Exploring the interplay between angiosperm chlorophyll metabolism and environmental factors.

MAIN CONCLUSION: In this review, we summarize how chlorophyll metabolism in angiosperm is affected by the environmental factors: light, temperature, metal ions, water, oxygen, and altitude. The significance of chlorophyll (Chl) in plant leaf morphogenesis and photosynthesis cannot be overstated. Over time, researchers have made significant advancements in comprehending the biosynthetic pathway of Chl in angiosperms, along with the pivotal enzymes and genes involved in this process, particularly those related to heme synthesis and light-responsive mechanisms. Various environmental factors influence the stability of Chl content in angiosperms by modulating Chl metabolic pathways. Understanding the interplay between plants Chl metabolism and environmental factors has been a prominent research topic. This review mainly focuses on angiosperms, provides an overview of the regulatory mechanisms governing Chl metabolism, and the impact of environmental factors such as light, temperature, metal ions (iron and magnesium), water, oxygen, and altitude on Chl metabolism. Understanding these effects is crucial for comprehending and preserving the homeostasis of Chl metabolism.

Eco-evolutionary processes shaping floral nectar sugar composition.

Floral nectar sugar composition is assumed to reflect the nutritional demands and foraging behaviour of pollinators, but the relative contributions of evolutionary and abiotic factors to nectar sugar composition remain largely unknown across the angiosperms. We compiled a comprehensive dataset on nectar sugar composition for 414 insect-pollinated plant species across central Europe, along with phylogeny, paleoclimate, flower morphology, and pollinator dietary demands, to disentangle their relative effects. We found that phylogeny was strongly related with nectar sucrose content, which increased with the phylogenetic age of plant families, but even more strongly with historic global surface temperature. Nectar sugar composition was also defined by floral morphology, though it was not related to our functional measure of pollinator dietary demands. However, specialist pollinators of current plant-pollinator networks predominantly visited plant species with sucrose-rich nectar. Our results suggest that both physiological mechanisms related to plant water balance and evolutionary effects related to paleoclimatic changes have shaped floral nectar sugar composition during the radiation and specialisation of plants and pollinators. As a consequence, the high velocity of current climate change may affect plant-pollinator interaction networks due to a conflicting combination of immediate physiological responses and phylogenetic conservatism.

A trait-based root acquisition-defence-decomposition framework in angiosperm tree species.

To adapt to the complex belowground environment, plants make trade-offs between root resource acquisition and defence ability. This includes forming partnerships with different types of root associating microorganisms, such as arbuscular mycorrhizal and ectomycorrhizal fungi. These trade-offs, by mediating root chemistry, exert legacy effects on nutrient release during decomposition, which may, in turn, affect the ability of new roots to re-acquire resources, thereby generating a feedback loop. However, the linkages at the basis of this potential feedback loop remain largely unquantified. Here, we propose a trait-based root 'acquisition-defence-decomposition' conceptual framework and test the strength of relevant linkages across 90 angiosperm tree species. We show that, at the plant species level, the root-fungal symbiosis gradient within the root economics space, root chemical defence (condensed tannins), and root decomposition rate are closely linked, providing support to this framework. Beyond the dichotomy between arbuscular mycorrhizal-dominated versus ectomycorrhizal-dominated systems, we suggest a continuous shift in feedback loops, from 'high arbuscular mycorrhizal symbiosis-low defence-fast decomposition-inorganic nutrition' by evolutionarily ancient taxa to 'high ectomycorrhizal symbiosis-high defence-slow decomposition-organic nutrition' by more modern taxa. This 'acquisition-defence-decomposition' framework provides a foundation for testable hypotheses on multidimensional linkages between species' belowground strategies and ecosystem nutrient cycling in an evolutionary context.

Elevated atmospheric CO2 has small, species-specific effects on pollen chemistry and plant growth across flowering plant species.

