Isolation and characterization of novel temperate virus Aeropyrum globular virus 1 infecting hyperthermophilic archaeon Aeropyrum

We isolate a novel archaeal temperate virus named Aeropyrum globular virus 1 (AGV1) from the host Aeropyrum culture. Reproduction of AGV1 was induced by adding 20 mM tris acetate buffer to exponentially growing host cells. Negatively stained virions showed spherical morphology (60 2 nm in diameter) similar to Globuloviridae viruses. The double-stranded circular DNA genome of AGV1 contains 18,222 bp encoding 34 open-reading frames. No ORFs showed significant similarity with Globuloviridae viruses. AGV1 shares three genes, including an integrase gene, with reported spindle-shaped temperate viruses. However we couldnt detect its integration site in the host genome. Moreover AGV1 seemed not to replicate autonomously because there are no origin recognition boxes in the genome. qPCR results showed that the genome copy number of AGV1 was lower than that of the host genome (1/1000 copies per host genome). Upon the addition of tris-acetate buffer, a steep increase in the AGV1 genome copy number (9.5 to 26 copies per host genome at 2 days post-treatment) was observed although clustered regularly interspaced short palindromic repeat (CRISPR) elements of the host genome showed significant matches with AGV1 protospacers. Our findings suggest that AGV1 is a novel globular virus exhibiting an unstable carrier state in the growing host and in that way AGV1 can escape from the host defense system and propagate under stressful host conditions.

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Nuclear-cytoplasmic balance: whole genome duplications induce elevated organellar genome copy number

10.1101/2021.06.08.447629 ◽

2021 ◽

Author(s):

Matheus Fernandes Gyorfy ◽

Emma R Miller ◽

Justin L Conover ◽

Corrinne E Grover ◽

Jonathan F Wendel ◽

...

Keyword(s):

Copy Number ◽

Nuclear Genome ◽

Plant Genome ◽

Whole Genome ◽

Genome Copy ◽

Relative Copy Number ◽

Organellar Genome ◽

Plastid Genomes ◽

Copy Numbers ◽

Genome Copy Number

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.

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