Grant: Discovery Grants Program - Individual

The long-term vision of my research program is to elucidate the mechanism(s) by which environmental stress is sensed and govern photosynthetic acclimation and adaptation to environmental stress. Recently, my focus has combined a comparison of non-model Antarctic and Arctic algal psychrophiles such as Chlamydomonas priscuii with the model algal mesophile, Chlamydomonas reinhardtii. Primary production in perpetually cold, aquatic Antarctic and Arctic environments is largely dependent on micro- and macroalgae that inhabit diverse aquatic polar habitats. Psychrotolerant algae tolerate a range of temperatures due to their ability to acclimate to their environment. In contrast, algal psychrophiles are obligately adapted to low temperature but die when exposed to temperatures near 20°C or higher. Because green algae are photosynthetic, psychrophilic algae are called photopsychrophiles. Cold temperatures can disrupt cellular energy homeostasis due to absorption of more light than can be used by the process of photosynthesis. This causes an inhibition photosynthesis due to photoinhibition and limits long-term survival. However, evolution has provided specific photoprotective mechanisms to overcome such inherent limitations in photosynthetic organisms. Stress induces the transition of single cells to multicellular palmelloids in species of Chlamydomonas. The molecular basis for this transition and its role in mitigating environmental stress remains an enigma. Cultures of polar algal photopsychrophiles typically are heterogenous mixtures of single cells and palmelloids. My hypothesis is that palmelloid formation is a photoprotective response to stress to maintain energy homeostasis. My short-term goal is to validate this hypothesis in Antarctic and Arctic algal photopsychrophiles. This goal encompasses three specific objectives: (1) To explain how the conversion of single cells into colonial palmelloids reorganizes the structure and function of the photosynthetic apparatus. (2) To establish that transition of single cells to palmelloids is governed by changes in chloroplast redox poise and (3) to elucidate the molecular biology that governs palmelloid formation and photoprotection in Chlamydomonas prisuii. To accomplish these goals, small, single, motile cells will be physically separated from the larger palmelloids by a rapid filtering technique we recently developed. Experimental techniques employed will include in vivo gas exchange, chlorophyll fluorescence and thermoluminescence spectroscopy combined with in vitro transcriptomic and proteomic approaches to identify differentially expressed genes (DEGs) and proteins (DEPs) associated with palmelloid formation and photoprotection. This research proposal will unravel the enigma of palmelloid formation and its novel role in photoprotection and survival of photopsychrophiles in their extreme Antarctic and Arctic polar habitats.