title: Melanization reaction products of shrimp display antimicrobial properties against their major bacterial and fungal pathogens.
abstract: Melanization is a rapid defense mechanism in invertebrates. The substrate specificity of phenoloxidases (POs) and the role of melanization reaction products were investigated in the black tiger shrimp, Penaeus monodon. Two PmPOs (PmproPO1 and PmproPO2) were found to display a substrate specificity towards monophenols and diphenols, and exhibit relatively weak activity against 5,6-dihydroxyindole (DHI). Systemic infection of the PmproPO1/2 co-silenced shrimp with the fungus, Fusarium solani, led to a significantly increased mortality, suggesting an important role of PmproPOs in shrimp's defense against fungal infection. Using L-DOPA, dopamine or DHI as a substrate, the melanization reaction products exhibited in vitro antimicrobial activities towards Gram-negative bacteria (Vibrio harveyi and Vibrioparahaemolyticus) and Gram-positive bacteria (Bacillus subtilis), whereas the lower effect was detected against the fungus (F. solani). SEM analysis revealed the morphological changes and damage of cell membranes of V. harveyi and F. solani after treatment with shrimp melanization reaction products. Together, these findings demonstrate the crucial functions of the proPO system and the importance of melanization reaction products in the shrimp's immune defense.
authors.affiliation: Center of Excellence for Molecular Biology and Genomics of Shrimp, Department of Biochemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Bangkok 10330, Thailand; Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Mahidol University, Rama VI Road, Bangkok 10400, Thailand; National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Walaiporn
authors.initials: W
authors.lastname: Charoensapsri
authors.affiliation: Center of Excellence for Molecular Biology and Genomics of Shrimp, Department of Biochemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Bangkok 10330, Thailand; National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Piti
authors.initials: P
authors.lastname: Amparyup
authors.affiliation: Center of Excellence for Molecular Biology and Genomics of Shrimp, Department of Biochemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Bangkok 10330, Thailand.
authors.forename: Chawapat
authors.initials: C
authors.lastname: Suriyachan
authors.affiliation: Center of Excellence for Molecular Biology and Genomics of Shrimp, Department of Biochemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Bangkok 10330, Thailand. Electronic address: anchalee.k@chula.ac.th.
authors.forename: Anchalee
authors.initials: A
authors.lastname: Tassanakajon
mesh_terms: D000818:Animals; D001412:Bacillus subtilis / Q000502:physiology; D005670:Fusarium / Q000502:physiology; D008543:Melanins / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D033561:Penaeidae / Q000276:immunology* / Q000382:microbiology*; D010636:Phenols / Q000378:metabolism; D013047:Specific Pathogen-Free Organisms; D014733:Vibrio / Q000502:physiology
chemical_list: D008543:Melanins; D010636:Phenols; D014442:Monophenol Monooxygenase
keywords: Fusarium solani; Melanization reaction products; Phenoloxidase; Shrimp; Vibrio harveyi