B Chromosomes – A Matter of Chromosome Drive

Houben, Andreas

doi:10.3389/fpls.2017.00210

Cited by 86 publications

(96 citation statements)

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“…An interesting feature of the nuclear genome in some accessions of crested wheatgrass is the presence of small‐sized Bs (Knowles, 1955; Baenziger, 1962), whose evolution, function, and molecular organization has long been controversial and still is (Jones, 1995; Jones and Houben, 2003). Because most Bs are nonessential, they can be lost without any consequence (Banaei‐Moghaddam et al, 2015; Houben, 2017; Ma et al, 2017). To persist, however, some Bs impose strong forms of intragenomic conflict (Nur et al, 1988; Swim et al, 2012; Aldrich et al, 2017).…”

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Dissecting the Complex Genome of Crested Wheatgrass by Chromosome Flow Sorting

et al. 2019

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Core Ideas Flow sorting enabled to dissect the genome of crested wheatgrass into chromosomes. This is a powerful approach to access the complex genome of a wheat wild relative. Chromosome genomics will support alien introgression breeding of the crop. Wheatgrass (Agropyron sp.) is a potential source of beneficial traits for wheat improvement. Among them, crested wheatgrass [A. cristatum (L.) Gaertn.] comprises a complex of diploid, tetraploid, and hexaploid forms with the basic genome P, with some accessions carrying supernumerary B chromosomes (Bs). In this work, we applied flow cytometry to dissect the complex genome of crested wheatgrass into individual chromosomes to facilitate its analysis. Flow karyotypes obtained after the analysis of 4ʹ,6‐diamidino‐2‐phenylindole (DAPI)‐stained mitotic chromosomes of diploid and tetraploid accessions consisted of three peaks, each corresponding to a group of two or three chromosomes. To improve the resolution, bivariate flow karyotyping after fluorescent labeling of chromosomes with fluorescein isothiocyanate (FITC)‐conjugated probe (GAA)7 microsatellite was applied and allowed discrimination and sorting of P genome chromosomes from wheat–crested wheatgrass addition lines. Chromosomes 1P–6P and seven telomeric chromosomes could be sorted at purities ranging from 81.7 to 98.2% in disomics and from 44.8 to 87.3% in telosomics. Chromosome 7P was sorted at purities reaching 50.0 and 39.5% in diploid and tetraploid crested wheatgrass, respectively. In addition to the whole complement chromosomes (A), Bs could be easily discriminated and sorted from a diploid accession at 95.4% purity. The sorted chromosomes will streamline genome analysis of crested wheatgrass, facilitating gene cloning and development of molecular tools to support alien introgression into wheat.

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Dissecting the Complex Genome of Crested Wheatgrass by Chromosome Flow Sorting

et al. 2019

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“…The drive is essential for the successful maintenance of Bs in populations, and for the balancing of their loss due mitotic and/or meiotic elimination. The timing, and the way that the drive works, is different for Bs of different species, but in many cases it plays a key role in both premeiotic and post meiotic drive, as reviewed by Houben ().…”

Section: B Chromosomes Can Be Used For Understanding Nondisjunctionmentioning

confidence: 99%

Are B chromosomes useful for crop improvement?

Jones

Ruban

2019

Plants People Planet

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Societal Impact Statement Ensuring the sustainable production of food within the context of an increasing world population is a huge challenge facing humankind. Here we review the existence of additional, non‐essential chromosomes, known as B chromosomes, and consider their potential usefulness for crop improvement. These enigmatic chromosomes have long fascinated scientists and although their origin and function in plants is somewhat obscure, new research is beginning to shed light on these mysterious chromosomes. This work suggests that B chromosomes may be useful for crop improvement, particularly in grasses, where they show promise as a mechanism to introduce new genes, which could potentially help us to produce more efficient crops. Summary The question of the usefulness of supernumerary B chromosomes (Bs) has long fascinated cytogeneticists. Since their discovery in 1907 thousands of species with Bs have been discovered, but their function in the genetics system remains enigmatic, from their origin, evolution, and adaptive significance, as well as their molecular structure and organization. New research is beginning to answer some of these tantalizing questions. Here, we summarize the known data and conclude that Bs are potentially useful, but only in a few known cases, especially in the grasses, and notably in terms of their engineering as plant artificial chromosomes (mini‐chromosomes) to carry whole suites of transgenes outside of, and free from interference with, the normal genome.

