Early Land Plants
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Constraining uncertainty in the timescale of angiosperm evolution and the veracity of a Cretaceous Terrestrial Revolution

Through the lens of the fossil record, angiosperm diversification precipitated a Cretaceous Terrestrial Revolution (KTR) in which pollinators, herbivores and predators underwent explosive co-diversification. Molecular dating studies imply that early angiosperm evolution is not documented in the fossil record. This mismatch remains controversial.
We used a Bayesian molecular dating method to analyse a dataset of 83 genes from 644 taxa and 52 fossil calibrations to explore the effect of different interpretations of the fossil record, molecular clock models, data partitioning, among other factors, on angiosperm divergence time estimation.
Controlling for different sources of uncertainty indicates that the timescale of angiosperm diversification is much less certain than previous molecular dating studies have suggested. Discord between molecular clock and purely fossil-based interpretations of angiosperm diversification may be a consequence of false precision on both sides.
We reject a post-Jurassic origin of angiosperms, supporting the notion of a cryptic early history of angiosperms, but this history may be as much as 121 Myr, or as little as 23 Myr. These conclusions remain compatible with palaeobotanical evidence and a more general KTR in which major groups of angiosperms diverged later within the Cretaceous, alongside the diversification of pollinators, herbivores and their predators.
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Extreme variation in rates of evolution in the plastid Clp protease complex - Williams - - The Plant Journal - Wiley Online Library

Eukaryotic cells represent an intricate collaboration between multiple genomes, even down to the level of multi‐subunit complexes in mitochondria and plastids. One such complex in plants is the caseinolytic protease (Clp), which plays an essential role in plastid protein turnover. The proteolytic core of Clp comprises subunits from one plastid‐encoded gene (clpP1) and multiple nuclear genes. TheclpP1 gene is highly conserved across most green plants, but it is by far the fastest evolving plastid‐encoded gene in some angiosperms. To better understand these extreme and mysterious patterns of divergence, we investigated the history ofclpP1 molecular evolution across green plants by extracting sequences from 988 published plastid genomes. We find thatclpP1 has undergone remarkably frequent bouts of accelerated sequence evolution and architectural changes (e.g. a loss of introns andRNA‐editing sites) within seed plants. AlthoughclpP1 is often assumed to be a pseudogene in such cases, multiple lines of evidence suggest that this is rarely true. We applied comparative native gel electrophoresis of chloroplast protein complexes followed by protein mass spectrometry in two species within the angiosperm genusSilene, which has highly elevated and heterogeneous rates ofclpP1 evolution. We confirmed thatclpP1 is expressed as a stable protein and forms oligomeric complexes with the nuclear‐encoded Clp subunits, even in one of the most divergentSilene species. Additionally, there is a tight correlation between amino acid substitution rates inclpP1 and the nuclear‐encoded Clp subunits across a broad sampling of angiosperms, suggesting continuing selection on interactions within this complex.
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Convergent recruitment of TALE homeodomain life cycle regulators to direct sporophyte development in land plants and brown algae

Three amino acid loop extension homeodomain transcription factors (TALE HD TFs) act as life cycle regulators in green algae and land plants. In mosses these regulators are required for the deployment of the sporophyte developmental program. We demonstrate that mutations in either of two TALE HD TF genes, OUROBOROS or SAMSARA, in the brown alga Ectocarpus result in conversion of the sporophyte generation into a gametophyte. The OUROBOROS and SAMSARA proteins heterodimerise in a similar manner to TALE HD TF life cycle regulators in the green lineage. These observations demonstrate that TALE-HD-TF-based life cycle regulation systems have an extremely ancient origin, and that these systems have been independently recruited to regulate sporophyte developmental programs in at least two different complex multicellular eukaryotic supergroups, Archaeplastida and Chromalveolata.
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Lycophyte plastid genomics: extreme variation in GC, gene and intron content and multiple inversions between a direct and inverted orientation of the rRNA repeat - Mower - - New Phytologist - Wiley...

