scholarly journals Multi-omics Analysis of the Symbiotic Green Algae, Chlorella Variabilis, Revealing the Genetic Basis of the Obligate Endosymbiotic Lifestyle

2021 ◽  
Author(s):  
Ryuhei Minei ◽  
Ryo Hoshina ◽  
Rina Higuchi ◽  
Lin Chen ◽  
Yuki Akizuki ◽  
...  
Keyword(s):  
Genetic Basis ◽  
Carbon Fixation ◽  
Absorption Efficiency ◽  
Secondary Endosymbiosis ◽  
Genomic Changes ◽  
Cell Wall Biogenesis ◽  
Chlorella Variabilis ◽  
Photosynthetic Eukaryotes ◽  
Living Species ◽  
Fixation Capacity

Abstract Background: Photosynthetic eukaryotes have evolved through the acquisition of plastids by secondary endosymbiosis, a process that requires several steps. Immediately before plastid acquisition, the genome of the symbiont is known to be dramatically reduced, but few studies have focused on the genomic changes in the symbiont at the early stages of secondary endosymbiosis. Methods: To investigate the genetic basis of the transition from facultative to obligate endosymbiosis, we compared the genomes of Chlorella variabilis, a representative symbiotic alga, with that of Paramecium bursaria, to compare closely related free-living species and transcriptomes between organisms in symbiotic and non-symbiotic conditions. Results: We found that the non-reduced genome of C. variabilis and its genes play a crucial role in endosymbiosis, being involved in cell wall biogenesis and degradation, and metabolic exchanges with the host. Our results suggest that the genetic mechanism underlying the enhancement of photosynthesis under symbiosis is the increasing light absorption efficiency and carbon fixation capacity of the endosymbiont, resulting in an increase in the supply of maltose to P. bursaria.

scholarly journals The World of Algae Reveals a Broad Variety of Cryptochrome Properties and Functions

2021 ◽  
Vol 12 ◽  
Author(s):  
Jan Petersen ◽  
Anxhela Rredhi ◽  
Julie Szyttenholm ◽  
Sabine Oldemeyer ◽  
Tilman Kottke ◽  
...  
Keyword(s):  
Carbon Fixation ◽  
Algal Cell ◽  
Algal Species ◽  
Life Cycles ◽  
Land Plants ◽  
Abiotic Factor ◽  
Secondary Endosymbiosis ◽  
Biological Clocks ◽  
Terrestrial Habitats ◽  
Broad Variety

Algae are photosynthetic eukaryotic (micro-)organisms, lacking roots, leaves, and other organs that are typical for land plants. They live in freshwater, marine, or terrestrial habitats. Together with the cyanobacteria they contribute to about half of global carbon fixation. As primary producers, they are at the basis of many food webs and they are involved in biogeochemical processes. Algae are evolutionarily distinct and are derived either by primary (e.g., green and red algae) or secondary endosymbiosis (e.g., diatoms, dinoflagellates, and brown algae). Light is a key abiotic factor needed to maintain the fitness of algae as it delivers energy for photosynthesis, regulates algal cell- and life cycles, and entrains their biological clocks. However, excess light can also be harmful, especially in the ultraviolet range. Among the variety of receptors perceiving light information, the cryptochromes originally evolved as UV-A and blue-light receptors and have been found in all studied algal genomes so far. Yet, the classification, biophysical properties, wavelength range of absorbance, and biological functions of cryptochromes are remarkably diverse among algal species, especially when compared to cryptochromes from land plants or animals.

scholarly journals Thinning effect on understory community and photosynthetic characteristics in a subtropical Pinus massoniana plantation

2017 ◽  
Vol 47 (8) ◽  
pp. 1104-1115 ◽  
Author(s):  
Chuanpeng Cheng ◽  
Yidong Wang ◽  
Xiaoli Fu ◽  
Mingjie Xu ◽  
Xiaoqin Dai ◽  
...  
Keyword(s):  
Carbon Fixation ◽  
Chlorophyll Concentration ◽  
Basal Area ◽  
Wiener Index ◽  
Pinus Massoniana ◽  
Leaf Length ◽  
Photosynthetic Characteristics ◽  
Leaf Chlorophyll ◽  
Fern Species ◽  
Fixation Capacity

