Abstract
The diamondback moth, Plutella xylostella (L.), is a destructive pest that attacks cruciferous crops worldwide. Immune responses are important for interactions between insects and pathogens and information on these underpins the development of strategies for biocontrol-based pest management. Little, however, is known about immune genes and their regulation patterns in P. xylostella. A total of 149 immune-related genes in 20 gene families were identified through comparison of P. xylostella genome with the genomes of other insects. Complete and conserved Toll, IMD and JAK-STAT signaling pathways were found in P. xylostella. Genes involved in pathogen recognition were expanded and more diversified than genes associated with intracellular signal transduction. Gene expression profiles showed that the IMD pathway may regulate expression of antimicrobial peptide (AMP) genes in the midgut, and be related to an observed down-regulation of AMPs in experimental lines of insecticide-resistant P. xylostella. A bacterial feeding study demonstrated that P. xylostella could activate different AMPs in response to bacterial infection. This study has established a framework of comprehensive expression profiles that highlight cues for immune regulation in a major pest. Our work provides a foundation for further studies on the functions of P. xylostella immune genes and mechanisms of innate immunity.
Highlights
Peptidoglycan recognition proteins (PGRPs) and beta-1, 3-glucan recognition proteins, detect microbial infection and trigger the signaling cascades to activate the Toll and immune deficiency (IMD) pathways[1]
By comparative analysis of immune genes among five insect species, 20 gene families were identified in the P. xylostella genome, including components of the conserved immune signaling pathways (Toll, IMD, JNK and JAK-STAT), pathogen recognition and immune effectors
Based on the identified genes (Table S1-2) and their functions documented in other insect species[35,36,54,67], we propose a model of the potential immune pathways in P. xylostella (Fig. 5) that need to be experimentally validated
Summary
Peptidoglycan recognition proteins (PGRPs) and beta-1, 3-glucan recognition proteins (βGRPs), detect microbial infection and trigger the signaling cascades to activate the Toll and IMD pathways[1]. Casanova-Torres and Goodrich-Blair[1] compared the genetic mechanisms related to the immune system of D. melanogaster (Order: Diptera) and Bombyx mori and Manduca sexta, two representatives of Order: Lepidoptera They showed, for example, that while some genetic components of the Toll signaling pathway may be similar between Lepidoptera and Diptera, some other genes differ. Expressed sequence tags and cDNA microarrays have been used to analyze immune-inducible genes[14] Whilst these studies of specific aspects are enlightening, there is a more fundamental need to develop an understanding of immune related genes based on genome-wide analysis, especially since the mechanisms of P. xylostella immunity at the molecular level are poorly understood. P. xylostella immune response to bacterial pathogens was studied
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