Functional Studies Of HaGBP And HaGBPB In Innate Immune Response In The Cotton Bollworm (Helicoverpa Armigera)

Insects rely on innate immune system to defend them against pathogens and parasites. Innate immune system is composed of cellular immunity and humoral immunity. Cellular immunity employs haemocyte-mediated phagocytosis, encapsulation and nodulation to combat against invading pathogens, while humoral immunity directly kills bacteria through synthesis and secretion of antimicrobial peptides (AMPs). A competing viewpoint has emerged that these two processes are not response at the same time, but initiate one after another and reciprocally switch. Switching between humoral and cellular immune responses is guided by the cytokine GBP. Here, we obtain a GBP (named HaGBP) and two GBP-binding protein (named HaGBPB1 and HaGBPB2, respectively) genes from our previous Helicoverpa armigera fat bodies transcriptome. To investigate the function of HaGBP and HaGBPB involved in innate immune response, we have expressed and purified recombinant HaGBPB protein in vitro. HaGBP synthesized by Biotechnology Company was used for functional analysis. Expression profile and functional analysis of HaGBP and HaGBPB were conducted. Preliminary results indicated that (i) HaGBP mainly expressed in fat body, while HaGBPB mainly expressed in hemocyte. (ii) HaGBPB1 was mainly expressed in feeding stage and before, while HaGBPB2 was mainly expressed in feeding stage and after, (iii) HaGBPB mRNAs were significantly upregulated upon 20-hydroxyecdysone (20E) injections. Moreover, knockdown of HaEcR and/or HaUSP significantly suppressed HaGBPB expression induced by 20E. (iv) The expression of HaGBPB was inhibited by beads challenge. HaGBP promoted plasmatocytes spreading, which could be suppressed by HaGBPB1. The relay expression of HaGBPB1 and HaGBPB2 is involved in regulation of HaGBP-mediated cellular immune response of 6th instar larvae. Further,20E plays important role in the process.