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Plant membrane-protein mediated intracellular traffic of fatty acids and acyl lipids
Li-Beisson, Yonghua,Neunzig, Jens,Lee, Youngsook,Philippar, Katrin Elsevier 2017 Current opinion in plant biology Vol.40 No.-
<P>In plants, <I>de novo</I> synthesis of fatty acids (FAs) occurs in plastids, whereas assembly and modification of acyl lipids is accomplished in the endoplasmic reticulum (ER) and plastids as well as in mitochondria. Subsequently, lipophilic compounds are distributed within the cell and delivered to their destination site. Thus, constant acyl-exchanges between subcellular compartments exist. These can occur via several modes of transport and plant membrane-intrinsic proteins for FA/lipid transfer have been shown to play an essential role in delivery and distribution. Lately, substantial progress has been made in identification and characterization of transport proteins for lipid compounds in plant organelle membranes. In this review, we focus on our current understanding of protein mediated lipid traffic between organelles of land plants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Increased seed oil synthesis by enhanced pyruvate transport into plastids. </LI> <LI> Identification of a membrane transporter for plastid fatty acid export. </LI> <LI> Mediation of ER to plastid lipid transfer by a P4-type ATPase in the ER. </LI> <LI> A mitochondrial membrane protein for lipid transfer during phosphate starvation. </LI> </UL> </P>
Cuticular lipid composition, surface structure, and gene expression in Arabidopsis stem epidermis.
Suh, Mi Chung,Samuels, A Lacey,Jetter, Reinhard,Kunst, Ljerka,Pollard, Mike,Ohlrogge, John,Beisson, Fred American Society of Plant Physiologists 2005 Plant Physiology Vol.139 No.4
<P>All vascular plants are protected from the environment by a cuticle, a lipophilic layer synthesized by epidermal cells and composed of a cutin polymer matrix and waxes. The mechanism by which epidermal cells accumulate and assemble cuticle components in rapidly expanding organs is largely unknown. We have begun to address this question by analyzing the lipid compositional variance, the surface micromorphology, and the transcriptome of epidermal cells in elongating Arabidopsis (Arabidopsis thaliana) stems. The rate of cell elongation is maximal near the apical meristem and decreases steeply toward the middle of the stem, where it is 10 times slower. During and after this elongation, the cuticular wax load and composition remain remarkably constant (32 microg/cm2), indicating that the biosynthetic flux into waxes is closely matched to surface area expansion. By contrast, the load of polyester monomers per unit surface area decreases more than 2-fold from the upper (8 microg/cm2) to the lower (3 microg/cm2) portion of the stem, although the compositional variance is minor. To aid identification of proteins involved in the biosynthesis of waxes and cutin, we have isolated epidermal peels from Arabidopsis stems and determined transcript profiles in both rapidly expanding and nonexpanding cells. This transcriptome analysis was validated by the correct classification of known epidermis-specific genes. The 15% transcripts preferentially expressed in the epidermis were enriched in genes encoding proteins predicted to be membrane associated and involved in lipid metabolism. An analysis of the lipid-related subset is presented.</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>
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>