Han Lanzhi, Han Chao, Liu Zewen, Chen Fajun, Jurat-Fuentes Juan Luis, Hou Maolin, Peng Yufa
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
Appl Environ Microbiol. 2014 Aug;80(16):5134-40. doi: 10.1128/AEM.01544-14. Epub 2014 Jun 13.
Chilo suppressalis and Sesamia inferens are two important lepidopteran rice pests that occur concurrently during outbreaks in paddy fields in the main rice-growing areas of China. Previous and current field tests demonstrate that the transgenic rice line Huahui 1 (HH1) producing a Cry1Ab-Cry1Ac hybrid toxin from the bacterium Bacillus thuringiensis reduces egg and larval densities of C. suppressalis but not of S. inferens. This differential susceptibility to HH1 rice correlates with the reduced susceptibility to Cry1Ab and Cry1Ac toxins in S. inferens larvae compared to C. suppressalis larvae. The goal of this study was to identify the mechanism responsible for this differential susceptibility. In saturation binding assays, both Cry1Ab and Cry1Ac toxins bound with high affinity and in a saturable manner to midgut brush border membrane vesicles (BBMV) from C. suppressalis and S. inferens larvae. While binding affinities were similar, a dramatically lower concentration of Cry1A toxin binding sites was detected for S. inferens BBMV than for C. suppressalis BBMV. In contrast, no significant differences between species were detected for Cry1Ca toxin binding to BBMV. Ligand blotting detected BBMV proteins binding Cry1Ac or Cry1Ca toxins, some of them unique to C. suppressalis or S. inferens. These data support that reduced Cry1A binding site concentration is associated with a lower susceptibility to Cry1A toxins and HH1 rice in S. inferens larvae than in C. suppressalis larvae. Moreover, our data support Cry1Ca as a candidate for pyramiding efforts with Cry1A-producing rice to extend the activity range and durability of this technology against rice stem borers.
二化螟和大螟是鳞翅目两种重要的水稻害虫，在中国主要水稻种植区的稻田爆发时会同时出现。以往和当前的田间试验表明，转苏云金芽孢杆菌Cry1Ab - Cry1Ac融合毒素基因的水稻品系华恢1号（HH1）可降低二化螟的卵和幼虫密度，但对大螟无效。大螟对HH1水稻的这种不同易感性与大螟幼虫相比二化螟幼虫对Cry1Ab和Cry1Ac毒素易感性降低有关。本研究的目的是确定导致这种不同易感性的机制。在饱和结合试验中，Cry1Ab和Cry1Ac毒素都以高亲和力且饱和的方式与二化螟和大螟幼虫中肠刷状缘膜囊泡（BBMV）结合。虽然结合亲和力相似，但检测到的大螟BBMV中Cry1A毒素结合位点的浓度显著低于二化螟BBMV。相反，Cry1Ca毒素与BBMV结合在物种间未检测到显著差异。配体印迹检测到与Cry1Ac或Cry1Ca毒素结合的BBMV蛋白，其中一些是二化螟或大螟特有的。这些数据支持，与二化螟幼虫相比，大螟幼虫中Cry1A结合位点浓度降低与对Cry1A毒素和HH1水稻的较低易感性相关。此外，我们的数据支持Cry1Ca作为与产生Cry1A的水稻进行基因叠加的候选者，以扩大该技术对水稻螟虫的活性范围和持效期。