Elevated atmospheric carbon dioxide (eCO2) can affect plant growth and physiology, which can, in turn, impact herbivorous insects, including by altering pollen or plant tissue nutrition. Previous research suggests that eCO2 can reduce pollen nutrition in some species, but it is unknown whether this effect is consistent across flowering plant species. We experimentally quantified the effects of eCO2 across multiple flowering plant species on plant growth in 9 species and pollen chemistry (%N an estimate for protein content and nutrition in 12 species; secondary chemistry in 5 species) in greenhouses. For pollen nutrition, only buckwheat significantly responded to eCO2, with %N increasing in eCO2; CO2 treatment did not affect pollen amino acid composition but altered secondary metabolites in buckwheat and sunflower. Plant growth under eCO2 exhibited two trends across species: plant height was taller in 44% of species and flower number was affected for 63% of species (3 species with fewer and 2 species with more flowers). The remaining growth metrics (leaf number, above-ground biomass, flower size, and flowering initiation) showed divergent, species-specific responses, if any. Our results indicate that future eCO2 is unlikely to uniformly change pollen chemistry or plant growth across flowering species but may have the potential to alter ecological interactions, or have particularly important effects on specialized pollinators.

A molecular atlas of plastid and mitochondrial proteins reveals organellar remodeling during plant evolutionary transitions from algae to angiosperms.

Algae and plants carry 2 organelles of endosymbiotic origin that have been co-evolving in their host cells for more than a billion years. The biology of plastids and mitochondria can differ significantly across major lineages and organelle changes likely accompanied the adaptation to new ecological niches such as the terrestrial habitat. Based on organelle proteome data and the genomes of 168 phototrophic (Archaeplastida) versus a broad range of 518 non-phototrophic eukaryotes, we screened for changes in plastid and mitochondrial biology across 1 billion years of evolution. Taking into account 331,571 protein families (or orthogroups), we identify 31,625 protein families that are unique to primary plastid-bearing eukaryotes. The 1,906 and 825 protein families are predicted to operate in plastids and mitochondria, respectively. Tracing the evolutionary history of these protein families through evolutionary time uncovers the significant remodeling the organelles experienced from algae to land plants. The analyses of gained orthogroups identifies molecular changes of organelle biology that connect to the diversification of major lineages and facilitated major transitions from chlorophytes en route to the global greening and origin of angiosperms.

Evolution of the WRKY Family in Angiosperms and Functional Diversity under Environmental Stress.

The transcription factor is an essential factor for regulating the responses of plants to external stimuli. The WRKY protein is a superfamily of plant transcription factors involved in response to various stresses (e.g., cold, heat, salt, drought, ions, pathogens, and insects). During angiosperm evolution, the number and function of WRKY transcription factors constantly change. After suffering from long-term environmental battering, plants of different evolutionary statuses ultimately retained different numbers of WRKY family members. The WRKY family of proteins is generally divided into three large categories of angiosperms, owing to their conserved domain and three-dimensional structures. The WRKY transcription factors mediate plant adaptation to various environments via participating in various biological pathways, such as ROS (reactive oxygen species) and hormone signaling pathways, further regulating plant enzyme systems, stomatal closure, and leaf shrinkage physiological responses. This article analyzed the evolution of the WRKY family in angiosperms and its functions in responding to various external environments, especially the function and evolution in Magnoliaceae plants. It helps to gain a deeper understanding of the evolution and functional diversity of the WRKY family and provides theoretical and experimental references for studying the molecular mechanisms of environmental stress.

Isolation of the Inner and Outer Membranes of the Chloroplast Envelope from Angiosperms.

The outer and the inner membranes of the chloroplast envelope, also called OEM and IEM, have distinct lipid and protein compositions. They host molecular systems involved in the biogenesis of the organelle, its cellular function, and its communication with other compartments. Here we describe a method for the isolation of these two membranes starting from intact chloroplast preparations, with two alternative procedures based on the starting material. One was developed from spinach leaves, the other from pea leaves. The two procedures differ in the method used to isolate and rupture chloroplasts and separate each membrane.

Therapeutic Potential of Pectin and Its Derivatives in Chronic Diseases.

