Dr Laura Moody
Research Interests
Genetic regulation of the 2D to 3D growth transition
A crucial episode in the history of life on earth was the colonization of land by plants; this transition coincided with and was most likely enabled by the evolution of 3-dimensional (3D) growth. In charophyte algae, the sister group to land plants, growth occurs from initial cells that can only divide in one or two planes to produce filaments, mats or branches. By acquiring initial cells that could cleave in three planes, plants were able to develop the morphological toolkit (e.g. vasculature, roots, flowers, seeds) that enabled them to survive and reproduce on land. 3D growth is an invariable and pivotal feature of all land plants, and the diverse morphologies exhibited across the terrestrial biosphere are all due to differential regulation of 3D growth processes during development. Yet, we know relatively little about how 3D growth is regulated at the genetic level.
Studies of 3D growth are difficult using flowering plants because the onset of 3D growth occurs very early during embryo development. Disrupting 3D growth in these plants would therefore result in lethality. On the other hand, in the moss Physcomitrella patens, a representative of the earliest evolving land plants, 3D growth is preceded by an extended 2D filamentous growth phase that can be continuously propagated in tissue culture. In fact, Physcomitrella undergoes the transition from 2D to 3D growth twice during its life cycle; firstly, during 3D shoot initiation and then during embryo development. Disrupting 3D growth in Physcomitrella would therefore not cause lethality, but any mutants generated would be reproductively sterile.
We are exploiting both well-established and innovative approaches to define the genetic interaction network underpinning 3D growth in Physcomitrella. Given that 3D growth is a defining feature of all land plants, and arose as part of the adaptive transition from water to land, our research will answer one of the most fundamental questions in biology – how was terrestrial life established?
Publications
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NO GAMETOPHORES 2 is a novel regulator of the 2D to 3D growth transition in the moss Physcomitrella patens
November 2020|Journal article|Current BiologyThe colonization of land by plants was one of the most transformative events in the history of life on Earth. The transition from water, which coincided with and was likely facilitated by the evolution of 3-dimensional (3D) growth, enabled the generation of morphological diversity on land. In many plants, the transition from 2-dimensional (2D) to 3D growth occurs during embryo development. However, in the early divergent moss Physcomitrella patens, 3D growth is preceded by an extended filamentous phase that can be maintained indefinitely. Here, we describe the identification of the cytokinin-responsive NO GAMETOPHORES 2 (PpNOG2) gene, which encodes a shikimate o-hydroxycinnamoyltransferase. In mutants lacking PpNOG2 function, transcript levels of CLAVATA and SCARECROW genes are significantly reduced, excessive gametophore initial cells are produced, and buds undergo premature developmental arrest. Mutants also exhibit misregulation of auxin-responsive genes. Our results suggest that PpNOG2 functions in the acid pathway leading to cuticle formation, and that NOG2-related genes were co-opted into the lignin biosynthesis pathway after the divergence of bryophytes and vascular plants. We present a revised model of 3D growth in which PpNOG2 comprises part of a feedback mechanism that is required for the modulation of gametophore initial cell frequency. We also propose that the 2D to 3D growth transition in P. patens is underpinned by complex auxin-cytokinin crosstalk that is regulated, at least in part, by changes in flavonoid metabolism. -
Three-dimensional growth: a developmental innovation that facilitated plant terrestrialization.
