ABSTRACT
Nuclear receptors (NRs) are ligand-regulated transcription factors that are important for the normal growth and development of insects. However, systematic function analysis of NRs in the molting process of Lasioderma serricorne has not been reported. In this study, we identified and characterized 16 NR genes from L. serricorne. Spatiotemporal expression analysis revealed that six NRs were mainly expressed in 3-d-old 4th-instar larvae; five NRs were primarily expressed in 5-d-old adults and four NRs were predominately expressed in prepupae. All the NRs were highly expressed in epidermis, fat body and foregut. RNA interference (RNAi) experiments revealed that knockdown of 15 NRs disrupted the larva-pupa-adult transitions and caused 64.44-100 % mortality. Hematoxylin-eosin staining showed that depletion of 12 NRs prevented the formation of new cuticle and disrupted apolysis of old cuticle. Silencing of LsHR96, LsSVP and LsE78 led to newly formed cuticle that was thinner than the controls. The 20E titer and chitin content significantly decreased by 17.67-95.12 % after 15 NR dsRNA injection and the gene expression levels of 20E synthesis genes and chitin metabolism genes were significantly reduced. These results demonstrated that 15 NR genes are essential for normal molting and metamorphosis of L. serricorne by regulating 20E synthesis and chitin metabolism.
Subject(s)
Coleoptera , Gene Expression Regulation, Developmental , Metamorphosis, Biological , Molting , Receptors, Cytoplasmic and Nuclear , Animals , Molting/genetics , Metamorphosis, Biological/genetics , Coleoptera/genetics , Coleoptera/growth & development , Coleoptera/metabolism , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolism , Larva/genetics , Larva/growth & development , Chitin/metabolism , RNA Interference , Insect Proteins/genetics , Insect Proteins/metabolism , Phylogeny , Ecdysterone/metabolismABSTRACT
The peptidoglycan recognition protein (PGRP), an important pattern recognition receptor of insects, is significant for reducing innate immunity and effective pest control. We cloned four PGRP genes (LsPGRP-LB, LsPGRP-LB1, LsPGRP-LE, and LsPGRP-SC2) from the cigarette beetle, Lasioderma serricorne (Fabricius), which encoded proteins of 216, 197, 317, and 190 amino acids, respectively. Three LsPGRPs were predominantly expressed in the larval and pupal stages, whereas LsPGRP-LE displayed high expression in adults. All the four LsPGRPs genes were highly expressed in the midgut and integument. Pathogen inoculation revealed that the four LsPGRPs actively responded to Escherichia coli and its peptidoglycan. The transcription levels of LsPGRP-LE and LsPGRP-SC2 increased significantly after Staphylococcus aureus stimulation. RNA interference-mediated knockdown of the four LsPGRPs led to increased larval mortality when challenged by E. coli, and the expression of four antimicrobial peptide genes (LsCole, LsAtt2, LsDef1 and LsDef2) had a significant decrease. Higher mortality and lower AMP expression were also observed in L. serricorne under S. aureus infection after silencing LsPGRP-LE and LsPGRP-SC2. Our results suggest that the four LsPGRP genes play important and distinct regulatory roles in the antibacterial defense response of L. serricorne.
