organellar genome
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2021 ◽  
Author(s):  
Tomáš Pánek ◽  
Dovilė Barcytė ◽  
Sebastian C. Treitli ◽  
Kristína Záhonová ◽  
Martin Sokol ◽  
...  

Background: The plastid genomes of the green algal order Chlamydomonadales tend to expand their non-coding regions, but this phenomenon is poorly understood. Here we shed new light on organellar genome evolution in Chlamydomonadales by studying a previously unknown non-photosynthetic lineage. We established cultures of two new Polytoma-like flagellates, defined their basic characteristics and phylogenetic position, and obtained complete organellar genome sequences and a transcriptome assembly for one of them. Results: We discovered a novel deeply diverged chlamydomonadalean lineage that has no close photosynthetic relatives and represents an independent case of photosynthesis loss. To accommodate these organisms, we establish a new genus, Leontynka, with two species L. pallida and L. elongata distinguished by both morphological and molecular characteristics. Notable features of the colourless plastid of L. pallida deduced from the plastid genome (plastome) sequence and transcriptome assembly include the retention of ATP synthase, thylakoid-associated proteins, carotenoid biosynthesis pathway, and plastoquinone-based electron transport chain, the latter two modules having an obvious functional link to the eyespot present in Leontynka. Most strikingly, the L. pallida plastome with its ~362 kbp is by far the largest among non-photosynthetic eukaryotes investigated to date. Instead of a high gene content, its size reflects extreme proliferation of sequence repeats. These are present also in coding sequences, with one repeat type found in exons of 11 out of 34 protein-coding genes and up to 36 copies per gene, affecting thus the encoded proteins. The mitochondrial genome of L. pallida is likewise exceptionally large, with its >104 kbp surpassed only by the mitogenome of Haematococcus lacustris among all members of Chlamydomonadales studied so far. It is also bloated with repeats, yet completely different from those in the L. pallida plastome, which contrasts with the situation in H. lacustris where both organellar genomes have accumulated related repeats. Furthermore, the L. pallida mitogenome exhibits an extremely high GC content in both coding and non-coding regions and, strikingly, a high number of predicted G-quadruplexes. Conclusions: With the unprecedented combination of plastid and mitochondrial genome characteristics, Leontynka pushes the frontiers of organellar genome diversity and becomes an interesting model for studying organellar genome evolution.


PLoS Biology ◽  
2021 ◽  
Vol 19 (8) ◽  
pp. e3001357
Author(s):  
Lingling Cheng ◽  
Wenjie Wang ◽  
Yao Yao ◽  
Qianwen Sun

Plant mitochondrial genomes undergo frequent homologous recombination (HR). Ectopic HR activity is inhibited by the HR surveillance pathway, but the underlying regulatory mechanism is unclear. Here, we show that the mitochondrial RNase H1 AtRNH1B impairs the formation of RNA:DNA hybrids (R-loops) and participates in the HR surveillance pathway in Arabidopsis thaliana. AtRNH1B suppresses ectopic HR at intermediate-sized repeats (IRs) and thus maintains mitochondrial DNA (mtDNA) replication. The RNase H1 AtRNH1C is restricted to the chloroplast; however, when cells lack AtRNH1B, transport of chloroplast AtRNH1C into the mitochondria secures HR surveillance, thus ensuring the integrity of the mitochondrial genome and allowing embryogenesis to proceed. HR surveillance is further regulated by the single-stranded DNA-binding protein ORGANELLAR SINGLE-STRANDED DNA BINDING PROTEIN1 (OSB1), which decreases the formation of R-loops. This study uncovers a facultative dual targeting mechanism between organelles and sheds light on the roles of RNase H1 in organellar genome maintenance and embryogenesis.


2021 ◽  
Author(s):  
Mari Takusagawa ◽  
Shoichi Kato ◽  
Sachihiro Matsunaga ◽  
Shinichiro Maruyama ◽  
Yayoi Tsujimoto-Inui ◽  
...  

Here we report the complete organellar genome sequences of Medakamo hakoo, a green alga identified in freshwater in Japan. It has 90.8-kb plastid and 36.5-kb mitochondrial genomes containing 80 and 33 putative protein coding genes, respectively, representing the smallest organellar genome among currently known core Trebouxiophyceae.


2021 ◽  
Author(s):  
Matheus Fernandes Gyorfy ◽  
Emma R. Miller ◽  
Justin L. Conover ◽  
Corrinne E. Grover ◽  
Jonathan F. Wendel ◽  
...  

