Molecular cloning and functional analyses of an adhesion molecule, neuroglian, in Mythimna separata (Lepidoptera: Noctuidae)

Abstract

Insect cellular immune reaction, which generally includes phagocytosis, encapsulation and nodule formation, is achieved by hemocytes circulating in insect haemolymph. The shift of hemocytes from the normal phase to the adhering phase is an important process in the cellular immune reaction, which includes the attachment of hemocytes to foreign surfaces or other hemocytes via adhesion factors. Neuroglian is one of the adhering factors associated with encapsulation in Manduca sexta and Drosophila melanogaster. Here we studied the localization of neuroglian (MsNrg) in Mythimna separata and its functional role in the cellular immune reaction. The distribution of MsNrg mRNA between hemocyte populations was determined using real-time quantitative reverse transcription PCR and in situ hybridization, which revealed that MsNrg was highly expressed in adhering hemocytes, especially in plasmatocytes. Unexpectedly, the transcript was observed as well in non-adhering hemocytes, implying neuroglian has a function in non-adhering hemocytes. Moreover, we showed that the amount of MsNrg mRNA was not changed by injections of either biotic or abiotic non-selves. Fewer latex beads were fully encapsulated by hemocytes in larvae treated with MsNrg double-stranded RNA than in control larvae, but their ability to achieve phagocytosis and nodule formation remained unchanged by the MsNrg knockdown. These results indicate that the function of neuroglian in the cellular immune reaction is conserved in D. melanogaster and lepidopteran species, and neuroglian in non-adhering hemocytes could possess unidentified function.

Keywords

• lepidoptera
• noctuidae
• mythimna separata
• neuroglian
• hemocyte adhesion
• encapsulation
• in situ hybridization
• real-time quantitative reverse transcript pcr
• rna interference