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Yamaoka, Yasuyo,Achard, Dorine,Jang, Sunghoon,Legé,ret, Bertrand,Kamisuki, Shogo,Ko, Donghwi,Schulz‐,Raffelt, Miriam,Kim, Yeongho,Song, Won‐,Yong,Nishida, Ikuo,Li‐,Beisson, Yon BLACKWELL 2016 PLANT BIOTECHNOLOGY JOURNAL Vol.14 No.11
<P><B>Summary</B></P><P>Despite a strong interest in microalgal oil production, our understanding of the biosynthetic pathways that produce algal lipids and the genes involved in the biosynthetic processes remains incomplete. Here, we report that <I>Chlamydomonas reinhardtii Cre09.g398289</I> encodes a plastid‐targeted 2‐lysophosphatidic acid acyltransferase (CrLPAAT1) that acylates the <I>sn</I>‐2 position of a 2‐lysophosphatidic acid to form phosphatidic acid, the first common precursor of membrane and storage lipids. <I>In vitro</I> enzyme assays showed that CrLPAAT1 prefers 16:0‐CoA to 18:1‐CoA as an acyl donor. Fluorescent protein‐tagged CrLPAAT1 was localized to the plastid membrane in <I>C. reinhardtii</I> cells. Furthermore, expression of CrLPAAT1 in plastids led to a > 20% increase in oil content under nitrogen‐deficient conditions. Taken together, these results demonstrate that CrLPAAT1 is an authentic plastid‐targeted LPAAT in <I>C. reinhardtii</I>, and that it may be used as a molecular tool to genetically increase oil content in microalgae.</P>
Yamaoka, Yasuyo,Shin, Seungjun,Choi, Bae Young,Kim, Hanul,Jang, Sunghoon,Kajikawa, Masataka,Yamano, Takashi,Kong, Fantao,Lé,geret, Bertrand,Fukuzawa, Hideya,Li-Beisson, Yonghua,Lee, Youngsook American Society of Plant Biologists 2019 The Plant cell Vol.31 No.5
<P>The mRNA of a Chlamydomonas bZIP transcription factor is spliced by CrIRE1 under ER stress, and the resulting protein protects Chlamydomonas cells from ER stress by modulating lipid remodeling.</P><P>Endoplasmic reticulum (ER) stress is caused by the stress-induced accumulation of unfolded proteins in the ER. Here, we identified proteins and lipids that function downstream of the ER stress sensor INOSITOL-REQUIRING ENZYME1 (CrIRE1) that contributes to ER stress tolerance in Chlamydomonas (<I>Chlamydomonas reinhardtii</I>). Treatment with the ER stress inducer tunicamycin resulted in the splicing of a 32-nucleotide fragment of a basic leucine zipper 1 (bZIP1) transcription factor (<I>CrbZIP1</I>) mRNA by CrIRE1 that, in turn, resulted in the loss of the transmembrane domain in CrbZIP1, and the translocation of CrbZIP1 from the ER to the nucleus. Mutants deficient in <I>CrbZIP1</I> failed to induce the expression of the unfolded protein response genes and grew poorly under ER stress. Levels of diacylglyceryltrimethylhomoserine (DGTS) and pinolenic acid (18:3Δ5,9,12) increased in the parental strains but decreased in the <I>crbzip1</I> mutants under ER stress. A yeast one-hybrid assay revealed that CrbZIP1 activated the expression of enzymes catalyzing the biosynthesis of DGTS and pinolenic acid. Moreover, two lines harboring independent mutant alleles of <I>Chlamydomonas desaturase</I> (<I>CrDES</I>) failed to synthesize pinolenic acid and were more sensitive to ER stress than were their parental lines. Together, these results indicate that <I>CrbZIP1</I> is a critical component of the ER stress response mediated by CrIRE1 in Chlamydomonas that acts via lipid remodeling.</P>
Characterization of a Chlamydomonas reinhardtii mutant defective in a maltose transporter
장성훈,YASUYO YAMAOKA,고동휘,Tomokazu Kurita,김경윤,송원용,황재웅,강병호,Ikuo Nishida,이영숙 한국식물학회 2015 Journal of Plant Biology Vol.58 No.5
Microalgae are potential sources of energy and high-value materials. To decipher the process of energy metabolism in green algae, we created a mutant pool of strain CC-503 of the model green microalga Chlamydomonas reinhardtii, by random insertion of an antibiotic resistance gene, and screened the pool for lines with altered carbon metabolism. We identified a mutant that harbored the antibiotic resistance gene in CrMEX1, a putative Maltose Exporter-Like protein 1 (Cre12.g486600.t1.2). The mutant had reduced levels of CrMEX1 expression and, similarly to the Arabidopsis mex1 knockout mutant, which cannot export maltose from the chloroplast, it over-accumulated starch granules in the chloroplast. The mutant’s lipid levels were slightly higher than those of the wild type, and its initial growth kinetics were not significantly different from those of the wild type, but the mutant culture did not reach the same high cell density as the wild type in acetate-containing culture medium under continuous light. These results suggest that CrMEX1 encodes a maltose transporter protein, and that export of photoassimilates from chloroplasts is necessary for normal Chlamydomonas growth, even under continuous light with an ample supply of carbon in the form of acetate.
