Liu Shuhua, Yang Baojun, Gu Jianhua, Yao Xiangmei, Zhang Yixi, Song Feng, Liu Zewen
Key Laboratory of Monitoring and Management of Plant Disease and Insect, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
J Insect Physiol. 2008 Dec;54(12):1495-502. doi: 10.1016/j.jinsphys.2008.08.010. Epub 2008 Aug 30.
Juvenile hormone (JH) plays key roles in the regulation of growth, development, diapause and reproduction in insects, and juvenile hormone esterase (JHE) plays an important role in regulating JH titers. We obtained a full-length cDNA encoding JHE in Nilaparvata lugens (NlJHE), the first JHE gene cloned from the hemipteran insects. The deduced protein sequence of Nljhe contains the five conserved motifs identified in JHEs of other insect species, including a consensus GQSAG motif that is required for the enzymatic activity of JHE proteins. Nljhe showed high amino acid similarities with Athalia rosae JHE (40%) and Apis mellifera JHE (39%). Recombinant NlJHE protein expressed in the baculovirus expression system hydrolyzed [3H] JH III at high activity and yielded the specificity constants (kcat/KM=4.28x10(6) M(-1) s(-1)) close to those of the validated JHEs from other insect species, indicating that Nljhe cDNA encodes a functional JH esterase. The Nljhe transcript was expressed mainly in the fat body and the expression level reached a peak at 48 h after ecdysis of the 5th instar nymphs. In the 5th instar, macropterous insects showed significantly higher Nljhe mRNA levels and JHE activities, but much lower JH III levels, than those detected in the brachypterous insects soon after ecdysis and at 48 h after ecdysis. These data suggest that NlJHE might play important roles in regulation of JH levels and wing form differentiation.
保幼激素（JH）在昆虫的生长、发育、滞育和繁殖调节中起关键作用，而保幼激素酯酶（JHE）在调节保幼激素滴度方面发挥重要作用。我们获得了褐飞虱中编码JHE的全长cDNA（NlJHE），这是从半翅目昆虫中克隆的首个JHE基因。Nljhe推导的蛋白质序列包含在其他昆虫物种的JHE中鉴定出的5个保守基序，包括JHE蛋白酶活性所需的共有GQSAG基序。Nljhe与玫瑰三节叶蜂JHE（40%）和意大利蜜蜂JHE（39%）显示出较高的氨基酸相似性。在杆状病毒表达系统中表达的重组NlJHE蛋白以高活性水解[3H]JH III，并产生与其他昆虫物种经验证的JHE接近的特异性常数（kcat/KM = 4.28x10(6) M(-1) s(-1)），表明Nljhe cDNA编码一种功能性保幼激素酯酶。Nljhe转录本主要在脂肪体中表达，且在五龄若虫蜕皮后48小时表达水平达到峰值。在五龄期，蜕皮后不久和蜕皮后48小时，长翅型昆虫显示出比短翅型昆虫显著更高的Nljhe mRNA水平和JHE活性，但JH III水平则低得多。这些数据表明，NlJHE可能在保幼激素水平调节和翅型分化中发挥重要作用。