May 2020|Journal article|Journal of plant researchOne of the most transformative events in the history of life on earth was the transition of plants from water to land approximately 470 million years ago. Within the Charophyte green algae, the closest living relatives of land plants, body plans have evolved from those that comprise simple unicells to those that are morphologically complex, large and multicellular. The Charophytes developed these broad ranging body plans by exploiting a range of one-dimensional and two-dimensional growth strategies to produce filaments, mats and branches. When plants were confronted with harsh conditions on land, they were required to make significant changes to the way they shaped their body plans. One of the fundamental developmental transitions that occurred was the evolution of three-dimensional growth and the acquisition of apical cells with three or more cutting faces. Plants subsequently developed a range of morphological adaptations (e.g. vasculature, roots, flowers, seeds) that enabled them to colonise progressively drier environments. 3D apical growth also evolved convergently in the brown algae, completely independently of the green lineage. This review summarises the evolving developmental complexities observed in the early divergent Charophytes all the way through to the earliest conquerors of land, and investigates 3D apical growth in the brown algae.Flowers, Plant Roots, Phylogeny, Phaeophyta, Chlorophyta, Biological Evolution, Embryophyta -
A Musashi-Related Protein is Essential for Gametogenesis in Arabidopsis
March 2019|Journal article<h4>SUMMARY</h4> Musashi (Msi) proteins are an evolutionarily conserved group of RNA-binding proteins, required for targeted control of mRNA translation during many important developmental processes in animals. Most notably, Msi proteins play important roles during both spermatogenesis and oogenesis. Msi proteins also exist in plants but these are largely uncharacterized. Here we report the functional characterization of an Arabidopsis Msi ortholog ABORTED GAMETOPHYTE 2 ( AOG2 ), which encodes a protein containing two RNA recognition motifs and an ER-targeting signal. AOG2-GFP translational fusions were localized to the ER in transient assays, suggesting that AOG2 most likely binds to ER-targeted mRNAs. We show that disrupted AOG2 function leads to a high rate of both ovule and seed abortion, and that homozygous loss of function mutants are embryo lethal. Furthermore, we demonstrate that AOG2 is required to establish asymmetry during pollen mitosis I, and that loss of AOG2 function leads to loss of pollen viability. Collectively the results reveal that AOG2 is required for the establishment of polarity and/or the progression of mitosis during gametophyte development in Arabidopsis, and thus Msi-related proteins have an evolutionarily conserved role in gametogenesis in both animals and plants. <h4>SIGNIFICANCE STATEMENT</h4> ABORTED GAMETOPHYTE 2 ( AOG2 ) encodes a Musashi-related RNA-binding protein that is required for gametogenesis and embryogenesis in Arabidopsis. AOG2 is required for the establishment of polarity and/or the progression of mitosis during gametophyte development in Arabidopsis, and thus Musashi-related proteins have an evolutionarily conserved role in gametogenesis in both animals and plants. -
The 2D to 3D growth transition in the moss Physcomitrella patens.
February 2019|Journal article|Current opinion in plant biologyThe colonization of land by plants coincided with and was most likely facilitated by the evolution of 3-dimensional (3D) growth. 3D growth is a pivotal feature of all land plants, but most develop in a way that precludes genetic investigation. In the moss Physcomitrella patens, 3D growth (gametophores) is preceded by an extended 2-dimensional (2D) growth phase (protonemata) that can be propagated indefinitely. Studies using P. patens have thus elucidated some of the molecular mechanisms underlying 3D growth regulation. This review summarizes the known molecular mechanisms underlying both the formation of gametophore initial cells and the development of the 3D growth in gametophores.Bryopsida, Cytokinins, Transcription Factors, Cell Division, Genes, Plant, Models, Biological -
Somatic hybridization provides segregating populations for the identification of causative mutations in sterile mutants of the moss Physcomitrella patens.
May 2018|Journal article|The New phytologistForward genetics is now straightforward in the moss Physcomitrella patens, and large mutant populations can be screened relatively easily. However, perturbation of development before the formation of gametes currently leaves no route to gene discovery. Somatic hybridization has previously been used to rescue sterile mutants and to assign P. patens mutations to complementation groups, but the cellular basis of the fusion process could not be monitored, and there was no tractable way to identify causative mutations. Here we use fluorescently tagged lines to generate somatic hybrids between Gransden (Gd) and Villersexel (Vx) strains of P. patens, and show that hybridization produces fertile diploid gametophytes that form phenotypically normal tetraploid sporophytes. Quantification of genetic variation between the two parental strains reveals single nucleotide polymorphisms at a frequency of 1/286 bp. Given that the genetic distinction between Gd and Vx strains exceeds that found between pairs of strains that are commonly used for genetic mapping in other plant species, the spore populations derived from hybrid sporophytes provide suitable material for bulk segregant analysis and gene identification by genome sequencing.Bryopsida, Anti-Bacterial Agents, Hybridization, Genetic, Chromosome Segregation, Phenotype, Mutation, Polymorphism, Single Nucleotide -
Genetic Regulation of the 2D to 3D Growth Transition in the Moss Physcomitrella patens.
