AUTHOR=Keshavarz Maryam , Jo Yong Hun , Edosa Tariku Tesfaye , Han Yeon Soo 

TITLE=Tenebrio molitor PGRP-LE Plays a Critical Role in Gut Antimicrobial Peptide Production in Response to Escherichia coli

JOURNAL=Frontiers in Physiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.00320

DOI=10.3389/fphys.2020.00320

ISSN=1664-042X

ABSTRACT=<p>Invading pathogens are recognized by peptidoglycan recognition proteins (PGRPs) that induce translocation of NF-κB transcription proteins and expression of robust antimicrobial peptides (AMPs). <italic>Tenebrio molitor</italic> PGRP-LE (<italic>Tm</italic>PGRP-LE) has been previously identified as a key sensor of <italic>Listeria monocytogenes</italic> infection. Here, we present that <italic>TmPGRP-LE</italic> is highly expressed in the gut of <italic>T. molitor</italic> larvae and 5-day-old adults in the absence of microbial infection. In response to <italic>Escherichia coli</italic> and <italic>Candida albicans</italic> infections, <italic>TmPGRP-LE</italic> mRNA levels are significantly upregulated in both the fat body and gut. Silencing of <italic>TmPGRP-LE</italic> by RNAi rendered <italic>T. molitor</italic> significantly more susceptible to challenge by <italic>E. coli</italic> infection and, to a lesser extent, <italic>Staphylococcus aureus</italic> and <italic>C. albicans</italic> infections. Reduction of <italic>TmPGRP-LE</italic> levels in the larval gut resulted in downregulation of eight AMP genes following exposure to <italic>E. coli</italic>, <italic>S. aureus</italic>, and <italic>C. albicans</italic>. However, the transcriptional levels of AMPs more rapidly reached a higher level in the ds<italic>EGFP</italic>-treated larval gut after challenge with <italic>E. coli</italic>, which may suggest that AMPs induction were more sensitive to <italic>E. coli</italic> than <italic>S. aureus</italic> and <italic>C. albicans.</italic> In addition, <italic>TmPGRP-LE</italic> RNAi following <italic>E. coli</italic> and <italic>C. albicans</italic> challenges had notable effects on <italic>TmRelish</italic>, <italic>TmDorsal X1</italic> isoform (<italic>TmDorX1</italic>), and <italic>TmDorX2</italic> expression level in the fat body and gut. Taken together, <italic>TmPGRP-LE</italic> acts as an important gut microbial sensor that induces AMPs via Imd activation in response to <italic>E. coli</italic>, whereas involvement of <italic>TmPGRP-LE</italic> in AMPs synthesize is barely perceptible in the hemocytes and fat body.</p>