complex plastids Dotaz Zobrazit nápovědu
A substantial portion of eukaryote diversity consists of algae with complex plastids, i.e., plastids originating from eukaryote-to-eukaryote endosymbioses. These plastids are characteristic by a deviating number of envelope membranes (higher than two), and sometimes a remnant nucleus of the endosymbiont alga, termed the nucleomorph, is present. Complex plastid-bearing algae are therefore much like living matryoshka dolls, eukaryotes within eukaryotes. In comparison, primary plastids of Archaeplastida (plants, green algae, red algae, and glaucophytes) arose upon a single endosymbiosis event with a cyanobacterium and are surrounded by two membranes. Complex plastids were acquired several times by unrelated groups nested within eukaryotic heterotrophs, suggesting complex plastids are somewhat easier to obtain than primary plastids. This is consistent with the existence of higher-order and serial endosymbioses, i.e., engulfment of complex plastid-bearing algae by (tertiary) eukaryotic hosts and functional plastid replacements, respectively. Plastid endosymbiosis is typical by a massive transfer of genetic material from the endosymbiont to the host nucleus and metabolic rearrangements related to the trophic switch to phototrophy; this is necessary to establish metabolic integration of the plastid and control over its division. Although photosynthesis is the main advantage of plastid acquisition, algae that lost photosynthesis often maintain complex plastids, suggesting their roles beyond photosynthesis. This chapter summarizes basic knowledge on acquisition and functions of complex plastid.
- MeSH
- Apicomplexa MeSH
- buněčný cyklus MeSH
- plastidy * MeSH
- symbióza * MeSH
- Publikační typ
- dopisy MeSH
- komentáře MeSH
- práce podpořená grantem MeSH
Diatoms are unicellular algae and evolved by secondary endosymbiosis, a process in which a red alga-like eukaryote was engulfed by a heterotrophic eukaryotic cell. This gave rise to plastids of remarkable complex architecture and ultrastructure that require elaborate protein importing, trafficking, signaling and intracellular cross-talk pathways. Studying both plastids and mitochondria and their distinctive physiological pathways in organello may greatly contribute to our understanding of photosynthesis, mitochondrial respiration and diatom evolution. The isolation of such complex organelles, however, is still demanding, and existing protocols are either limited to a few species (for plastids) or have not been reported for diatoms so far (for mitochondria). In this work, we present the first isolation protocol for mitochondria from the model diatom Thalassiosira pseudonana. Apart from that, we extended the protocol so that it is also applicable for the purification of a high-quality plastids fraction, and provide detailed structural and physiological characterizations of the resulting organelles. Isolated mitochondria were structurally intact, showed clear evidence of mitochondrial respiration, but the fractions still contained residual cell fragments. In contrast, plastid isolates were virtually free of cellular contaminants, featured structurally preserved thylakoids performing electron transport, but lost most of their stromal components as concluded from Western blots and mass spectrometry. Liquid chromatography electrospray-ionization mass spectrometry studies on mitochondria and thylakoids, moreover, allowed detailed proteome analyses which resulted in extensive proteome maps for both plastids and mitochondria thus helping us to broaden our understanding of organelle metabolism and functionality in diatoms.
Photosystem I (PSI) is a multi-subunit integral pigment-protein complex that performs light-driven electron transfer from plastocyanin to ferredoxin in the thylakoid membrane of oxygenic photoautotrophs. In order to achieve the optimal photosynthetic performance under ambient irradiance, the absorption cross section of PSI is extended by means of peripheral antenna complexes. In eukaryotes, this role is played mostly by the pigment-protein complexes of the LHC family. The structure of the PSI-antenna supercomplexes has been relatively well understood in organisms harboring the primary plastid: red algae, green algae and plants. The secondary endosymbiotic algae, despite their major ecological importance, have so far received less attention. Here we report a detailed structural analysis of the antenna-PSI association in the stramenopile alga Nannochloropsis oceanica (Eustigmatophyceae). Several types of PSI-antenna assemblies are identified allowing for identification of antenna docking sites on the PSI core. Instances of departure of the stramenopile system from the red algal model of PSI-Lhcr structure are recorded, and evolutionary implications of these observations are discussed.