February 2018|Journal article|Current biology : CBOne of the most important events in the history of life on earth was the colonization of land by plants; this transition coincided with and was most likely enabled by the evolution of 3-dimensional (3D) growth. Today, the diverse morphologies exhibited across the terrestrial biosphere arise from the differential regulation of 3D growth processes during development. In many plants, 3D growth is initiated during the first few divisions of the zygote, and therefore, the genetic basis cannot be dissected because mutants do not survive. However, in mosses, which are representatives of the earliest land plants, 3D shoot growth is preceded by a 2D filamentous phase that can be maintained indefinitely. Here, we used the moss Physcomitrella patens to identify genetic regulators of the 2D to 3D transition. Mutant screens yielded individuals that could only grow in 2D, and through an innovative strategy that combined somatic hybridization with bulk segregant analysis and genome sequencing, the causative mutation was identified in one of them. The NO GAMETOPHORES 1 (NOG1) gene, which encodes a ubiquitin-associated protein, is present only in land plant genomes. In mutants that lack PpNOG1 function, transcripts encoding 3D-promoting PpAPB transcription factors [1] are significantly reduced, and apical initial cells specified for 3D growth are not formed. PpNOG1 acts at the earliest identified stage of the 2D to 3D transition, possibly through degradation of proteins that suppress 3D growth. The acquisition of NOG1 function in land plants could thus have enabled the evolution and development of 3D morphology.Bryopsida, Plant Proteins, Gene Expression Regulation, Plant -
Non-reciprocal complementation of KNOX gene function in land plants
September 2017|Journal article|New Phytologist<p>Class I KNOTTED1-LIKE homeobox (KNOX) proteins regulate development of the multicellular diploid sporophyte in both mosses and flowering plants; however, the morphological context in which they function differs. </p> <p>To determine how Class I KNOX function was modified as land plants evolved, phylogenetic analyses and cross-species complementation assays were performed.</p> <p>Our data reveal that a duplication within the charophyte sister group to land plants led to distinct Class I and Class II KNOX gene families. Subsequently, Class I sequences diverged substantially in the non-vascular bryophyte groups (liverworts, mosses and hornworts), with moss sequences being most similar to those in vascular plants. Despite this similarity, moss mutants were not complemented by vascular plant KNOX genes. Conversely, the Arabidopsis brevipedicellus (bp-9) mutant was complemented by the PpMKN2 gene from the moss Physcomitrella patens. Lycophyte KNOX genes also complemented bp-9 whereas fern genes only partially complemented. This lycophyte/fern distinction is mirrored in the phylogeny of KNOX-interacting BELL proteins, in that a gene duplication occurred after divergence of the two groups. </p> <p>Together our results imply that the moss MKN2 protein can function in a broader developmental context than vascular plant KNOX proteins, the narrower scope having evolved progressively as lycophytes, ferns and flowering plants diverged. </p>Selaginella kraussiana, KNOTTED homeobox genes, phylogeny, Arabidopsis, Ceratopteris richardii, Physcomitrella patens, cross-species complementation, land plant evolution -
ARABIDILLO gene homologues in basal land plants: species-specific gene duplication and likely functional redundancy.
December 2012|Journal article|PlantaARABIDILLO proteins regulate multicellular root development in Arabidopsis thaliana. Conserved ARABIDILLO homologues are present throughout land plants, even in early-evolving plants that do not possess complex root architecture, suggesting that ARABIDILLO genes have additional functions. Here, we have cloned and characterised ARABIDILLO gene homologues from two early-evolving land plants, the bryophyte Physcomitrella patens and the lycophyte Selaginella moellendorffii. We show that two of the PHYSCODILLO genes (PHYSCODILLO1A and -1B) exist as a tail-to-tail tandem array of two almost identical 12 kb sequences, while a third related gene (PHYSCODILLO2) is located elsewhere in the Physcomitrella genome. Physcomitrella possesses a very low percentage of tandemly arrayed genes compared with the later-evolving plants whose genomes have been sequenced to date. Thus, PHYSCODILLO1A and -1B genes represent a relatively unusual gene arrangement. PHYSCODILLO promoters are active largely in the haploid gametophyte, with additional activity at the foot of the sporophyte. The pattern of promoter activity is uniform in filamentous and leafy tissues, suggesting pleiotropic gene functions and likely functional redundancy: the latter possibility is confirmed by the lack of discernible phenotype in a physcodillo2 deletion mutant. Interestingly, the pattern of PHYSCODILLO promoter activity in female reproductive organs is strikingly similar to that of an Arabidopsis homologue, suggesting co-option of some PHYSCODILLO functions or regulation into both the sporophyte and gametophyte. In conclusion, our work identifies and characterises some of the earliest-evolving land plant ARABIDILLO homologues. We confirm that all land plant ARABIDILLO genes arose from a single common ancestor and suggest that PHYSCODILLO proteins have novel and pleiotropic functions, some of which may be conserved in later-evolving plants.Arabidopsis, Base Sequence, Bryopsida, Gene Expression Regulation, Plant, Genes, Reporter, Genome, Plant, Molecular Sequence Data, Phenotype, Phylogeny, Plant Proteins, Plants, Genetically Modified, Promoter Regions, Genetic, Selaginellaceae, Sequence Alignment, Sequence Analysis, DNA, Sequence Deletion, Sequence Homology, Nucleic Acid, Species Specificity
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