Non-communicable diseases (NCDs) are described as a collection of chronic diseases that do not typically develop from an acute infection, have long-term health effects, and frequently require ongoing care and therapy. These diseases include heart disease, stroke, cancer, chronic lung disease, neurological diseases, osteoporosis, mental health disorders, etc. Known synthetic drugs for the treatment or prevention of NCDs become increasingly dangerous over time and pose high risks due to side effects such as hallucination, heart attack, liver failure, etc. As a result, scientists have had to look for other alternatives that are natural products and that are known to be less detrimental and contain useful bioactive compounds. The increasing understanding of the biological and pharmacological significance of carbohydrates has helped to raise awareness of their importance in living systems and medicine, given they play numerous biological roles. For example, pectin has been identified as a class of secondary metabolites found in medicinal plants that may play a significant role in the treatment and management of a variety of NCDs. Pectin is mainly made of homogalacturonan, which is a linear polymer composed primarily of D-galacturonic acid units (at least 65%) linked in a chain by α-(1,4)-glycosidic linkages. There are also modified pectins or derivatives that improve pectin's bioavailability. Pectin is found in the cell walls of higher plants (pteridophytes, angiosperms, and gymnosperms), particularly in the middle lamella of the plant material. Citrus pectin is used in various industries. This article compiles information that has been available for years about the therapeutic importance of pectin in chronic diseases, different modes of pectin extraction, the chemistry of pectin, and the potency of pectin and its derivatives.

Epigenetic variation in early and late flowering plants of the rubber-producing Russian dandelion Taraxacum koksaghyz provides insights into the regulation of flowering time.

The Russian dandelion (Taraxacum koksaghyz) grows in temperate zones and produces large amounts of poly(cis-1,4-isoprene) in its roots, making it an attractive alternative source of natural rubber. Most T. koksaghyz plants require vernalization to trigger flower development, whereas early flowering varieties that have lost their vernalization dependence are more suitable for breeding and domestication. To provide insight into the regulation of flowering time in T. koksaghyz, we induced epigenetic variation by in vitro cultivation and applied epigenomic and transcriptomic analysis to the resulting early flowering plants and late flowering controls, allowing us to identify differences in methylation patterns and gene expression that correlated with flowering. This led to the identification of candidate genes homologous to vernalization and photoperiodism response genes in other plants, as well as epigenetic modifications that may contribute to the control of flower development. Some of the candidate genes were homologous to known floral regulators, including those that directly or indirectly regulate the major flowering control gene FT. Our atlas of genes can be used as a starting point to investigate mechanisms that control flowering time in T. koksaghyz in greater detail and to develop new breeding varieties that are more suited to domestication.

The annonalide diterpene extracted from Casimirella ampla (Miers) reduces inflammatory and antinociceptive events in general models of inflammation.

ETHNOPHARMACOLOGICAL RELEVANCE: The plants of the genus Casimirella ampla (Miers) (C. ampla) are extensively used in folk medicine. For a long time, rural communities have been using extracts from its roots for food and therapeutic purposes. The extract is rich in diterpenoid annonalide (Annona), which has antiophidic, anti-inflammatory and antinociceptive properties. Inflammation is the body's primary defense mechanism against cell damage and invasion by pathogens, which can trigger acute and chronic inflammatory processes. The first line of treatment for this condition consists of the use of non-steroidal anti-inflammatory drugs, but these have numerous associated collateral damages, based on scientific knowledge about diterpenoids from C. ampla, as well as their already reported antinociceptive and anti-inflammatory properties. AIMS OF THE STUDY: Evaluate the effect of Annona in classic models of inflammation and pain. MATERIALS AND METHODS: Animals were pretreated with Annona (0.1, 1.0 and 10 mg/kg), or Tween 80 (2%), or indomethacin (Indo) (10 mg/kg) orally in the paw edema tests induced by carrageenan (Cg), serotonin (5-HT), histamine, bradykinin, 48/80 and, prostaglandin E2 (PGE2), evaluating microscopic lesion scores, migration of leukocytes to the peritoneal cavity, concentration of myeloperoxide (MPO), malonyldialdehyde (MDA) and glutathione (GSH), abdominal contortion test by acetic acid and formalin test. RESULTS: Treatment with Annona compound at a dose of 0.1 mg/kg was more effective in reducing inflammatory, oxidant and nociceptive parameters, as it reduced paw edema induced by carrageenan, through different mediators and migration of inflammatory cells. Furthermore, it worked by reducing the concentration of MPO, MDA, preserving GSH levels and reducing nociception caused by formalin and acetic acid.

