In Drosophila secretion of antimicrobial peptides is mediated by two distinct pathways, the Toll pathway and Immune Deficiency (IMD) pathway. The Toll pathway is activated primarily in response to fungal and Gram positive bacterial infections, whereas the IMD pathway is activated

predominantly in response to Gram negative buy Alisertib and other Gram positive bacterial infections [19] and [12]. Toll activates expression of antifungal peptide genes, Dorsomycin and Metchnikowin, whereas, IMD induces transcription of genes, which encode the antibacterial peptides i.e., Diptericins, Cecropins, Drosocins and Attacins. A pathway similar to that of Drosophila IMD, termed as LvIMD was reported from L. vannamei. Expression of LvIMD mRNA is influenced by LPS and Gram negative Vibrio alginolyticus and expression of LvIMD could induce a 3 fold increase in the expression find more of PEN 4 [36]. Presence of Toll-like receptor in L. vannamei (Lv Toll1) was first reported by Yang et al. [39]. Two more Toll-like receptors, Lv Toll2 and Lv Toll3 were reported by Wang et al. [37]. In comparison to Lv Toll1 and Lv Toll3, Lv Toll2 was found to be more significant in the activation of AMP promoters in L. vannamei [37]. Mechanisms similar to these might be involved in the cleavage of precursor derived antimicrobial peptides. In case of 51-mer Hipposin, fragment containing 1 to 19 amino acid residues from the N terminal

did not exhibit marked antimicrobial activity, whereas fragment consisting of 16–39 amino acid (similar to buforin II) had such activity indicating that this part of Hipposin possesses antimicrobial sequence motif and the activity was found enhanced by the presence of the fragment having 40–51 amino acid residues [3]. Fragment consisting of 4–39 amino acid residues from N-terminal of Himanturin exhibit striking similarity to 16–39 amino acid fraction of Hipposin

which has been shown to contain the antimicrobial sequence motif. Almost all previously reported histone H2A derived AMPs have fragments similar to this fraction of Hipposin and it could be deduced that their activity is mainly due to this portion. Fraction 4–39 of Farnesyltransferase Himanturin is similar to 16 to 51 amino acid fraction of hipposin except for Thr at position 16 of Hipposin which has been replaced by Ser (position 4) in Himanturin and His at position 41 of Hipposin being replaced by Glu (position 29) in Himanturin. Presence of Ser instead of Thr at position 16 of Hipposin can also be seen in Abhisin and histone H2A derived AMPs reported from L. vannamei and Chlamys farreri. Histone H2A AMPs reported from marine organisms exhibit broad spectrum antimicrobial activity. Hipposin and Parasin I are the most studied Histone H2A derived antimicrobial peptides. Hipposin showed strong antibacterial activity against several Gram positive and Gram negative bacteria and the activity could be detected down to concentrations of 1.6 μg/ml [2].