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Rescheduling Behavioral Subunits of a Fixed Action Pattern by Genetic Manipulation of Peptidergic Signaling.

Kim DH, Han MR, Lee G, Lee SS, Kim YJ, Adams ME - PLoS Genet. (2015)

Bottom Line: Activation of CCAP or CAMB neurons through temperature-sensitive TRPM8 gating is sufficient to trigger ecdysis behavior.Our findings demonstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the ecdysis FAP.Moreover, temporal organization of the FAP is likely a function of ETH receptor density in target neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, University of California, Riverside, Riverside, California, United States of America.

ABSTRACT
The ecdysis behavioral sequence in insects is a classic fixed action pattern (FAP) initiated by hormonal signaling. Ecdysis triggering hormones (ETHs) release the FAP through direct actions on the CNS. Here we present evidence implicating two groups of central ETH receptor (ETHR) neurons in scheduling the first two steps of the FAP: kinin (aka drosokinin, leucokinin) neurons regulate pre-ecdysis behavior and CAMB neurons (CCAP, AstCC, MIP, and Bursicon) initiate the switch to ecdysis behavior. Ablation of kinin neurons or altering levels of ETH receptor (ETHR) expression in these neurons modifies timing and intensity of pre-ecdysis behavior. Cell ablation or ETHR knockdown in CAMB neurons delays the switch to ecdysis, whereas overexpression of ETHR or expression of pertussis toxin in these neurons accelerates timing of the switch. Calcium dynamics in kinin neurons are temporally aligned with pre-ecdysis behavior, whereas activity of CAMB neurons coincides with the switch from pre-ecdysis to ecdysis behavior. Activation of CCAP or CAMB neurons through temperature-sensitive TRPM8 gating is sufficient to trigger ecdysis behavior. Our findings demonstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the ecdysis FAP. Moreover, temporal organization of the FAP is likely a function of ETH receptor density in target neurons.

No MeSH data available.


Related in: MedlinePlus

Altered ETHR expression in central ensembles modifies scheduling of the ecdysis FAP.(A) Knockdown of ETHR expression using three independent ETHR-RNAi lines: UAS-ETHR-IR1, UAS-ETHR-IR2, and UAS-ETHR-sym carrying UAS-Dicer2. ETHR knockdown in kinin neurons reduced pre-ecdysis duration. ETHR knockdown in CAMB neurons (Pburs-Gal4) delays the switch to ecdysis behavior. A model below depicts how ETHR knockdown in kinin neurons or CAMB neurons changes pre-ecdysis duration. Bars represent mean time (± SEM, min) of the switch from pre-ecdysis to ecdysis onset relative to pre-ecdysis initiation (time zero). Data was analyzed using Mann-Whitney test (* p < 0.01; ** p < 0.001; *** p < 0.0001.) (B) ETHR over-expression in kinin neurons causes increased pre-ecdysis duration due to premature onset of pre-ecdysis. On the other hand, over-expression of ETHR in CAMB neurons accelerates the switch to ecdysis behavior due to increased sensitivity to ETH. See model below depicting how ETHR overexpression in kinin neurons or CAMB neurons affects pre-ecdysis duration. Error-bars represent standard error of mean (S.E.M). Data was analyzed using Mann-Whitney test (** P < 0.001, *** P < 0.0001).
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pgen.1005513.g003: Altered ETHR expression in central ensembles modifies scheduling of the ecdysis FAP.(A) Knockdown of ETHR expression using three independent ETHR-RNAi lines: UAS-ETHR-IR1, UAS-ETHR-IR2, and UAS-ETHR-sym carrying UAS-Dicer2. ETHR knockdown in kinin neurons reduced pre-ecdysis duration. ETHR knockdown in CAMB neurons (Pburs-Gal4) delays the switch to ecdysis behavior. A model below depicts how ETHR knockdown in kinin neurons or CAMB neurons changes pre-ecdysis duration. Bars represent mean time (± SEM, min) of the switch from pre-ecdysis to ecdysis onset relative to pre-ecdysis initiation (time zero). Data was analyzed using Mann-Whitney test (* p < 0.01; ** p < 0.001; *** p < 0.0001.) (B) ETHR over-expression in kinin neurons causes increased pre-ecdysis duration due to premature onset of pre-ecdysis. On the other hand, over-expression of ETHR in CAMB neurons accelerates the switch to ecdysis behavior due to increased sensitivity to ETH. See model below depicting how ETHR overexpression in kinin neurons or CAMB neurons affects pre-ecdysis duration. Error-bars represent standard error of mean (S.E.M). Data was analyzed using Mann-Whitney test (** P < 0.001, *** P < 0.0001).

Mentions: We have shown that kinin neurons are early responders to ETH and are necessary for normal pre-ecdysis behavior. We next tested hypotheses that: 1) they are direct targets of ETH and 2) sensitivity to ETH affects the timing of pre-ecdysis behavior. This was accomplished by modifying ETHR expression levels in vivo through RNAi knockdown or overexpression using the Gal4>UAS system. We reasoned that ETHR knockdown in kinin neurons would decrease receptor density, thus reducing sensitivity to rising ETH levels. If kinin neurons indeed are direct targets of ETH, this manipulation should cause a delay in initiation of the behavior and reduce its duration (Fig 3A). We employed two independent RNAi constructs, one an inverted repeat (UAS-ETHR-IR2), the other a symmetric UAS flanking a part of the ETHR coding sequence (UAS-ETHR-Sym). Both RNAi constructs decreased pre-ecdysis duration, indicating that kinin neurons are direct targets of ETH.


