Shao Ensi, Lin Li, Liu Sijun, Zhang Jiao, Chen Xuelin, Sha Li, Huang Zhipeng, Huang Biwang, Guan Xiong
State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China.
Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China.
J Insect Sci. 2018 Feb 5;18(1). doi: 10.1093/jisesa/iex102.
The brown planthopper (BPH) Nilaparvata lugens is one of the most destructive insect pests in the rice fields of Asia. Like other hemipteran insects, BPH is not susceptible to Cry toxins of Bacillus thuringiensis (Bt) or transgenic rice carrying Bt cry genes. Lack of Cry receptors in the midgut is one of the main reasons that BPH is not susceptible to the Cry toxins. The main Cry-binding proteins (CBPs) of the susceptible insects are cadherin, aminopeptidase N (APN), and alkaline phosphatase (ALP). In this study, we analyzed and validated de novo assembled transcripts from transcriptome sequencing data of BPH to identify and characterize homologs of cadherin, APN, and ALP. We then compared the cadherin-, APN-, and ALP-like proteins of BPH to previously reported CBPs to identify their homologs in BPH. The sequence analysis revealed that at least one cadherin, one APN, and two ALPs of BPH contained homologous functional domains identified from the Cry-binding cadherin, APN, and ALP, respectively. Quantitative real-time polymerase chain reaction used to verify the expression level of each putative Cry receptor homolog in the BPH midgut indicated that the CBPs homologous APN and ALP were expressed at high or medium-high levels while the cadherin was expressed at a low level. These results suggest that homologs of CBPs exist in the midgut of BPH. However, differences in key motifs of CBPs, which are functional in interacting with Cry toxins, may be responsible for insusceptibility of BPH to Cry toxins.
褐飞虱（Nilaparvata lugens）是亚洲稻田中最具破坏性的害虫之一。与其他半翅目昆虫一样，褐飞虱对苏云金芽孢杆菌（Bt）的Cry毒素或携带Bt cry基因的转基因水稻不敏感。中肠缺乏Cry受体是褐飞虱对Cry毒素不敏感的主要原因之一。易感昆虫的主要Cry结合蛋白（CBP）是钙黏蛋白、氨肽酶N（APN）和碱性磷酸酶（ALP）。在本研究中，我们分析并验证了褐飞虱转录组测序数据的从头组装转录本，以鉴定和表征钙黏蛋白、APN和ALP的同源物。然后，我们将褐飞虱的钙黏蛋白样、APN样和ALP样蛋白与先前报道的CBP进行比较，以鉴定它们在褐飞虱中的同源物。序列分析表明，褐飞虱至少有一个钙黏蛋白、一个APN和两个ALP分别包含从Cry结合钙黏蛋白、APN和ALP中鉴定出的同源功能域。用于验证褐飞虱中肠中每个假定的Cry受体同源物表达水平的定量实时聚合酶链反应表明，与CBP同源的APN和ALP表达水平高或中高，而钙黏蛋白表达水平低。这些结果表明，CBP的同源物存在于褐飞虱的中肠中。然而，CBP关键基序的差异可能是褐飞虱对Cry毒素不敏感的原因，这些关键基序在与Cry毒素相互作用中起作用。
