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Evolutionary Drivers and Adaptive Mechanisms in Algal Organellar Genomes

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Plant Sciences".

Deadline for manuscript submissions: 20 August 2026 | Viewed by 1417

Special Issue Editor

CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences (IOCAS), Qingdao, China
Interests: organellar genome of algae; adaptive evolution; molecular evolution; evolutionary driving force; group I/II intron; horizontal gene transfer; molecular marker; comparative genomics; molecular diversity; biodiversity; genome rearrangement; gene duplication, inverted repeats; phylogenomic analysis; circular plasmid; DNA-directed RNA polymerase; intron-encoded protein

Special Issue Information

Dear Colleagues,

Algae, as a phylogenetically diverse group of photosynthetic eukaryotes, serve as pivotal models for exploring organellar genome evolution due to their unique evolutionary trajectories shaped by endosymbiotic events, environmental adaptability, and genomic plasticity. Their chloroplast genomes and mitochondrial genomes exhibit remarkable diversity in genome architecture, including gene loss, horizontal gene transfer (HGT), structural rearrangements, intron content and diversity, and varying evolutionary rates. These features are influenced by complex drivers such as natural selection (e.g., optimizing photosynthesis under fluctuating light or nutrient conditions), genetic drift, and host-endosymbiont conflicts. Additionally, algal organellar genomes have evolved adaptive strategies to thrive in extreme habitats, from polar oceans to hypersaline lakes, offering insights into stress response mechanisms and ecological diversification. Advances in comparative genomics, phylogenomics, and molecular ecology have uncovered conserved functional modules (e.g., photosynthetic machinery) and lineage-specific innovations (e.g., novel metabolic pathways), yet critical gaps remain in understanding how evolutionary forces interact to shape organellar genome dynamics. This field is further enriched by interdisciplinary approaches linking genomic data with environmental adaptation, symbiosis, and biotechnology applications.

This special issue aims to compile cutting-edge research addressing unresolved questions in algal organellar genome evolution. We invite contributions spanning genome sequencing, molecular mechanisms of adaptation, evolutionary modeling, and ecological genomics. Topics of interest include but are not limited to: (1) drivers of organellar genome reduction and expansion, (2) adaptive evolution under abiotic/biotic stresses, (3) horizontal gene transfer and its functional implications, (4) co-evolution between nuclear and organellar genomes, and (5) biotechnological innovations inspired by algal organellar adaptability. By integrating studies across taxonomic groups and environments, this issue will advance mechanistic insights into how organellar genomes respond to evolutionary pressures and enhance their utility in synthetic biology, bioenergy, and climate resilience research. We encourage submissions employing innovative methodologies—from single-cell omics to CRISPR-based functional assays—to bridge knowledge gaps and foster cross-disciplinary collaborations. Join us in illuminating the evolutionary ingenuity of algal organelles and their broader implications for life sciences.

Dr. Feng Liu
Guest Editor

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Keywords

  • organellar genome of algae
  • molecular evolution
  • secondary structure of intron
  • evolutionary driving force
  • horizontal gene transfer

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Published Papers (2 papers)

