β-1,3-Glucan recognition protein (βGRP) is essential for resistance against fungal pathogen and opportunistic pathogenic gut bacteria in Locusta migratoria manilensis

Pattern recognition proteins, which form part of the innate immune system, initiate host defense reactions in response to pathogen surface molecules. The pattern recognition protein beta-1,3-glucan recognition protein (beta GRP) binds to beta-1,3-glucan on fungal surfaces to mediate melanization via the prophenoloxidase (PPO)-activating cascade. In this study, cDNA encoding a 53-kDa beta GRP (Lm beta GRP) was cloned from Locusta migratoria manilensis. Lm beta GRP mRNA shown to be constitutively expressed specifically in hemocytes and was highly upregulated following fungal infection. Lm beta GRP-silenced (Lm beta GRP-RNAi) mutant locusts exhibited significantly reduced survival rate following fungal infection (Metarhizium acridum) compared with the wild-type. Furthermore, Lm beta GRP-RNAi mutants exhibited abnormally loose stools indicative of a gut defect. 16S rRNA gene analysis detected the opportunistic pathogenic bacterium, Vibrio vulnificus in Lm beta GRP mutant but not wild-type locusts, suggesting changes in the composition of gut bacterial communities. These results indicate that Lm beta GRP is essential to gut immunity in L. migratoria manilensis. (c) 2011 Elsevier Ltd. All rights reserved.