Our knowledge on the physiological function of the insect Neuropeptide F (NPF) mostly comes from studies in the fruit fly, Drosophila melanogaster, where NPF was shown to regulate diverse processes, such as feeding, learning and responding to stress. In the desert locust, Schistocerca gregaria, only a truncated form of the "full-length" NPF (the biologically active "trNPF") has been isolated. In this study, we investigated whether this peptide is involved in the regulation of feeding in this orthopteran species. In the S. gregaria EST-database, an NPF-precursor encoding transcript was found. Alignment with other insect NPF-precursors showed relatively highest sequence conservation within the trNPF region (and the flanking dibasic cleavage site), as compared to other regions of the NPF-precursor. Quantitative real-time RT-PCR revealed that the Schgr-NPF-precursor encoding transcript occurs throughout the central nervous system with relatively high transcript levels in the brain, optic lobes and suboesophageal ganglion. It was also detected at relatively high levels in the midgut, which suggests that the encoded peptide also functions in the digestive system. Moreover, Schgr-NPF-transcript levels were notably higher in starved animals than in animals fed ad libitum, while transcript levels were also shown to be regulated after the consumption of a meal. Injection of locust trNPF in adults stimulated food intake, while RNAi knockdown reduced food intake. Furthermore, injection of trNPF in adults stimulated weight increase, while RNAi knockdown reduced weight gain. This effect of trNPF on body weight gain may result from its stimulatory effect on food intake. Taken together, we provide clear evidence for an important role of trNPF in the regulation of feeding in the desert locust, S. gregaria.

译文

我们对昆虫神经肽F (NPF) 的生理功能的了解主要来自果蝇果蝇的研究,其中NPF被证明可以调节多种过程,例如进食,学习和应对压力。在沙漠蝗虫中,仅分离出 “全长” NPF (具有生物活性的 “trNPF”) 的截短形式。在这项研究中,我们调查了该肽是否参与了该直翅目物种的进食调节。在S. gregaria EST数据库中,发现了NPF前体编码转录本。与NPF前体的其他区域相比,与其他昆虫NPF前体的比对在trNPF区域 (和侧翼的二元切割位点) 内显示出相对最高的序列保守性。实时定量rt-pcr显示,Schgr-NPF前体编码转录本发生在整个中枢神经系统中,在大脑,视神经叶和食管下神经节中具有相对较高的转录本水平。在中肠中也检测到相对较高的水平,这表明编码的肽也在消化系统中起作用。此外,饥饿动物的Schgr-NPF转录水平明显高于随意喂养的动物,而食用餐后转录水平也受到调节。成人注射刺槐trNPF刺激了食物摄入,而RNAi敲低则减少了食物摄入。此外,在成年人中注射trNPF可刺激体重增加,而RNAi敲低可减少体重增加。trNPF对体重增加的这种影响可能是由于其对食物摄入的刺激作用所致。总而言之,我们为trNPF在沙漠蝗虫 (S. gregaria) 的摄食调节中的重要作用提供了明确的证据。

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