Nitraria sibirica adapts to long-term soil water deficit by reducing photosynthesis, stimulating antioxidant systems, and accumulating osmoregulators.

Amid climate change and shifts in precipitation patterns, drought conditions are expanding worldwide. Drought stress severely threatens plant growth in arid and semi-arid regions, wherein shrubs play a crucial role in maintaining ecological stability. Despite its ecological significance, studies are lacking on how Nitraria sibirica adapts to long-term drought stress. Therefore, in this study, to elucidate the mechanism of drought stress adaptation in N. sibirica, we analysed morphological, physiological, and transcriptional characteristics of plants in two soil habitats: riparian (moist) and desert (arid). The results showed that in desert soils, as soil water content decreased, leaf thickness increased, while plant height and leaf area decreased. Physiologically, photosynthesis decreased; soluble sugar, starch, proline, and hydrogen peroxide content increased significantly; while soluble proteins decreased significantly. Additionally, membrane lipid peroxidation products and antioxidant enzyme activities significantly increased under drought stress. Then, Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analysis identified 313 key genes, which were considered the most significantly enriched in the photosynthesis and photosynthetic antenna protein pathways. Further, we found that the proteins encoding photosystem II (PsbP, PsbQ, PsbR, PsbY, and Psb27), photosystem I (PsaD, PsaF, PsaG, PsaH, PsaK, and PsaO), photosynthetic electron transport (PetF), and light-trapping antenna proteins were significantly downregulated under drought stress. Taken together, these results suggest that N. sibirica adapts to long-term drought conditions by suppressing photosynthesis, activating antioxidant systems, and recruiting osmoregulators. This study provides a basis for elucidating the growth mechanisms of N. sibirica under long-term drought stress conditions.

Mechanically-primed voltage-gated proton channels from angiosperm plants.

Voltage-gated and mechanically-gated ion channels are distinct classes of membrane proteins that conduct ions across gated pores and are turned on by electrical or mechanical stimuli, respectively. Here, we describe an Hv channel (a.k.a voltage-dependent H+ channel) from the angiosperm plant A. thaliana that gates with a unique modality as it is turned on by an electrical stimulus only after exposure to a mechanical stimulus, a process that we call priming. The channel localizes in the vascular tissue and has homologs in vascular plants. We find that mechanical priming is not required for activation of non-angiosperm Hvs. Guided by AI-generated structural models of plant Hv homologs, we identify a set of residues playing a crucial role in mechanical priming. We propose that Hvs from angiosperm plants require priming because of a network of hydrophilic/charged residues that locks the channels in a silent resting conformation. Mechanical stimuli destabilize the network allowing the conduction pathway to turn on. In contrast to many other channels and receptors, Hv proteins are not thought to possess mechanisms such as inactivation or desensitization. Our findings demonstrate that angiosperm Hv channels are electrically silent until a mechanical stimulation turns on their voltage-dependent activity.

Large-scale analysis of trihelix transcription factors reveals their expansion and evolutionary footprint in plants.

