Prominent down-regulation of storage protein genes after bacterial challenge in eri-silkworm, Samia cynthia ricini
Prominent down-regulation of storage protein genes after bacterial challenge in eri-silkworm, Samia cynthia ricini
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DOI：
10.1002/arch.20214
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发表时间：
2008-01-01
影响因子：
2.2
通讯作者：
Shimada, Toru
中科院分区：
文献类型：
--
作者：
Meng, Yan;Omuro, Naoko;Shimada, Toru
我们从大肠杆菌和白色念珠菌攻毒的桑蚕幼虫脂肪体中构建了两个独立的cDNA文库。我们对两个cDNA文库进行了比较表达序列标签（EST）分析，发现与白色念珠菌注射液相比，大肠杆菌注射液明显抑制了两个假定的储存蛋白基因ScSP1和ScSP2。通过实时定量RT-PCR分析，我们发现，与注射PBS相比，注射大肠杆菌12-36 h后，雌性和雄性幼虫脂肪体中ScSP1 mRNA显著减少至1/32-1/3，ScSP2 mRNA分别减少至1/7-1/3和1/22-1/5。此外，SDS-PAGE分析显示，在大肠杆菌注射后36 h，这两种ScSP蛋白在幼虫血淋巴中的积累明显减少。然而，注射后48 h，两种ScSP蛋白的数量恢复到与注射PBS的幼虫相同的水平，表明细菌攻击引起的ScSP减少是短暂的。此外，在ScSP1和ScSP2的5'上游调控区发现了果蝇ReI/NF-kappa B蛋白的潜在结合位点，提示ReI/NF-kappa B蛋白参与控制细菌对ScSP基因的抑制。这些结果提出了一种假设，即蓖麻毒素具有一种遗传程序，可以暂时关闭必要的基因表达，以诱导急性和有效地表达免疫相关基因。这些发现可能为鳞翅目昆虫的先天免疫系统提供新的见解。
We constructed two independent cDNA libraries from the fat body of Escherichia coli- or Candida albicans-challenged eri-silkworm Samia cynthia ricini larvae. We performed comparative expressed sequence tag (EST) analysis of the two cDNA libraries and found that two putative storage protein genes, ScSP1 and ScSP2, were markedly repressed by E. coli injection as compared with C. albicans injection. By quantitative real-time RT-PCR analysis, we showed that ScSP1 mRNA significantly reduced to 1/32-1/3 in the fat body of the female larvae, and ScSP2 mRNA reduced to 1/7-1/3 and 1/22-1/5 in the females and males, respectively, 12-36 h after E. coli injection as compared with PBS injection. In addition, SDS-PAGE analysis revealed that the accumulation of both the ScSP proteins in the larval hemolymph apparently decreased up to 36 h after E. coli injection. However, the amounts of the two ScSP proteins returned to the some level as those in the larvae injected with PBS by 48 h after injection, showing that the reduction in ScSPs caused by the bacterial challenge was transient. Moreover, potential binding sites for the Drosophila ReI/NF-kappa B protein Dorsal were found in the 5' upstream regulatory regions of ScSP1 and ScSP2, suggesting the participation of the ReI/NF-kappa B proteins in controlling the bacterial suppression of the ScSP genes. These results suggested the hypothesis that S. c. ricini has a genetic program to shut down temporarily dispensable gene expression in order to induce an acute and efficient expression of immune-related genes. These findings may provide new insight into the innate immune system in lepidopteran insects.