Ministry of Agriculture Key Laboratory of Crop Physiology, Ecology and Cultivation (The Middle Reaches of Yangtze River), Huazhong Agricultural University, Wuhan, Hubei, China.
PLoS One. 2018 Mar 29;13(3):e0195058. doi: 10.1371/journal.pone.0195058. eCollection 2018.
Genetic modification of Cry-proteins from Bacillus thuringiensis (Bt) is a common practice in economically important crops to improve insecticide resistance and reduce the use of pesticides. However, introduction of these genes can have unintended side effects, which should be closely monitored for effective breeding and crop management. To determine the potential cause of these negative effects, we explored assimilate partitioning in the transgenic Bt rice line T1c-19 (Cry1C*), which was compared with that of its wild-type counterpart Minghui 63 (MH63) under different potassium fertilization application treatment conditions. In a pot experiment, 0, 0.4, and 0.6 g K2O was applied per kg of dry soil to determine the phloem transport characteristics of the two rice lines. We used a variety of assessment indicators ranging from morphological to physiological aspects, including the number of large and small vascular bundles in the neck internode at the heading stage, the diameter and bleeding intensity of the neck internode at the filling stage, and the content and apparent ratio of transferred non-structural carbohydrates (NSC) in the culm and sheath from the heading to maturing stages. The K utilization and grain yield at the maturing stage were also concerned. Results presented that the mean setting rate and grain yield of T1c-19 (Cry1C*) decreased by 22.3% and 26.2% compared to those in MH63, respectively. Compared to MH63, the K concentration and accumulation were significantly higher in the culms and leaves, but significantly lower in grain of T1c-19 (Cry1C*). T1c-19 (Cry1C*) had less apparent NSC efflux in the culm and sheath, fewer small vascular bundles, and a smaller diameter and bleeding intensity of the neck internode than MH63. In addition, linear correlation analysis indicated that there were positive correlations among grain yield, setting rate, the apparent NSC efflux in the culm and sheath, number of small vascular bundles, and the neck internode diameter and bleeding intensity. These unintended effects may directly or indirectly be caused by insertion of exogenous Bt (Cry1C*) gene, which should be further considered in the future breeding of transgenic crops.
转 Bt 杀虫晶体蛋白基因改良是提高作物抗虫性和减少农药使用的重要手段，但外源基因的导入可能会带来意想不到的副作用，因此需要密切监测，以实现有效的品种选育和田间管理。为了明确这些负面影响的潜在原因，我们以转 Bt 水稻品系 T1c-19（Cry1C*）和其野生型对照品种明恢 63（MH63）为材料，在不同施钾水平下，探讨了转 Bt 水稻的同化物分配特征。通过盆栽试验，设置 0、0.4、0.6 g K2O/kg 土 3 个施钾水平，研究了两个品系的韧皮部运输特性。我们从形态到生理等多个方面，利用多个评价指标，包括抽穗期颈节大、小维管束数，灌浆期颈节直径和伤流强度，以及从抽穗到成熟过程中茎鞘中非结构性碳水化合物（NSC）的含量和表观比值等，研究了品系的钾素利用和结实期产量。同时，我们还关注了成熟后期的籽粒产量和钾素积累。结果表明，与 MH63 相比，T1c-19（Cry1C*）的结实率和产量分别降低了 22.3%和 26.2%。与 MH63 相比，T1c-19（Cry1C*）的茎和叶中钾浓度和积累量显著增加，而籽粒中的钾浓度和积累量显著降低。T1c-19（Cry1C*）的茎和鞘中 NSC 外排表观值较低，小维管束数量较少，颈节直径和伤流强度较小。此外，线性相关分析表明，产量、结实率、茎鞘中 NSC 外排表观值、小维管束数量和颈节直径与伤流强度之间呈正相关。这些非预期的效应可能直接或间接由外源 Bt（Cry1C*）基因的插入引起，在未来的转基因作物选育中应进一步考虑。