The trihelix transcription factor (TTF) gene family is an important class of transcription factors that play key roles in regulating developmental processes and responding to various stresses. To date, no comprehensive analysis of the TTF gene family in large-scale species has been performed. A cross-genome exploration of its origin, copy number variation, and expression pattern in plants is also unavailable. Here, we identified and characterized the TTF gene family in 110 species representing typical plant phylogenetic taxa. Interestingly, we found that the number of TTF genes was significantly expanded in Chara braunii compared to other species. Based on the available plant genomic datasets, our comparative analysis suggested that the TTF gene family likely originated from the GT-1-1 group and then expanded to form other groups through duplication or deletion of some domains. We found evidence that whole-genome duplication/triplication contributed most to the expansion of the TTF gene family in dicots, monocots and basal angiosperms. In contrast, dispersed and proximal duplications contributed to the expansion of the TTF gene family in algae and bryophyta. The expression patterns of TTF genes and their upstream and downstream genes in different treatments showed a functional divergence of TTF-related genes. Furthermore, we constructed the interaction network between TTF genes and the corresponding upstream and downstream genes, providing a blueprint for their regulatory pathways. This study provided a cross-genome comparative analysis of TTF genes in 110 species, which contributed to understanding their copy number expansion and evolutionary footprint in plants.

Spatio-temporal expression of candidate genes for nectar spur development in Tropaeolum (Tropaeolaceae: Brassicales).

BACKGROUND AND AIMS: Tropaeolaceae (Brassicales) comprise ~100 species native to South and Central America. Tropaeolaceae flowers have a nectar spur, formed by a late expansion and evagination of the fused proximal region of the perianth (i.e. the floral tube). This spur is formed in the domain of the tube oriented towards the inflorescence axis, which corresponds to the adaxial floral region. However, little is known about the molecular mechanisms responsible for the evolution of spurs in Tropaeolaceae. METHODS: In this study, we examined the spatio-temporal expression of genes putatively responsible for differential patterns of cell division between the adaxial and abaxial floral regions in Tropaeolaceae. These genes include previously identified TCP and KNOX transcription factors and the cell division marker HISTONE H4 (HIS4). KEY RESULTS: We found a TCP4 homologue concomitantly expressed with spur initiation and elaboration. Tropaeolaceae possess two TCP4-like (TCP4L) copies, as a result of a Tropaeolaceae-specific duplication. The two copies (TCP4L1 and TCP4L2) in Tropaeolum longifolium show overlapping expression in the epidermis of reproductive apices (inflorescence meristems) and young floral buds, but only TlTCP4L2 shows differential expression in the floral tube at early stages of spur formation, restricted to the adaxial region. This adaxial expression of TlTCP4L2 overlaps with the expression of TlHIS4. Later in development, only TlTCP4L2 is expressed in the nectariferous tissue of the spur. CONCLUSIONS: Based on these results, we hypothesize that Tropaeolaceae TCP4L genes had a plesiomorphic role in epidermal development and that, after gene duplication, TCP4L2 acquired a new function in spur initiation and elaboration. To better understand spur evolution in Tropaeolaceae, it is critical to expand developmental genetic studies to their sister group, the Akaniaceae, which possess simultaneously an independent duplication of TCP4L genes and a spurless floral tube.

Genome-wide analyses of calmodulin and calmodulin-like proteins in the halophyte Nitraria sibirica reveal their involvement in response to salinity, drought and cold stress.

The calmodulin (CaM) and calmodulin-like (CML) proteins are major calcium sensors that play a critical role in environmental stimulus response in plants. Nevertheless, the CaM/CML proteins from the specific plants with extreme tolerance to abiotic stresses remained so far uncharacterized. In this study, 66 candidate proteins (three NsCaMs and sixty-three NsCMLs) were identified from the halophyte Nitraria sibirica, which can withstand an extreme salinity. Bioinformatic analysis of upstream cis-acting elements predicted the potential involvement of NsCaM/CMLs in abiotic stress responses and various hormone responses. Additionally, the Nitraria sibirica transcriptome revealed that 17 and 7 NsCMLs were significantly upregulated under 100 mM or 400 mM NaCl treatment. Transcription of most salt-responsive genes was similarly upregulated under cold stress, yet downregulated under drought treatment. Moreover, predictive subcellular localization analysis suggested that the stress-responsive NsCML proteins mainly localize at the cellular membrane and within the nucleus. Furthermore, transgenic overexpression of two NsCMLs (NISI03G1136 and NISI01G1645) was found to mitigate H2O2 accumulation caused by salt stress. These results provide insights into the potential function of Nitraria sibirica CaM/CML proteins, which could aid the investigation of molecular mechanisms of extreme tolerance to abiotic stresses in halophytes.

