A systems biology approach to improve nitrate-uptake in Chlamydomonas reinhardtii during day-phase
P. Kießling1, J. Kelm1, O. Voytsekh1, S. Schäuble2, I. Heiland2, S. Schuster2, and M. Mittag1
1) Institute of General Botany and Plant Physiology, Friedrich Schiller University Jena, Am Planetarium 1, 07743 Jena, Germany
2) Department of Bioinformatics, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany
The circadian RNA-binding protein CHLAMY1 from the green alga Chlamydomonas reinhardtii recognizes UG-repeat elements situated in the 3'-UTRs of several mRNAs (1). Some of them encode proteins for nitrogen-metabolism, such as nitrite reductase1, glutamine synthetase2 (GS2) or arginino succinate lyase (ASL). Insertion of the UG-repeats of nii1, gs2 and arg7 into the 3'-UTR of a luciferase reporter can trigger circadian expression of the reporter with a maximum during day-phase (2, 3). We have selected further components of nitrogen metabolism involving a key enzyme, a transporter and a transcriptional regulator to insert UG-repeat elements in their 3'-UTRs. After having cloned the first chimeric constructs, we are now on the way to transform wild type and mutant strains where these genes are defect. With such strains, we aim to achieve an improvement in nitrate uptake and metabolism during day-phase. In parallel, we have started to model the pathways involved in nitrogen metabolism of C. reinhardtii using the concept of elementary flux modes (4) by analyzing incorporation of nitrogen compounds via asparagine, lysine or arginine biosynthesis. This should enable us to select further critical components for experimental modulation. Moreover, we simulated three different day times that provide clues about the diurnal behavior of the uptake of nitrogen compounds in C. reinhardtii.
Literature: (1) Waltenberger et al. (2001) Mol. Genet. Genomics 265:180-188. (2) Kiaulehn et al., (2007) J. Biol. Rhythms 22:275-277 (3) Voytsekh et al. (2008) Plant Physiol. 147:2179-2193 (4) Schuster et al. (1999) Trends Biotechnol. 17:53-60.
e-mail address of presenting author: p.kiessling@mac.com