FATTY ACID DESATURASE4 of Arabidopsis encodes a protein distinct from characterized fatty acid desaturases
Jinpeng GaoImad AjjawiArthur ManoliAndrew SawinChangcheng XuJohn E. FroehlichRobert L. LastChristoph Benning
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Abstract:
Polar membrane glycerolipids occur in a mixture of molecular species defined by a polar head group and characteristic acyl groups esterified to a glycerol backbone. A molecular species of phosphatidylglycerol specific to chloroplasts of plants carries a Delta(3-trans) hexadecenoic acid in the sn-2 position of its core glyceryl moiety. The fad4-1 mutant of Arabidopsis thaliana missing this particular phosphatidylglycerol molecular species lacks the necessary fatty acid desaturase, or a component thereof. The overwhelming majority of acyl groups associated with membrane lipids in plants contains double bonds with a cis configuration. However, FAD4 is unusual because it is involved in the formation of a trans double bond introduced close to the carboxyl group of palmitic acid, which is specifically esterified to the sn-2 glyceryl carbon of phosphatidylglycerol. As a first step towards the analysis of this unusual desaturase reaction, the FAD4 gene was identified by mapping of the FAD4 locus and coexpression analysis with known lipid genes. FAD4 encodes a predicted integral membrane protein that appears to be unrelated to classic membrane bound fatty acid desaturases based on overall sequence conservation. However, the FAD4 protein contains two histidine motifs resembling those of metalloproteins such as fatty acid desaturases. FAD4 is targeted to the plastid. Overexpression of the cDNA in transgenic Arabidopsis led to increased accumulation of the Delta(3-trans) hexadecanoyl group in phosphatidylglycerol relative to wild type. Taken together these results are consistent with the hypothesis that FAD4 is the founding member of a novel class of fatty acid desaturases.Keywords:
Phosphatidylglycerol
Acyl group
Acyl carrier protein
Abstract Fatty acid synthesis in bacteria is catalyzed by a set of individual enzymes known as the type II fatty acid synthase. Acyl carrier protein (ACP) shuttles the acyl intermediates between individual pathway enzymes. In this study, we determined the solution structures of three different forms of ACP, apo‐ACP, ACP, and butyryl‐ACP under identical experimental conditions. The structural studies revealed that attachment of butyryl acyl intermediate to ACP alters the conformation of ACP. This finding supports the more general notion that the attachment of different acyl intermediates alters the ACP structure to facilitate their recognition and turnover by the appropriate target enzymes.
Acyl carrier protein
Acyl group
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In a previous publication we reported the purification of formate dehydrogenase (FDH, EC 1.2.1.2.) from Arabidopsis thaliana (L.) Heyn. and some of its properties. Here we report the identification of an Arabidopsis FDH cDNA, as well as studies of the molecular characterization and regulation of the enzyme in Arabidopsis. FDH is present as a single-copy gene in the Arabidopsis genome and is located on chromosome V. The deduced amino acid sequence of the Arabidopsis enzyme shows over 80% identity with those from other plants (potato, barley, rice). Northern and western blots show that the FDH mRNA and protein levels in Arabidopsis leaves are similar to those in flowers and stems and higher than those in roots. The effects of chemical and environmental factors on FDH expression in leaves were investigated and compared with their effects on formaldehyde dehydrogenase (FADH, EC 1.2.1.1.). Induction of FDH by one-carbon metabolites, such as methanol, formaldehyde, and formate, was observed at the protein level, but changes at the transcript level were small and different from those observed for FADH. While the steady-state levels of FDH transcripts increased quickly (within hours) and strongly in response to various stresses, protein amounts increased slowly, after 1 to 3 days; FADH transcripts showed no observable change. The possible mechanism of regulation of FDH at both the transcript and protein levels is discussed.Key words: Arabidopsis, formate dehydrogenase, formate metabolism, one-carbon metabolites, stress.
