Differential gene expression of a anthox-like gene in the gorgonian, Pseudopterogorgia elisabethae
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Phenotypic plasticity, the ability of an organism to alter its phenotype in response to environmental change, is a fundamental component in the development of many organisms. Gorgonian coral branching provides an excellent example of phenotypic plasticity in which colony branching patterns change with depth and current. Colonies can vary in the spacing and length of branches among environments varying in current energies and/or light levels. Developing an experimental approach to study pattern in gorgonian branching is crucial to understanding the process and plasticity of branching in these common marine invertebrates. The goal of this research was to develop molecular markers to detect initiation of branching in the gorgonian Pseudopterogorgia elisabethae. In this study, a member of the homeobox gene family ( HOX ), anthox was assessed as a possible molecular marker. Real time PCR was used to determine expression of anthox in a number of samples collected from various branch points on each colony. Real time PCR protocols were also developed for β-actin, GAPDH, and cyclophilin in P. elisabethae for use as normalization controls. In this study, 50 branch samples were collected from San Salvador, Bahamas from 10 colonies. Samples were collected from different parts of the coral branch representing locations where branch growth was expected (branch locations 1 and 2) and where it was not (location 5). Results indicate that there were large and significant differences among colonies (ANOVA, Wilks' Lambda = 0.0054, P<0.025) for anthox gene expression. Anthox expression was highest at branch location 2 though only significant in comparison with branch location 5 (t-test, Bonferroni corrected, P=0.0005). Further analysis was conducted using repeated measures analysis to see if there was a significant difference in expression that may have been overshadowed by the difference in expression among colonies. Anthox gene expression data once again showed a significant difference between branch locations 2 and 5 (t-test, p<0.025). Although some differences were found among branch location in anthox expression this gene does not appear to be useful marker for branch initiation.