Lycophytes are a key group for understanding vascular plant evolution. Lycophyte plastomes are highly distinct, indicating a dynamic evolutionary history, but detailed evaluation is hindered by the limited availability of sequences.
Eight diverse plastomes were sequenced to assess variation in structure and functional content across lycophytes.
Lycopodiaceae plastomes have remained largely unchanged compared with the common ancestor of land plants, whereas plastome evolution in Isoetes and especially Selaginella is highly dynamic. Selaginella plastomes have the highest GC content and fewest genes and introns of any photosynthetic land plant. Uniquely, the canonical inverted repeat was converted into a direct repeat (DR) via large‐scale inversion in some Selaginella species. Ancestral reconstruction identified additional putative transitions between an inverted and DR orientation in Selaginella and Isoetes plastomes. A DR orientation does not disrupt the activity of copy‐dependent repair to suppress substitution rates within repeats.
Lycophyte plastomes include the most archaic examples among vascular plants and the most reconfigured among land plants. These evolutionary trends correlate with the mitochondrial genome, suggesting shared underlying mechanisms. Copy‐dependent repair for DR‐localized genes indicates that recombination and gene conversion are not inhibited by the DR orientation. Gene relocation in lycophyte plastomes occurs via overlapping inversions rather than transposase/recombinase‐mediated processes.
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Structural Basis of Karrikin and Non-natural Strigolactone Perception in Physcomitrella patens

In plants, strigolactones are perceived by the dual receptor-hydrolase DWARF14 (D14). D14 belongs to the superfamily of α/β hydrolases and is structurally similar to the karrikin receptor KARRIKIN INSENSITIVE 2 (KAI2). The moss Physcomitrella patens is an ideal model system for studying this receptor family, because it includes 11 highly related family members with unknown ligand specificity. We present the crystal structures of three Physcomitrella D14/KAI2-like proteins and describe a loop-based mechanism that leads to a permanent widening of the hydrophobic substrate gorge. We have identified protein clades that specifically perceive the karrikin KAR1 and the non-natural strigolactone isomer (−)-5-deoxystrigol in a highly stereoselective manner.
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POLQ plays a key role in repair of CRISPR/Cas9 induced double strand breaks in the moss Physcomitrella patens - Mara - - New Phytologist - Wiley Online Library

Double strand breaks can be repaired by different mechanisms such as homologous recombination (HR), classical non‐homologous end joining (C‐NHEJ) and alternative end joining (Alt‐EJ). The polymerase Q (POLQ) has been proposed to be the main factor involved in Alt‐EJ mediated DNA repair.

•Here we describe the role of POLQ in DNA repair and gene targeting in Physcomitrella patens. The disruption of the POLQ gene does not influence the genetic stability of P. patens nor its development.

•The polq mutant shows the same sensitivity as wild‐type towards most of the genotoxic agents tested (UV, MMS and cisplatin) with the notable exception of bleomycin for which it shows less sensitivity than the wild‐type. Furthermore, we show that POLQ is involved in the repair of CRISPR‐Cas9 induced double strand breaks in P. patens. We also demonstrate that POLQ is a potential competitor and/or inhibitor of the HR repair pathway.

•This has a consequence in terms of genetic engineering as in absence of POLQ the frequency of gene targeting is significantly increased and the number of clean two‐sided HR‐mediated insertions is enhanced. Thus, controlling POLQ activity in plants could be a useful strategy to optimize the tools of genome engineering for plant breeding.
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Abscisic Acid Acts as a Regulator of Molecular Trafficking through Plasmodesmata in the Moss Physcomitrella patens | Plant and Cell Physiology | Oxford Academic

