A New approach to the practical use of insect-tolerant lines of sugar beet via foreign gene transfer

白菜粘虫（Mamestra brassicae L.）的幼虫通过食用甜菜植物的茎和叶，对甜菜根的最终产量和随后的糖产量造成严重损害。为了培育对卷心菜粘虫等昆虫具有抗性的甜菜品种，我们一直在开发含有cryIA(b)基因的转基因甜菜品系，cryIA(b)基因编码苏云金芽孢杆菌的杀虫剂蛋白。本研究在已有研究成果的基础上，以转基因甜菜品系的实际应用为目标，尝试构建具有较高杀虫剂活性的转基因甜菜品系。首先，我们将cryIC导入甜菜植株，分析其表达的影响。我们从多种候选杀虫剂蛋白基因中选择了cryIC，因为其基因产物在大肠杆菌中表达克隆基因获得的多种杀虫剂蛋白中对卷心菜粘虫的杀虫活性最高。与此同时，有报道称，将杀虫剂蛋白基因引入叶绿体，增加了蛋白质的积累，从而提高了植物的杀虫剂活性。因此，为了将杀虫剂蛋白基因导入甜菜叶绿体，我们开发了叶绿体转化的载体和转化后的叶绿体选择系统。我们还成功地引入了几个对甜菜生产实际有用的基因，并评估了基因表达的效果。此外，我们还分析了外源基因在植物细胞中表达的稳定性，以确定它们的表达。

The larvae of cabbage armyworm (Mamestra brassicae L.) bring heavy damage on the final yield of beet-roots and subsequently, sugar production, by eating stems and leaves of sugar beet plants. In order to establish sugar beet cultivars that are tolerant to insects including cabbage armyworm, we have been developing transgenic sugar beet lines harboring cryIA(b), a gene encoding insecticide protein from Bacillus thuringiensis. In the present study, based on the results so far obtained, we tried to make transgenic sugar beet lines that show increased insecticide activity aiming at practical use of the transgenic lines. First, we introduced cryIC into sugar beet plants and analyzed the effect of its expression. We chose cryIC from various candidates of insecticide protein genes, since its gene product showed highest insecticide activity against cabbage armyworm among various insecticide proteins that were obtained by expressing cloned genes in E. coli. Meanwhile, reports were published that described that the introduction of insecticide protein genes into chloroplast gave increased accumulation of the protein and consequently, gave increased insecticide activity of plants. We, therefore, developed vectors available for chloroplast transformation and selection system of transformed chloroplast in order to introduce insecticide protein genes into sugar beet chloroplasts. We also succeeded in introducing several genes practically useful for sugar beet production and evaluated the effect of gene expression. In addition, we analyzed the stability of the expression of foreign genes in plant cells in order to make sure their experssion.