Gene targeting is a powerful tool for functional genetic analysis. It has proved especially effec... more Gene targeting is a powerful tool for functional genetic analysis. It has proved especially effective in the model plant, Physcomitrella ( Physcomitrium patens (Hedw.) Mitt.), in which integration of exogenous DNA into the genome occurs with very high efficiency at targeted positions by homologous recombination. Here, we present a preliminary characterisation of a poorly documented property of Physcomitrella targeted gene knockout lines, namely, silencing of reporter and selective marker genes of integrated targeting constructs. We discovered a high incidence of transgene silencing among Physcomitrella knockout lines and, as is the case in seed plants, cytosine (DNA) methylation of the transgenes is correlated with their silencing. Silencing in Physcomitrella is characterised by metastable epigenetic inheritance through repetitive mitosis and variable stability through meiosis.
Although the evolution of spores was critical to the diversification of plants on land, sporogene... more Although the evolution of spores was critical to the diversification of plants on land, sporogenesis is incompletely characterized for model plants such as Physcomitrium patens. In this study, the complete process of P. patens sporogenesis is detailed from capsule expansion to mature spore formation, with emphasis on the construction of the complex spore wall and proximal aperture. Both diploid (sporophytic) and haploid (spores) cells contribute to the development and maturation of spores. During capsule expansion, the diploid cells of the capsule, including spore mother cells (SMCs), inner capsule wall layer (spore sac), and columella, contribute a locular fibrillar matrix that contains the machinery and nutrients for spore ontogeny. Nascent spores are enclosed in a second matrix that is surrounded by a thin SMC wall and suspended in the locular material. As they expand and separate, a band of exine is produced external to a thin foundation layer of tripartite lamellae. Dense globu...
Two amino acid analogue-resistant lines of Physcomitrium (formerly Physcomitrella) patens, DSR8 a... more Two amino acid analogue-resistant lines of Physcomitrium (formerly Physcomitrella) patens, DSR8 and PFR4, are resistant to a range of D-amino acids and an inhibitory concentration of L-lysine. Both are defective in the uptake of [35S]-L-methionine. Uptake by the wild-type line is pH-dependent (decreasing with raised external proton concentrations) and is depressed by dinitrophenol and by ammonium ions. We discuss the possible involvement of an active proton-general amino acid antiport pump in the plasma membrane.
The Physcomitrella pseudochromosomal genome assembly revealed previously invisible synteny enabli... more The Physcomitrella pseudochromosomal genome assembly revealed previously invisible synteny enabling realisation of the full potential of shared synteny as a tool for probing evolution of this plant's MADS-box gene family. Assembly of the sequenced genome of Physcomitrella patens into 27 mega-scaffolds (pseudochromosomes) has confirmed the major predictions of our earlier model of expansion of the MADS-box gene family in the Physcomitrella lineage. Additionally, microsynteny has been conserved in the immediate vicinity of some recent duplicates of MADS-box genes. However, comparison of non-syntenic MIKC MADS-box genes and neighbouring genes indicates that chromosomal rearrangements and/or sequence degeneration have destroyed shared synteny over longer distances (macrosynteny) around MADS-box genes despite subsets comprising two or three MIKC genes having remained syntenic. In contrast, half of the type I MADS-box genes have been transposed creating new syntenic relations with MIK...
The investigation of mechanisms responsible for the morphogenesis of complex biological organisms... more The investigation of mechanisms responsible for the morphogenesis of complex biological organisms is an important area in biology. P. patens is an especially suitable plant for this research because it is a rather simple organism, facilitating its observation, yet it possesses developmental phenomena analogous to those which occur in higher plants, allowing the extrapolation of hypotheses to more complex organisms.
We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by c... more We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by comparative genomics identify genes that likely played important roles in the early evolution of vascular plants and their subsequent evolution
We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by c... more We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by comparative genomics identify genes that likely played important roles in the early evolution of vascular plants and their subsequent evolution
We report the draft genome sequence of the model moss Physcomitrella patens and compare its featu... more We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics.