Photosynthetic eukaryotes whose cells harbor plastids originating from secondary endosymbiosis of a red alga include species of major ecological and economic importance. Since utilization of solar energy relies on the efficient light-harvesting, one of the critical factors for the success of the red lineage in a range of environments is to be found in the adaptability of the light-harvesting machinery, formed by the proteins of the light-harvesting complex (LHC) family. A number of species are known to employ mainly a unique class of LHC containing red-shifted chlorophyll a (Chl a) forms absorbing above 690 nm. This appears to be an adaptation to shaded habitats. Here we present a detailed investigation of excitation energy flow in the red-shifted light-harvesting antenna of eustigmatophyte Trachydiscus minutus using time-resolved fluorescence and ultrafast transient absorption measurements. The main carotenoid in the complex is violaxanthin, hence this LHC is labeled the red-violaxanthin-Chl a protein, rVCP. Both the carotenoid-to-Chl a energy transfer and excitation dynamics within the Chl a manifold were studied and compared to the related antenna complex, VCP, that lacks the red-Chl a. Two spectrally defined carotenoid pools were identified in the red antenna, contributing to energy transfer to Chl a, mostly via S2 and hot S1 states. Also, Chl a triplet quenching by carotenoids is documented. Two separate pools of red-shifted Chl a were resolved, one is likely formed by excitonically coupled Chl a molecules. The structural implications of these observations are discussed.
- MeSH
- chlorofyl a * MeSH
- Chlorophyta fyziologie MeSH
- fluorescenční spektrometrie metody MeSH
- Heterokontophyta fyziologie MeSH
- plastidy MeSH
- přenos energie fyziologie MeSH
- Rhodophyta fyziologie MeSH
- světlosběrné proteinové komplexy chemie MeSH
- xanthofyly MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Polyploidization is one of the leading forces in the evolution of land plants, providing opportunities for instant speciation and rapid gain of evolutionary novelties. Highly selective conditions of serpentine environments act as an important evolutionary trigger that can be involved in various speciation processes. Whereas the significance of both edaphic speciation on serpentine and polyploidy is widely acknowledged in plant evolution, the links between polyploid evolution and serpentine differentiation have not yet been examined. To fill this gap, we investigated the evolutionary history of the perennial herb Knautia arvensis (Dipsacaceae), a diploid-tetraploid complex that exhibits an intriguing pattern of eco-geographic differentiation. Using plastid DNA sequencing and AFLP genotyping of 336 previously cytotyped individuals from 40 populations from central Europe, we unravelled the patterns of genetic variation among the cytotypes and the edaphic types. Diploids showed the highest levels of genetic differentiation, likely as a result of long term persistence of several lineages in ecologically distinct refugia and/or independent immigration. Recurrent polyploidization, recorded in one serpentine island, seems to have opened new possibilities for the local serpentine genotype. Unlike diploids, the serpentine tetraploids were able to escape from the serpentine refugium and spread further; this was also attributable to hybridization with the neighbouring non-serpentine tetraploid lineages. The spatiotemporal history of K. arvensis allows tracing the interplay of polyploid evolution and ecological divergence on serpentine, resulting in a complex evolutionary pattern. Isolated serpentine outcrops can act as evolutionary capacitors, preserving distinct karyological and genetic diversity. The serpentine lineages, however, may not represent evolutionary 'dead-ends' but rather dynamic systems with a potential to further influence the surrounding populations, e.g., via independent polyplodization and hybridization. The complex eco-geographical pattern together with the incidence of both primary and secondary diploid-tetraploid contact zones makes K. arvensis a unique system for addressing general questions of polyploid research.