Thinning forest stands changes biotic and abiotic conditions, subsequently altering understory communities including their photosynthetic characteristics. We investigated the effects of thinning (25% basal area decrease) in a subtropical Pinus massoniana Lamb. plantation at two post-thinning times: 0.5 years (PT0.5) and 2.5 years (PT2.5). Thinning (PT0.5 and PT2.5) significantly increased understory density (+104.9% and +142.4%, respectively), aboveground biomass (+191.1% and +239.2%, respectively), the Shannon–Wiener index, and the Pielou index and decreased the Simpson index (p < 0.05). Species richness significantly increased at PT0.5 and decreased at PT2.5 (p < 0.05). Photosynthetic characteristics of new and old leaves of three dominant species (Woodwardia japonica (Linn. f.) Sm., Dryopteris championii (Benth.) C. Chr., and Dicranopteris dichotoma (Thunb.) Bernh.) showed different variations at 0.5 and 2.5 years after thinning, depending on their various adaptive strategies. Generally, thinning improved leaf carbon fixation capacity of these dominant plants (except W. japonica old leaves). Leaf photosynthetic characteristics of these species exhibited some common changes with respect to leaf morphological attributes and chlorophyll content. Thinning increased new-leaf length (or width) and reduced old-leaf chlorophyll b concentration at PT0.5 but reduced new-leaf length, specific leaf area, and all-leaf chlorophyll concentration at PT2.5. In conclusion, thinning is a useful tool for increasing understory abundance and carbon fixation capacity of some fern species.

scholarly journals Fatty acid photodecarboxylase is an ancient photoenzyme responsible for hydrocarbon formation in the thylakoid membranes of algae

2020 ◽  
Author(s):  
Solène Moulin ◽  
Audrey Beyly ◽  
Stéphanie Blangy ◽  
Bertrand Légeret ◽  
Magali Floriani ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Growth Conditions ◽  
Secondary Endosymbiosis ◽  
Chlorella Variabilis ◽  
Green Microalga ◽  
Specific Subgroup ◽  
Hydrocarbon Formation

ABSTRACTFatty acid photodecarboxylase (FAP) is one of the three enzymes that require light for their catalytic cycle (photoenzymes). FAP has been first identified in the green microalga Chlorella variabilis NC64A and belongs an algae-specific subgroup of the glucose-methanol-choline oxidoreductase family. While the FAP from Chlorella and its Chlamydomonas reinhardtii homolog CrFAP have demonstrated in vitro activity, their activity and physiological function have not been studied in vivo. Besides, the conservation of FAP activity beyond green microalgae remains hypothetical. Here, using a Chlamydomonas FAP knockout line (fap), we show that CrFAP is responsible for the formation of 7-heptadecene, the only hydrocarbon present in this alga. We further show that CrFAP is associated to the thylakoids and that 90% of 7-heptadecene is recovered in this cell fraction. In the fap mutant, photosynthesis activity was not affected under standard growth conditions but was reduced after cold acclimation. A phylogenetic analysis including sequences from Tara Ocean identified almost 200 putative FAPs and indicated that FAP was acquired early after primary endosymbiosis. Within Bikonta, FAP was kept in photosynthetic secondary endosymbiosis lineages but absent in those that lost the plastid. Characterization of recombinant FAPs from various algal genera (Nannochloropsis, Ectocarpus, Galdieria, Chondrus) provided experimental evidence that FAP activity is conserved in red and brown algae and is not limited to unicellular species. These results thus indicate that FAP has been conserved during evolution of most algal lineages when photosynthesis was kept and suggest that its function is linked to photosynthetic membranes.One sentence summaryFAP is present in thylakoids and conserved beyond green algae.

scholarly journals Genomic and Meiotic Changes Accompanying Polyploidization

Plants ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 125
Author(s):  
Francesco Blasio ◽  
Pilar Prieto ◽  
Mónica Pradillo ◽  
Tomás Naranjo
Keyword(s):  
Genetic Variants ◽  
Genetic Basis ◽  
Chromosome Doubling ◽  
Average Frequency ◽  
Unreduced Gametes ◽  
Hybrid Speciation ◽  
Interspecific Gene Flow ◽  
Genomic Changes ◽  
Evolutionary Forces ◽  
Homoploid Hybrid