Rescheduling Behavioral Subunits of a Fixed Action Pattern by Genetic Manipulation of Peptidergic Signaling.

Kim DH, Han MR, Lee G, Lee SS, Kim YJ, Adams ME - PLoS Genet. (2015)

Altered ETHR expression in central ensembles modifies scheduling of the ecdysis FAP.(A) Knockdown of ETHR expression using three independent ETHR-RNAi lines: UAS-ETHR-IR1, UAS-ETHR-IR2, and UAS-ETHR-sym carrying UAS-Dicer2. ETHR knockdown in kinin neurons reduced pre-ecdysis duration. ETHR knockdown in CAMB neurons (Pburs-Gal4) delays the switch to ecdysis behavior. A model below depicts how ETHR knockdown in kinin neurons or CAMB neurons changes pre-ecdysis duration. Bars represent mean time (± SEM, min) of the switch from pre-ecdysis to ecdysis onset relative to pre-ecdysis initiation (time zero). Data was analyzed using Mann-Whitney test (* p < 0.01; ** p < 0.001; *** p < 0.0001.) (B) ETHR over-expression in kinin neurons causes increased pre-ecdysis duration due to premature onset of pre-ecdysis. On the other hand, over-expression of ETHR in CAMB neurons accelerates the switch to ecdysis behavior due to increased sensitivity to ETH. See model below depicting how ETHR overexpression in kinin neurons or CAMB neurons affects pre-ecdysis duration. Error-bars represent standard error of mean (S.E.M). Data was analyzed using Mann-Whitney test (** P < 0.001, *** P < 0.0001).
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pgen.1005513.g003: Altered ETHR expression in central ensembles modifies scheduling of the ecdysis FAP.(A) Knockdown of ETHR expression using three independent ETHR-RNAi lines: UAS-ETHR-IR1, UAS-ETHR-IR2, and UAS-ETHR-sym carrying UAS-Dicer2. ETHR knockdown in kinin neurons reduced pre-ecdysis duration. ETHR knockdown in CAMB neurons (Pburs-Gal4) delays the switch to ecdysis behavior. A model below depicts how ETHR knockdown in kinin neurons or CAMB neurons changes pre-ecdysis duration. Bars represent mean time (± SEM, min) of the switch from pre-ecdysis to ecdysis onset relative to pre-ecdysis initiation (time zero). Data was analyzed using Mann-Whitney test (* p < 0.01; ** p < 0.001; *** p < 0.0001.) (B) ETHR over-expression in kinin neurons causes increased pre-ecdysis duration due to premature onset of pre-ecdysis. On the other hand, over-expression of ETHR in CAMB neurons accelerates the switch to ecdysis behavior due to increased sensitivity to ETH. See model below depicting how ETHR overexpression in kinin neurons or CAMB neurons affects pre-ecdysis duration. Error-bars represent standard error of mean (S.E.M). Data was analyzed using Mann-Whitney test (** P < 0.001, *** P < 0.0001).
Mentions: We have shown that kinin neurons are early responders to ETH and are necessary for normal pre-ecdysis behavior. We next tested hypotheses that: 1) they are direct targets of ETH and 2) sensitivity to ETH affects the timing of pre-ecdysis behavior. This was accomplished by modifying ETHR expression levels in vivo through RNAi knockdown or overexpression using the Gal4>UAS system. We reasoned that ETHR knockdown in kinin neurons would decrease receptor density, thus reducing sensitivity to rising ETH levels. If kinin neurons indeed are direct targets of ETH, this manipulation should cause a delay in initiation of the behavior and reduce its duration (Fig 3A). We employed two independent RNAi constructs, one an inverted repeat (UAS-ETHR-IR2), the other a symmetric UAS flanking a part of the ETHR coding sequence (UAS-ETHR-Sym). Both RNAi constructs decreased pre-ecdysis duration, indicating that kinin neurons are direct targets of ETH.

Bottom Line: Activation of CCAP or CAMB neurons through temperature-sensitive TRPM8 gating is sufficient to trigger ecdysis behavior.Our findings demonstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the ecdysis FAP.Moreover, temporal organization of the FAP is likely a function of ETH receptor density in target neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, University of California, Riverside, Riverside, California, United States of America.

ABSTRACT
The ecdysis behavioral sequence in insects is a classic fixed action pattern (FAP) initiated by hormonal signaling. Ecdysis triggering hormones (ETHs) release the FAP through direct actions on the CNS. Here we present evidence implicating two groups of central ETH receptor (ETHR) neurons in scheduling the first two steps of the FAP: kinin (aka drosokinin, leucokinin) neurons regulate pre-ecdysis behavior and CAMB neurons (CCAP, AstCC, MIP, and Bursicon) initiate the switch to ecdysis behavior. Ablation of kinin neurons or altering levels of ETH receptor (ETHR) expression in these neurons modifies timing and intensity of pre-ecdysis behavior. Cell ablation or ETHR knockdown in CAMB neurons delays the switch to ecdysis, whereas overexpression of ETHR or expression of pertussis toxin in these neurons accelerates timing of the switch. Calcium dynamics in kinin neurons are temporally aligned with pre-ecdysis behavior, whereas activity of CAMB neurons coincides with the switch from pre-ecdysis to ecdysis behavior. Activation of CCAP or CAMB neurons through temperature-sensitive TRPM8 gating is sufficient to trigger ecdysis behavior. Our findings demonstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the ecdysis FAP. Moreover, temporal organization of the FAP is likely a function of ETH receptor density in target neurons.

No MeSH data available.


Related in: MedlinePlus