title: Reduction of PII signaling protein enhances lipid body production in Chlamydomonas reinhardtii.
abstract: In all examined organisms that have the PII signal transduction machinery, PII coordinates the central C/N anabolic metabolism. In green algae and land plants, PII is localized in the chloroplast and controls the L-arginine biosynthetic pathway pathway. To elucidate additional functions of PII in the model photosynthetic organism Chlamydomonas reinhardtii (CrPII), we generated and analyzed four strains, in which PII was strongly under-expressed by artificial microRNA (GLB1-amiRNA strains). In response to nitrogen deficiency, Chlamydomonas produces triacylglycerols (TAGs) that are accumulated in lipid bodies (LB). Quantification of LBs by confocal microscopy in four GLB1-amiRNA strains showed that reduced PII levels resulted in over-accumulation of LBs compared to their parental strains. Moreover, knock-down of PII caused also an increase in the total TAG level. We propose that the larger yields of TAG-filled LBs in N-starved GLB1-amiRNA cells can be attributed to the strain's depleted PII level and their inability to properly control acetyl-CoA carboxylase activity (ACCase). Together, our results imply that PII in Chlamydomonas negatively controls TAG accumulation in LBs during acclimation to nitrogen starvation of the alga.
authors.affiliation: Laboratory of Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia.
authors.forename: Zhanneta
authors.initials: Z
authors.lastname: Zalutskaya
authors.affiliation: Laboratory of Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia.
authors.forename: Nina
authors.initials: N
authors.lastname: Kharatyan
authors.affiliation: Department of Microbiology/Organismic Interactions, Faculty of Biology, University of Tübingen, Auf der Morgenstelle 28, 72,076 Tübingen, Germany.
authors.forename: Karl
authors.initials: K
authors.lastname: Forchhammer
authors.affiliation: Laboratory of Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia. Electronic address: ermilova@bio.spbu.ru.
authors.forename: Elena
authors.initials: E
authors.lastname: Ermilova
mesh_terms: D020418:Algal Proteins / Q000235:genetics* / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D066292:Lipid Droplets / Q000378:metabolism*; D009584:Nitrogen / Q000172:deficiency*; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics* / Q000378:metabolism; D014280:Triglycerides / Q000096:biosynthesis*
chemical_list: D020418:Algal Proteins; D051922:PII Nitrogen Regulatory Proteins; D014280:Triglycerides; D009584:Nitrogen
keywords: Artificial microRNA approach; Chlamydomonas reinhardtii; Lipid bodies; PII signal transduction protein; Triacylglycerol biosynthesis