Gene targeting is a powerful tool for functional genetic analysis. It has proved especially effec... more Gene targeting is a powerful tool for functional genetic analysis. It has proved especially effective in the model plant, Physcomitrella ( Physcomitrium patens (Hedw.) Mitt.), in which integration of exogenous DNA into the genome occurs with very high efficiency at targeted positions by homologous recombination. Here, we present a preliminary characterisation of a poorly documented property of Physcomitrella targeted gene knockout lines, namely, silencing of reporter and selective marker genes of integrated targeting constructs. We discovered a high incidence of transgene silencing among Physcomitrella knockout lines and, as is the case in seed plants, cytosine (DNA) methylation of the transgenes is correlated with their silencing. Silencing in Physcomitrella is characterised by metastable epigenetic inheritance through repetitive mitosis and variable stability through meiosis.
Although the evolution of spores was critical to the diversification of plants on land, sporogene... more Although the evolution of spores was critical to the diversification of plants on land, sporogenesis is incompletely characterized for model plants such as Physcomitrium patens. In this study, the complete process of P. patens sporogenesis is detailed from capsule expansion to mature spore formation, with emphasis on the construction of the complex spore wall and proximal aperture. Both diploid (sporophytic) and haploid (spores) cells contribute to the development and maturation of spores. During capsule expansion, the diploid cells of the capsule, including spore mother cells (SMCs), inner capsule wall layer (spore sac), and columella, contribute a locular fibrillar matrix that contains the machinery and nutrients for spore ontogeny. Nascent spores are enclosed in a second matrix that is surrounded by a thin SMC wall and suspended in the locular material. As they expand and separate, a band of exine is produced external to a thin foundation layer of tripartite lamellae. Dense globu...
Two amino acid analogue-resistant lines of Physcomitrium (formerly Physcomitrella) patens, DSR8 a... more Two amino acid analogue-resistant lines of Physcomitrium (formerly Physcomitrella) patens, DSR8 and PFR4, are resistant to a range of D-amino acids and an inhibitory concentration of L-lysine. Both are defective in the uptake of [35S]-L-methionine. Uptake by the wild-type line is pH-dependent (decreasing with raised external proton concentrations) and is depressed by dinitrophenol and by ammonium ions. We discuss the possible involvement of an active proton-general amino acid antiport pump in the plasma membrane.
The Physcomitrella pseudochromosomal genome assembly revealed previously invisible synteny enabli... more The Physcomitrella pseudochromosomal genome assembly revealed previously invisible synteny enabling realisation of the full potential of shared synteny as a tool for probing evolution of this plant's MADS-box gene family. Assembly of the sequenced genome of Physcomitrella patens into 27 mega-scaffolds (pseudochromosomes) has confirmed the major predictions of our earlier model of expansion of the MADS-box gene family in the Physcomitrella lineage. Additionally, microsynteny has been conserved in the immediate vicinity of some recent duplicates of MADS-box genes. However, comparison of non-syntenic MIKC MADS-box genes and neighbouring genes indicates that chromosomal rearrangements and/or sequence degeneration have destroyed shared synteny over longer distances (macrosynteny) around MADS-box genes despite subsets comprising two or three MIKC genes having remained syntenic. In contrast, half of the type I MADS-box genes have been transposed creating new syntenic relations with MIK...
The investigation of mechanisms responsible for the morphogenesis of complex biological organisms... more The investigation of mechanisms responsible for the morphogenesis of complex biological organisms is an important area in biology. P. patens is an especially suitable plant for this research because it is a rather simple organism, facilitating its observation, yet it possesses developmental phenomena analogous to those which occur in higher plants, allowing the extrapolation of hypotheses to more complex organisms.
We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by c... more We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by comparative genomics identify genes that likely played important roles in the early evolution of vascular plants and their subsequent evolution
We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by c... more We report the genome sequence of the nonseed vascular plant, Selaginella moellendorffii, and by comparative genomics identify genes that likely played important roles in the early evolution of vascular plants and their subsequent evolution
We report the draft genome sequence of the model moss Physcomitrella patens and compare its featu... more We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics.
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Papers by Neil Ashton