Formate dehydrogenase
Formaldehyde dehydrogenase
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Two Arabidopsis mutants atmyb123 and atkor1 were identified from the T-DNA insertion knockout mutant lines SAIL_005260 and SAIL_2_G11,respectively,and then a double mutant atmyb123/atkor1 was established by crossing method.The two mutants are lacking expression for ATMYB123 and ATKOR1 genes,respectively,which two were found to be tightly related to root development in Arabidopsis thaliana.The results obtained here showed that lack of ATMYB123 gene in expression led to a slow growth of plant rosettes and a yellow skin of seeds in Arabidopsis,while lack of ATKOR1 gene in expression had no marked effects on these two factors.Any one of the two genes ATMYB123 and ATKOR1 knockout extremely repressed the root development in Arabidopsis,especially the knockout of ATKOR1 gene,the mutant atkor1 showed only one third of length of roots as compared to wild type(WT).Interestingly,the double mutant atmyb123/atkor1 exhibited the characteristics of the single mutant atmyb123 has in plant rosette morphology and seed skins but presented intermediated root length between the two single mutants.In addition,the growth trend of roots among the three mutants had no fundamental changes when the plants were cultivated under different pH,NaCl treatments and GA concentration conditions,which imply that these three factors were not concerned in the root shortening event induced by lack of any one of ATMYB123 or/and ATKOR1 proteins in A.thaliana.These results suggest that both ATMYB123 and ATKOR1 genes participate in the root development of Arabidopsis and a specific relationship in functions exist between the two proteins,ATMYB123 and ATKOR1.The transcription factor ATMYB123 might act as a major regulator of ATKOR1 protein for participating the control of root development in Arabidopsis.
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Gene knockout
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Lateral root
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尽管高活动性组 B (HMGB ) 蛋白质被识别了从许多在对改变环境条件的植物回答的植物种类，他们的重要性和功能的角色大部分是未知的。这里，我们调查了在对环境刺激的植物回答从黄瓜(Cucumis sativus L.) 孤立的 CsHMGB 的功能的角色。在正常生长条件下面或当使遭到了到冷应力时，在植物生长的差别都没在表示 CsHMGB 上在野类型、转基因的 Arabidopsis thaliana 之间被发现。由对比，当在高盐或脱水压力条件下面成长时，转基因的 Arabidopsis 植物与野类型的植物相比显示了延迟的萌芽。转基因的植物的萌芽被 abscisic 酸(骆驼毛的织物) 的增加推迟，暗示 CsHMGB 影响通过一个骆驼毛的织物依赖者方法的萌芽。CsHMGB 的表示影响了仅仅萌芽阶段，并且 CsHMGB 没在压力条件下面影响转基因的植物的幼苗生长。几萌芽应答的基因的抄本层次被 CsHMGB 的表示在 Arabidopsis 调制。总起来说，这些结果建议在 Arabidopsis 的 CsHMGB 的那宫外的表情调制几萌芽应答的基因的表示，并且从而在不同压力条件下面影响 Arabidopsis 植物的萌芽。
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Drought stress
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Research Article: The effects of aluminum toxicity on the protein expression of Arabidopsis thaliana
Wild type and mutant Arabidopsis thaliana plants were used to investigate the protein expression of plants exposed to elevated concentrations of aluminum. Plants were grown in a growth chamber at 25°C, 16-hour day, and 8-hour dark for eight weeks before subjecting them to different concentrations of AlCl3 solution. Time course experiments showed that Arabidopsis plants respond to aluminum toxicity by altering their protein expression. Our data indicate that aluminum toxicity caused Arabidopsis plants to express a protein in the range of 97 kD, and a medium-molecular weight protein in the range of 45 kD. Our data also indicate that responses by Arabidopsis plants to Al toxicity are not similar to responses to stresses that cause the induction of HSP70.