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“…The maximum number of Bs tolerated by the host varies between species and depends on a balance between the B chromosome drive, and the negative effects, especially on fertility and vigour, caused by B chromosomes if they occur in higher numbers (Bougourd and Jones, 1997). Among the relatively small number of B chromosome-positive species that have been investigated, relative to the total number of known species, there is a variety of mechanisms of B chromosome drive that occurs before, during or after meiosis, while in some cases drive has not been found (reviewed in (Austin et al, 2009; Burt and Trivers, 2006; Carlson, 1988; Houben, 2017; Jones, 1991; Jones, 2018)). Besides drive, the non-Mendelian inheritance of Bs could also be affected by mitotic and meiotic instabilities.…”

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confidence: 99%

Nondisjunction and unequal spindle organization accompany the drive ofAegilops speltoidesB chromosomes

Houben

Ruban

et al. 2019

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18Supernumerary B chromosomes (Bs), which are often preferentially inherited, 19 deviating from usual Mendelian segregation. This chromosome drive is one of the 20 most important features of Bs. Here we analyzed the drive mechanism of Aegilops 21 speltoides Bs and provide direct insight into its cellular mechanism. Comparative 22 genomics resulted in the identification of the tandem repeat AesTR-183 of Ae. 23 speltoides Bs, which also can be found on the Bs of Ae. mutica and rye, was used to 24 track Bs during microgametogenesis. Nondisjunction of CENH3-positive, tubulin 25 interacting B sister chromatids and an asymmetric spindle during first pollen grain 26 mitosis are likely components of the accumulation process. A quantitative flow 27 cytometric approach revealed, that independent on the number of Bs present in the 28 mother plant Bs accumulate in the generative nuclei with more than 93%. Nine of 29 eleven tested (peri)centromeric repeats were shared by A and B chromosomes. A 30 common origin of the drive process in Poaceae is likely. 31 32 33 Keywords 34 supernumerary B chromosome, chromosome drive, chromosome nondisjunction, 35 centromere, pollen grain mitosis, chromosome segregation, asymmetric spindle, flow 36 cytometry, Aegilops speltoides 37 38 39 Introduction 40 Supernumerary B chromosomes (Bs) are considered as dispensable chromosomes, 41 which under standard conditions do not confer advantages on the organisms that 42 harbour them. Bs are found in thousands of fungi, plant and animal species and are 43 thought to stand for a specific type of selfish DNA (Jones and Rees, 1982). Recent 44 advances in deciphering the sequence composition of B chromosomes provided a 45 unique opportunity for the analysis of the origin and evolution of this enigmatic 46 genome component. It was shown that the Bs of several plant and animal species 47 harbour gene-derived sequences. This allowed to trace their origin from duplicated 48 fragments of multiple A chromosomes of their host species (reviewed in (Ruban et 49 al., 2017). Hence, Bs could be considered as a by-product of standard chromosome 50 (As) evolution. 51 52 Often the transmission rate of B chromosomes is higher than 0.5, not obeying the 53 Mendelian law of equal segregation. The resulting transmission advantage is 54 collectively referred to as 'drive'. The maximum number of Bs tolerated by the host 55 varies between species and depends on a balance between the B chromosome 56 drive, and the negative effects, especially on fertility and vigour, caused by B 57 chromosomes if they occur in higher numbers (Bougourd and Jones, 1997). Among 58 the relatively small number of B chromosome-positive species that have been 59 investigated, relative to the total number of known species, there is a variety of 60 mechanisms of B chromosome drive that occurs before, during or after meiosis, while 61 in some cases drive has not been found (reviewed in (Austin et al., 2009; Burt and drive, the non-Mendelian inheritance of Bs could also be affected by mitotic and 64 m...

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B Chromosomes – A Matter of Chromosome Drive

Cited by 86 publications

References 58 publications

Dissecting the Complex Genome of Crested Wheatgrass by Chromosome Flow Sorting

Dissecting the Complex Genome of Crested Wheatgrass by Chromosome Flow Sorting

Are B chromosomes useful for crop improvement?

Nondisjunction and unequal spindle organization accompany the drive ofAegilops speltoidesB chromosomes

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