| The brown planthopper is an important pest that damages rice.It can be directly damaged by sucking phloem sap,because of the lack of nutrition plant stem base turns black and rotten.Clearing the feeding behavior mechanism of the brown planthopper can provide a theoretical basis for its prevention and control.However,there are few studies on the feeding behavior mechanism of the brown planthopper.Sulfakinin(SK)is an important neuropeptide in invertebrates,which corresponds to the gastrin hormone Gastrin and cholecystokinin(CCK)in mammals.SK participates in the regulation of various physiological and behavioral processes such as satiety,food intake,intestinal peristalsis,aggressiveness,mating and hyperactivity.However,the intrinsic mechanism of SK inhibiting insect feeding is unknown.SK functions in insects mainly by binding to specific sulfakinin Receptor(SKR).In recent years,sulfakinin and its receptors have been widely studied as the targets of new pesticides.Sweet taste receptors play an important role in regulating insect feeding.Research on insect sweet taste perception is currently mainly focused on the model insect Drosophila melanogaster.Sweetness receptors such as Gr64f(Gustatory receptor 64f)genes and sweetness-sensing neurons have been identified in the peripheral sensing receptors of Drosophila melanogaster such as the proboscis and proleg tarsi.Early research in our laboratory found that sulfakinin can inhibit brown planthopper feeding.Transcriptome sequencing found that silencing the sulfakinin gene can induce the up-regulation of sweet receptor expression,so sulfakinin may interfere with sweetness perception and thereby inhibit the feeding of brown planthopper.This thesis takes the agricultural pest Nilaparvata lugens and the model insect Drosophila melanogaster as the research objects through behavior assay,pharmacology,genetics,immunohistochemistry,and molecular biology to analyze the molecular mechanism of neuropeptide sulfakinin to reduce sweetness perception and inhibit insect feeding.And the ultrastructure of the mouthparts of Nilaparvata lugens was studied by scanning electron microscope technology.The specific research results are as follows:1.Sulfakinin inhibits the expression of sweet receptor genes and thus inhibits the feeding of Nilaparvata lugensGene silencing and behavioral techniques were used to study the molecular mechanisms by which sulfakinin interferes with sweet taste perception and inhibits feeding behavior of brown planthopper.Results showed that silencing the sulfakinin gene can increase the expression of the sweet receptor Nl Gr64 f gene of Nilaparvata lugens.Interference with Nl Gr64 f gene expression can significantly inhibit the feeding of Nilaparvata lugens.It is shown that sulfakinin can inhibit the feeding of Nilaparvata lugens by inhibiting the expression of the sweetness receptor Nl Gr64 f gene.2.Sulfakinin inhibits sweet receptor gene expression and sweet neuron activity,thereby inhibiting Drosophila melanogaster feedingUsing genetics,electrophysiology and behavioral techniques to study the molecular and neural mechanisms of sulfakinin interfering with sweet taste perception and thereby inhibiting fruit flies feeding behavior.The results showed that feeding after starvation can increase the expression of sulfakinin gene and protein synthesis in Drosophila melanogaster.It can also increase the activity of Drosophila melanogaster sulfakinin neurons,indicating that sulfakinin can sense satiety.Further silencing the expression of sulfakinin gene can increase the expression of sweet receptor gene,indicating that sulfakinin inhibits the expression of sweet receptor gene.Interfering with the expression of sweet taste receptor genes can inhibit the feeding of fruit flies and activating sulfakinin neurons can inhibit the activity of sweet taste neurons.The results show that satiety after starvation can increase the expression and secretion of sulfakinin,thereby inhibiting the expression of sweet taste receptors and the activity of sweet taste-sensing neurons,inhibiting sweet taste perception,and ultimately inhibiting the feeding behavior of Drosophila melanogaster.3.Observation of the ultrastructure of the mouthparts of Nilaparvata lugensThe morphology and ultrastructure of the mouthparts of Nilaparvata lugens were studied by scanning electron microscopy.Studies have shown that the mouthparts of Nilaparvata lugens are composed of labrum,labium,two mandibular stylets and maxillary stylets.The labium divided into three sections and surrounds the stylet fascicle.The two mandibular stylets are closely attached to both sides of the two maxillary stylets that are tightly interlocked.The small conical labrum covers the labium.The surface of the labium is distributed with sensilla trichoid and sensillum basiconic,the sensilla trichodea are arranged symmetrically on both sides of the labium groove,and some are born on the top of labium,the basiconic sensilla are mainly distributed at the top of the labium.We speculated that the taste receptors of the brown planthopper(BPH)may be mainly concentrated underneath the basiconic sensilla.This section clarified the shape and type of the sensilla on the mouth organ of the BPH,which could provide a research basis for future research on the function of the taste receptors and the regulation mechanism of feeding in BPH.In summary,this thesis studied the molecular and neural mechanisms of sulfakinin interfering with sweet taste perception and inhibiting the feeding of Nilaparvata lugens and Drosophila melanogaster and described the ultrastructure of the mouthparts of Nilaparvata lugens.Research results revealed the molecular and neural mechanisms of sulfakinin regulating insect feeding behavior.On the other hand,these results can provide help for the development of new insect feeding inhibitors. |
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