Pheromones regulate male social behaviors in Drosophila, but the identities and behavioral role(s) of these chemosensory signals, and how they interact, are incompletely understood. Here we show that (Z)-7-tricosene (7-T), a male-enriched cuticular hydrocarbon (CH) previously shown to inhibit male-male courtship, is also essential for normal levels of aggression. The opposite influences of 7-T on aggression and courtship are independent, but both require the gustatory receptor Gr32a. Surprisingly, sensitivity to 7-T is required for the aggression-promoting effect of 11-cis-vaccenyl acetate (cVA), an olfactory pheromone, but 7-T sensitivity is independent of cVA. 7-T and cVA therefore regulate aggression in a hierarchical manner. Furthermore, the increased courtship caused by depletion of male CHs is suppressed by a mutation in the olfactory receptor Or47b. Thus, male social behaviors are controlled by gustatory pheromones that promote and suppress aggression and courtship, respectively, and whose influences are dominant to olfactory pheromones that enhance these behaviors.

CaMKII is critical for structural and functional plasticity. Here we show that Camguk (Cmg), the Drosophila homolog of CASK/Lin-2, associates in an ATP-regulated manner with CaMKII to catalyze formation of a pool of calcium-insensitive CaMKII. In the presence of Ca(2+)/CaM, CaMKII complexed to Cmg can autophosphorylate at T287 and become constitutively active. In the absence of Ca(2+)/CaM, ATP hydrolysis results in phosphorylation of T306 and inactivation of CaMKII. Cmg coexpression suppresses CaMKII activity in transfected cells, and the level of Cmg expression in Drosophila modulates postsynaptic T306 phosphorylation. These results suggest that Cmg, in the presence of Ca(2+)/CaM, can provide a localized source of active kinase. When Ca(2+)/CaM or synaptic activity is low, Cmg promotes inactivating autophosphorylation, producing CaMKII that requires phosphatase to reactivate. This interaction provides a mechanism by which the active postsynaptic pool of CaMKII can be controlled locally to differentiate active and inactive synapses.

Calcium/calmodulin-dependent protein kinase II (CaMKII) is abundant in the CNS and is crucial for cellular and behavioral plasticity. It is thought that the ability of CaMKII to autophosphorylate and become Ca 2ϩ independent allows it to act as a molecular memory switch. We have shown previously that inhibition of Drosophila CaMKII leads to impaired performance in the courtship conditioning associative memory assay, but it was unknown whether the constitutive form of the kinase had a special role in learning. In this study, we use a tripartite transgenic system combining GAL4/UAS with the tetracycline-off system to spatially and temporally manipulate levels of Ca 2ϩ -independent CaMKII activity in Drosophila. We find an enhancement of information processing during the training period with Ca 2ϩ -independent, but not Ca 2ϩ -dependent, CaMKII. During training, control animals have a lag before active suppression of courtship begins. Animals expressing Ca 2ϩ -independent CaMKII have no lag, implying that there is a threshold level of Ca 2ϩ -independent activity that must be present to suppress courtship. This is the first demonstration, in any organism, of enhanced behavioral plasticity with overexpression of constitutively active CaMKII. Anatomical studies indicate that transgene expression in antennal lobes and extrinsic mushroom body neurons drives this behavioral enhancement. Interestingly, immediate memory was unaffected by expression of T287D CaMKII in mushroom bodies, although previous studies have shown that CaMKII activity is required in this brain region for memory formation. These results suggest that the biochemical mechanisms of CaMKII-dependent memory formation are threshold based in only a subset of neurons.

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In Drosophila, calcium/calmodulin-dependent protein kinase II (CaMKII) activity is crucial in associative courtship conditioning for both memory formation and suppression of courtship during training with a mated female. We have previously shown that increasing levels of constitutively active CaMKII, but not calcium-dependent CaMKII, in a subset of neurons can decrease the initial level of courtship and enhance the rate of suppression of courtship in response to a mated female. In this study, we demonstrate that a subpopulation of noncholinergic, nondopaminergic, non-GABAergic neurons can cause CaMKII-dependent reductions in initial courtship, but only cholinergic neurons enhance training-dependent suppression. These data suggest that processing of pheromonal signals in two subpopulations of neurons, likely antennal lobe projection neurons, is critical for behavioral plasticity.Modification of behavior on short time scales requires fast, likely cell signaling, changes in neuronal circuits. One molecule that has been shown in many systems to be responsible for both short-term and long-term changes in neuronal activity is calcium/calmodulin-dependent protein kinase II (CaMKII). This kinase can act a molecular switch, becoming calcium independent after autophosphorylation at T287. Production of constitutively active kinase is believed to be a first step toward establishing short-and long-term changes in neuronal properties that underlie learning (for review, see Lisman et al. 2002).In Drosophila courtship conditioning, CaMKII is important for behavioral changes that occur during the training period and for formation of associative memory (Griffith et al. 1993; Griffith 1997, 1999). In this behavioral paradigm, a male is exposed to a previously mated female for 1 h, and the effects of training are assessed by measuring courtship of a subsequently presented virgin female. Naive males exposed to virgin females sense female-specific stimulatory pheromones and rapidly initiate courtship, usually copulating within 15 min. In comparison, trained males show reduced courtship of virgins, and this is believed to be the result of association of stimulatory pheromones with an aversive substance given off by mated females (Tompkins et al. 1983). Memory formation can be blocked by inhibition of CaMKII in mushroom bodies, central complex, and parts of the lateral protocerebrum (Joiner and Griffith 1999). The behavior of males during training is also plastic; they initiate vigorous courtship, but over the course of training they decrease their intensity of courtship and rarely copulate. The suppression of courtship during training is driven by a neuronal circuit distinct from that mediating associative memory formation, involving neurons in the antennal lobes and lateral protocerebrum (Joiner and Griffith 1999).The requirement for CaMKII activity was determined using spatially restricted expression of a peptide, which inhibits both the calcium-dependent and the calcium-independent (autophosphorylated at T287) forms of the kinase. ...

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Recent studies have shown that male fruit flies use close-range olfactory cues to assess the status of potential mating partners. The presence of a volatile, male-derived pheromone can suppress the default male behavioral state of courting females.