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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.
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.
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>