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Functional differences between galactolipids and glucolipids revealed in photosynthesis of higher plants.

ABSTRACT: Galactolipids represent the most abundant lipid class in thylakoid membranes, where oxygenic photosynthesis is performed. The identification of galactolipids at specific sites within photosynthetic complexes by x-ray crystallography implies specific roles for galactolipids during photosynthetic electron transport. The preference for galactose and not for the more abundant sugar glucose in thylakoid lipids and their specific roles in photosynthesis are not understood. Introduction of a bacterial glucosyltransferase from Chloroflexus aurantiacus into the galactolipid-deficient dgd1 mutant of Arabidopsis thaliana resulted in the accumulation of a glucose-containing lipid in the thylakoids. At the same time, the growth defect of the dgd1 mutant was complemented. However, the degree of trimerization of light-harvesting complex II and the photosynthetic quantum yield of transformed dgd1 plants were only partially restored. These results indicate that specific interactions of the galactolipid head group with photosynthetic protein complexes might explain the preference for galactose in thylakoid lipids of higher plants. Therefore, galactose in thylakoid lipids can be exchanged with glucose without severe effects on growth, but the presence of galactose is crucial to maintain maximal photosynthetic efficiency.

SUBMITTER: Holzl G

PROVIDER: S-EPMC1464369 | biostudies-other | 2006 May

REPOSITORIES: biostudies-other

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Functional differences between galactolipids and glucolipids revealed in photosynthesis of higher plants.

Hölzl Georg G Witt Sandra S Kelly Amélie A AA Zähringer Ulrich U Warnecke Dirk D Dörmann Peter P Heinz Ernst E

Proceedings of the National Academy of Sciences of the United States of America 20060428 19

Galactolipids represent the most abundant lipid class in thylakoid membranes, where oxygenic photosynthesis is performed. The identification of galactolipids at specific sites within photosynthetic complexes by x-ray crystallography implies specific roles for galactolipids during photosynthetic electron transport. The preference for galactose and not for the more abundant sugar glucose in thylakoid lipids and their specific roles in photosynthesis are not understood. Introduction of a bacterial ...[more]

PMID: 16648262

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Project description:BackgroundRheum tanguticum (Rh. tanguticum) is an important traditional Chinese medicine plant, "Dahuang", which contains productive metabolites and occupies wide habitats on the Qinghai-Tibet plateau. Plants occupying wide habitats usually vary in phenotypes such as in morphology and metabolism, thereby developing into different ecotypes. Under canopy and open habitats are a pair of dissimilar habitats which possess Rh. tanguticum plants. However, few studies have focused on the effect of habitats on Rh. tanguticum growth, particularly combining morphological and metabolic changes. This study focused on Rh. tanguticum plants growing in under canopy and open habitats where morphology and metabolism changes were quantified using non-target metabolism methods.ResultsThe obtained results indicated that the two dissimilar habitats led to Rh. tanguticum developing into two distinct ecotypes where the morphology and metabolism were simultaneously changed. Under canopy habitats bred morphologically smaller Rh. tanguticum plants which had a higher level of metabolites (22 out of 31) which included five flavonoids, four isoflavonoids, and three anthracenes. On the other hand, the open habitats produced morphologically larger Rh. tanguticum plants having a higher level of metabolites (9 out of 31) including four flavonoids. 6 of the 31 metabolites were predicted to have effect targets, include 4 represent for under canopy habitats and 2 for open habitats. Totally, 208 targets were connected, among which 42 were communal targets for both under canopy and open habitats represent compounds, and 100 and 66 were unique targets for under canopy superior compounds and open habitats superior compounds, respectively. In addition, aloe-emodin, emodin, chrysophanol, physcion, sennoside A and sennoside B were all more accumulated in under canopy habitats, and among which aloe-emodin, emodin, chrysophanol and physcion were significantly higher in under canopy habitats.ConclusionsThis study determined that Rh. tanguticum growing in under canopy and in open habitats developed into two distinct ecotypes with morphological and metabolic differences. Results of network pharmacology study has indicated that "Dahuang" coming from different habitats, such as under canopy and open habitats, are different in effect targets and thus may have different medicinal use. According to target metabolomics, under canopy habitats may grow better "Dahuang".

Project description:Transcriptional regulation is a universal mechanism for a wide array of biological processes, and is driven in large part by genetic enhancer elements. These regulatory elements have been well-studied in animal species, yet their plant counterparts remain poorly characterized. While high-throughput profiling of animal genomes has yielded great success in identifying genetic enhancers through secondary characteristics – flanking histone posttranslational modifications (PTMs), chromatin accessibility, and the production of enhancer RNAs (eRNAs) – it is an active line of investigation as to whether these secondary characteristics can be used in a similar way to locate regulatory regions of plant genomes. Here, we compare the enrichment of the four histone PTMs most commonly associated with animal enhancers – H3K27ac, H3K27me3, H3K4me1, and H3K4me3 – between Drosophila melanogaster, Homo sapiens, and Arabidopsis thaliana genomes. Regions of accessible chromatin were identified through ATAC-seq or DNase-seq, and were analyzed as putative enhancer regions. Additionally, as it has been shown that enhancer activity varies widely from cell type to cell type, matched, single-cell type datasets were used for each species whenever available. Through the intersection of these data it becomes clear that there are distinct differences between the epigenetic makeup of plant and animal genomes. While these four histone PTMs are present at transcription start sites (TSSs) in all three of the species investigated, A. thaliana showed a marked depletion of these modifications upstream of the TSS, while the animal species showed bimodal enrichment. The plant histone PTM pattern is consistent with the pattern observed at unidirectional promoters, which was further supported by GRO-seq data. When intergenic regions of accessible chromatin were examined – putative enhancer regions – the plant epigenomes showed a one-sided, rather than bimodal, enrichment of all four of the histone PTMs. However, these sites retain the ability to produce eRNAs, suggesting that they are likely functionally active enhancer elements. While it is known that animal promoters and enhancers have bidirectional transcription, this analysis revealed that plant promoters and enhancers have a distinct pattern, and only exhibit histone PTM deposition and transcription in the sense direction. While further investigation is merited, this may speak to a fundamental difference between the transcriptional machinery of plant and animal kingdoms.

Dataset Information

Functional differences between galactolipids and glucolipids revealed in photosynthesis of higher plants.

Publications

Functional differences between galactolipids and glucolipids revealed in photosynthesis of higher plants.

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