- MeSH
- analýza polymorfismu délky amplifikovaných restrikčních fragmentů MeSH
- biologická evoluce * MeSH
- chrysotilový azbest MeSH
- Dipsacaceae genetika metabolismus MeSH
- ekosystém MeSH
- fenotyp MeSH
- fylogeneze MeSH
- genom rostlinný MeSH
- haplotypy MeSH
- plastidy genetika MeSH
- polyploidie * MeSH
- půda chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Evropa MeSH
Tryptophan is an essential amino acid that, in eukaryotes, is synthesized either in the plastids of photoautotrophs or in the cytosol of fungi and oomycetes. Here we present an in silico analysis of the tryptophan biosynthetic pathway in stramenopiles, based on analysis of the genomes of the oomycetes Phytophthora sojae and P. ramorum and the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum. Although the complete pathway is putatively located in the complex chloroplast of diatoms, only one of the involved enzymes, indole-3-glycerol phosphate synthase (InGPS), displays a possible cyanobacterial origin. On the other hand, in P. tricornutum this gene is fused with the cyanobacteria-derived hypothetical protein COG4398. Anthranilate synthase is also fused in diatoms. This fusion gene is almost certainly of bacterial origin, although the particular source of the gene cannot be resolved. All other diatom enzymes originate from the nucleus of the primary host (red alga) or secondary host (ancestor of chromalveolates). The entire pathway is of eukaryotic origin and cytosolic localization in oomycetes; however, one of the enzymes, anthranilate phosphoribosyl transferase, was likely transferred to the oomycete nucleus from the red algal nucleus during secondary endosymbiosis. This suggests possible retention of the complex plastid in the ancestor of stramenopiles and later loss of this organelle in oomycetes.
- MeSH
- aldoso-ketosoisomerasy genetika metabolismus MeSH
- anthranilátfosforibosyltransferasa genetika metabolismus MeSH
- anthranilátsynthasa genetika metabolismus MeSH
- chloroplasty metabolismus MeSH
- financování organizované MeSH
- fylogeneze MeSH
- indol-3-glycerolfosfátsynthasa genetika metabolismus MeSH
- molekulární evoluce MeSH
- molekulární sekvence - údaje MeSH
- molekulární struktura MeSH
- Phytophthora metabolismus MeSH
- rozsivky cytologie genetika metabolismus MeSH
- sekvence aminokyselin MeSH
- tryptofan biosyntéza chemie MeSH
- tryptofansynthasa genetika metabolismus MeSH
- MeSH
- Bacteria MeSH
- biotechnologie MeSH
- chaperoniny fyziologie klasifikace MeSH
- mitochondrie MeSH
- molekulární evoluce MeSH
- plastidy MeSH
- Publikační typ
- přehledy MeSH
Primary plastids of green algae (including land plants), red algae and glaucophytes are bounded by two membranes and are thought to be derived from a single primary endosymbiosis of a cyanobacterium in a eukaryotic host. Complex plastids of euglenids and chlorarachneans bounded by three and four membranes, respectively, most likely arose via two separate secondary endosymbioses of a green alga in a eukaryotic host. Secondary plastids of cryptophyta, haptophyta, heterokontophyta and apicomplexan parasites bounded by four membranes, and plastids of dinoflagellates bounded by three membranes could have arisen via a single secondary endosymbiosis of a red alga in a eukaryotic host (chromalveolate hypothesis). However, the scenario of separate tertiary origins (symbioses of an alga possessing secondary plastids in a eukaryotic host) of some (or even most) chromalveolate plastids can be also consistent with the current data. The protein import into complex plastids differs from the import into primary plastids, as complex plastids contain one or two extra membrane(s). In organisms with primary plastids, plastid-targeted proteins contain N-terminal transit peptide which ferries proteins through the protein import machineries (multiprotein complexes) of the two (originally cyanobacterial) membranes. In organisms with complex plastids, the secretory signal sequence directing proteins to endomembrane system and afterwards through extra outermost membrane(s) is generally present upstream of the classical transit peptide. Several free-living as well as parasitic eukaryotes possess non-photosynthetic plastids. These plastids have generally retained the plastid genome, functional plastid transcriptional and translational apparatus, and various metabolic pathways, suggesting that though these plastids lost their photosynthetic ability, they are essential for the mentioned organisms. Nevertheless, some eukaryotes could have lost chloroplast compartment completely.
