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Molecular cloning and analysis of PGRP-L1 and IMD from silkworm Bombyx mori
Ming-Yue Zhan1, Pei-Jin Yang1, Xiang-Jun Rao1
1School of Plant Protection, Anhui Agricultural University, Hefei, Anhui 230036, China.
Abstract:
Peptidoglycan is one of the major components of bacterial cell wall. The innate immune system of insects utilizes a group of peptidoglycan recognition proteins (PGRPs) for the recognition of specific peptidoglycans and activating immune signaling pathways. In Drosophila melanogaster, PGRP-LC and IMD (immune deficiency) are two important signaling molecules of the IMD pathway. Here we cloned and characterized PGRP-L1 and IMD from the domesticated silkworm Bombyx mori (BmPGRP-L1 and BmIMD). BmPGRP-L1 gene consists of five exons that encodes a polypeptide of 304 amino acids with a transmembrane region and an extracellular PGRP domain. The PGRP domain lacks key residues for the amidase activity. BmIMD cDNA encodes a polypeptide of 250 amino acids with a death domain. BmPGRP-L1 and BmIMD were expressed in various tissues and induced by bacterial challenges. In addition, in vivo blocking of the PGRP domain by the antiserum or purified antibody significantly reduced the expression of some antimicrobial peptide genes. The extracellular region of BmPGRP-L1 bound to diaminopimelic acid-type and lysine-type peptidoglycans. Overexpression of full-length BmIMD in Drosophila Schneider 2 cells significantly induced three antimicrobial peptide genes. These results suggest that BmPGRP-L1 and BmIMD may be players in the IMD pathway of B. mori. This study provides a foundation for further studies on the functions of silkworm IMD pathway.
Insights
The silkworm Bombyx mori has peptidoglycan recognition proteins (PGRPs) and immune deficiency (IMD) pathway components, BmPGRP-L1 and BmIMD. These molecules are involved in recognizing bacterial peptidoglycans and activating immune responses, crucial for insect immunity.
Area of Science:
- Insect immunity
- Molecular biology
- Biochemistry
Background:
- Peptidoglycan recognition proteins (PGRPs) are key in insect innate immunity.
- The IMD pathway is a critical immune signaling cascade in insects.
- Understanding these pathways in silkworms (Bombyx mori) is vital for agricultural and biomedical applications.
Purpose of the Study:
- To clone and characterize PGRP-L1 and IMD from Bombyx mori (BmPGRP-L1 and BmIMD).
- To investigate the expression patterns and functional roles of BmPGRP-L1 and BmIMD in response to bacterial challenges.
- To establish a foundation for studying the silkworm IMD pathway.
Main Methods:
- Gene cloning and sequencing of BmPGRP-L1 and BmIMD.
- Analysis of protein structure, including transmembrane and PGRP domains.
- Tissue expression analysis and induction studies following bacterial challenge.
- In vivo functional assays using antibodies and cell-based overexpression systems.
Main Results:
- BmPGRP-L1 possesses a PGRP domain lacking amidase activity, while BmIMD has a death domain.
- Both BmPGRP-L1 and BmIMD are expressed in various tissues and induced by bacterial infection.
- Blocking BmPGRP-L1 function reduced antimicrobial peptide gene expression.
- BmPGRP-L1 binds to specific peptidoglycan types, and BmIMD overexpression induces antimicrobial peptide genes.
Conclusions:
- BmPGRP-L1 and BmIMD are likely components of the Bombyx mori IMD pathway.
- These findings provide insights into the molecular mechanisms of silkworm innate immunity.
- This study lays the groundwork for future research on silkworm immune signaling.
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