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The expression of Arabidopsis unknown gene At1g142600 was induced by a variety of abiotic stresses.The expression of At1g14260 was significantly increased under the treatment of NaCl.The results suggested that At1g14260 was involved in the process of salt stress response.Analysis of the TDNA mutant of at1g14260(salk-118406)demonstrated that knocking out At1g14260 in Arabidopsis resulted in plants more sensitive to NaCl than the wild type.In addition,fusion vector PBi221-At1g14260-GFP was constructed and transfected into Arabidopsis protoplast.The observation by fluorescence microscope revealed that the fusion protein localized innucleus of the protoplasts.Therefore,At1g14260 may participate in the process of salt stress in Arabidopsis thaliana.
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Abstract: Polyclonal antisera against a fusion protein of β‐galactosidase and the 20 C‐terminal amino acids of the Arabidopsis thaliana sucrose carrier AtSUC2 were used to determine the cellular localization of the AtSUC2 protein. Using fluorescence‐labelling on sections from different organs of Arabidopsis the AtSUC2 protein was immunolocalized exclusively in companion cells. The presented data indicate that phloem loading in Arabidopsis may be catalyzed by the AtSUC2 sucrose carrier which transports sucrose into the companion cells. No evidence for a participation of the second Arabidopsis sucrose transporter AtSUC1 has been obtained.
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Ozet. Arabidopsis thaliana (Arabidopsis)’nin kromozom sayisinin az olmasi, bu bitkinin genetik yapisinin diger bitki turlerine gore daha kolay calisilmasina olanak saglamakta, ayrica diger bitkilerde patojenlere karsi gozlenen ana savunma mekanizmalari bu bitkide de bulunmaktadir. Bu acidan, konukcu bitkilerin patojen saldirilarina karsi savunma mekanizmalarini calisma konusunda Arabidopsis bitkisi ideal bir model sistem olusturmaktadir. Bu derlemenin amaci, patojenlere karsi bitki savunma mekanizmasinin genetigini anlamada Arabidopsis’in bir sablon olarak nasil kullanildigini, bitki ekotiplerinin patojen izolatlarina karsi gosterdigi farkliliklari (duyarlilik ve dayaniklilik) ortaya koyacak inceleme metodlarini aciklamaktadir. Anahtar Kelimeler: Arabidopsis thaliana, Peronospora parasitica, hastaliklara dayaniklilik, mutant bitkiler A Model Plant In Host-Pathogen Interaction: Arabidopsis thaliana Abstract. Because of its small genome, genetic studies are performed easier in Arabidopsis thaliana (Arabidopsis) compared to other plants and it exhibits all of the major kinds of defense responses described in other plants. Thus, Arabidopsis provides to be an ideal model system for studies of host defense responses to pathogen attack. This review details methods to isolate and utilize phytopathogens useful as probes in understanding the genetics of plant defense responses in Arabidopsis. As well, it will be defined how screening systems can be set up to detirmine differential responses (resistance and susceptibility) of Arabidopsis ecotypes to pathogen isolates. Key Words: Arabidopsis thaliana, Peronospora parasitica, disease resistance, mutant plants
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The article presents a study on the mutual influence of mutant genes in productivity of Arabidopsis plant ( Arabidopsis thaliana (L.) Heynh.), in different growing models of plant communities. It is shown that under the joint cultivation of five genetically pure lines of Arabidopsis is occurring mutual inhibition and aid, which leads decreasing or increasing of seed production plants.
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[Objective]The aim was to study the action mode of high mobility group B(HMGB)proteins of higher eukaryotic cells in the transcriptional regulation of plant stress responses.[Method]The At2G33450 gene encoding AT2G34450 protein in Arabidopsis thaliana was cloned.Then,binary vectors carrying the gene were transformed into Arabidopsis thaliana and the over-expression strains were selected to detect the influences of environmental stimuli on transgenic Arabidopsis.[Result]Under salt or drought stress,the transgenic Arabidopsis plants which over-expressed At2G33450 displayed retarded germination and subsequent growth compared with wild-type plants.[Conclusion]At2G33450 protein of HMGB protein family played an important role in the growth and development of Arabidopsis plants under various stress conditions.
Heterologous expression
Heterologous
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