Molecular Mechanisms Of Spermatogenesis Regulation By Fat Body-like Tissue In Migratory Locusts

Spermatogenesis is the process by which male germ cells undergo mitosis,meiosis and differentiation to form haploid spermatozoa containing a set of chromosomes.The spermathecae of flying locusts are mainly composed of spermathecal tubules and the fatty body tissue between them.Our previous study found that the fat body enveloping the seminiferous tubules is a specialized fat body-like tissue(FLT),which differs significantly in morphological structure and cellular characteristics from the fat body in the body cavity of the flying locust.Its absence severely interferes with spermatogenesis in the seminiferous tubules.However,the molecular regulatory mechanisms by which the FLT affects spermatogenesis remain unclear.We first refined the phenotype of the entire process of spermatogenesis by means of fluorescent staining.In a spermatocyte,a primary spermatocyte undergoes two meiotic divisions through continuous mitosis through 2,4,8,16,32 cell phases to form 128 round spermatocytes,then chromatin condensation occurs and the spermatozoa enter the elongation phase,which undergoes three phases: lobular,canoe-like and needle-like before forming a mature sperm bundle with aligned ends and a brighter head.Inter-tissue influences are generally accomplished in three ways: structural support,nutrient provision and signal exchange.We have previously shown that the spermathecae lose support following FLT deprivation to assume a curled-up morphology.To determine how this works in terms of nutrient provision and signal communication,we compared the transcriptomes of FLT-deprived and non-deprived spermathecae during adult development through surgical experiments to search for receptor candidate genes in the spermathecae that may influence spermatogenesis.The differentially expressed transporter proteins were first enriched.The enrichment revealed the more common substrate transporter proteins,amino acid transporter proteins and sugar transporter proteins.Next,IPR enrichment was performed for up-and down-regulated receptors,and the first gene enriched was Odorant receptors(Or).We then validated the 24 candidate Or genes enriched by fluorescence quantitative PCR.13 genes were significantly different before and after surgery,and quantification of the 13 differential genes in male and female tissues revealed that Or83 was specifically expressed in male Tsl.To clarify the function of Or83 in spermatogenesis,RNA interference was performed on Or83 and the number of mature spermatozoa in the growth,maturation and deformation zones in the seminiferous tubules and in the spermatophore was counted at 8,10 and 12 days after plumage,and it was found that the number of mature sperm bundles in the deformation zone of the seminiferous tubules and in the spermatophore was significantly reduced after interference.Further,to determine the site of Or83 protein expression,we localized Or83 protein expression in the seminiferous tubules by immunofluorescence and found that Or83 was specifically expressed only in the cells of the maturation zone,and was expressed in the cytoplasm.Our results suggest that FLT can regulate spermatogenesis through the regulation of gene expression in the seminiferous tubules.The odour receptor Or83,which is expressed in cells in the maturation zone of the seminiferous tubules,partially performs the regulation of spermatogenesis by FLT,but how FLT regulates spermatogenesis through Or needs further investigation.