In multi-cellular organisms, cell-to-cell communication is crucial for adapting to changes in the surrounding environment. In plants, plasmodesmata (PD) provide a unique pathway for cell-to-cell communication. PD interconnect most cells and generate a cytoplasmic continuum, allowing the trafficking of various micro- and macromolecules between cells. This molecular trafficking through PD is dynamically regulated by altering PD permeability dependent on environmental changes, thereby leading to an appropriate response to various stresses; however, how PD permeability is dynamically regulated is still largely unknown. Moreover, studies on the regulation of PD permeability have been conducted primarily in a limited number of angiosperms. Here, we studied the regulation of PD permeability in the moss Physcomitrella patens and report that molecular trafficking through PD is rapidly and reversibly restricted by abscisic acid (ABA). Since ABA plays a key role in various stress responses in the moss, PD permeability can be controlled by ABA to adapt to surrounding environmental changes. This ABA-dependent restriction of PD trafficking correlates with a reduction in PD pore size. Furthermore, we also found that the rate of macromolecular trafficking is higher in an ABA-synthesis defective mutant, suggesting that the endogenous level of ABA is also important for PD-mediated macromolecular trafficking. Thus, our study provides compelling evidence that P. patens exploits ABA as one of the key regulators of PD function.
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Algal photoprotection is regulated by the E3 ligase CUL4–DDB1 DET1

Algal photoprotection is regulated by the E3 ligase CUL4–DDB1 DET1 | Early Land Plants | Scoop.it
Light is essential for photosynthesis, but the amounts of light that exceed an organism’s assimilation capacity can cause serious damage1. Photosynthetic organisms minimize such potential harm through protection mechanisms collectively referred to as non-photochemical quenching2. One mechanism of non-photochemical quenching called energy-dependent quenching (qE quenching) is readily activated under high-light conditions and dissipates excess energy as heat. LIGHT-HARVESTING COMPLEX STRESS-RELATED PROTEINS 1 and 3 (LHCSR1 and LHCSR3) have been proposed to mediate qE quenching in the green alga Chlamydomonas reinhardtii when grown under high-light conditions3. LHCSR3 induction requires a blue-light photoreceptor, PHOTOTROPIN (PHOT)4, although the signal transduction pathway between PHOT and LHCSR3 is not yet clear. Here, we identify two phot suppressor loci involved in qE quenching: de-etiolated 1 (det1)5 and damaged DNA-binding 1 (ddb1)6. Using a yeast two-hybrid analysis and an inhibitor assay, we determined that these two genetic elements are part of a protein complex containing CULLIN 4 (CUL4). These findings suggest a photoprotective role for the putative E3 ubiquitin ligase CUL4–DDB1DET1 in unicellular photosynthetic organisms that may mediate blue-light signals to LHCSR1 and LHCSR3 gene expression.
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Paleobotany: Did flowering plants exist in the Jurassic period?

"This shouldn't be here," said Ellie, the paleobotanist in Jurassic Park, as she stared at a leaf. "This species of veriforman has been extinct since... the Cretaceous period." Ellie might have been equally impressed and surprised if she had stumbled across a fossil recently discovered in China that appears to be of a flowering plant that dates to the Jurassic period.
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Lycophyte plastid genomics: extreme variation in GC, gene and intron content and multiple inversions between a direct and inverted orientation of the rRNA repeat - Mower - - New Phytologist - Wiley...

Lycophytes are a key group for understanding vascular plant evolution. Lycophyte plastomes are highly distinct, indicating a dynamic evolutionary history, but detailed evaluation is hindered by the limited availability of sequences.

Eight diverse plastomes were sequenced to assess variation in structure and functional content across lycophytes.

Lycopodiaceae plastomes have remained largely unchanged compared with the common ancestor of land plants, whereas plastome evolution in Isoetes and especially Selaginella is highly dynamic. Selaginella plastomes have the highest GC content and fewest genes and introns of any photosynthetic land plant. Uniquely, the canonical inverted repeat was converted into a direct repeat (DR) via large‐scale inversion in some Selaginella species. Ancestral reconstruction identified additional putative transitions between an inverted and DR orientation in Selaginella and Isoetes plastomes. A DR orientation does not disrupt the activity of copy‐dependent repair to suppress substitution rates within repeats.

