Chromosome Numbers in Gymnosperms - An Update

Rastogi, Shubhi; Ohri, Deepak

doi:10.2478/sg-2020-0003

Cited by 11 publications

(7 citation statements)

References 42 publications

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“…Despite the generally low frequency of polyploidy encountered across gymnosperms (see Introduction), interest in documenting the occurrence and frequency of different ploidy levels in gymnosperms, especially Cupressaceae, has remained high, given (i) the high frequency of polyploidy in Ephedra (ca. 83% of species, with ploidy levels up to 2 n = 8 x ) (Ickert‐Bond et al, 2014; Wu et al, 2016; Ickert‐Bond et al, 2020; Rastogi & Ohri, 2020), (ii) the recent discovery that polyploidy is not uncommon in Juniperus (Farhat et al, 2019a), and (iii) the observation that the only other naturally occurring polyploids reported in conifers are all within Cupressaceae. Such observations have promoted considerable interest in exploring the significance of polyploidy in this family.…”

Section: Discussionmentioning

confidence: 99%

Polyploidy in Cupressaceae: Discovery of a new naturally occurring tetraploid, Xanthocyparis vietnamensis

Farhat

Siljak‐Yakovlev

Hidalgo

et al. 2021

J of Sytematics Evolution

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While polyploidy (whole‐genome multiplication) is generally considered rare in extant gymnosperms (with the exception of Ephedra, Ephedraceae), the occurrence of sporadic polyploid individuals belonging to various genera in the conifer family Cupressaceae has been reported in the literature. In addition, recent studies have revealed that polyploidy is not uncommon in the genus Juniperus (Cupressaceae), with tetraploid and hexaploid individuals reported in individuals collected from wild populations. Given these findings, we undertook a comprehensive screening of ploidy levels in 32 species belonging to the four genera that are phylogenetically closest to Juniperus (i.e., Callitropsis, Hesperocyparis, Xanthocyparis, and Cupressus), referred to as the CaHXCu complex. In addition, we also determined the ploidy level of two accessions in the poorly studied tetraploid, Fitzroya cupressoides. Using flow cytometry together with published chromosome counts to assign ploidy levels, we show that all species of the CaHXCu complex are diploid except Xanthocyparis vietnamensis, which is tetraploid, with a genome size of 44.60 pg/2 C. This study opens up new opportunities for studying the impact and consequences of polyploidy on the evolution and adaptation of species in Cupressaceae.

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Section: Discussionmentioning

confidence: 99%

Polyploidy in Cupressaceae: Discovery of a new naturally occurring tetraploid, Xanthocyparis vietnamensis

Farhat

Siljak‐Yakovlev

Hidalgo

et al. 2021

J of Sytematics Evolution

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“…Nevertheless, the macroevolutionary dynamics of ploidy level changes presented here emphasize the importance of diploidization events, suggesting that both WGD and PPD are widespread phenomena in angiosperms. Patterns of early WGD were also suggested in gymnosperms (Li et al ., 2015), where, however, polyploidy is rare (Rastogi & Ohri, 2020). By contrast, repeated WGD events in the ancestors of monilophytes have contributed to their diversity and high chromosome numbers (Clark et al ., 2016).…”

Section: Discussionmentioning

confidence: 99%

A deep dive into the ancestral chromosome number and genome size of flowering plants

2020

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Chromosome number and genome variation in flowering plants have stimulated growing speculation about the ancestral chromosome number of angiosperms, but estimates so far remain equivocal. We used a probabilistic approach to model haploid chromosome number (n) changes along a phylogeny embracing more than 10 000 taxa, to reconstruct the ancestral chromosome number of the common ancestor of extant angiosperms and the most recent common ancestor for single angiosperm families. Independently, we carried out an analysis of 1C genome size evolution, including over 5000 taxa. Our analyses revealed an ancestral haploid chromosome number for angiosperms of n = 7, a diploid status, and an ancestral 1C of 1.73 pg. For 160 families, inferred ancestral n are provided for the first time. Both descending dysploidy and polyploidy played crucial roles in chromosome number evolution. While descending dysploidy is equally distributed early and late across the phylogeny, polyploidy is detected mainly towards the tips. Similarly, 1C genome size also increases (or decreases) significantly in late-branching lineages. Therefore, no evidence exists of a clear link between ancestral chromosome numbers and ancient polyploidization events, suggesting that further insights are needed to elucidate the organization of genome packaging into chromosomes.

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“…Combining comparative studies of xylem form and function with phylogenetic analyses is one of the most promising areas of research to uncover the mechanisms behind tree longevity (Sperry et al ., 2006; Brodribb et al ., 2012; Roskilly et al ., 2019). Another open question with regard to the genetic control of longevity is the role of polyploidy, which only occurs in 5% of 685 gymnosperm taxa (Rastogi & Ohri, 2020) but is present in Sequoia , Fitzroya and Juniperus , that is in the majority of Cupressaceae taxa that include trees older than 2000 yr.…”

Section: Evolutionary Features and Trade‐off Theoriesmentioning

confidence: 99%

On tree longevity

Piovesan

Biondi

2021

New Phytologist

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Large, majestic trees are iconic symbols of great age among living organisms. Published evidence suggests that trees do not die because of genetically programmed senescence in their meristems, but rather are killed by an external agent or a disturbance event. Long tree lifespans are therefore allowed by specific combinations of life history traits within realized niches that support resistance to, or avoidance of, extrinsic mortality. Another requirement for trees to achieve their maximum longevity is either sustained growth over extended periods of time or at least the capacity to increase their growth rates when conditions allow it. The growth plasticity and modularity of trees can then be viewed as an evolutionary advantage that allows them to survive and reproduce for centuries and millennia. As more and more scientific information is systematically collected on tree ages under various ecological settings, it is becoming clear that tree longevity is a key trait for global syntheses of life history strategies, especially in connection with disturbance regimes and their possible future modifications. In addition, we challenge the long-held notion that shade-tolerant, late-successional species have longer lifespans than earlysuccessional species by pointing out that tree species with extreme longevity do not fit this paradigm. Identifying extremely old trees is therefore the groundwork not only for protecting and/or restoring entire landscapes, but also to revisit and update classic ecological theories that shape our understanding of environmental change.

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Chromosome Numbers in Gymnosperms - An Update

Cited by 11 publications

References 42 publications

Polyploidy in Cupressaceae: Discovery of a new naturally occurring tetraploid, Xanthocyparis vietnamensis

Polyploidy in Cupressaceae: Discovery of a new naturally occurring tetraploid, Xanthocyparis vietnamensis

A deep dive into the ancestral chromosome number and genome size of flowering plants

On tree longevity

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