Reinventing metabolic pathways: Independent evolution of benzoxazinoids in flowering plants.

Benzoxazinoids (BXDs) form a class of indole-derived specialized plant metabolites with broad antimicrobial and antifeedant properties. Unlike most specialized metabolites, which are typically lineage-specific, BXDs occur sporadically in a number of distantly related plant orders. This observation suggests that BXD biosynthesis arose independently numerous times in the plant kingdom. However, although decades of research in the grasses have led to the elucidation of the BXD pathway in the monocots, the biosynthesis of BXDs in eudicots is unknown. Here, we used a metabolomic and transcriptomic-guided approach, in combination with pathway reconstitution in Nicotiana benthamiana, to identify and characterize the BXD biosynthetic pathways from both Aphelandra squarrosa and Lamium galeobdolon, two phylogenetically distant eudicot species. We show that BXD biosynthesis in A. squarrosa and L. galeobdolon utilize a dual-function flavin-containing monooxygenase in place of two distinct cytochrome P450s, as is the case in the grasses. In addition, we identified evolutionarily unrelated cytochrome P450s, a 2-oxoglutarate-dependent dioxygenase, a UDP-glucosyltransferase, and a methyltransferase that were also recruited into these BXD biosynthetic pathways. Our findings constitute the discovery of BXD pathways in eudicots. Moreover, the biosynthetic enzymes of these pathways clearly demonstrate that BXDs independently arose in the plant kingdom at least three times. The heterogeneous pool of identified BXD enzymes represents a remarkable example of metabolic plasticity, in which BXDs are synthesized according to a similar chemical logic, but with an entirely different set of metabolic enzymes.

Chlorahololide D, a Lindenane-Type Sesquiterpenoid Dimer from Chloranthus holostegius Suppressing Breast Cancer Progression.

Aimed at discovering small molecules as anticancer drugs or lead compounds from plants, a lindenane-type sesquiterpene dimer, chlorahololide D, was isolated from Chloranthus holostegius. The literature review showed that there were few reports on the antitumor effects and mechanisms of chlorahololide D. Our biological assay suggested that chlorahololide D blocked the growth and triggered apoptosis of MCF-7 cells by stimulating the reactive oxygen species (ROS) levels and arresting the cell cycle at the G2 stage. Further mechanism exploration suggested that chlorahololide D regulated apoptosis-related proteins Bcl-2 and Bax. Moreover, chlorahololide D inhibited cell migration by regulating the FAK signaling pathway. In the zebrafish xenograft model, chlorahololide D was observed to suppress tumor proliferation and migration significantly. Considering the crucial function of angiogenesis in tumor development, the anti-angiogenesis of chlorahololide D was also investigated. All of the research preliminarily revealed that chlorahololide D could become an anti-breast cancer drug.

MYB transcription factors and their roles in the male reproductive development of flowering plants.

As one of the largest transcription factor families with complex functional differentiation in plants, the MYB transcription factors (MYB TFs) play important roles in the physiological and biochemical processes of plant growth and development. Male reproductive development, an essential part of sexual reproduction in flowering plants, is undoubtedly regulated by MYB TFs. In this review, we summarize the roles of the MYB TFs involved in the three stages of male reproductive development: pollen grains formation and maturation, filament elongation and anther dehiscence, and fertilization. Also, the potential downstream target genes and upstream regulators of these MYB TFs are discussed. Furthermore, we propose the underlying regulatory mechanisms of these MYB TFs: (1) A complex network of MYB TFs regulates various aspects of male reproductive development; (2) MYB homologous genes in different species may be functionally conserved or differentiated; (3) MYB TFs often form regulatory complexes with bHLH TFs.

