Characterization of two groups of Spodoptera exigua Hübner (Lepidoptera: Noctuidae) C‐type lectins and insights into their role in defense against the densovirus JcDV

Abstract

Insect innate immunity relies on numerous soluble and membranebound receptors, named pattern recognition proteins (PRPs), which enable the insect to recognize pathogen-associated molecular patterns. C-type lectins are among the best-studied PRPs and constitute the most diverse family of animal lectins. Here we have charac- The results showed that Se-BLL3 specifically reduce the mortality of Spodoptera frugiperda larvae caused by JcDV. In contrast, no such effect was observed with S. exigua larvae. In a previous work, we have also shown that Se-BLL2 increased the tolerance of S. exigua larvae to baculovirus infection. Taken together, these results confirm the implication of two different C-type lectins in antiviral response and reflect the biological relevance of the acquisition of bracoviral genes in Spodoptera spp.

The Dual Functions of a Bracovirus C-Type Lectin in Caterpillar Immune Response Manipulation

“…The details of these CTLs spatial structures are shown in Supplementary Table 3 . It has been reported that CTLs are widespread in lepidopteran insects and some CTLs from bracoviruses horizontally transferred into genomes of nonparasitized hosts ( 50 , 52 ), we performed the PCR experiment with specific primers of CvBV_28-1 using the DNA as template from parasitized and nonparasitized P. xylostella larvae. The results showed that CvBV_28-1 derived from C. vestalis bracovirus could be detected in the parasitized hosts, but this gene did not exist in nonparasitized host larvae ( Figure 2C ).…”

“…In addition to two classic properties of CTLs mentioned above, insect CTLs are able to mediate other innate immune responses, including opsonization, nodule formation, phagocytosis, encapsulation/melanization and prophenoloxidase activation ( 48 , 49 ). Recently, it has been reported that some insect CTLs originated from PDVs through horizontal gene transfer, and the domestication of these CTLs presents new adaptations and confers the host with protection against baculoviruses ( 50 – 52 ). Given the special biological features of PDVs, CTLs from PDVs in parasitized hosts might be necessary for wasp offspring survival.…”

Transcriptome Analysis Reveals Early Hemocyte Responses upon In Vivo Stimulation with LPS in the Stick Insect Bacillus rossius (Rossi, 1788)

“…Most insect CTLs are established as strongly inducible secretory proteins produced in response to in vivo stimulations or challenges with pathogens [ 15 , 19 , 20 ]. CTLs act as PRRs in the extracellular environment; they recognize and bind to PAMPs via characteristic motifs localized within the CTL carbohydrate-recognition domain (CRD)—referred to as CLECT on SMART (accession number: SM00034)—overall playing an important role in both antiviral and antibacterial defenses [ 19 , 20 ]. In vertebrates, such motifs are conserved as Glu-Pro-Asn (EPN) or Gln-Pro-Asp (QPD) and are specific for mannose/glucose or galactose carbohydrates [ 21 ].…”