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Research

24 pages, 3872 KB  
Article
Structural Remodeling and Enzymatic Replacement Shape the Evolution of Organellar Group II Introns in Ulva
by Feng Liu, Shuangle Jin and Huiyin Song
Int. J. Mol. Sci. 2026, 27(6), 2613; https://doi.org/10.3390/ijms27062613 - 12 Mar 2026
Cited by 1 | Viewed by 429
Abstract
Group II introns are catalytic RNAs that combine self-splicing ribozyme activity with mobility and have played major roles in shaping organellar genome evolution. In green macroalgae of the genus Ulva, organellar genomes are highly compact, yet they harbor unusually diverse and dynamic [...] Read more.
Group II introns are catalytic RNAs that combine self-splicing ribozyme activity with mobility and have played major roles in shaping organellar genome evolution. In green macroalgae of the genus Ulva, organellar genomes are highly compact, yet they harbor unusually diverse and dynamic repertoires of group II introns. To understand how organellar group II introns diversify and persist within compact organellar genomes, we performed a comparative analysis of mitochondrial and chloroplast group II introns across Ulva, integrating secondary structure reconstruction, intron occurrence patterns, and phylogenetic inference based on both conserved intron RNA regions and intron-encoded proteins (IEPs), including reverse transcriptase/maturase (RT/M) and LAGLIDADG homing endonuclease (LHE). A total of 168 mitochondrial and 123 chloroplast introns were identified and classified into 32 families belonging to seven major subgroups (IIA1-RT/M, IIA2-RT/M, IIB1-RT/M, IIB1-LHE, IIB2-RT/M, IIB2-LHE, and IIB-like). Most intron families retain the canonical six-domain architecture (DI–DVI), but four mitochondrial IIA families display a seven-domain configuration generated by the lineage-specific insertion of an additional stem-loop structure (DIIIa). Phylogenetic analyses revealed a high degree of congruence, supporting persistent coevolution between RNA scaffolds and their IEPs. Notably, the LHE-encoding families were scattered across distinct IIB lineages instead of forming a single clade, suggesting that at least two independent invasion events occurred within the IIB1 and IIB2 lineages. Analysis of intron occurrence frequency revealed an evolutionary continuum ranging from structurally intact and broadly distributed families to lineage-specific families exhibiting progressive scaffold degeneration, with the chloroplast infA-62 family representing a stably inherited lineage maintained through vertical transmission. These results suggest that organellar group II introns in Ulva evolve through coordinated scaffold remodeling, enzymatic replacement, and differential distribution patterns across genomic compartments, highlighting Ulva organellar genomes as a valuable comparative model for investigating the long-term evolution of mobile ribozymes within compact genomic environments. Full article
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20 pages, 4273 KB  
Article
The Impact of Mitochondrial DNA Depletion on Mitochondrial Ultrastructure, Photosynthesis, and the mTERF Gene Family in Chlamydomonas reinhardtii
by Asadullah Khan, Ye Ziyi, Faiz Ur Rahman, Haolin Luo and Zhangli Hu
Int. J. Mol. Sci. 2026, 27(4), 2034; https://doi.org/10.3390/ijms27042034 - 21 Feb 2026
Viewed by 618
Abstract
Mitochondrial biogenesis requires coordinated expression from both nuclear and mitochondrial genomes. To understand the consequences of mitochondrial genome loss, we generated a mitochondrial DNA-depleted line (crm) in Chlamydomonas reinhardtii via long-term ethidium bromide treatment. We then examined how mtDNA disruption [...] Read more.
Mitochondrial biogenesis requires coordinated expression from both nuclear and mitochondrial genomes. To understand the consequences of mitochondrial genome loss, we generated a mitochondrial DNA-depleted line (crm) in Chlamydomonas reinhardtii via long-term ethidium bromide treatment. We then examined how mtDNA disruption affects mitochondrial ultrastructure, chloroplast function, and the mitochondrial transcription termination factor (mTERF) gene family. Our results reveal that mitochondrial dysfunction is associated with severe organelle remodeling, including mitochondrial elongation, matrix condensation, and cristae collapse. Consequently, mitochondria reduce the electron sink capacity which appears to over-reduce the chloroplast electron transport chain, correlating with causing damage to photosystem II (PSII), as indicated by higher plastoquinone PQ redox state and PSII excitation pressure and lower non-photochemical quantum yield [Y(NPQ)]. Furthermore, we identified and characterized eight nuclear-encoded mTERF genes in C. reinhardtii (CrmTERFs). Phylogenetic analysis grouped them into three clades with potential functional conservation. Collinearity analysis suggested potential evolutionary relationships between mTERF genes in Chlamydomonas and Marchantia polymorpha. Gene ontology annotation linked CrmTERFs to transcription termination and RNA biosynthesis regulation. Additionally, in silico prediction identified twelve putative miRNAs targeting seven of the eight CrmTERFs, with CrmTERF3 as the only exception, providing candidates for future experimental validation. This study provides the first comprehensive analysis of the nuclear encoded mTERF gene family in Chlamydomonas and demonstrates that mtDNA loss is correlated with mTERF genes expression, as well as mitochondrial structure and chloroplast photoprotective impairments. These findings suggest a potential role for CrmTERFs in mitochondrial retrograde signaling and organellar crosstalk, though functional validation is required to establish causality. Full article
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