title: Dual recognition activity of a rhamnose-binding lectin to pathogenic bacteria and zooxanthellae in stony coral Pocillopora damicornis.
abstract: Rhamnose-binding lectin (RBL) is a type of Ca2+-independent lectin with tandem repeat carbohydrate-recognition domain, and is crucial for the innate immunity in many invertebrates. In this study, the cDNA sequence encoding RBL in coral Pocillopora damicornis (PdRBL-1) was cloned. The PdRBL-1 protein shared highest amino acid sequence similarity (55%) with the polyp of Hydra vulgaris, and contained a signal peptide and two tandem carbohydrate-recognition domains in which all cysteine residues were conserved. Surface plasmon resonance method revealed that the recombinant PdRBL-1 protein bound to LPS and Lipid A, but not to LTA, β-glucan, mannose and Poly (I:C). Results also showed that it bonded with zooxanthellae using western blotting method, and that the bound protein was detectable only at concentrations higher than 102zooxanthellae cell mL-1. When recombinant PdRBL-1 protein was preincubated with LPS, lower amounts of protein bound to zooxanthellae compared to cells not preincubated with LPS. Furthermore, PdRBL-1 mRNA expression increased significantly at 12 h, and declined to the baseline at 24 h after heat stress at 31 °C. These results collectively suggest that PdRBL-1 could recognize not only pathogenic bacteria but also symbiotic zooxanthellae, and that the recognition of zooxanthellae by PdRBL-1 could be repressed by pathogenic bacteria through competitive binding. This information allows us to gain new insights in the mechanisms influencing the establishment and maintenance of coral-zooxanthella symbiosis in coral P. damicornis.
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China. Electronic address: zhouzhi@hainu.edu.cn.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Yu
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Tang
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China.
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China.
authors.forename: Guangmei
authors.initials: G
authors.lastname: Chen
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China; Beijing Normal University, Beijing 100875, China. Electronic address: 2457010689@qq.com.
authors.forename: Liping
authors.initials: L
authors.lastname: Guo
authors.affiliation: Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Huang
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000276:immunology*; D003001:Cloning, Molecular; D004141:Dinoflagellida / Q000276:immunology*; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000378:metabolism; D037102:Lectins / Q000378:metabolism*; D008050:Lipid A / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D011070:Poly I-C / Q000276:immunology; D011528:Protozoan Infections / Q000276:immunology*; D012210:Rhamnose / Q000378:metabolism; D016415:Sequence Alignment; D013312:Stress, Physiological / Q000276:immunology*; D013559:Symbiosis
chemical_list: D006360:Heat-Shock Proteins; D037102:Lectins; D008050:Lipid A; D008070:Lipopolysaccharides; D011070:Poly I-C; D012210:Rhamnose
keywords: Coral; PAMPs; Rhamnose-binding lectin; Symbiosis; Zooxanthellae