Lycophyte plastomes include the most archaic among vascular plants and the most reconfigured among land plants. These evolutionary trends correlate with the mitochondrial genome, suggesting shared underlying mechanisms. Copy‐dependent repair for DR‐localized genes indicates that recombination and gene conversion are not inhibited by the DR orientation. Gene relocation in lycophyte plastomes occurs via overlapping inversions rather than transposase/recombinase‐mediated processes.
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The Selaginella rhizophore has a unique transcriptional identity compared to root and shoot meristems - Mello - - New Phytologist - Wiley Online Library

The genus Selaginella resides in an early branch of the land plant lineage that possesses a vasculature and roots. The majority of the Selaginella root system is shoot borne and emerges through a distinctive structure known as the rhizophore, the organ identity of which has been a long‐debated question.

The rhizophore of S. moellendorffii – a model for the lycophytes – shows plasticity to develop into a root or shoot up until 8 d after angle meristem emergence, after which it is committed to root fate. We subsequently use morphology and plasticity to define the stage of rhizophore identity.

Transcriptomic analysis of the rhizophore during its plastic stage reveals that despite some resemblance to the root meristem, rhizophore gene expression patterns are largely distinct from both shoot and root meristems.

Based on this transcriptomic analysis and on historical anatomical work, we conclude that the rhizophore is a distinct organ with unique features.
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ROLE OF CYCLIC AND PSEUDO‐CYCLIC ELECTRON TRANSPORT IN RESPONSE TO DYNAMIC LIGHT CHANGES IN PHYSCOMITRELLA PATENS - Storti - - Plant, Cell & Environment - Wiley Online Library

Photosynthetic organisms support cell metabolism by harvesting sunlight and driving the electron transport chain at the level of thylakoid membranes. Excitation energy and electron flow in the photosynthetic apparatus is continuously modulated in response to dynamic environmental conditions. Alternative electron flow around photosystem I plays a seminal role in this regulation contributing to photo‐protection by mitigating over‐reduction of the electron carriers.

Different pathways of alternative electron flow coexist in the moss Physcomitrella patens, including cyclic electron flow mediated by the PGRL1/PGR5 complex and pseudo‐cyclic electron flow mediated by the flavodiiron proteins FLV. In this work we generated P. patens plants carrying both pgrl1 and flva knock‐out (KO) mutations. A comparative analysis of the WT, pgrl1, flva and pgrl1 flva lines suggests that cyclic and pseudo‐cyclic processes have a synergic role in the regulation of photosynthetic electron transport. However, while both contribute to photosystem I protection from over‐reduction by modulating electron flow following changes in environmental conditions, FLV activity is particularly relevant in the first seconds after a light change while PGRL1 has a major role upon sustained strong illumination.
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Frontiers | Abiotic Stresses: General Defenses of Land Plants and Chances for Engineering Multistress Tolerance | Plant Science

Abiotic stresses, such as low or high temperature, deficient or excessive water, high salinity, heavy metals, and ultraviolet radiation, are hostile to plant growth and development, leading to great crop yield penalty worldwide. It is getting imperative to equip crops with multistress tolerance to relieve the pressure of environmental changes and to meet the demand of population growth, as different abiotic stresses usually arise together in the field. The feasibility is raised as land plants actually have established more generalized defenses against abiotic stresses, including the cuticle outside plants, together with unsaturated fatty acids, reactive species scavengers, molecular chaperones, and compatible solutes inside cells. In stress response, they are orchestrated by a complex regulatory network involving upstream signaling molecules including stress hormones, reactive oxygen species, gasotransmitters, polyamines, phytochromes, and calcium, as well as downstream gene regulation factors, particularly transcription factors. In this review, we aimed at presenting an overview of these defensive systems and the regulatory network, with an eye to their practical potential via genetic engineering and/or exogenous application.
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An Evolutionarily Conserved Abscisic Acid Signaling Pathway Regulates Dormancy in the Liverwort Marchantia polymorpha

