lower than the level of Cry1Ab/c and Hd3a co-expression. Thus, the downregulation of expression and the interaction between Cry1Ab/c and Hd3a interfere with Hd3a protein expression and might cooperatively delay HH1 flowering time. To the best of our knowledge, this study is the first to explain the delay in flowering time in insect-resistant transgenic rice, mediated by interactions between exogenous and endogenous proteins. This information might help elucidate the molecular mechanisms associated with these unwanted phenotypes effects and improve the process of biosafety assessment of transgenic rice.
导致水稻产生抗虫性的基因改造已被证明非常有效。然而，这些改造也引发了一些不良的次生表型，比如花期延迟。与这些不良影响相关的分子机制仍不清楚。在此，我们发现，在农田和盐碱地上种植时，抗虫转基因水稻华恢1号（HH1）的开花时间比其亲本水稻明恢63（MH63）延迟。相比之下，抗虫转基因水稻品种T1C-19和MH63在相同条件下开花时间相似。我们对以下内容进行了量化：HH1、T1C-19和MH63中五个主要开花基因的表达；HH1和MH63中开花素Hd3a蛋白的表达水平；Cry1Ab/c与五种主要开花蛋白之间的相互作用；以及E3泛素连接酶介导的Cry1Ab/c表达对开花素Hd3a的影响。与MH63相比，HH1中Hd3a转录显著降低，但T1C-19中没有。酵母双杂交、双分子荧光互补和免疫共沉淀分析结果表明，开花素Hd3a与HH1中表达的外源Cry1Ab/c相互作用，而不与T1C-19中表达的外源Cry1C相互作用。当Cry1Ab/c、Hd3a和E3融合蛋白在烟草细胞中瞬时共表达时，Hd3a表达水平显著低于Cry1Ab/c和Hd3a共表达水平。因此，表达下调以及Cry1Ab/c与Hd3a之间的相互作用干扰了Hd3a蛋白表达，并可能共同延迟HH1的开花时间。据我们所知，本研究首次解释了抗虫转基因水稻开花时间延迟是由外源蛋白和内源蛋白之间的相互作用介导的。这些信息可能有助于阐明与这些不良表型效应相关的分子机制，并改进转基因水稻的生物安全性评估过程。
