Root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism.

Root angle in crops represents a key trait for efficient capture of soil resources. Root angle is determined by competing gravitropic versus antigravitropic offset (AGO) mechanisms. Here we report a root angle regulatory gene termed ENHANCED GRAVITROPISM1 (EGT1) that encodes a putative AGO component, whose loss-of-function enhances root gravitropism. Mutations in barley and wheat EGT1 genes confer a striking root phenotype, where every root class adopts a steeper growth angle. EGT1 encodes an F-box and Tubby domain-containing protein that is highly conserved across plant species. Haplotype analysis found that natural allelic variation at the barley EGT1 locus impacts root angle. Gravitropic assays indicated that Hvegt1 roots bend more rapidly than wild-type. Transcript profiling revealed Hvegt1 roots deregulate reactive oxygen species (ROS) homeostasis and cell wall-loosening enzymes and cofactors. ROS imaging shows that Hvegt1 root basal meristem and elongation zone tissues have reduced levels. Atomic force microscopy measurements detected elongating Hvegt1 root cortical cell walls are significantly less stiff than wild-type. In situ analysis identified HvEGT1 is expressed in elongating cortical and stele tissues, which are distinct from known root gravitropic perception and response tissues in the columella and epidermis, respectively. We propose that EGT1 controls root angle by regulating cell wall stiffness in elongating root cortical tissue, counteracting the gravitropic machinery's known ability to bend the root via its outermost tissues. We conclude that root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism.

The auxin efflux carrier PIN1a regulates vascular patterning in cereal roots.

Barley (Hordeum vulgare) is an important global cereal crop and a model in genetic studies. Despite advances in characterising barley genomic resources, few mutant studies have identified genes controlling root architecture and anatomy, which plays a critical role in capturing soil resources. Our phenotypic screening of a TILLING mutant collection identified line TM5992 exhibiting a short-root phenotype compared with wild-type (WT) Morex background. Outcrossing TM5992 with barley variety Proctor and subsequent SNP array-based bulk segregant analysis, fine mapped the mutation to a cM scale. Exome sequencing pinpointed a mutation in the candidate gene HvPIN1a, further confirming this by analysing independent mutant alleles. Detailed analysis of root growth and anatomy in Hvpin1a mutant alleles exhibited a slower growth rate, shorter apical meristem and striking vascular patterning defects compared to WT. Expression and mutant analyses of PIN1 members in the closely related cereal brachypodium (Brachypodium distachyon) revealed that BdPIN1a and BdPIN1b were redundantly expressed in root vascular tissues but only Bdpin1a mutant allele displayed root vascular defects similar to Hvpin1a. We conclude that barley PIN1 genes have sub-functionalised in cereals, compared to Arabidopsis (Arabidopsis thaliana), where PIN1a sequences control root vascular patterning.

Novel Insights Into the Architecture of Macro and Microstructures in Cattle Ossa Cordis.

Ossa cordis, bones located within the heart trigones, are often classified as heterotopic or ectopic bones. Despite their high prevalence in cattle and some other bovids, little is known about their structure or development. Scanning electron microscopy, X-ray microtomography, gross dissections, and measurements showed the anatomical locations, prevalence, shapes, and measurements of the cardiac bones in both Egyptian Baladi cattle and Holstein-Friesians. All cattle (n = 12) had an Ossa cordis dextrum (average = 50.70 × 20.91 × 5.40 mm). Additionally, 80% Egyptian Baladi and 57% Holstein-Friesian had a smaller Ossa cordis sinistrum (average = 24.94 × 12.75 × 4.12 mm). Egyptian Baladi Ossa cordis were smaller than observed in Holstein-Friesians. Energy-dispersive X-ray analysis showed the elemental constitution (carbon, oxygen, calcium, nitrogen, phosphorus, sodium, and magnesium) of Ossa cordis and Cartilago cordis. These imaging techniques, plus four histological stains (hematoxylin and eosin, Crossman's trichrome, Alcian blue with Van Gieson, and Sirius Red) and microscopy, demonstrated osteoblasts, osteocytes, osteoclasts, astrocytes, blood vessels, bone marrow, lamellar and woven bone, cortical bone, trabeculations with pores and canaliculi, and fibrous components including collagen in the Ossa cordis dextrum and sinistrum. Hyaline cartilage and fibrocartilage (chondrocytes and cartilage matrix) were found within and surrounding the Ossa cordis. These findings were additionally compared against other cattle breeds and species.

Cretaceous pollen cone with three-dimensional preservation sheds light on the morphological evolution of cycads in deep time.

The Cycadales are an ancient and charismatic group of seed plants. However, their morphological evolution in deep time is poorly understood. While molecular divergence time analyses estimate a Cretaceous origin for most major living cycad clades, much of the extant diversity is inferred to be a result of Neogene diversifications. This leads to long branches throughout the cycadalean phylogeny that, with few exceptions, have yet to be rectified by unequivocal fossil cycads. We report a permineralized pollen cone from the Campanian Holz Shale located in Silverado Canyon, CA, USA (c. 80 million yr ago). This fossil was studied via serial sectioning, SEM, 3D reconstruction and phylogenetic analyses. Microsporophyll and pollen morphology indicate this cone is assignable to Skyttegaardia, a recently described genus based on disarticulated lignitized microsporophylls from the Early Cretaceous of Denmark. Data from this new species, including a simple cone architecture, anatomical details and vasculature organization, indicate cycadalean affinities for Skyttegaardia. Phylogenetic analyses support this assignment and recover Skyttegaardia as crown-group Cycadales, nested within Zamiaceae. Our findings support a Cretaceous diversification for crown-group Zamiaceae, which included the evolution of morphological divergent extinct taxa with unique traits that have yet to be widely identified in the fossil record.

