| The chemoconnectome(CCT)is defined as the entire set of neurotransmitters,neuromodulators,neuropeptides,and their receptors underlying chemotransmission in an animal.We use Drosophila as a model system to investigate the molecular and neural circuits underlying female mating behaviors.In this study,123 mutants,which is related to 60 CCT-related genes,were systematically screened for the female mating behavior.We found that mutations in 18 genes significantly decreased female receptivity,whereas mutations in 10 genes promoted female receptivity.Mutation of neuropeptide SIF could lead to significant increase in female mating behavior.Previous studies have reported that SIF is involved in regulating fly sexual behavior,but the circuit mechanism is still unclear.For the first time,we provide evidences that SIF regulates female mating behavior at the molecular level.Female mating behavior is significantly increased in SIF mutants compared with control flies,and display a dose-dependent effect.In order to further investigate the function of downstream SIF receptors,we examined the mating behavior of female flies in the knock-out of SIF receptors.Our results showed that female mating behavior was significantly increased in SIF receptor mutants.Therefore,SIF modulate female mating behavior through downstream SIF receptor.We also found that the SIF receptor and fruitless,a key transcription factor in the sex determination pathway,co-express in multiple brain regions,including olfactory neuropil antenna lobe(AL)and auditory neuropil AMMC(antennal mechanosensory and motor center)region.Therefore,we speculate that SIF may affect mating behavior by regulating olfactory and auditory pathways in Drosophila.We found that knock-out of SIF and SIF receptor could still enhance the mating behavior even after amputating the auditory or olfactory organs(arista or antennae)of female flies,indicating that SIF may regulate mating behavior through modulating olfactory and auditory sensory pathways.Serotonin(5-HT)is an important neurotransmitter,which is widely found in both the nervous and non-nervous systems of insects,and is involved in the regulation of various behaviors.The production of serotonin is blocked by the mutation of tryptophanhydroxylase(TRH)gene,which is a key enzyme for the synthesis of 5-HT.The females lacking 5-HT showed strongly suppressed mating behavior: female receptivity was near 0%.Furthermore,feeding 5HTP to TRH mutant could rescue the reduced mating phenotype caused by 5-HT deficiency,indicating that 5-HT plays an important role in regulating the female mating behavior.The serotonergic neurons are broadly distributed in most brain regions,but our genetic intersection approach identifies two clusters of serotonergic neurons in the female brain.Activation of these neuronal clusters promote female mating behavior,indicating that these neurons are important for female mating behavior.In order to further investigate the role of the downstream receptor genes,we examined the mating behavior of female mutants for the 5-HT receptor genes.We found that knocking out 5HT2 a and 5HT1 b receptors did not affect female mating behavior,while knocking out 5HT1 a and 5HT7 receptors significantly reduce female mating behavior.5HT1 a receptor neurons are widely expressed in the female brain.We used genetic tools to manipulate subsets of 5HT1 a and 5HT7 receptor neurons and found that activation of small subsets of 5HT1 a and 5HT7 receptor neurons affect female mating behavior.Furthermore,5HT1 a receptor and fruitless were co-expressed in the AL and AMMC brain regions.We also,firstly,validated a TH antibody using Drosophila and outlined a universal immunostaining protocol in Aedes aegypti using TH antibody to visualize the expression pattern of dopaminergic neurons in the central nervous system.Secondly,our result show that 4th-instar larvae and adults of H.axyridis are most effective in controlling A.craccivora,and proper density of H.axyridis released will reduce intraspecific competition.Taken together,we systematically investigated the roles of CCT-related gene in female mating behavior,and further studied the function of neuropeptide SIF and neurotransmitter 5-HT in female mating behavior at the neural circuit level.We also identify the expression pattern of dopaminergic neurons in the brain of Aedes aegypti and consumption patterns of the multicolored Asian ladybird Harmonia axyridis on the broad bean aphid Aphis craccivora. |
