Department of Chemical and Biological Engineering Colorado State University 1370 Campus Delivery Fort Collins, CO, 80523 Phone: (970) 491 - 6505 Fax: (970) 491 - 7369 kenneth.reardon@colostate.edu Chlamydomonas reinhardtii has long been the standard laboratory strain of microalgal research for everything from basic investigations of photosynthesis to biofuel production. This popularity is due to its rapid growth, as well as the available suite of genetic manipulation techniques. There have been many studies that analyze the effects of nitrogen stress upon Chlamydomonas, all of which have shown that nitrogen stress causes a cessation of cell-division and induces carbon storage in the form of starch and/or triacylglycerides (TAG). To date, there has been very little research into the specific mechanism used by Chlamydomonas to sense the nitrogen starvation and to explain the cellular response. To further understand the mechanism of adaptation to nitrogen-depleted environment, we utilized amiRNA techniques to produce a strain of Chlamydomonas with lowered levels of the global nitrogen regulator protein, PII. PII has been shown to be one of the most widespread signaling molecules in nature. PII is well characterized as a sensor for 2-oxoglutarate (a proxy for intracellular nitrogen levels), and recently its known effects have been expanded to include repression of acetyl-CoA carboxylase in nitrogen-replete environments. Our research expands the known effects of PII further by demonstrating that a PII knock-down induces a significant effect on cell division. PII knock-down strains achieved higher cell densities, dry cell weight concentrations, and volumetric lipid composition when compared to control cultures. Increasing the volumetric productivity of microalgae is the primary issue preventing widespread algal biofuel adoption, and knock-down of PII increases these desirable characteristics. This analysis is a first step toward understanding the role of PII during adaptation to nitrogen-free conditions in Chlamydomonas, through which it may be possible to move one step closer towards microalgal biofuel production.

Role of PII in the nitrogen-stress response of Chlamydomonas reinhardtii

249th National Meeting (2015)

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