Low-density lipoprotein receptor-related protein 2(LRP2)is required for lipid export in the midgut of the migratory locust,Locusta migratoria

Low-density lipoprotein receptor-related protein 2(LRP2)is a multifunctional endocytic receptor expressed in epithelial cells.In mammals,it acts as an endocytic receptor that mediates the cellular uptake of cholesterol-containing apolipoproteins to maintain lipid homeostasis.However,little is known about the role of LRP2 in lipid homeostasis in insects.In the present study,we investigated the function of LRP2 in the migratory locust Locusta migratoria(LmLRP2).The mRNA of LmLRP2 is widely distributed in various tissues,including integument,wing pads,foregut,midgut,hindgut,Malpighian tubules and fat body,and the amounts of LmLRP2 transcripts decreased gradually in the early stages and then increased in the late stages before ecdysis during the nymphal developmental stage.Fluorescence immunohistochemistry revealed that the LmLRP2 protein is mainly located in cellular membranes of the midgut and hindgut.Using RNAi to silence LmLRP2 caused molting defects in nymphs(more than 60%),and the neutral lipid was found to accumulate in the midgut and surface of the integument,but not in the fat body,of dsLmLRP2-treated nymphs.The results of a lipidomics analysis showed that the main components of lipids(diglyceride and triglyceride)were significantly increased in the midgut,but decreased in the fat body and hemolymph.Furthermore,the content of total triglyceride was significantly increased in the midgut,but markedly decreased in the fat body and hemolymph in dsLmLRP2-injected nymphs.Our results indicate that LmLRP2 is located in the cellular membranes of midgut cells,and is required for lipid export from the midgut to the hemolymphand fat body in locusts.

Development and formation of wing cuticle based on transcriptomic analysis in Locusta migratoria during metamorphosis

Wings are an important flight organ of insects.Wing development is a complex process controlled by a series of genes.The flightless wing pad transforms into a mature wing with the function of migratory flight during the nymphto-adult metamorphosis.However,the mechanism of wing morphogenesis in locusts is still unclear.This study analyzed the microstructures of the locust wing pads at pre-eclosion and the wings after eclosion and performed the comparative transcriptome analysis.RNA-seq identified 25,334 unigenesand 3,430 differentially expressed genes(DEGs)(1,907 up-regulated and 1,523 down-regulated).The DEGs mainly included cuticle development(LmACPs),chitin metabolism(Lm Idgf4),lipid metabolism-related genes,cell adhesion(Integrin),zinc finger transcription factors(LmSalm,LmZF593 andLmZF521),and others.Functional analysis based on RNA interference and hematoxylin and eosin(H&E)staining showed that the three genes encoded zinc finger transcription factors are essential for forming wing cuticle and maintaining morphology in Locusta migratoria.Finally,the study found that the LmSalm regulates the expression of LmACPs in the wing pads at pre-eclosion,and LmZF593 and LmZF521 regulate the expression of LmIntegrin/LmIdgf4/LmHMT420 in the wings after eclosion.This study revealed that the molecular regulatory axis controls wing morphology in nymphal and adult stages of locusts,offering a theoretical basis for the study of wing development mechanisms in hemimetabolous insects.

Role of CYP311A1 in wing development of Drosophila melanogaster

Lipid homeostasis is crucial for growth and development of organisms.Several cytochrome P450 monooxygenases(CYPs)are involved in lipid metabolism.The function of Cyp3llal in the anterior midgut as a regulator of phosphatidylethanolamine(PE)metabolism in Drosophila melanogaster has been demonstrated,as depletion of Cyp31lal caused larval growth arrest that was partially rescued by supplying PE.In this study,we investigated the role of CYP311A1 in wing morphogenesis in Drosophila.Using the GAL4-UAS system,Cyp31lal was selectively knocked down in the wing disc.A deformed wing phenotype was observed in flies with reduced Cyp31lal transcripts.BODIPY and oil red O staining revealed a reduction of neutral lipids in the wing disc after the depletion of Cyp31lal.In addition,we observed an enhanced sensitivity to Eosin Y penetration in the wings of Cyp31lal knocked-down flies.Moreover,the reduction of CYP311A1 function in developing wings does not affect cell proliferation and apoptosis,but entails disordered Phalloidin or Cadherin distribution,suggesting an abnormal cell morphology and cell cortex structure in wing epithelial cells.Taken together,our results suggest that Cyp3llal is needed for wing morphogenesis by participating in lipid assembly and cell homeostasis.

Knickkopf (LmKnk) is required for chitin organization in the foregut of Locusta migratoria

The foregut,located at the front of the digestive tract,serves a vital role in in-sects by storing and grinding food into small particles.The innermost layer of the foregut known as the chitinous intima,comes into direct contact with the food and acts as a protec-tive barrier against abrasive particles.Knickkopf(Knk)is required for chitin organization in the chitinous exoskeleton,tracheae and wings.Despite its significance,lttle is known about the biological function of Knk in the foregut.In this study,we found that LmKnk was stably expressed in the foregut,and highly expressed before molting in Locusta migrato-ria.To ascertain the biological function of LmKnk in the foregut,we synthesized specific double-stranded LmKnk(dsLmKnk)and injected it into locusts.Our findings showed a significant decrease in the foregut size,along with reduced food intake and accumulation of residues in the foregut after dsLmKnk injection.Morphological observations revealed that newly formed intima became thinner and lacked chitin lamella.Furthermore,fluores-cence immunohistochemistry revealed that LmKnk was located in the apical region of new intima and epithelial cells.Taken together,this study provides insights into the biological function of LmKnk in the foregut,and identifies the potential target gene for exploring biological pest management strategies.