Characterization of novel β‐1,3‐glucan recognition proteins from a Tibetan Plateau ghost moth Thitarodes pui (Lepidoptera, Hepialidae)

Abstract

β‐1,3‐glucan recognition proteins (βGRPs) function as pattern recognition receptors in the innate immune response against invading pathogens. In the present study, we obtain full‐length cDNA clones for two novel putative βGRPs: TpβGRPc and TpβGRPd from the ghost moth Thitarodes pui (Lepidoptera: Hepialidae). Phylogenetic analysis shows a small distinct lineage, βGRP clade 4, consisting of T. pui βGRPs including TpβGRPa and TpβGRPb that have been identified previously. TpβGRPc and TpβGRPd, comprising 488 and 229 amino acids, have calculated molecular masses of 52 596 and 24 589 Da, respectively. TpβGRPc is 85.52% identical in sequence to TpβGRPa. TpβGRPb and TpβGRPd share the same deletion start site located at the conserved residue Pro 43, although TpβGRPd exhibits a much larger deletion of up to approximately 270 residues covering both the N‐ and C‐terminal regions. Affinity purification, associated with subsequent peptide sequencing, confirms the constitutive occurrence of TpβGRPa and TpβGRPc of similar size (approximately 65 kDa) in sixth‐instar larval haemolymph. These two βGRPs show clear binding affinities to curdlan, an insoluble β‐1,3‐glucan. A quantitative real‐time polymerase chain reaction analysis reveals the high‐level constitutive expression of TpβGRPc and TpβGRPd in the fat body of mid‐instar larvae, which are found to be susceptible to fungal pathogens in field investigations. Remarkable induction of both TpβGRPs occurs in response to haemocoelic challenge with entomopathogenic fungus Beauveria bassiana. The results of the present study suggest that TpβGRPs may contribute to the detection and control of fungal infections.

Molecular characterization and functional analysis of a beta‐1,3‐glucan recognition protein from oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae)

“…In the current study, the expression levels of GmBGRP gene were the highest in the pupal stage, and the lowest in the adult stage. This is consistent with the report that TpβGRPa and TpβGRPb may be required for pupal development in Thitarodes pui (Sun et al, 2019). However, the developmental expression level of BGRP has been investigated in other insects, but the results were inconsistent with this study.…”

“…In addition, the expression level of GmBGRP is also different at different times after infection. Previous studies reported that, in T. pui , TpβGRPc transcript significantly decreased at 1 h and then increased approximately twofold at 3 h after fungal infection (Sun et al, 2019). These results indicate that GmBGRP plays an important role in the immune response to fungal infections, but the specific mechanism in G. molesta needs to be further studied.…”

Fungal α-1,3-Glucan as a New Pathogen-Associated Molecular Pattern in the Insect Model Host Galleria mellonella

“…This polysaccharide is detected by β-1,3-glucan recognition proteins (βGRPs/GNBPs) [ 60 , 61 ]. Receptors of this type have been identified, e.g., in B. mori, D. melanogaster, G. mellonella, Manduca sexta, Plodia interpuncella, Tenebrio molitor , and Thitarodes pui [ 44 , 62 , 63 , 64 ].…”