title: Nitrogen starvation-induced accumulation of triacylglycerol in the green algae: evidence for a role for ROC40, a transcription factor involved in circadian rhythm.
abstract: Microalgal triacylglycerol (TAG), a promising source of biofuel, is induced upon nitrogen starvation (-N), but the proteins and genes involved in this process are poorly known. We performed isobaric tagging for relative and absolute quantification (iTRAQ)-based quantitative proteomics to identify Chlorella proteins with modulated expression under short-term -N. Out of 1736 soluble proteins and 2187 membrane-associated proteins identified, 288 and 56, respectively, were differentially expressed under -N. Gene expression analysis on select genes confirmed the same direction of mRNA modulation for most proteins. The MYB-related transcription factor ROC40 was the most induced protein, with a 9.6-fold increase upon -N. In a previously generated Chlamydomonas mutant, gravimetric measurements of crude total lipids revealed that roc40 was impaired in its ability to increase the accumulation of TAG upon -N, and this phenotype was complemented when wild-type Roc40 was expressed. Results from radiotracer experiments were consistent with the roc40 mutant being comparable to the wild type in recycling membrane lipids to TAG but being impaired in additional de novo synthesis of TAG during -N stress. In this study we provide evidence to support the hypothesis that transcription factor ROC40 has a role in -N-induced lipid accumulation, and uncover multiple previously unknown proteins modulated by short-term -N in green algae.
authors.affiliation: Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA.
authors.forename: Elton C
authors.initials: EC
authors.lastname: Goncalves
authors.affiliation: Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, 32610, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Koh
authors.affiliation: Department of Biology, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhu
authors.affiliation: Department of Biology, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Mi-Jeong
authors.initials: MJ
authors.lastname: Yoo
authors.affiliation: Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA.|Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, 32610, USA.|Department of Biology, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Sixue
authors.initials: S
authors.lastname: Chen
authors.affiliation: Center for Gene Research, Nagoya University, Furo, Chikusa, Nagoya, 464-8602, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsuo
authors.affiliation: Chemistry Department, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Jodie V
authors.initials: JV
authors.lastname: Johnson
authors.affiliation: Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA.
authors.forename: Bala
authors.initials: B
authors.lastname: Rathinasabapathi
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism; D002708:Chlorella / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D050356:Lipid Metabolism / Q000502:physiology; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors; D014280:Triglycerides; D009584:Nitrogen
keywords: Chlamydomonas; Chlorella spp; algae; nitrogen starvation; proteomics; triacylglycerol