Changes in the photosynthetic apparatus and lipid droplet formation in Chlamydomonas reinhardtii under iron deficiency

Elsinraju Devadasu, Dinesh Kumar Chinthapalli, Nisha Chouhan, Sai Kiran Madireddi, Girish Kumar Rasineni, Prabhakar Sripadi, S. Rajagopal

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The unicellular photosynthetic alga Chlamydomonas reinhardtii was propagated in iron deficiency medium and patterns of growth, photosynthetic efficiency, lipid accumulation, as well as the expression of lipid biosynthetic and photosynthesis-related proteins were analysed and compared with iron-sufficient growth conditions. As expected, the photosynthetic rate was reduced (maximally after 4 days of growth) as a result of increased non-photochemical quenching (NPQ). Surprisingly, the stress-response protein LHCSR3 was expressed in conditions of iron deficiency that cause NPQ induction. In addition, the protein contents of both the PSI and PSII reaction centres were gradually reduced during growth in iron deficiency medium. Interestingly, the two generations of Fe deficiency cells could be able to recover the photosynthesis but the second generation cells recovered much slower as these cells were severely in shock. Analysis by flow cytometry with fluorescence-activated cell sorting and thin layer chromatography showed that iron deficiency also induced the accumulation of triacylglycerides (TAG), which resulted in the formation of lipid droplets. This was most significant between 48 and 72 h of growth. Dramatic increases in DGAT2A and PDAT1 levels were caused by iron starvation, which indicated that the biosynthesis of TAG had been increased. Analysis using gas chromatography mass spectrometry showed that levels of 16:0, 18:0, 18:2 and 18:3Δ9,12,15 fatty acids were significantly elevated. The results of this study highlight the genes/enzymes of Chlamydomonas that affect lipid synthesis through their influence on photosynthesis, and these represent potential targets of metabolic engineering to develop strains for biofuel production.

Original languageEnglish
JournalPhotosynthesis Research
DOIs
Publication statusAccepted/In press - Jan 1 2018

Fingerprint

Chlamydomonas reinhardtii
droplets
Iron
iron
Lipids
Photosynthesis
lipids
Growth
photosynthesis
algae
flow cytometry
Quenching
Flow Cytometry
Metabolic engineering
Chlamydomonas
Metabolic Engineering
Thin layer chromatography
metabolic engineering
Proteins
Biofuels

Keywords

  • Electron transport
  • Iron deficiency
  • LHCSR3
  • Major lipid droplet protein
  • Photosystems
  • Triacylglycerol

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

Cite this

Changes in the photosynthetic apparatus and lipid droplet formation in Chlamydomonas reinhardtii under iron deficiency. / Devadasu, Elsinraju; Chinthapalli, Dinesh Kumar; Chouhan, Nisha; Madireddi, Sai Kiran; Rasineni, Girish Kumar; Sripadi, Prabhakar; Rajagopal, S.

In: Photosynthesis Research, 01.01.2018.

Research output: Contribution to journalArticle

Devadasu, Elsinraju ; Chinthapalli, Dinesh Kumar ; Chouhan, Nisha ; Madireddi, Sai Kiran ; Rasineni, Girish Kumar ; Sripadi, Prabhakar ; Rajagopal, S. / Changes in the photosynthetic apparatus and lipid droplet formation in Chlamydomonas reinhardtii under iron deficiency. In: Photosynthesis Research. 2018.
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AB - The unicellular photosynthetic alga Chlamydomonas reinhardtii was propagated in iron deficiency medium and patterns of growth, photosynthetic efficiency, lipid accumulation, as well as the expression of lipid biosynthetic and photosynthesis-related proteins were analysed and compared with iron-sufficient growth conditions. As expected, the photosynthetic rate was reduced (maximally after 4 days of growth) as a result of increased non-photochemical quenching (NPQ). Surprisingly, the stress-response protein LHCSR3 was expressed in conditions of iron deficiency that cause NPQ induction. In addition, the protein contents of both the PSI and PSII reaction centres were gradually reduced during growth in iron deficiency medium. Interestingly, the two generations of Fe deficiency cells could be able to recover the photosynthesis but the second generation cells recovered much slower as these cells were severely in shock. Analysis by flow cytometry with fluorescence-activated cell sorting and thin layer chromatography showed that iron deficiency also induced the accumulation of triacylglycerides (TAG), which resulted in the formation of lipid droplets. This was most significant between 48 and 72 h of growth. Dramatic increases in DGAT2A and PDAT1 levels were caused by iron starvation, which indicated that the biosynthesis of TAG had been increased. Analysis using gas chromatography mass spectrometry showed that levels of 16:0, 18:0, 18:2 and 18:3Δ9,12,15 fatty acids were significantly elevated. The results of this study highlight the genes/enzymes of Chlamydomonas that affect lipid synthesis through their influence on photosynthesis, and these represent potential targets of metabolic engineering to develop strains for biofuel production.

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