Nanjing Agricultural University, Nanjing, China.
Insect Biochem Mol Biol. 2010 Feb;40(2):113-8. doi: 10.1016/j.ibmb.2010.01.001. Epub 2010 Jan 14.
Transgenic cotton expressing Bacillus thuringiensis (Bt) toxins has been widely adopted to control some key lepidopteran pests including the bollworm Helicoverpa armigera. Evolution of resistance to Bt cotton by target pests is a major threat to the continued success of Bt cotton. Previous results revealed 3 null alleles (r1-r3) of a cadherin gene (Ha_BtR) conferring Cry1Ac resistance in H. armigera. An F(1) screen of 123 single-pair families was conducted between a Cry1Ac-resistant strain (the SCD-r1 strain, homozygous for the r1 allele of Ha_BtR) and field-derived insects from Jiangpu population (Jiangsu province, China) in 2008. Five new null alleles of Ha_BtR (r4-r8) were identified in six candidate single-pair families. These null alleles were created through either an insertion or a point mutation. Interestingly, intact alleles of Ha_BtR were found in two field-derived insects from another two candidate single-pair families. It suggests that these two field-derived insects may carry novel resistance alleles of Ha_BtR, with missense mutations resulting in a non-functional cadherin protein, or a major dominant mutation at a locus other than cadherin. The resistance allele frequency of Ha_BtR was detected at an appreciable level (0.024) in the Jiangpu population of H. armigera in 2008. Together with previous findings, a total of eight different resistance alleles of Ha_BtR were identified from three Chinese strains of H. armigera. Mutational diversity of Ha_BtR could impair DNA screening for Bt resistance allele frequency in the field, and an F(1) screen should be used routinely for monitoring cadherin-based resistance allele frequencies in H. armigera.
转 Bt 基因棉花被广泛用于防治鳞翅目害虫，包括棉铃虫。靶标害虫对 Bt 棉花产生抗性是对 Bt 棉花持续成功的主要威胁。先前的研究结果表明，棉铃虫 cadherin 基因（Ha_BtR）的 3 个无义突变（r1-r3）导致对 Cry1Ac 的抗性。2008 年，在 Cry1Ac 抗性品系（SCD-r1 品系，携带 Ha_BtR 的 r1 等位基因纯合）与来自中国江苏省江浦种群的田间昆虫之间进行了 123 个单对家系的 F1 筛选。在 6 个候选单对家系中鉴定出 Ha_BtR 的 5 个新的无义突变（r4-r8）。这些无义突变是通过插入或点突变产生的。有趣的是，在另外 2 个候选单对家系的 2 个田间昆虫中发现了 Ha_BtR 的完整等位基因。这表明这两个田间昆虫可能携带 Ha_BtR 的新的抗性等位基因，错义突变导致无功能的钙粘蛋白，或者在钙粘蛋白以外的基因座上发生主要显性突变。2008 年，在江浦种群中，Ha_BtR 的抗性等位基因频率达到了可观的水平（0.024）。结合以前的研究结果，从中国的 3 个棉铃虫种群中鉴定出了总共 8 个不同的 Ha_BtR 抗性等位基因。Ha_BtR 的突变多样性可能会损害田间 Bt 抗性等位基因频率的 DNA 筛选，因此应该常规使用 F1 筛选来监测棉铃虫中基于钙粘蛋白的抗性等位基因频率。
