73 research outputs found
Reconstructing the evolution of Brachypodium genomes using comparative chromosome painting.
Brachypodium distachyon is a model for the temperate cereals and grasses and has a biology, genomics infrastructure and cytogenetic platform fit for purpose. It is a member of a genus with fewer than 20 species, which have different genome sizes, basic chromosome numbers and ploidy levels. The phylogeny and interspecific relationships of this group have not to date been resolved by sequence comparisons and karyotypical studies. The aims of this study are not only to reconstruct the evolution of Brachypodium karyotypes to resolve the phylogeny, but also to highlight the mechanisms that shape the evolution of grass genomes. This was achieved through the use of comparative chromosome painting (CCP) which hybridises fluorescent, chromosome-specific probes derived from B. distachyon to homoeologous meiotic chromosomes of its close relatives. The study included five diploids (B. distachyon 2nā=ā10, B. sylvaticum 2nā=ā18, B. pinnatum 2nā=ā16; 2nā=ā18, B. arbuscula 2nā=ā18 and B. stacei 2nā=ā20) three allotetraploids (B. pinnatum 2nā=ā28, B. phoenicoides 2nā=ā28 and B. hybridum 2nā=ā30), and two species of unknown ploidy (B. retusum 2nā=ā38 and B. mexicanum 2nā=ā40). On the basis of the patterns of hybridisation and incorporating published data, we propose two alternative, but similar, models of karyotype evolution in the genus Brachypodium. According to the first model, the extant genome of B. distachyon derives from B. mexicanum or B. stacei by several rounds of descending dysploidy, and the other diploids evolve from B. distachyon via ascending dysploidy. The allotetraploids arise by interspecific hybridisation and chromosome doubling between B. distachyon and other diploids. The second model differs from the first insofar as it incorporates an intermediate 2nā=ā18 species between the B. mexicanum or B. stacei progenitors and the dysploidic B. distachyon
From Single Cell to Plants: Mesophyll Protoplasts as a Versatile System for Investigating Plant Cell Reprogramming
Plants are sessile organisms that have a remarkable developmental plasticity, which ensures
their optimal adaptation to environmental stresses. Plant cell totipotency is an extreme example
of such plasticity, whereby somatic cells have the potential to form plants via direct shoot
organogenesis or somatic embryogenesis in response to various exogenous and/or endogenous
signals. Protoplasts provide one of the most suitable systems for investigating molecular mechanisms
of totipotency, because they are e ectively single cell populations. In this review, we consider
the current state of knowledge of the mechanisms that induce cell proliferation from individual,
di erentiated somatic plant cells. We highlight initial explant metabolic status, ploidy level and
isolation procedure as determinants of successful cell reprogramming. We also discuss the importance
of auxin signalling and its interaction with stress-regulated pathways in governing cell cycle induction
and further stages of plant cell totipotency
Plant cell and organism development
"Plants represent a unique and fascinating group of living organisms. By utilising photosynthesis, they are primary producers, which in one way or another are indispensable to the existence of heterotrophs, including humans. They also absorb carbon dioxide and release oxygen into the atmosphere, which is crucial to sustain not only the Earthās biosphere but also the geosphere. As sessile organisms, plants had to develop unique strategies to deal with environmental stresses. These involve, inter alia, the presence of the cell wall, plant cell totipotency and a predisposition of plants to panorganismal polyploidisation, including interspecific or even intergeneric hybridisation followed by a stable restoration of sexual reproduction via allopolyploidisation." (fragm.
Plant cell and organism development 2.0
"In the editorial summarising the first edition of the Special Issue on āPlant Cell and
Organism Developmentā, we listed the key features that make plants a unique and fascinating
group of living organisms [1]. However, current climate changes are affecting plants
in their natural environments and those that are under cultivation. Global warming will
likely redefine many plant habitats regarding temperature, water availability, soil erosion,
salinity and other abiotic and biotic parameters. The ever-growing human population and
increasing food demand require more extensive or more efficient agriculture, all within the
limited capacity of our planet. For those and many other reasons, comprehensive research
on plants has become more vital than ever." [...] (fragm.
Ribosomal DNA loci derived from Brachypodium stacei are switched off for major parts of the life cycle of Brachypodium hybridum
Nucleolar dominance (ND) is an epigenetic phenomenon that occurs in some plant and animal allopolyploids and hybrids, whereby only one ancestral set of 35S rRNA genes retains the ability to form the nucleolus, whilst the rDNA loci derived from the other progenitor are transcriptionally silenced. Since there is substantial evidence that ND is regulated developmentally, this study focusses upon the establishment and/or maintenance of ND during different stages of development in the model grass allotetraploid, Brachypodium hybridum. Fluorescence in situ hybridisation with a 25S rDNA probe to 3-D cells shows that ND is present not only in root meristematic and differentiated cells of this species, but is also present in male meiocytes at prophase I, tetrads of microspores and different embryonic tissues. The inactive state of B. stacei-originated rDNA loci is confirmed by silver staining method. We show that only B. distachyon-derived 35S rDNA loci form a nucleolus/nucleoli in the aforementioned tissues, whereas B. stacei-like loci remain highly condensed and thus transcriptionally suppressed. The establishment of ND during earlier stages of B. hybridum embryo development cannot be ruled out. However, our proposal of gradual pseudogenisation of B. stacei-like loci in the evolution of the allotetraploid seems to be more likely
Defining the Genetic Basis of Plant-Endophytic Bacteria Interactions
Endophytic bacteria, which interact closely with their host, are an essential part of the
plant microbiome. These interactions enhance plant tolerance to environmental changes as well
as promote plant growth, thus they have become attractive targets for increasing crop production.
