A new chromosome was born: comparative chromosome painting in Boechera

Koch, Marcus A.

doi:10.1016/j.tplants.2015.07.001

Cited by 5 publications

(5 citation statements)

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“…This process is analogous to recombinant inbred line (RIL) production where multiple generations of selfing produce new chromosomes consisting of alternating segments of the original parental chromosomes. Chromosome painting studies provide evidence that such inter-genomic recombination in apomictic Boechera is extensive (Kantama et al, 2007; Koch, 2015).…”

Section: Discussionmentioning

confidence: 99%

Apospory and Diplospory in Diploid Boechera (Brassicaceae) May Facilitate Speciation by Recombination-Driven Apomixis-to-Sex Reversals

et al. 2019

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Apomixis (asexual seed formation) in angiosperms occurs either sporophytically, through adventitious embryony, or gametophytically, where an unreduced female gametophyte (embryo sac) forms and produces an unreduced egg that develops into an embryo parthenogenetically. Multiple types of gametophytic apomixis occur, and these are differentiated based on where and when the unreduced gametophyte forms, a process referred to as apomeiosis. Apomeiotic gametophytes form directly from ameiotic megasporocytes, as in Antennaria-type diplospory, from unreduced spores derived from 1st division meiotic restitutions, as in Taraxacum-type diplospory, or from cells of the ovule wall, as in Hieracium-type apospory. Multiple types of apomeiosis occasionally occur in the same plant, which suggests that the different types occur in response to temporal and/or spatial shifts in termination of sexual processes and onset timing of apomeiosis processes. To better understand the origins and evolutionary implications of apomixis in Boechera (Brassicaceae), we determined apomeiosis type for 64 accessions representing 44 taxonomic units. Plants expressing apospory and diplospory were equally common, and these generally produced reduced and unreduced pollen, respectively. Apospory and diplospory occurred simultaneously in individual plants of seven taxa. In Boechera , apomixis perpetuates otherwise sterile or semisterile interspecific hybrids (allodiploids) through multiple generations. Accordingly, ample time, in these multigenerational clones, is available for rare meioses to produce haploid, intergenomically recombined male and female gametes. The fusion of such gametes could then produce segmentally autoploidized progeny. If sex re-emerges among such progeny, then new and genomically unique sexual species could evolve. Herein, we present evidence that such apomixis-facilitated speciation is occurring in Boechera , and we hypothesize that it might also be occurring in facultatively apomictic allodiploids of other angiospermous taxa.

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Section: Discussionmentioning

confidence: 99%

Apospory and Diplospory in Diploid Boechera (Brassicaceae) May Facilitate Speciation by Recombination-Driven Apomixis-to-Sex Reversals

et al. 2019

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“…Likewise, comparative transcriptome analyses of anthers containing pollen mother cells in sexual and apomictic Boechera identified that the activity of UPGRADE (UPG) is correlated with apomixis [65]. While it is inviting to hypothesize that APOLLO and UPG are likely to be localized on the heterochromatic HET and DEL chromosomes, a direct proof has so far not been presented [66]. APOLLO encodes for an Aspartate Glutamate Aspartate Aspartate Histidine exonuclease and is heterozygous for apomixis specific alleles in apomicts [63].…”

Section: Genes Located On Apomixis Loci Suggest That Different Regulamentioning

confidence: 99%

Controlling Apomixis: Shared Features and Distinct Characteristics of Gene Regulation

Schmidt

2020

Genes

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In higher plants, sexual and asexual reproduction through seeds (apomixis) have evolved as alternative strategies. As apomixis leads to the formation of clonal offspring, its great potential for agricultural applications has long been recognized. However, the genetic basis and the molecular control underlying apomixis and its evolutionary origin are to date not fully understood. Both in sexual and apomictic plants, reproduction is tightly controlled by versatile mechanisms regulating gene expression, translation, and protein abundance and activity. Increasing evidence suggests that interrelated pathways including epigenetic regulation, cell-cycle control, hormonal pathways, and signal transduction processes are relevant for apomixis. Additional molecular mechanisms are being identified that involve the activity of DNA- and RNA-binding proteins, such as RNA helicases which are increasingly recognized as important regulators of reproduction. Together with other factors including non-coding RNAs, their association with ribosomes is likely to be relevant for the formation and specification of the apomictic reproductive lineage. Subsequent seed formation appears to involve an interplay of transcriptional activation and repression of developmental programs by epigenetic regulatory mechanisms. In this review, insights into the genetic basis and molecular control of apomixis are presented, also taking into account potential relations to environmental stress, and considering aspects of evolution.

