UBC Theses and Dissertations
The physiological and proteomic response of two strains of the diatom Thalassiosira oceanica to copper and/or iron limitation Hippmann, Anna Angelika
Diatoms are responsible for over 20% of the Earth's photosynthetic productivity, thus impact global fisheries, biogeochemical cycles and climate. However, marine primary productivity is limited by the micronutrient iron (Fe) in ~40% of the ocean. Diatoms inhabiting these regions have evolved unique physiological strategies to survive under these extremely low Fe conditions. Several physiological adaptations to Fe-limitation in diatoms require an increased dependency on copper (Cu), suggesting an interaction between Fe and Cu nutrition and the potential for Fe-Cu co-limitation in these regions. Though some published work has illustrated transcriptomic and proteomic adaptations of some diatoms to low Fe, there is limited knowledge on diatoms' acclimation strategies to low Cu or Fe-Cu co-limitation. My thesis research focused on elucidating concomitant physiological and proteomic responses of two strains of the open ocean diatom Thalassiosira oceanica (CCMP1003 and CCMP1005) acclimated to Fe, Cu, and Fe-Cu limiting conditions. I measured over 20 physiological parameters, including carbon assimilation rate, oxygen production, respiration rate, an array of photosynthetic parameters [such as electron transport rate of photosystem II (ETRPSII), non-photochemical quenching (NPQ), and antenna absorption cross section of photosystem II, ϬPSII], and photosynthetic rates as a function of light intensity. Moreover, I investigated the differential expression of proteins in T. oceanica in response to these three metal limitations, using stable isotope dimethyl labelling proteomics. I first describe the physiological and proteomic responses to Cu limitation in T. oceanica, focusing on the changes to and the interplay among proteins and pathways involved in the light reactions of photosynthesis, the carbon and nitrogen metabolisms, and the prevention of oxidative stress. I then compare unique changes to the photosynthetic apparatus induced by each metal limitation (Fe, Cu and Fe-Cu) vs. changes induced by general cellular stress. Furthermore, given that my research investigated two strains of T. oceanica, I uncovered stunning intraspecific differences in their proteomic and physiological responses to trace metal limitation. My research unveiled a comprehensive restructuring of the photosynthetic apparatus, and a sophisticated interaction among metabolic pathways in T. oceanica (CCMP1003) in response to low metal availability (especially Cu), demonstrating exceptional adaptations to low trace metal availabilities.
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