Dormancy is a key process allowing land plants to adapt to changing conditions in the terrestrial habitat, allowing the cessation of growth in response to environmental or physiological cues, entrance into a temporary quiescent state, and subsequent reactivation of growth in more favorable environmental conditions [1, 2, 3]. Dormancy may be induced seasonally, sporadically (e.g., in response to drought), or developmentally (e.g., seeds and apical dominance). Asexual propagules, known as gemmae, derived via clonal reproduction in bryophytes, are often dormant until displaced from the parent plant. In the liverwort Marchantia polymorpha, gemmae are produced within specialized receptacles, gemma cups, located on the dorsal side of the vegetative thallus [4]. Mature gemmae are detached from the parent plant but may remain in the cup, with gemma growth suppressed as long as the gemmae remain in the gemma cup and the parental plant is alive [5]. Following dispersal of gemmae from gemma cups by rain, the gemmae germinate in the presence of light and moisture, producing clonal offspring [6]. In land plants, the plant hormone abscisic acid (ABA) regulates many aspects of dormancy and water balance [7]. Here, we demonstrate that ABA plays a central role in the control of gemma dormancy as transgenic M. polymorpha gemmae with reduced sensitivity to ABA fail to establish and/or maintain dormancy. Thus, the common ancestor of land plants used the ABA signaling module to regulate germination of progeny in response to environmental cues, with both gemmae and seeds being derived structures co-opting an ancestral response system.
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Chloroplast cold-avoidance response in Marchantia polymorpha occurs independently of changes in endogenous phototropin expression

When exposed to fluctuating light intensity, chloroplasts move towards weak light (accumulation response), and away from strong light (avoidance response). In addition, cold treatment (5°C) induces the avoidance response even under weak light conditions (cold-avoidance response). These three responses are mediated by the phototropin (phot), which is a blue-light photoreceptor and has also been found to act as a thermosensory protein that perceives temperature variation. Our previous report indicated that cold-induced changes in phot biochemical activity initiate the cold-avoidance response. In this study, we further explored the induction mechanism of the cold-avoidance response in the liverwort Marchantia polymorpha and examined the relationship between changes in the amount of phot and the induction of the cold-avoidance response. The switch between the accumulation and avoidance responses occurs at a so-called transitional light intensity. Our physiological experiments revealed that a cold-mediated decrease in the transitional light intensity leads to the induction of the cold-avoidance response. While artificial overexpression of phot decreased the transitional light intensity as much as cold treatment did, the amount of endogenous phot remained unchanged by cold treatment in wild-type M. polymorpha. Taken together, these findings show that the cold-avoidance response is initiated by a cold-mediated reduction of the transitional light intensity, independent of the amount of endogenous phot. This study provides a clue to understand the mechanism underlying the switch in direction of chloroplast relocation in response to light and temperature.
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Membrane Lipids, Waxes and Oxylipins In The Moss Model Organism Physcomitrella patens | Plant and Cell Physiology | Oxford Academic

The moss Physcomitrella patens receives increased scientific interest since its genome was sequenced a decade ago. As a bryophyte, it represents the first group of plants that evolved in a terrestrial habitat still without a vascular system, that developed later in tracheophytes. It is easily transformable via homologous recombination, which enables the formation of targeted loss-of-function mutants. Even though genetics, development and life cycle in Physcomitrella are well studied nowadays, research on lipids in Physcomitrella is still underdeveloped. This review aims on presenting an overview on the state of the art of lipid research with a focus on membrane lipids, surface lipids and oxylipins. We discuss in this review that Physcomitrella possesses very interesting features regarding its membrane lipids. Here, the presence of very-long-chain poly-unsaturated fatty acids (VLC-PUFA) still shows a closer similarity to marine microalgae than to vascular plants. Unlike algae, Physcomitrella has a cuticle comparable to vascular plants composed of cutin and waxes. The presence of VLC-PUFA in Physcomitrella also leads to a greater variability of signaling lipids even though the phytohormone jasmonic acid is not present in this organism, which is different to vascular plants. In summary, the research on lipids in Physcomitrella is still in its infancy, especially considering membrane lipids. We hope that this review will help to promote the further advancement of lipid research in this important model organism in the future, so we can better understand how lipids are involved in the evolution of land plants.
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Mucoromycotina fine root endophyte fungi form nutritional mutualisms with vascular plants.

