TAILIEUCHUNG - Báo cáo khoa học: Increased bacterial load in shrimp hemolymph in the absence of prophenoloxidase

Invertebrates rely on their innate immune responses to protect themselves from pathogens, one of which is melanization of bacteria mediated by the activation of phenoloxidase (PO). Furthermore, invertebrate hemo-lymph, even that of healthy individuals, has been shown to contain bacterial species. | ễFEBS Journal Increased bacterial load in shrimp hemolymph in the absence of prophenoloxidase Fernand F. Fagutao1 Takashi Koyama1 Akihiro Kaizu1 Tatsuo Saito-Taki2 Hidehiro Kondo1 Takashi Aoki1 and Ikuo Hirono1 1 Laboratory of Genome Science Tokyo University of Marine Science and Technology Japan 2 Department of Microbiology Schoolof Allied Health Science Kitasato University Japan Keywords gene silencing innate immunity melanization prophenoloxidase proPO shrimp Correspondence I. Hirono Laboratory of Genome Science Tokyo University of Marine Science and Technology Konan 4-5-7 Minato Tokyo 108-8477 Japan Fax 81 35463 0689 Tel 81 35463 0689 E-mail hirono@ Received 1 June 2009 revised 14 July 2009 accepted 21 July 2009 doi Invertebrates rely on their innate immune responses to protect themselves from pathogens one of which is melanization of bacteria mediated by the activation of phenoloxidase PO . Furthermore invertebrate hemolymph even that of healthy individuals has been shown to contain bacterial species. The mechanisms that prevent these bacteria from proliferating and becoming deleterious to the host are however poorly understood. Here we show that knocking down the activity of the inactive precursor of PO prophenoloxidase proPO by RNA interference resulted in a significant increase in the bacterial load of kuruma shrimp Marsupenaeus japonicus even in the absence of a bacterial or viral challenge. Silencing of proPO also led to a sharp increase in shrimp mortality. In addition the hemolymph of proPO-depleted shrimp had significantly lower hemocyte counts and PO activity than control samples. Microarray analysis after proPO silencing also showed a decrease in the expression of a few antimicrobial peptides but no effect on the expression of the genes involved in the clotting system. Treatment with antibiotics prior to and after proPO dsRNA injection to counteract the loss of proPO resulted in a significant increase in

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