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“…Many Boechera species are diploid and predominantly inbreeding, as indicated by genetic and molecular analyses ( Schranz et al , 2005 ; Song and Mitchell-Olds, 2007 ). Recent data indicate that nearly 50 % of the members of this genus are polyploid (mainly triploid) and characterized by apomictic reproduction ( Koch, 2015 ). Furthermore, Boechera is the best-studied example of diploid apomixis in angiosperms ( Dobeš et al , 2006 ; Ozias-Akins and van Dijk, 2007 ).…”

Section: Introductionmentioning

confidence: 99%

“…The expression of two alleles, APOLLO (apomixis-linked locus) ( Corral et al , 2013 ) and UPGRADE2 (unreduced pollen grain development) ( Mau et al , 2013 ), is highly correlated with apomeiotic egg and pollen formation in Boechera , and the biogeographical distribution of APOLLO demonstrates that its repeated introduction into novel sexual genetic backgrounds is associated with multiple independent origins of the apomixis phenotype ( Mau et al , 2015 ). Direct evidence for these alleles’ position on the heterochromatic Het chromosomes of Boechera is still lacking (according to Koch, 2015 ). A study comparing transcriptomes of microdissected MMCs from sexual Arabidopsis and apomictic Boechera gunnisoniana found multiple differences in pathways related to transcriptional regulation, cell cycle control, epigenetic regulation and hormone production ( Schmidt et al , 2014 ).…”

Section: Introductionmentioning

confidence: 99%

“…The basic chromosome number of Boechera , x = 7 ( Koch et al , 1999 ; Koch, 2015 and references therein), has evolved from an ancestral karyotype ( n = 8) of Brassicaceae lineage I. Comparative chromosome painting allowed Mandáková et al (2015) to characterize an aberrant chromosome Het and its two derivatives ( Het′ and Del ; previously defined as B chromosomes; Camacho et al , 2000 ; Sharbel et al , 2004 , 2005 ; Kantama et al , 2007 ) in apomictic diploid (2 n = 14), triploid (2 n = 21) and aneuploid (2 n = 15, 2 n = 22) apomictic Boechera , showing that new chromosomes can be formed by a centric fission and can be fixed in populations through apomixis (for more details see Mandáková et al , 2015 ).…”

Section: Introductionmentioning

confidence: 99%

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Establishing the cell biology of apomictic reproduction in diploid Boechera stricta (Brassicaceae)

Rojek

Kapusta

Kozieradzka-Kiszkurno

et al. 2018

Annals of Botany

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Background and aimsIn the Brassicaceae family, apomictic development is characteristic of the genus Boechera. Hybridization, polyploidy and environmental adaptation that arose during the evolution of Boechera may serve as (epi)genetic regulators of apomictic initiation in this genus. Here we focus on Boechera stricta, a predominantly diploid species that reproduces sexually. However, apomictic development in this species has been reported in several studies, indicating non-obligate sexuality.MethodsA progressive investigation of flower development was conducted using three accessions to assess the reproductive system of B. stricta. We employed molecular and cyto-embryological identification using histochemistry, transmission electron microscopy and Nomarski and epifluorescence microscopy.Key ResultsData from internal transcribed spacer (ITS) and chloroplast haplotype sequencing, in addition to microsatellite variation, confirmed the B. stricta genotype for all lines. Embryological data indicated irregularities in sexual reproduction manifested by heterochronic ovule development, longevity of meiocyte and dyad stages, diverse callose accumulation during meiocyte-to-gametophyte development, and the formation of triads and tetrads in several patterns. The arabinogalactan-related sugar epitope recognized by JIM13 immunolocalized to one or more megaspores. Furthermore, pollen sterility and a high frequency of seed abortion appeared to accompany reproduction of the accession ES512, along with the initiation of parthenogenesis. Data from flow cytometric screening revealed both sexual and apomictic seed formation.ConclusionThese results imply that B. stricta is a species with an underlying ability to initiate apomixis, at least with respect to the lines examined here. The existence of apomixis in an otherwise diploid sexual B. stricta may provide the genomic building blocks for establishing highly penetrant apomictic diploids and hybrid relatives. Our findings demonstrate that apomixis per se is a variable trait upon which natural selection could act.

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A new chromosome was born: comparative chromosome painting in Boechera

Cited by 5 publications

References 12 publications

Apospory and Diplospory in Diploid Boechera (Brassicaceae) May Facilitate Speciation by Recombination-Driven Apomixis-to-Sex Reversals

Apospory and Diplospory in Diploid Boechera (Brassicaceae) May Facilitate Speciation by Recombination-Driven Apomixis-to-Sex Reversals

Controlling Apomixis: Shared Features and Distinct Characteristics of Gene Regulation

Establishing the cell biology of apomictic reproduction in diploid Boechera stricta (Brassicaceae)

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