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Open Access Highly Accessed Research article

Development and immunity-related microRNAs of the lepidopteran model host Galleria mellonella

Krishnendu Mukherjee1 and Andreas Vilcinskas12*

Author Affiliations

1 Fraunhofer Institute for Molecular Biology and Applied Ecology, Department of Bioresources, Winchester Str. 2, 35395 Giessen, Germany

2 Institute of Phytopathology and Applied Zoology, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany

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BMC Genomics 2014, 15:705  doi:10.1186/1471-2164-15-705

Published: 23 August 2014

Abstract

Background

MicroRNAs (miRNAs) are small non-coding RNAs that act as key players in the post-transcriptional regulation of protein synthesis. Although little is known about their role in complex physiological processes such as development and immunity, our knowledge is expanding rapidly, thanks to the use of model systems. The larvae of the greater wax moth Galleria mellonella are now established as model hosts for pathogens that infect insects or humans. To build on our previously-reported comprehensive G. mellonella transcriptome, here we describe the identification and analysis of development and immunity-related miRNAs, thus providing valuable additional data to promote the use of this model host for the analysis of complex processes.

Results

To screen for miRNAs that are differentially expressed in G. mellonella (1) during metamorphosis or (2) following infection with the entomopathogenic bacterium Serratia entomophila or (3) with the parasitic fungus Metarhizium anisopliae, we designed a microarray containing more than 2000 insect miRNA probe sequences. We identified miRNAs that were significantly expressed in pre-pupae (16), pupae (22) and last-instar larvae infected with M. anisopliae (1) in comparison with untreated last-instar larvae which were used as a reference. We then used our transcriptomic database to identify potential 3′ untranslated regions that form miRNA–mRNA duplexes by considering both base pair complementarity and minimum free energy hybridization. We confirmed the co-expression of selected miRNAs (such as miR-71, miR-263a and miR-263b) with their predicted target mRNAs in last-instar larvae, pre-pupae and pupae by RT-PCR. We also identified miRNAs that were expressed in response to infection with bacterial or fungal pathogens, and one miRNA that may act as a candidate mediator of trans-generational immune priming.

Conclusions

This is the first study to identify miRNAs that are predicted to regulate genes expressed during metamorphosis or in response to infection in the lepidopteran model host G. mellonella.

Keywords:
MicroRNA; MicroRNA target prediction; Development; Metamorphosis; Immunity; Trans-generational immune priming; Galleria mellonella; Metarhizium anisopliae