Characterization of proteorhodopsins in an oceanic diatom (2014)

Undergraduate: Dylan Catlett

Faculty Advisor: Adrian Marchetti
Department: Biology

---

Proteorhodopsins (PR) are retinal-binding membrane proteins that may act as light-driven proton pumps to generate energy that can be used in metabolism and growth. Originally characterized in prokaryotes, bacteria-like PR gene homologs have recently been identified in many marine protists, and were likely acquired through lateral gene transfer. One eukaryotic species that contains rhodopsins is the photosynthetic pennate diatom Pseudo-nitzschia granii, isolated from Fe-limited waters in the NE Pacific Ocean. Evidence suggests these proteins are expressed in P. granii during iron-limiting conditions to function in the formation of ATP when the photosynthetic machinery, which is dependent upon iron availability, is compromised. The objective of this study was to elucidate the environmental conditions that result in an up-regulation of the P. granii rhodopsin gene (RHO). Cultures of P. granii were acclimated to a matrix of light and iron growth conditions. From these cultures, RNA was extracted and transcript copies of RHO were quantified using quantitative PCR. We anticipate that P. granii RHO will be up-regulated in cells grown under low iron treatments, and that light availability may also influence expression patterns. Our findings will provide further insight into how photosynthetic diatoms cope with iron-limited environments as well as into the precise function of rhodopsins in photosynthetic eukaryotes.