CLONING AND CHARACTERIZATION OF TWO EcR ISOFORMS FROM JAPANESE PINE SAWYER,Monochamus alternates

Abstract

The ecdysone receptor (EcR) is the hormonal receptor of ecdysteroids, which regulates insect growth and development. In this study, we cloned and characterized two isoforms of EcR in Monochamus alternates named MaEcR A and MaEcR B. The cDNAs of MaEcR A and MaEcR B have open repeating frames of 1,695 and 1,392 bp, respectively. The deduced proteins have the same C-terminal sequence and varied in N-terminal, and are consistent with reports on other insect species, particularly with the receptor of another coleopteran, Tribolium castaneum. The isoform-specific developmental expression profile of EcR in the epidermis and the midgut were analyzed with quantitative real-time reverse-transcriptase polymerase chain reaction in the pupal stage. RNA interference (RNAi) with common or isoform-specific regions induced developmental stagnation. When treated in the later larval stage, RNAi with either the common sequence or an EcR A specific sequence caused more severe effects and most larvae died prior to adulthood. The EcR B specific sequence caused less severe effects and about half of the treated larvae became adults, but some showed developmental defects. RNAi with both isoforms at early pupal stage attenuated the expression of 20E-regulated genes E74, E75, and HR3. The study demonstrates the role of EcR in the transduction of ecdysteroid response in Monochamus alternatus.

Functional characterization of ultraspiracle in Leptinotarsa decemlineata using RNA interference assay

“…Consistently, whereas all the larvae injected with ds EcR or ds EcRA arrest their development during the quiescent stage and die, around 80% and 60% of the larvae injected ds EcRB progress in larval development and survive to the adult stage respectively in T. castaneum (Tan and Palli, ). Similarly, most larvae depletion of both EcR isoforms or EcRA die prior to adulthood in M. alternates , whereas about half of the EcRB RNAi larvae become adults (Weng et al , ). In this paper, the activity of EcRA is only partially restored by dietary supplement with 20E.…”

“…As for EcRB , its expression is regulated by EcRA in at least two Coleopteran species (Tan and Palli, ; Weng et al , ). Injection of ds EcRB does not affect EcRA mRNA levels, whereas EcRB levels are lower in larvae injected with ds EcRA in T. castaneum (Tan and Palli, ) and Monochamus alternates (Weng et al , ).…”

“…As for EcRB, its expression is regulated by EcRA in at least two Coleopteran species (Tan and Palli, 2008;Weng et al, 2013). Injection of dsEcRB does not affect EcRA mRNA levels, whereas EcRB levels are lower in larvae injected with dsEcRA in T. castaneum (Tan and Palli, 2008) and Monochamus alternates (Weng et al, 2013). Consistently, whereas all the larvae injected with dsEcR or dsEcRA arrest their development during the quiescent stage and die, around 80% and 60% of the larvae injected dsEcRB progress in larval development and survive to the adult stage respectively in T. castaneum (Tan and Palli, 2008).…”

Ecdysone receptor isoforms play distinct roles in larval–pupal–adult transition in Leptinotarsa decemlineata

“…The physiological importance of EcR during larval metamorphosis has been well explored in the common fruit fly Drosophila melanogaster (Koelle et al ., ; Talbot et al ., ; Bender et al ., ; Schubiger et al ., ; Davies et al ., ). Moreover, a very small fraction of EcRs from non‐drosophilid insects have been functionally characterized by in vivo RNA interference (RNAi) (Cruz et al ., ; Tan & Palli, ; Yao et al ., ; Wu et al ., ; Weng et al ., ; Tan et al ., , b) and in vitro analysis (Chen et al ., ). Despite these findings, the molecular aspects for EcR to control juvenile development in non‐drosophilid species have not been well studied.…”

“…Each EcR isoform exerts specific functions during development (Bender et al ., ; Davies et al ., ; Gautam et al ., ). Similar results have been documented in the red flour beetle Tribolium castaneum (Tan & Palli, ), the Japanese pine sawyer Monochamus alternates (Weng et al ., ) and the cotton mirid bug Apolygus lucorum (Tan et al ., , b). Which EcR isoform is mainly responsible for the transduction of 20E signal in non‐drosophilid insect species?…”