Numerous studies have aimed to characterise how endophytic bacteria infect and colonise their
hosts as well as conferring important traits to the plant. In this review, we summarise the current
knowledge regarding endophytic colonisation and focus on the insights that have been obtained from
the mutants of bacteria and plants as well as āomic analyses. These show how endophytic bacteria
produce various molecules and have a range of activities related to chemotaxis, motility, adhesion,
bacterial cell wall properties, secretion, regulating transcription and utilising a substrate in order to
establish a successful interaction. Colonisation is mediated by plant receptors and is regulated by
the signalling that is connected with phytohormones such as auxin and jasmonic (JA) and salicylic
acids (SA). We also highlight changes in the expression of small RNAs and modifications of the cell
wall properties. Moreover, in order to exploit the beneficial plant-endophytic bacteria interactions
in agriculture successfully, we show that the key aspects that govern successful interactions remain
to be defined
Stability and instability processes in the calli of Fagopyrum tataricum that have different morphogenic potentials
The morphogenic callus (MC) of Fagopyrum tataricum contains a large amount of flavonoids, especially rutin, and exhibits
a high level of antioxidant activity. A non-morphogenic callus (NC) may appear on the surface of the MC after two to
three years of cultivation and is then subjected to a consistently high level of oxidative stress. The elucidation of the molecular
background of this instability is essential for gaining a better understanding of the somaclonal variation mechanisms in
tissue cultures that have different morphogenic potentials. Thus, in this study we show that continuous oxidative stress in a
NC might be connected with a rapid senescence process and as a result, in the upregulation of the genes that are connected
with the telomere complexity, ethylene biosynthesis and the expression of DNA methyltransferases. Moreover, we analysed
the presence of the hydroxyproline-rich glycoproteins in the calli and demonstrated the differences between the MC and NC.
The LM2 antibody can be useful as a marker of the cells in the MC that are embryogenically determined, while the MAC207
antibody seems to be a positive marker of a MC as its signal was absent in the NC. This study also provides the first report
on the effect of trichostatin A on the DNA methyltransferases and demethylases in a MC
Buckwheat in Tissue Culture Research: Current Status and Future Perspectives
Buckwheat is a member of a genus of 23 species, where the two most common species
are Fagopyrum esculentum (common buckwheat) and Fagopyrum tataricum (Tartary buckwheat). This
pseudocereal is a source of micro and macro nutrients, such as gluten-free proteins and amino acids,
fatty acids, bioactive compounds, dietary fibre, fagopyrins, vitamins and minerals. It is gaining
increasing attention due to its health-promoting properties. Buckwheat is widely susceptible to
in vitro conditions which are used to study plantlet regeneration, callus induction, organogenesis,
somatic embryogenesis, and the synthesis of phenolic compounds. This review summarises the
development of buckwheat in in vitro culture and describes protocols for the regeneration of plantlets
from various explants and differing concentrations of plant growth regulators. It also describes callus
induction protocols as well as the role of calli in plantlet regeneration. Protocols for establishing
hairy root cultures with the use of Agrobacterium rhizogens are useful in the synthesis of secondary
metabolites, as well as protocols used for transgenic plants. The review also focuses on the future
prospects of buckwheat in tissue culture and the challenges researchers are addressing
Chromosome identification and reconstruction of evolutionary rearrangements in Brachypodium distachyon, B. stacei and B. hybridum
Background and Aims The Brachypodium genus represents a useful model system to study grass genome
organization. Palaeogenomic analyses (e.g. Murat F, Armero A, Pont C, Klopp C, Salse J. 2017. Reconstructing
the genome of the most recent common ancestor of flowering plants. Nature Genetics 49: 490ā496) have identified
polyploidization and dysploidy as the prime mechanisms driving the diversity of plant karyotypes and nested
chromosome fusions (NCFs) crucial for shaping grass chromosomes. This study compares the karyotype structure
and evolution in B. distachyon (genome Bd), B. stacei (genome Bs) and in their putative allotetraploid B. hybridum
(genomes BdBs).
ā¢ Methods Brachypodium chromosomes were measured and identified using multicolour fluorescence in situ
hybridization (mcFISH). For higher resolution, comparative chromosome barcoding was developed using sets of
low-repeat, physically mapped B. distachyon-derived bacterial artificial chromosome (BAC) clones.
ā¢ Key Results All species had rather small chromosomes, and essentially all in the Bs genome were
morphometrically indistinguishable. Seven BACs combined with two rDNA-based probes provided unambiguous
and reproducible chromosome discrimination. Comparative chromosome barcoding revealed NCFs that contributed
to the reduction in the x = 12 chromosome number that has been suggested for the intermediate ancestral grass
karyotype. Chromosome Bd3 derives from two NCFs of three ancestral chromosomes (Os2, Os8, Os10).
Chromosome Bs6 shows an ancient Os8/Os10 NCF, whilst Bs4 represents Os2 only. Chromosome Bd4 originated
from a descending dysploidy that involves two NCFs of Os12, Os9 and Os11. The specific distribution of BACs
along Bs9 and Bs5, in both B. stacei and B. hybridum, suggests a Bs genome-specific Robertsonian rearrangement.
ā¢ Conclusions mcFISH-based karyotyping identifies all chromosomes in Brachypodium annuals. Comparative
chromosome barcoding reveals rearrangements responsible for the diverse organization of Bd and Bs genomes and
provides new data regarding karyotype evolution since the split of the two diploids. The fact that no chromosome
rearrangements were observed in B. hybridum compared with the karyotypes of its phylogenetic ancestors suggests
prolonged genome stasis after the formation of the allotetraploid
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