2021 ◽  
Vol 17 (7) ◽  
pp. 20210123
Author(s):  
Felix Grewe ◽  
Marcus R. Kronforst ◽  
Naomi E. Pierce ◽  
Corrie S. Moreau

The last Xerces blue butterfly was seen in the early 1940s, and its extinction is credited to human urban development. This butterfly has become a North American icon for insect conservation, but some have questioned whether it was truly a distinct species, or simply an isolated population of another living species. To address this question, we leveraged next-generation sequencing using a 93-year-old museum specimen. We applied a genome skimming strategy that aimed for the organellar genome and high-copy fractions of the nuclear genome by a shallow sequencing approach. From these data, we were able to recover over 200 million nucleotides, which assembled into several phylogenetically informative markers and the near-complete mitochondrial genome. From our phylogenetic analyses and haplotype network analysis we conclude that the Xerces blue butterfly was a distinct species driven to extinction.


Phytotaxa ◽  
2021 ◽  
Vol 507 (3) ◽  
pp. 266-270
Author(s):  
DEE AMOS ◽  
VILMA AGUILAR ◽  
KRISTIN BARBER-SCOTT ◽  
DANILO E. BUSTAMANTE ◽  
MARTHA S. CALDERON ◽  
...  

2021 ◽  
Author(s):  
Matheus Fernandes Gyorfy ◽  
Emma R Miller ◽  
Justin L Conover ◽  
Corrinne E Grover ◽  
Jonathan F Wendel ◽  
...  

The plant genome is partitioned across three distinct subcellular compartments: the nucleus, mitochondria, and plastids. Successful coordination of gene expression among these organellar genomes and the nuclear genome is critical for plant function and fitness. Whole genome duplication events (WGDs) in the nucleus have played a major role in the diversification of land plants and are expected to perturb the relative copy number (stoichiometry) of nuclear, mitochondrial, and plastid genomes. Thus, elucidating the mechanisms whereby plant cells respond to the cytonuclear stoichiometric imbalance that follow WGDs represents an important yet underexplored question in understanding the evolutionary consequences of genome doubling. We used droplet digital PCR (ddPCR) to investigate the relationship between nuclear and organellar genome copy numbers in allopolyploids and their diploid progenitors in both wheat and Arabidopsis. Polyploids exhibit elevated organellar genome copy numbers per cell, largely preserving the cytonuclear stoichiometry observed in diploids despite the change in nuclear genome copy number. To investigate the timescale over which cytonuclear stoichiometry may respond to WGD, we also estimated organellar genome copy number in Arabidopsis synthetic autopolyploids and in a haploid-induced diploid line. We observed corresponding changes in organellar genome copy number in these laboratory-generated lines, indicating that at least some of the cellular response to cytonuclear stoichiometric imbalance is immediate following WGD. We conclude that increases in organellar genome copy numbers represent a common response to polyploidization, suggesting that maintenance of cytonuclear stoichiometry is an important component in establishing polyploid lineages.


PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252207
Author(s):  
Yukio Nagano ◽  
Kei Kimura ◽  
Genta Kobayashi ◽  
Yoshio Kawamura

Some Pyropia species, such as nori (P. yezoensis), are important marine crops. We conducted a phylogenetic analysis of 39 samples of Pyropia species grown in Japan using organellar genome sequences. A comparison of the chloroplast DNA sequences with those from China showed a clear genetic separation between Japanese and Chinese P. yezoensis. Conversely, comparing the mitochondrial DNA sequences did not separate Japanese and Chinese P. yezoensis. Analysis of organellar genomes showed that the genetic diversity of Japanese P. yezoensis used in this study is lower than that of Chinese wild P. yezoensis. To analyze the genetic relationships between samples of Japanese Pyropia, we used whole-genome resequencing to analyze their nuclear genomes. In the offspring resulting from cross-breeding between P. yezoensis and P. tenera, nearly 90% of the genotypes analyzed by mapping were explained by the presence of different chromosomes originating from two different parental species. Although the genetic diversity of Japanese P. yezoensis is low, analysis of nuclear genomes genetically separated each sample. Samples isolated from the sea were often genetically similar to those being farmed. Study of genetic heterogeneity of samples within a single aquaculture strain of P. yezoensis showed that samples were divided into two groups and the samples with frequent abnormal budding formed a single, genetically similar group. The results of this study will be useful for breeding and the conservation of Pyropia species.


2020 ◽  
Vol 21 (11) ◽  
pp. 3883 ◽  
Author(s):  
Hector Mendoza ◽  
Michael H. Perlin ◽  
Jan Schirawski

Mitochondria are important organelles in eukaryotes that provide energy for cellular processes. Their function is highly conserved and depends on the expression of nuclear encoded genes and genes encoded in the organellar genome. Mitochondrial DNA replication is independent of the replication control of nuclear DNA and as such, mitochondria may behave as selfish elements, so they need to be controlled, maintained and reliably inherited to progeny. Phytopathogenic fungi meet with special environmental challenges within the plant host that might depend on and influence mitochondrial functions and services. We find that this topic is basically unexplored in the literature, so this review largely depends on work published in other systems. In trying to answer elemental questions on mitochondrial functioning, we aim to introduce the aspect of mitochondrial functions and services to the study of plant-microbe-interactions and stimulate phytopathologists to consider research on this important organelle in their future projects.


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