Fungi and plants have engaged in intimate symbioses that are globally widespread and have driven terrestrial biogeochemical processes since plant terrestrialisation >500 Mya. Recently, hitherto unknown nutritional mutualisms involving ancient lineages of fungi and non-vascular plants have been discovered. However, their extent and functional significance in vascular plants remains uncertain. Here, we provide first evidence of abundant carbon-for-nitrogen exchange between an early-diverging vascular plant (Lycopodiaceae) and Mucoromycotina (Endogonales) fine root endophyte regardless of changes in atmospheric CO2 concentration. Furthermore, we provide evidence that the same fungi also colonize neighbouring non-vascular and flowering plants. These findings fundamentally change our understanding of the evolution, physiology, interrelationships and ecology of underground plant-fungal symbioses in terrestrial ecosystems by revealing an unprecedented nutritional role of Mucoromycotina fungal symbionts in vascular plants.
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Exploring the natural microbiome of the model liverwort: fungal endophyte diversity in Marchantia polymorpha L

Within their tissues, plants host diverse communities of fungi, termed fungal endophytes. These fungi can affect plant growth, competitiveness, and resistance to stressors, thereby influencing plant community structure. Research characterizing fungal endophyte communities has so far mostly focused on seed plants, but information on the endophytes of other plant lineages is needed to understand how plant microbiomes impact whole ecosystems and how major changes through land plant evolution have affected plant-microbe relationships. In this study, we assess the fungal endophyte community of the model liverwort Marchantia polymorpha L. by both culturing and Illumina amplicon sequencing methods. We detect a very diverse fungal community that is distinct between M. polymorpha patches and only shares a few core fungi between populations across the United States. We also show low overlap in taxa detected by the different methods. This study helps build a foundation for using M. polymorpha and other Marchantia species as models for the ecology and dynamics of bryophyte microbiomes.
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Anatomical constraints to non‐stomatal diffusion conductance and photosynthesis in lycophytes and bryophytes - Carriquí - - New Phytologist - Wiley Online Library

Photosynthesis in bryophytes and lycophytes has received less attention than terrestrial plant groups. In particular, few studies have addressed the non‐stomatal diffusion conductance to CO2 (gnsd) of these plant groups.

Their lower photosynthetic rate per leaf mass area at any given nitrogen concentration as compared to vascular plants suggested a stronger limitation by CO2 diffusion. We hypothesized that bryophyte and lycophyte photosynthesis is largely limited by low gnsd. Here we studied CO2 diffusion inside the photosynthetic tissues and its relationships with photosynthesis and anatomical parameters in bryophyte and lycophyte species in Antarctica, Australia, Estonia, Hawaii and Spain.

On average, lycophytes and, specially, bryophytes had the lowest photosynthetic rates and non‐stomatal diffusion conductance reported for terrestrial plants. These low values are related to their very thick cell walls and their low exposure of chloroplasts to cell perimeter.

