Carbonic Anhydrase Expression and Synthesis in the Sea Anemone Anthopleura elegantissima Are Enhanced by the Presence of Dinoflagellate Symbionts

Endosymbiotic dinoflagellates resident within cnidarian hosts are extremely productive primary producers. This high productivity may be due in part to an inorganic carbon transport system, present in host tissue, that accelerates carbon delivery to the algae. The enzyme carbonic anhydrase (CA; EC 4.2.1.1) has been shown to be important in this transport system in a variety of tropical symbiotic cnidarians. This study extends the examination of CA to a temperate anemone, Anthopleura elegantissima, and documents symbiosis-enhanced production of CA at the biochemical and molecular level. Depending on light availability, A. elegantissima can occur naturally with (symbiotic) or without (aposymbiotic) dinoflagellates, making it an ideal study organism for symbiosis-enhanced gene expression. We compared (1) CA activities, (2) quantities of CA using an anti-human CA immunoprobe, and (3) quantities of transcript using a semiquantitative PCR in symbiotic versus aposymbiotic A. elegantissima host tissue. Amounts of activity, enzyme, and transcript were greatly enhanced in symbiotic animals compared with aposymbiotic animals. This is the first direct evidence that the presence of symbionts affects the expression of a host cnidarian gene. In addition, we report a full-length A. elegantissima CA cDNA sequence, obtained from subcloned reverse transcriptase-PCR products, and its relatedness to α-CAs from a variety of other metazoa, including higher vertebrates.