Expression Patterns of Calreticulin from Bombyx mori After Immune Challenge

Calreticulin is a 46-kDa chaperone protein with multifunction, mainly involved in directing proper conformation of proteins, controlling calcium level, and participating in immune responses. In previous study, calreticulin from Bombyx mori (BmCRT) was identified, and BmCRT was significantly induced by some stimuli of intracellular calcium disturbance. In this study, we report that BmCRT mRNA and protein were detected in all organs of 5 larvae stage. BmCRT mRNA was specially abundant expressed in testis, ovary and hemocytes, but BmCRT protein was higher in testis and fat body than other tissues. To study the involvement of BmCRT in insect immune response, B. mori larvae were challenged by Escherichia coli, Micrococcus lysodeikticus, Beauveri bassiana or nucleopolyhedrovirus, respectively. After 1, 4 and 12 h microorganism injection, BmCRT mRNA and protein expression level in fat body were detected by qPCR and western blot methods. BmCRT expression in fat body can be induced by microorganisms, but with different expression patterns by different microorganisms. And BmCRT protein was induced later than the mRNA expression. Our results indicated BmCRT in fat body may be involved in humoral immune response against pathogenic microorganisms, and helpful to understand the comprehensive function of insect calreticulin.