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Nitrogen starvation‐induced accumulation of triacylglycerol in the green algae: evidence for a role for ROC 40, a transcription factor involved in circadian rhythm
Author(s) -
Goncalves Elton C.,
Koh Jin,
Zhu Ning,
Yoo MiJeong,
Chen Sixue,
Matsuo Takuya,
Johnson Jodie V.,
Rathinasabapathi Bala
Publication year - 2016
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13144
Subject(s) - biology , transcription factor , chlamydomonas reinhardtii , quantitative proteomics , gene , gene expression , biochemistry , chlamydomonas , microbiology and biotechnology , mutant , proteomics
Summary 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 ROC 40 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 ROC 40 has a role in −N‐induced lipid accumulation, and uncover multiple previously unknown proteins modulated by short‐term −N in green algae.