Je Sujeong,Yamaoka Yasuyo 한국미생물·생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.11
Heavy reliance on fossil fuels has been associated with increased climate disasters. As an alternative, microalgae have been proposed as an effective agent for biomass production. Several advantages of microalgae include faster growth, usage of non-arable land, recovery of nutrients from wastewater, efficient CO2 capture, and high amount of biomolecules that are valuable for humans. Microalgae Chlorella spp. are a large group of eukaryotic, photosynthetic, unicellular microorganisms with high adaptability to environmental variations. Over the past decades, Chlorella has been used for the large-scale production of biomass. In addition, Chlorella has been actively used in various food industries for improving human health because of its antioxidant, antidiabetic, and immunomodulatory functions. However, the major restrictions in microalgal biofuel technology are the cost-consuming cultivation, processing, and lipid extraction processes. Therefore, various trials have been performed to enhance the biomass productivity and the lipid contents of Chlorella cells. This study provides a comprehensive review of lipid enhancement strategies mainly published in the last five years and aimed at regulating carbon sources, nutrients, stresses, and expression of exogenous genes to improve biomass production and lipid synthesis.
Yoshinori Hayakawa,Zhongrui Duan,Miki Yadake,Yasuyo Yamaoka,Rie Inatsugi,Yuki Fujiki,Akira Oikawa,Kazuki Saito,Ikuo Nishida 한국식물학회 2015 Journal of Plant Biology Vol.58 No.3
The apetala3 (ap3)-like homeotic mutation (ap3-HM) is recognized among pD991-AP3-derived Arabidopsis thaliana T-DNA-tagged lines carrying the -448 to +47 region of AP3 in their T-DNA. In the corresponding mutant lines for CTP:phosphorylcholine cytidylyltransferase genes, cct1-1 and cct2 (Inatsugi et al. 2009), some flowers of cct1-1 (F4) and many flowers of cct1-1 cct2 (F3) showed ap3-HM, and all flowers of cct1-1 (F5) and cct1-1 cct2 (F4) became increasingly homeotic. In contrast, cct2 flowers were normal for all generations tested. These results demonstrated that ap3-HM is linked to the cct1-1 allele and is enhanced by the cct2 allele. The ap3-HM in cct mutants was inversely correlated with AP3 transcript levels in enriched flower buds. Bisulfite sequencing revealed severe methylation within endogenous AP3 promoter regions in cct1-1 (F3; -317 to -2) and cct1-1 cct2 (F3; -473 to -2), but wild-type (Wassilevskaja) and cct2 plants showed no corresponding methylation. The ap3-HM in cct1-1 cct2 mutants was fully rescued by expressing a PISTILLATA promoter–AP3 construct, and was better alleviated in the F1 offspring of a cross with the CCT1-overexpressing mutant cct1-2 (Columbia) than with the wild type. We discuss possible links between expression of CCT and suppression of ap3-HM.
Lee, Dongyeop,Jeong, Dae-Eun,Son, Heehwa G.,Yamaoka, Yasuyo,Kim, Hyunmin,Seo, Keunhee,Khan, Abdul Aziz,Roh, Tae-Young,Moon, Dae Won,Lee, Youngsook,Lee, Seung-Jae V. Cold Spring Harbor Laboratory Press 2015 Genes & development Vol.29 No.23
<P>In this study, Lee et al. show that SREBP and MDT-15 prevent the life-shortening effects of a glucose-rich diet by regulating fat-converting processes in <I>C. elegans</I>. By using a genome-wide screen, they found that inhibition of SREBP or MDT-15 further accelerated aging in glucose-rich conditions, and up-regulation of SREBP or MDT-15 reversed accelerated aging.</P><P>Glucose-rich diets shorten the life spans of various organisms. However, the metabolic processes involved in this phenomenon remain unknown. Here, we show that sterol regulatory element-binding protein (SREBP) and mediator-15 (MDT-15) prevent the life-shortening effects of a glucose-rich diet by regulating fat-converting processes in <I>Caenorhabditis elegans</I>. Up-regulation of the SREBP/MDT-15 transcription factor complex was necessary and sufficient for alleviating the life-shortening effect of a glucose-rich diet. Glucose feeding induced key enzymes that convert saturated fatty acids (SFAs) to unsaturated fatty acids (UFAs), which are regulated by SREBP and MDT-15. Furthermore, SREBP/MDT-15 reduced the levels of SFAs and moderated glucose toxicity on life span. Our study may help to develop strategies against elevated blood glucose and free fatty acids, which cause glucolipotoxicity in diabetic patients.</P>
Choi, Hyunju,Ohyama, Kiyoshi,Kim, Yu-Young,Jin, Jun-Young,Lee, Saet Buyl,Yamaoka, Yasuyo,Muranaka, Toshiya,Suh, Mi Chung,Fujioka, Shozo,Lee, Youngsook American Society of Plant Biologists 2014 The Plant cell Vol.26 No.1
<P>This work identified two ABC transporters important for normal pollen coat deposition and, thus, critical for pollen fitness. The transporters are probably involved in the transfer of pollen coat material from maternal tissues to the pollen surface.</P>