Table1_Coexistence of nonfluorescent chromoproteins and fluorescent proteins in massive Porites spp. corals manifesting a pink pigmentation response.pdf

IntroductionSeveral fluorescent proteins (FPs) and chromoproteins (CPs) are present in anthozoans and play possible roles in photoprotection. Coral tissues in massive corals often display discoloration accompanied by inflammation. Incidences of the pink pigmentation response (PPR) in massive Porites, described as inflammatory pink lesions of different shapes and sizes, has recently increased worldwide. FPs are reported to be present in PPR lesions, wherein a red fluorescent protein (RFP) appears to play a role in reducing reactive oxygen species. However, to date, the biochemical characterization and possible roles of the pigments involved are poorly understood. The present study aimed to identify and characterize the proteins responsible for pink discoloration in massive Porites colonies displaying PPRs, as well as to assess the differential distribution of pigments and the antioxidant properties of pigmented areas.
MethodCPs were extracted from PPR lesions using gel-filtration chromatography and identified via genetic analysis using liquid chromatography-tandem mass spectrometry. The coexistence of CPs and RFP in coral tissues was assessed using microscopic observation. Photosynthetic antivity and hydrogen peroxide-scavenging activitiy were measured to assess coral stress conditions.
ResultsThe present study revealed that the same CP (plut2.m8.16902.m1) isolated from massive Porites was present in both the pink spot and patch morphologies of the PPR. CPs were also found to coexist with RFP in coral tissues that manifested a PPR, with a differential distribution (coenosarc or tip of polyps’ tentacles). High hydrogen peroxide-scavenging rates were found in tissues affected by PPR.
Discussion and ConclusionThe coexistence of CPs and RFP suggests their possible differential role in coral immunity. CPs, which are specifically expressed in PPR lesions, may serve as an antioxidant in the affected coral tissue. Overall, this study provides new knowledge to our understanding of the role of CPs in coral immunity.

引言
多种荧光蛋白（fluorescent proteins, FPs）与发色蛋白（chromoproteins, CPs）广泛存在于珊瑚虫纲动物（anthozoans）中，推测其可能参与光保护过程。块状珊瑚的珊瑚组织常出现变色症状并伴随炎症反应。近年来，全球范围内块状滨珊瑚（Porites）的粉色色素沉着反应（pink pigmentation response, PPR）发生率呈上升趋势，该反应表现为形态、大小各异的炎症性粉色病灶。已有研究报道PPR病灶中存在荧光蛋白，其中红色荧光蛋白（red fluorescent protein, RFP）似乎可参与清除活性氧。然而迄今为止，相关色素的生化特性与潜在功能仍未得到充分阐明。本研究旨在鉴定并表征表现出PPR的块状滨珊瑚菌落中，导致粉色变色的相关蛋白，并评估色素的差异化分布特征以及色素沉着区域的抗氧化活性。
材料与方法
采用凝胶过滤色谱法从PPR病灶中提取发色蛋白，并通过液相色谱-串联质谱法（liquid chromatography-tandem mass spectrometry）完成蛋白鉴定。通过显微镜观察评估珊瑚组织中发色蛋白与红色荧光蛋白的共存情况。检测光合活性与过氧化氢清除活性，以评估珊瑚的应激状态。
结果
本研究发现，从块状滨珊瑚中分离得到的同一发色蛋白（plut2.m8.16902.m1），同时存在于PPR的粉色斑点与斑块两种形态的病灶中。研究还证实，在表现出PPR的珊瑚组织中，发色蛋白与红色荧光蛋白共存，且二者存在差异化分布（分布于共肉组织或珊瑚虫触手顶端）。受PPR影响的组织表现出较高的过氧化氢清除速率。
讨论与结论
发色蛋白与红色荧光蛋白的共存现象，提示二者在珊瑚免疫中可能发挥差异化的功能。特异性在PPR病灶中表达的发色蛋白，可能在受影响的珊瑚组织中充当抗氧化剂。总体而言，本研究为阐明发色蛋白在珊瑚免疫中的作用提供了新的科学认知。