Hybridization and polyploidy have been considered as significant evolutionary forces in adaptation and speciation, especially among plants. Interspecific gene flow generates novel genetic variants adaptable to different environments, but it is also a gene introgression mechanism in crops to increase their agronomical yield. An estimate of 9% of interspecific hybridization has been reported although the frequency varies among taxa. Homoploid hybrid speciation is rare compared to allopolyploidy. Chromosome doubling after hybridization is the result of cellular defects produced mainly during meiosis. Unreduced gametes, which are formed at an average frequency of 2.52% across species, are the result of altered spindle organization or orientation, disturbed kinetochore functioning, abnormal cytokinesis, or loss of any meiotic division. Meiotic changes and their genetic basis, leading to the cytological diploidization of allopolyploids, are just beginning to be understood especially in wheat. However, the nature and mode of action of homoeologous recombination suppressor genes are poorly understood in other allopolyploids. The merger of two independent genomes causes a deep modification of their architecture, gene expression, and molecular interactions leading to the phenotype. We provide an overview of genomic changes and transcriptomic modifications that particularly occur at the early stages of allopolyploid formation.

Endosymbiont change as a key innovation in the adaptive radiation of Soritida (Foraminifera)

Paleobiology ◽  
2001 ◽  
Vol 27 (2) ◽  
pp. 262-289 ◽  
Author(s):  
Susan. L. Richardson
Keyword(s):  
Shallow Water ◽  
Adaptive Radiation ◽  
Free Living ◽  
Fossil Species ◽  
Subsequent Change ◽  
Photosynthetic Eukaryotes ◽  
Key Innovation ◽  
Clade B ◽  
Stem Lineage ◽  
Living Species

A phylogeny of 54 Recent and fossil species of Soritacea (Foraminifera) was used to test the hypothesis that endosymbiosis has driven the evolution of the clade. Endosymbiosis with photosynthetic eukaryotes is the plesiomorphic condition for the entire clade Soritacea. Living species dwell in tropical-subtropical, shallow-water habitats and are characterized by the possession of rhodophyte, chlorophyte, or dinophyte photosymbionts. Two distinct changes in endosymbiont type are recognized when endosymbiont type is mapped in the cladogram of Soritacea: (1) a change from rhodophyte to chlorophyte endosymbionts occurred in the stem lineage of the least inclusive clade containing New clade B, Orbiculinida, and Soritida; and (2) a change from chlorophyte to dinophyte endosymbionts occurred in the stem lineage of the least inclusive clade containing New clade G, New clade H, New clade I, Sorites, Amphisorus, and Orbitolites. When habitat and ontogeny are optimized on the cladogram of Soritida, the acquisition of dinophyte endosymbionts appears as a key innovation that facilitated a switch in habitat from free-living to attached living on nonphytal and phytal substrata. A subsequent change in the attached habitat from nonphytal to predominantly phytal (seagrasses and macroalgae) substrata is accompanied by a peramorphic trend in the megalospheric tests. The diversification (adaptive radiation) of the crown Soritida subclade resulted from the interplay between the acquisition of a key innovation (dinophyte endosymbionts) and the subsequent change in the ecology of the group (radiation to phytal substrates).

scholarly journals Crystal Structure of Chloroplastic Thioredoxin f2 from Chlamydomonas reinhardtii Reveals Distinct Surface Properties

Antioxidants ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 171 ◽  
Author(s):  
Stéphane Lemaire ◽  
Daniele Tedesco ◽  
Pierre Crozet ◽  
Laure Michelet ◽  
Simona Fermani ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Active Sites ◽  
Carbon Fixation ◽  
Disulfide Reduction ◽  
Photosynthetic Eukaryotes ◽  
Multimeric Complex ◽  
Different Types ◽  
Multigenic Family ◽  
Living Organisms ◽  
Protein Disulfide

Protein disulfide reduction by thioredoxins (TRXs) controls the conformation of enzyme active sites and their multimeric complex formation. TRXs are small oxidoreductases that are broadly conserved in all living organisms. In photosynthetic eukaryotes, TRXs form a large multigenic family, and they have been classified in different types: f, m, x, y, and z types are chloroplastic, while o and h types are located in mitochondria and cytosol. In the model unicellular alga Chlamydomonas reinhardtii, the TRX family contains seven types, with f- and h-types represented by two isozymes. Type-f TRXs interact specifically with targets in the chloroplast, controlling photosynthetic carbon fixation by the Calvin–Benson cycle. We solved the crystal structures of TRX f2 and TRX h1 from C. reinhardtii. The systematic comparison of their atomic features revealed a specific conserved electropositive crown around the active site of TRX f, complementary to the electronegative surface of their targets. We postulate that this surface provides specificity to each type of TRX.

