Formation of triploid plants via possible polyspermy

Toda, Erika; Okamoto, Takashi

doi:10.1080/15592324.2016.1218107

Cited by 7 publications

(5 citation statements)

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“…To compare the DNA methylation patterns of sperm and vegetative cells in rice, we manually isolated sperm cells and vegetative cell nuclei from Nipponbare. The plants we used ubiquitously express an H2B-GFP transgene (20) that facilitated purification of vegetative cell nuclei visualized under fluorescence microscopy ( SI Appendix , Fig. S1).…”

Section: Resultsmentioning

confidence: 99%

DNA demethylation by ROS1a in rice vegetative cells promotes methylation in sperm

Kim

Ono

Scholten

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Epigenetic reprogramming is required for proper regulation of gene expression in eukaryotic organisms. In Arabidopsis, active DNA demethylation is crucial for seed viability, pollen function, and successful reproduction. The DEMETER (DME) DNA glycosylase initiates localized DNA demethylation in vegetative and central cells, so-called companion cells that are adjacent to sperm and egg gametes, respectively. In rice, the central cell genome displays local DNA hypomethylation, suggesting that active DNA demethylation also occurs in rice; however, the enzyme responsible for this process is unknown. One candidate is the rice REPRESSOR OF SILENCING1a (ROS1a) gene, which is related to DME and is essential for rice seed viability and pollen function. Here, we report genome-wide analyses of DNA methylation in wild-type and ros1a mutant sperm and vegetative cells. We find that the rice vegetative cell genome is locally hypomethylated compared with sperm by a process that requires ROS1a activity. We show that many ROS1a target sequences in the vegetative cell are hypomethylated in the rice central cell, suggesting that ROS1a also demethylates the central cell genome. Similar to Arabidopsis, we show that sperm non-CG methylation is indirectly promoted by DNA demethylation in the vegetative cell. These results reveal that DNA glycosylase-mediated DNA demethylation processes are conserved in Arabidopsis and rice, plant species that diverged 150 million years ago. Finally, although global non-CG methylation levels of sperm and egg differ, the maternal and paternal embryo genomes show similar non-CG methylation levels, suggesting that rice gamete genomes undergo dynamic DNA methylation reprogramming after cell fusion.

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Section: Resultsmentioning

confidence: 99%

DNA demethylation by ROS1a in rice vegetative cells promotes methylation in sperm

Kim

Ono

Scholten

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…However, we also found two specimens with an apparently triploid 3n = 9 karyotype (Figure h), with three metacentrics and six submetacentrics. Shifts from diploidy to triploidy could result from polyspermy (Snook, Hosken, & Karr, ; Toda & Okamoto, ), which might occur since this species mates by hypodermic insemination (Ramm, Schlatter, Poirier, & Schärer, ; Schärer et al, ). The notion that M. hystrix has a simple karyotype was also supported by our flow cytometric genome size estimates (Figure ), which showed a single peak having a relative fluorescence that was on average 1.27× that of D. melanogaster , corresponding to a haploid genome size in M. hystrix of 217 Mbp.…”

Section: Resultsmentioning

confidence: 99%

A phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology, and genome size

Schärer

Brand

Singh

et al. 2019

J Zool Syst Evol Res

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The free‐living flatworm Macrostomum lignano is used as a model in a range of research fields—including aging, bioadhesion, stem cells, and sexual selection—culminating in the establishment of genome assemblies and transgenics. However, the Macrostomum community has run into a roadblock following the discovery of an unusual genome organization in M. lignano, which could now impair the development of additional resources and tools. Briefly, M. lignano has undergone a whole‐genome duplication, followed by rediploidization into a 2n = 8 karyotype (distinct from the canonical 2n = 6 karyotype in the genus). Although this karyotype appears visually diploid, it is in fact a hidden tetraploid (with rarer 2n = 9 and 2n = 10 individuals being pentaploid and hexaploid, respectively). Here, we report on a phylogenetically informed search for close relatives of M. lignano, aimed at uncovering alternative Macrostomum models with the canonical karyotype and a simple genome organization. We taxonomically describe three new species: the first, Macrostomum janickei n. sp., is the closest known relative of M. lignano and shares its derived genome organization; the second, Macrostomum mirumnovem n. sp., has an even more unusual genome organization, with a highly variable karyotype based on a 2n = 9 base pattern; and the third, Macrostomum cliftonensis n. sp., does not only show the canonical 2n = 6 karyotype, but also performs well under standard laboratory culture conditions and fulfills many other requirements. M. cliftonensis is a viable candidate for replacing M. lignano as the primary Macrostomum model, being outcrossing and having an estimated haploid genome size of only 231 Mbp.

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“…There are till now no reports of unreduced gamete formation and vegetative reproduction in pines, two critical pre-requisites for the formation and survival of initial polyploids. Besides, in addition to the unreduced gametes polyspermy has also been shown to result in triploid progeny in wheat, maize and orchids and also in experimentally produced triploid rice from polyspermic zygotes (see Toda and Okamoto 2016). However, while polyspermy might be one of the pathways for the production of triploids in angiosperms, selective karyogamy as a polyspermy barrier has been observed in Pinus nigra and Picea glauca where only one sperm migrates towards egg and fuses with it to produce a diploid zygote (Williams 2009).…”

Section: Discussionmentioning

confidence: 99%

Polyploidy in Gymnosperms-A Reappraisal

Ohri

2021

Silvae Genetica

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Recent polyploidy in gymnosperms is unusually scarce being present in only 9.80 % of the 714 taxa studied cytologically. Polyploid forms are represented by sporadic seedlings and individual trees, intraspecific polyploidy in cultivation or in wild and entirely polyploid species and genera. Polyploidy shows a non-random distribution in different genera being mostly prevalent in Ephedra and Juniperus, besides the classic examples of Sequoia and Fitzroya. Remarkably, both Ephedra and Juniperus show adaptive radiation by interspecific hybridization followed by polyploidy while in Ginkgo viable polyploid cytotypes are found in cultivation. Induced polyploidy has not provided any tangible results in the past but recent attempts on certain genera of Cupressaceae hold some promise of producing cultivars for horticulture trade. Lastly, various evidences derived from cytological analysis, fossil pollen, guard cells and comparative genomic studies indicating the occurrence of paleopolyploidy have been discussed.

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Formation of triploid plants via possible polyspermy

Cited by 7 publications

References 50 publications

DNA demethylation by ROS1a in rice vegetative cells promotes methylation in sperm

DNA demethylation by ROS1a in rice vegetative cells promotes methylation in sperm

A phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology, and genome size

Polyploidy in Gymnosperms-A Reappraisal

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