We conclude that the reason why bryophytes lie at the lower end of the leaf economics spectrum is their strong non‐stomatal diffusion conductance limitation to photosynthesis, which is driven by their specific anatomical characteristics.
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A cis‐acting bidirectional transcription switch controls sexual dimorphism in the liverwort

Plant life cycles alternate between haploid gametophytes and diploid sporophytes. While regulatory factors determining male and female sexual morphologies have been identified for sporophytic reproductive organs, such as stamens and pistils of angiosperms, those regulating sex‐specific traits in the haploid gametophytes that produce male and female gametes and hence are central to plant sexual reproduction are poorly understood. Here, we identified a MYB‐type transcription factor, MpFGMYB, as a key regulator of female sexual differentiation in the haploid‐dominant dioicous liverwort, Marchantia polymorpha. MpFGMYB is specifically expressed in females and its loss resulted in female‐to‐male sex conversion. Strikingly, MpFGMYB expression is suppressed in males by a cis‐acting antisense gene SUF at the same locus, and loss‐of‐function suf mutations resulted in male‐to‐female sex conversion. Thus, the bidirectional transcription module at the MpFGMYB/SUF locus acts as a toggle between female and male sexual differentiation in M. polymorpha gametophytes. Arabidopsis thaliana MpFGMYB orthologs are known to be expressed in embryo sacs and promote their development. Thus, phylogenetically related MYB transcription factors regulate female gametophyte development across land plants.
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Massive tandem proliferation of ELIPs supports convergent evolution of desiccation tolerance across land plants

Desiccation tolerance was a critical adaptation for the colonization of land by early non-vascular plants. Resurrection plants have maintained or rewired these ancestral protective mechanisms and desiccation-tolerant species are dispersed across the land plant phylogeny. Though common physiological, biochemical, and molecular signatures are observed across resurrection plant lineages, features underlying the recurrent evolution of desiccation tolerance are unknown. Here we used a comparative approach to identify patterns of genome evolution and gene duplication associated with desiccation tolerance. We identified a single gene family with dramatic expansion in all sequenced resurrection plant genomes and no expansion in desiccation-sensitive species. This gene family of early light-induced proteins (ELIPs) expanded in resurrection plants convergent through repeated tandem gene duplication. ELIPS are universally highly expressed during desiccation in all surveyed resurrection plants and may play a role in protecting against photooxidative damage of the photosynthetic apparatus during prolonged dehydration. Photosynthesis is particularly sensitive to dehydration and the increased abundance of ELIPs may help facilitate the rapid recovery observed for most resurrection plants. Together, these observations support convergent evolution of desiccation tolerance in land plants through tandem gene duplication.
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An unexpected noncarpellate epigynous flower from the Jurassic of China

The origin of angiosperms has been a long-standing botanical debate. The great diversity of angiosperms in the Early Cretaceous makes the Jurassic a promising period in which to anticipate the origins of the angiosperms. Here, based on observations of 264 specimens of 198 individual flowers preserved on 34 slabs in various states and orientations, from the South Xiangshan Formation (Early Jurassic) of China, we describe a fossil flower, Nanjinganthus dendrostyla gen. et sp. nov.. The large number of specimens and various preservations allow for an evidence-based reconstruction of the flower. From the evidence of the combination of an invaginated receptacle and ovarian roof, we infer that the seeds of Nanjinganthus were completely enclosed. Evidence of an actinomorphic flower with a dendroid style, cup-form receptacle, and angiospermy, is consistent with Nanjinganthus being a bona fide angiosperm from the Jurassic, an inference that we hope will re-invigorate research into angiosperm origins
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Mechanistic insights into the evolution of DUF26-containing proteins in land plants