In-silico, evolutionary, and functional analysis of CHUP1 and its related proteins in Bienertia sinuspersici-a comparative study across C3, C4, CAM, and SCC4 model plants.

Single-cell C4 (SCC4) plants with bienertioid anatomy carry out photosynthesis in a single cell. Chloroplast movement is the underlying phenomenon, where chloroplast unusual positioning 1 (CHUP1) plays a key role. This study aimed to characterize CHUP1 and CHUP1-like proteins in an SCC4 photosynthetic plant, Bienertia sinuspersici. Also, a comparative analysis of SCC4 CHUP1 was made with C3, C4, and CAM model plants including an extant basal angiosperm, Amborella. The CHUP1 gene exists as a single copy from the basal angiosperms to SCC4 plants. Our analysis identified that Chenopodium quinoa, a recently duplicated allotetraploid, has two copies of CHUP1. In addition, the numbers of CHUP1-like and its associated proteins such as CHUP1-like_a, CHUP1-like_b, HPR, TPR, and ABP varied between the species. Hidden Markov Model analysis showed that the gene size of CHUP1-like_a and CHUP1-like_b of SCC4 species, Bienertia, and Suaeda were enlarged than other plants. Also, we identified that CHUP1-like_a and CHUP1-like_b are absent in Arabidopsis and Amborella, respectively. Motif analysis identified several conserved and variable motifs based on the orders (monocot and dicot) as well as photosynthetic pathways. For instance, CAM plants such as pineapple and cactus shared certain motifs of CHUP1-like_a irrespective of their distant phylogenetic relationship. The free ratio model showed that CHUP1 maintained purifying selection, whereas CHUP1-like_a and CHUP1-like_b have adaptive functions between SCC4 plants and quinoa. Similarly, rice and maize branches displayed functional diversification on CHUP1-like_b. Relative gene expression data showed that during the subcellular compartmentalization process of Bienertia, CHUP1 and actin-binding proteins (ABP) genes showed a similar pattern of expression. Altogether, the results of this study provide insight into the evolutionary and functional details of CHUP1 and its associated proteins in the development of the SCC4 system in comparison with other C3, C4, and CAM model plants.

Activation of Strigolactone Biosynthesis by the DWARF14-LIKE/KARRIKIN-INSENSITIVE2 Pathway in Mycorrhizal Angiosperms, but Not in Arabidopsis, a Non-mycorrhizal Plant.

Strigolactones (SLs) are a class of plant hormones that regulate many aspects of plant growth and development. SLs also improve symbiosis with arbuscular mycorrhizal fungi (AMF) in the rhizosphere. Recent studies have shown that the DWARF14-LIKE (D14L)/KARRIKIN-INSENSITIVE2 (KAI2) family, paralogs of the SL receptor D14, are required for AMF colonization in several flowering plants, including rice. In this study, we found that (-)-GR5, a 2'S-configured enantiomer of a synthetic SL analog (+)-GR5, significantly activated SL biosynthesis in rice roots via D14L. This result is consistent with a recent report, showing that the D14L pathway positively regulates SL biosynthesis in rice. In fact, the SL levels tended to be lower in the roots of the d14l mutant under both inorganic nutrient-deficient and -sufficient conditions. We also show that the increase in SL levels by (-)-GR5 was observed in other mycorrhizal plant species. In contrast, the KAI2 pathway did not upregulate the SL level and the expression of SL biosynthetic genes in Arabidopsis, a non-mycorrhizal plant. We also examined whether the KAI2 pathway enhances SL biosynthesis in the liverwort Marchantia paleacea, where SL functions as a rhizosphere signaling molecule for AMF. However, the SL level and SL biosynthetic genes were not positively regulated by the KAI2 pathway. These results imply that the activation of SL biosynthesis by the D14L/KAI2 pathway has been evolutionarily acquired after the divergence of bryophytes to efficiently promote symbiosis with AMF, although we cannot exclude the possibility that liverworts have specifically lost this regulatory system.