Differential tissue distribution of two acetylcholinesterase transcripts in the German cockroach, Blattella germanica

Abstract

Recent studies have revealed that non-Cyclorrhapha insects possess two acetylcholinesterases (AChEs): Drosophila Ace-orthologous (o-Ace) and -paralogous (p-Ace) forms. In these insects, p-Ace is considered as a neural target of insecticides because mutations conferring insecticide insensitivity have been consistently identified in equivalent forms from various insects. To clarify the functional differentiation between the two AChE isoforms, we characterized the expression of two AChE genes in nerve cell-rich and -poor tissues of German cockroaches. The two AChE genes were expressed at comparable levels in both the nerve cord and head. Two AChE isoforms with mutually discriminatory fenitroxon sensitivities were exhibited in the nerve cord, indicating that o-Ace and p-Ace function in the neurons. pAce was mainly expressed in the nerve cord and head, while o-Ace was ubiquitously expressed at a comparable level. Moreover, o-Ace transcripts as well as AChE activity were detected in the fat body where no nervous tissue is observed. No AChE activity was detected in the hemolymph. These results show that p-Ace is better as an insecticidal target because of its abundant transcripts in nervous tissue. In addition, the roles of o-Ace, which is present ubiquitously without secretion into the hemolymph in insects, are discussed.

Functional analysis and molecular characterization of two acetylcholinesterases from the German cockroach, Blattella germanica

“…3). This finding is in contrast to a previous report in which BgAChE2 is more extensively distributed in the PNS based on quantitative profiling of BgAChE2 transcription (Mizuno et al. , 2007).…”

Cholinergic and non-cholinergic functions of two acetylcholinesterase genes revealed by gene-silencing in Tribolium castaneum

“…The transcript levels of TcAce1 at these stages and in the brain were 1.2- to 8.7- fold higher than those of TcAce2 ( P ≤0.05), indicating that TcAce1 transcript is more abundant than TcAce2 at all the developmental stages and in the brains. Our data are consistent with those found in other insect species, including B. germanica 18, the diamondback moth ( Plutella xylostella )28, the oriental tobacco budworm ( Helicoverpa assulta )29, and the mosquito ( Culex pipiens )30. Nevertheless, the relative transcript abundances of the two genes vary significantly among the insect species and different tissues of the same species, ranging from 13- to 250-fold in the different tissues of P. xylostella 28 and 3-fold in the nerve cord of B. germanica 18.…”

RNAi of ace1 and ace2 in Blattella germanica reveals their differential contribution to acetylcholinesterase activity and sensitivity to insecticides

“…It is noteworthy that the knockdown of Bgace2 mRNA did not alter Bgace1 expression and vice versa, which might suggest noncoordinated transcription and thus, a functional differentiation of ace genes. Thus, RNAi appears as a valuable tool to discriminate the activities of both AChE1 and AChE2 in non-Cyclorrhapha insects, besides the inhibitor sensitivity studies previously reported (Bourguet et al, 1996;Huchard et al, 2006;Mizuno et al, 2007). In this sense, our data agree with previous data that indicate a minor, but measurable contribution (ca.…”

“…Altogether, the similar depletion of Bgace1 and Bgace2 mRNAs (95%) and the differential reduction in AChE activity by either dsBgace1 or dsBgace2, suggest that AChE1 is responsible for approximately 65e75% of total AChE activity. This confirms that AChE1 is mainly responsible for AChE activity in ganglia of B. germanica, as suggested by previous findings that showed predominant transcription of Bgace1 in nerve tissues Mizuno et al, 2007). A moderate, but significant contribution to ACh hydrolysis is accomplished by AChE2, which suggests either a low or localized enzymatic activity of the ace2 protein.…”

“…Based on the transcription pattern and fluorescence in situ hybridization, Bgace1 appears to be the primary AChE responsible for the physiological hydrolysis of ACh, whereas Bgace2 may have supplementary functions. While it was obvious that the two types of AChE were expressed at the mRNA level in ganglia and other tissues, AChE activity was measured as a mixture of the two types Mizuno et al, 2007). Thus, the respective contribution of both ace1 and ace2 to catalytic activity of AChE in B. germanica and insects in general remains to be elucidated.…”