Large protein families are a prominent feature of plant genomes and their size variation is a key element for adaptation in plants. Here we infer the evolutionary history of a representative protein family, the DOMAIN OF UNKNOWN FUNCTION (DUF) 26-containing proteins. The DUF26 first appeared in secreted proteins. Domain duplications and rearrangements led to the emergence of CYSTEINE-RICH RECEPTOR-LIKE PROTEIN KINASES (CRKs) and PLASMODESMATA-LOCALIZED PROTEINS (PDLPs). While the DUF26 itself is specific to land plants, structural analyses of Arabidopsis PDLP5 and PDLP8 ectodomains revealed strong similarity to fungal lectins. Therefore, we propose that DUF26-containing proteins constitute a novel group of plant carbohydrate-binding proteins. Following their appearance, CRKs expanded both through tandem duplications and preferential retention of duplicates in whole genome duplication events, whereas PDLPs evolved according to the dosage balance hypothesis. Based on our findings, we suggest that the main mechanism of expansion in new gene families is small-scale duplication, whereas genome fractionation and genetic drift after whole genome multiplications drive families towards dosage balance.
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Hydraulics regulates stomatal responses to changes in leaf water status in Athyrium filix-femina

Stomatal responses to changes in leaf water status are important for the diurnal regulation of gas exchange and the survival of plants during drought. These stomatal responses in angiosperm species are well characterized, yet an ongoing debate surrounds the role of metabolism, particularly the role of the hormone abscisic acid (ABA), in functionally regulating stomatal responses to changes in leaf water status in species of non-seed plants. Here we measured the stomatal response to changes in vapour pressure deficit (VPD) in two natural forms of the fern species Athyrium filix-femina, recently suggested to have stomata that are regulated by ABA. The two forms measured had considerable differences in key hydraulic traits, including leaf hydraulic conductance and capacitance, as well as the kinetics of stomatal response to changes in VPD. In both forms the stomatal responses to VPD could be accurately predicted by a dynamic, mechanistic model that assumes guard cell turgor changes in concert with leaf turgor in the light, and not via metabolic processes including the level of ABA. During drought, endogenous ABA was found to play no role in closing stomata, while exogenous ABA applied to live and intact leaves did not close stomata. Our results indicate that functional stomatal responses to changes in leaf water status in ferns are regulated by leaf hydraulics and not metabolism. With ferns being sister to seed plants, this result has implications for the evolutionary reconstruction of functional stomatal responses across vascular land plants lineages.
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Evolutionary and ecological functional genomics, from lab to the wild - Zaidem - - The Plant Journal - Wiley Online Library

Plant phenotypes are the result of both genetic and environmental forces that act to modulate trait expression. Over the least few years, numerous approaches in functional genomics and systems biology have led to a greater understanding of plant phenotypic variation and plant responses to the environment. These approaches, and the questions that they can address, have been loosely termed evolutionary and ecological functional genomics (EEFG), and have been providing key insights on how plants adapt and evolve. In particular, by bringing these studies from the laboratory to the field, EEFG studies allow us to gain greater knowledge of how plants function in their natural contexts.
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Nuclear protein phylogenies support the monophyly of the three bryophyte groups (Bryophyta Schimp.) - de Sousa - - New Phytologist - Wiley Online Library

Unraveling the phylogenetic relationships between the four major lineages of terrestrial plants (mosses, liverworts, hornworts, and vascular plants) is essential for an understanding of the evolution of traits specific to land plants, such as their complex life cycles, and the evolutionary development of stomata and vascular tissue.

Well supported phylogenetic hypotheses resulting from different data and methods are often incongruent due to processes of nucleotide evolution, which are difficult to model: for example, substitutional saturation and composition heterogeneity. We reanalyse a large published dataset of nuclear data and model these processes using degenerate codon recoding and tree‐heterogeneous composition substitution models.

Our analyses resolve bryophytes as a monophyletic group and show that the non‐monophyly of the clade, that is supported by the analysis of nuclear nucleotide data, is due solely to fast‐evolving synonymous substitutions.

The current congruence among phylogenies of both nuclear and chloroplast analyses lend considerable support to the conclusion that the bryophytes are a monophyletic group. An initial split between bryophytes and vascular plants implies that the bryophyte life cycle (with a dominant gametophyte nurturing an unbranched sporophyte) may not be ancestral to all land plants and that stomata are likely a symplesiomorphy among embryophytes.
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