Abstract
The sesquiterpenoid methyl farnesoate (MF), a juvenile hormone (JH) analog, plays important roles in many physiological processes of crustaceans, such as morphogenesis, molting and reproduction. Juvenile hormone esterase-like (JHE-like) carboxylesterase (CXE) is a key enzyme in MF degradation, playing a significant role in regulating MF titer. However, its function is barely known in shrimp. In this study, a total of 21 JHE-like CXEs (LvCXEs) were characterized in Pacific white shrimp Litopenaeus vannamei, based on the full genome and multi-transcriptomic data. LvCXE has a conserved triplet catalytic site (Ser-Glu-His) and a characteristic GxSxG motif. Most LvCXEs were highly expressed in the hepatopancreas, which was the main site for MF degradation. LvCXEs containing a GESAG motif showed a specific expansion in the L. vannamei genome. Those GESAG-containing LvCXEs presented differential expressions at different larvae stages and different molting stages of L. vannamei, which suggested their potential functions in development and molting. Additionally, when the transcription level of CXEs was inhibited, it could lead to failed molt and death of L. vannamei. When we further detected the expression levels of the key ecdysone responsive transcription factors including LvE75, LvBr-C, LvHr3 and LvFtz-f1 after the CXE inhibitor was injected into L. vannamei, they all showed apparent down-regulation. These results suggested that the expansion of LvCXEs in the L. vannamei genome should contribute to the regulation of metamorphosis at larvae stages and frequent molting during the growth of L. vannamei.
Highlights
Carboxylesterase is a superfamily of multifunctional enzyme which ubiquitously exists in animals, plants and microbes [1,2]
juvenile hormone esterases (JHE) is considered to be the predominant enzyme involved in degradation of juvenile hormone (JH), which is a group of sesquiterpenoid compounds with pleiotropic functions in development, metamorphosis, molting, growth, reproduction and pheromone biosynthesis of insects [4,5]
E3 were distributed in scaffold883, LvCXE4 and LvCXE5 located in scaffold962, LvCXE9 and LvCXE10 were distributed in scaTffaobldle181.3C9.haOrathcteerriLstviCcsXoEf s21scLavtCteXrEesdidinenLt.ifvieadnninampeeni ageeindosmhreim(Tpagbelneo1m).e
Summary
Carboxylesterase is a superfamily of multifunctional enzyme which ubiquitously exists in animals, plants and microbes [1,2]. Based on sequence similarity and substrate specificity, carboxylesterases can be divided into eight subfamilies—α-esterases (Ae), β-esterases (Be), juvenile hormone esterases (JHE), gliotactins (Gli), acetylcholinesterases (AChE), neurotactins (Nrt), neuroligins (Nrl) and glutactins (Glt) [3]. JHE is considered to be the predominant enzyme involved in degradation of juvenile hormone (JH), which is a group of sesquiterpenoid compounds with pleiotropic functions in development, metamorphosis, molting, growth, reproduction and pheromone biosynthesis of insects [4,5]. JHE converts JH to JH acid and regulates JH titer at appropriate levels, and thereby directs development and metamorphosis in insects [6,7]. Inhibition of JHE activity maintained JH titer, led to abnormally large larvae and delayed metamorphosis [10,11] The increase of JHE activity at late developmental stage is one of the important biochemical events that leads to pupation [8,9].
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