Green fluorescent protein regulation in the coral Acropora yongei during photoacclimation

Abstract

). Green fluorescence increased ~1.9 times in high light corals and decreased ~1.9 times in low light corals compared with medium light corals. GFP concentration and green fluorescence intensity were significantly correlated. Typical photoacclimation responses in the dinoflagellates were observed including changes in density, photosynthetic pigment concentration and photosynthetic efficiency. Although fluorescent proteins are ubiquitous and abundant in scleractinian corals, their functions remain ambiguous. These results suggest that scleractinian corals regulate GFP to modulate the internal light environment and support the hypothesis that GFP has a photoprotective function. The success of photoprotection and photoacclimation strategies, in addition to stress responses, will be critical to the fate of scleractinian corals exposed to climate change and other stressors.Supplementary material available online at http://jeb.biologists.org/cgi/content/full/213/21/3644/DC1 Key words: acclimation, dinoflagellate, fluorescence, GFP, light, photoprotection, Symbiodinium, symbiosis. THE JOURNAL OF EXPERIMENTAL BIOLOGY 3645Coral GFP photoacclimation isolated from jellyfish and now a widely used tool in cellular and molecular biology (Tsien, 1998). FPs inherently affect the internal light microenvironment of the coral by absorbing high-energy light and emitting lower-energy light. FPs are ubiquitous in scleractinian corals (Alieva et al., 2008;Gruber et al., 2008;Salih et al., 2000) and can constitute a significant portion of the total protein content (up to 14%) .The functions of FPs in corals remain ambiguous and controversial. Hypothesized roles for FPs include photoprotection (Kawaguti, 1944;Salih et al., 2000), photosynthesis enhancement (Kawaguti, 1969), camouflage , antioxidant (BouAbdallah et al., 2006;Palmer et al., 2009b), regulation of symbiotic dinoflagellates Field et al., 2006) and as part of the coral immune response (Palmer et al., 2009a). Corals produce a number of FPs with different spectral properties (Alieva et al., 2008), including FPs that do not emit visible fluorescence, which are often called pocilloporins or GFP-like proteins (Dove et al., 1995;Dove et al., 2001). FPs contribute to the diversity of coral coloration (Dove et al., 2001;Labas et al., 2002;Oswald et al., 2007), and it is possible that dissimilar FPs will have different functions while the same FP could have multiple functions. The principal hypothesis, photoprotection, is weakened by a lack of correlation between FPs and depth (Dove, 2004;Mazel et al., 2003;Vermeij et al., 2002). Recently, variation of exposure to blue light was shown to regulate FP concentration (D'Angelo et al., 2008), suggesting a physiological connection between FPs and the high-energy portion of the light spectrum. In addition, corals with and without the GFP-like proteins can have different ecological and physiological characteristics (Takabayashi and Hoegh-Guldberg, 1995).The objective of this study was to investigate the dynamics of GFP concentration in corals...

Fluorescent protein content and stress tolerance of two color morphs of the coral <i>Galaxea fascicularis</i>

“…In the greenpigmented tentacles of G. fascicularis, GFP is located in the epidermis above the zooxanthellae and the content of GFP was higher on the sunlit side of the tentacles than on the shaded side. This is consistent with the report by Roth et al (2010) …”

In situ Analysis of Coral Recruits Using Fluorescence Imaging

“…In addition, there are corals that express a very weak GFP signal if any, (e.g., Porites sp.) (Roth et al, 2010) whose identification was only possible by their texture and shape in the fluorescence images. Light intensity is known to modulate pigmentation in corals of the species Acroporidae, Merulinidae, and Pocilloporidae (D'Angelo et al, 2008).…”

Fluorescent proteins in dominant mesophotic reef-building corals

“…Previous studies have also shown that corals can also vary the amount of FPs within their tissues in response to changes in environmental and physiological conditions (D'Angelo et al 2008, Roth et al 2010. However, in shallow Caribbean corals (3−30 m), there is no correlation between depth and GFP abundance in Montastrea cavernosa and M. faveolata (Mazel et al 2003).…”

“…While reef-building corals have the capacity to produce significant quantities of FPs (Leutenegger et al 2007), the function of FPs is unknown. As a result of ambiguous data which may be caused by the diversity of FPs and corals, hypothesized roles for the function of FPs include photoprotection (Salih et al 2000, Roth et al 2010, Smith et al 2013, antioxidant activity (Mazel et al 2003, Bou-Abdallah et al 2006, Palmer et al 2009a), photosynthesis enhancement (Salih et al 2000), Symbiodinium regulation (Field et al 2006), part of an immune response (Palmer et al 2009b, D'Angelo et al 2012, camouflage (Matz et al 2006b), maintenance of color diversity (Dove et al 2001), and attraction of free-living Symbiodinium (Hollingsworth et al 2004). It is possible that different FPs could have different roles, particularly in distinct environments such as shallow or mesophotic habitats.…”