scholarly journals A novel Ca2+ signalling pathway co-ordinates environmental phosphorus sensing and nitrogen metabolism in marine diatoms

2020 ◽  
Author(s):  
K. E. Helliwell ◽  
E. Harrison ◽  
J. Christie-Oleza ◽  
A. P. Rees ◽  
J. Downe ◽  
...  
Keyword(s):  
Aquatic Ecosystems ◽  
Carbon Fixation ◽  
Resource Competition ◽  
Phosphorus Limitation ◽  
Nutrient Sensing ◽  
Signalling Pathway ◽  
Photosynthetic Eukaryotes ◽  
Highly Sensitive ◽  
Sense And Respond ◽  
Phytoplankton Group

AbstractDiatoms are a diverse and globally important phytoplankton group, responsible for an estimated 20% of carbon fixation on Earth. They frequently form spatially extensive phytoplankton blooms, responding rapidly to increased availability of nutrients including phosphorus and nitrogen. Although it is well established that diatoms are common first-responders to nutrient influxes in aquatic ecosystems, little is known of the sensory mechanisms that they employ for nutrient perception. Here we show that diatoms use a novel and highly-sensitive Ca2+-dependent signalling pathway, not previously described in eukaryotes, to sense and respond to the critical macronutrient phosphorus. We demonstrate that phosphorus-Ca2+ signalling is essential for regulating diatom recovery from phosphorus limitation, by controlling rapid and substantial increases in nitrogen assimilation. Phosphorus-Ca2+ signalling thus mediates fundamental cross-talk between the vital nutrients P and N to maximise resource competition, and likely governs the success of diatoms as major bloom formers in regions of pulsed nutrient supply. Importantly, our study demonstrates that distinct mechanisms for nutrient sensing have evolved in photosynthetic eukaryotes.

scholarly journals Adaptive signals in algal Rubisco reveal a history of ancient atmospheric carbon dioxide

2012 ◽  
Vol 367 (1588) ◽  
pp. 483-492 ◽  
Author(s):  
J. N. Young ◽  
R. E. M. Rickaby ◽  
M. V. Kapralov ◽  
D. A. Filatov
Keyword(s):  
Carbon Dioxide ◽  
Positive Selection ◽  
Dna Sequences ◽  
Atmospheric Carbon Dioxide ◽  
Carbon Fixation ◽  
Large Subunit ◽  
Kinetic Properties ◽  
Secondary Endosymbiosis ◽  
History Of ◽  
Carbon Concentrating Mechanisms

Rubisco, the most abundant enzyme on the Earth and responsible for all photosynthetic carbon fixation, is often thought of as a highly conserved and sluggish enzyme. Yet, different algal Rubiscos demonstrate a range of kinetic properties hinting at a history of evolution and adaptation. Here, we show that algal Rubisco has indeed evolved adaptively during ancient and distinct geological periods. Using DNA sequences of extant marine algae of the red and Chromista lineage, we define positive selection within the large subunit of Rubisco, encoded by rbcL , to occur basal to the radiation of modern marine groups. This signal of positive selection appears to be responding to changing intracellular concentrations of carbon dioxide (CO 2 ) triggered by physiological adaptations to declining atmospheric CO 2 . Within the ecologically important Haptophyta (including coccolithophores) and Bacillariophyta (diatoms), positive selection occurred consistently during periods of falling Phanerozoic CO 2 and suggests emergence of carbon-concentrating mechanisms. During the Proterozoic, a strong signal of positive selection after secondary endosymbiosis occurs at the origin of the Chromista lineage (approx. 1.1 Ga), with further positive selection events until 0.41 Ga, implying a significant and continuous decrease in atmospheric CO 2 encompassing the Cryogenian Snowball Earth events. We surmise that positive selection in Rubisco has been caused by declines in atmospheric CO 2 and hence acts as a proxy for ancient atmospheric CO 2 .

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