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CrABCA2 Facilitates Triacylglycerol Accumulation in Chlamydomonas reinhardtii under Nitrogen Starvation

Molecules and Cells 2020년 43권 1호 p.48 ~ 57
 ( Jang Sung-Hoon ) - Pohang University of Science and Technology Department of Life Sciences

 ( Kong Fantao ) - Dalian University of Technology School of Bioengineering
 ( Lee Ji-Hyeon ) - Pohang University of Science and Technology Department of Integrative Biosciences and Biotechnology
 ( Choi Bae-Young ) - Pohang University of Science and Technology Department of Integrative Biosciences and Biotechnology
 ( Wang Pengfei ) - Chinese University of Hong Kong School of Life Sciences
 ( Gao Peng ) - Chinese University of Hong Kong School of Life Sciences
 ( Yamano Takashi ) - Kyoto University Graduate School of Biostudies
 ( Fukuzawa Hideya ) - Kyoto University Graduate School of Biostudies
 ( Kang Byung-Ho ) - Chinese University of Hong Kong School of Life Sciences
이영숙 ( Lee Young-Sook ) - Pohang University of Science and Technology Department of Integrative Biosciences and Biotechnology

Abstract


The microalga Chlamydomonas reinhardtii accumulates triacylglycerols (TAGs) in lipid droplets under stress conditions, such as nitrogen starvation. TAG biosynthesis occurs mainly at the endoplasmic reticulum (ER) and requires fatty acid (FA) substrates supplied from chloroplasts. How FAs are transferred from chloroplast to ER in microalgae was unknown. We previously reported that an Arabidopsis thaliana ATP-binding cassette (ABC) transporter, AtABCA9, facilitates FA transport at the ER during seed development. Here we identified a gene homologous to AtABCA9 in the C. reinhardtii genome, which we named CrABCA2. Under nitrogen deprivation conditions, CrABCA2 expression was upregulated, and the CrABCA2 protein level also increased. CrABCA2 knockdown lines accumulated less TAGs and CrABCA2 overexpression lines accumulated more TAGs than their untransformed parental lines. Transmission electron microscopy showed that CrABCA2 was localized in swollen ER. These results suggest that CrABCA2 transports substrates for TAG biosynthesis to the ER during nitrogen starvation. Our study provides a potential tool for increasing lipid production in microalgae.

키워드

ABC transporter; Chlamydomonas reinhardtii; endoplasmic reticulum; triacylglycerol accumulation
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