Zirabia cylindrica comb. nov. provides evidence of Doyleales in the Jurassic.

PREMISE: In recent years, Doyleales have played an important role in the discussion and exploration of seed plant relationships and the origin of angiosperms. This order comprises a diversity of recently described genera with cupule-bearing compound ovulate cones recovered from Early Cretaceous deposits in North America and Asia. Their relatively late appearance in the fossil record, stratigraphically near the appearance of angiosperms in the Early Cretaceous, has been noteworthy. Here, we report a new genus of Doyleales, Zirabia gen. nov. from the Early Jurassic of Iran, that was originally described as the ginkgophyte Karkenia. METHODS: We reinvestigated material previously assigned to Karkenia cylindrica from the Lower Jurassic of the Zirab locality, Alborz Mountains, northern Iran. RESULTS: The studied specimen features a main axis bearing helically to irregularly arranged bract-cupule complexes, each composed by a long laminar bract subtending and sheathing a cupule stalk that bears a single-seeded cupule with a dorsal protrusion. The morphological features of this taxon do not conform with those of Karkenia, and suggest affinities with Doyleales rather than Ginkgoales. Within Doyleales, this fossil has a unique combination of characters indicating that it is a new genus within the order; thus, a new combination is erected, Zirabia cylindrica. CONCLUSIONS: Our results indicate that Doyleales is significantly older than previously thought, with their stratigraphic range now extending from the Lower Jurassic to the Cretaceous. The Early Jurassic occurrence of Doyleales provides important data on the emergence of seed-enclosing structures seen in seed plants throughout the Mesozoic.

Lethal and Sub-lethal Implications of Sodium Chloride Exposure for Adult Unionid Mussel Species: Eurynia dilatata and Lasmigona costata.

The elevated use of salt as a de-icing agent on roads in Canada is causing an increase in the chloride concentration of freshwater ecosystems. Freshwater Unionid mussels are a group of organisms that are sensitive to increases in chloride levels. Unionids have greater diversity in North America than anywhere else on Earth, but they are also one of the most imperiled groups of organisms. This underscores the importance of understanding the effect that increasing salt exposure has on these threatened species. There are more data on the acute toxicity of chloride to Unionids than on chronic toxicity. This study investigated the effect of chronic sodium chloride exposure on the survival and filtering activity of two Unionid species (Eurynia dilatata, and Lasmigona costata) and assessed the effect on the metabolome in L. costata hemolymph. The concentration causing mortality after 28 days of exposure was similar for E. dilatata (1893 mg Cl-/L) and L. costata (1903 mg Cl-/L). Significant changes in the metabolome of the L. costata hemolymph were observed for mussels exposed to non-lethal concentrations. For example, several phosphatidylethanolamines, several hydroxyeicosatetraenoic acids, pyropheophorbide-a, and alpha-linolenic acid were significantly upregulated in the hemolymph of mussels exposed to 1000 mg Cl-/L for 28 days. While no mortality occurred in the treatment, elevated metabolites in the hemolymph are an indicator of stress.

Extending beyond Gondwana: Cretaceous Cunoniaceae from western North America.

Cunoniaceae are important elements of rainforests across the Southern Hemisphere. Many of these flowering plants are considered Paleo-Antarctic Rainforest Lineages that had a Gondwanan distribution since the Paleocene. Fossils of several modern genera within the family, such as Ceratopetalum, have indicated biogeographical connections between South America and Australia in the Cenozoic. Here, we report a dramatic geographical range extension for Ceratopetalum, and Cunoniaceae as a whole, based on two exceptionally preserved fossil winged fruits from Campanian (c. 82-80 Ma old) deposits on Sucia Island, Washington, USA. The fossils were studied using physical sectioning, light microscopy, micro-computed tomography scanning and multiple phylogenetic analyses. The fossil fruits share diagnostic characters with Ceratopetalum such as the presence of four to five persistent calyx lobes, a prominent nectary disk, persistent stamens, a semi-inferior ovary and two persistent styles. Based on morphological comparisons with fruits of extant species and support from phylogenetic analyses, the fossils are assigned to a new species Ceratopetalum suciensis. These fossils are the first unequivocal evidence of crown Cunoniaceae from the Cretaceous of North America, indicating a more complicated biogeographical history for this important Gondwanan family.

Emergent Protective Organogenesis in Date Palms: A Morpho-Devo-Dynamic Adaptive Strategy during Early Development.

Desert plants have developed mechanisms for adapting to hostile desert conditions, yet these mechanisms remain poorly understood. Here, we describe two unique modes used by desert date palms (Phoenix dactylifera) to protect their meristematic tissues during early organogenesis. We used x-ray micro-computed tomography combined with high-resolution tissue imaging to reveal that, after germination, development of the embryo pauses while it remains inside a dividing and growing cotyledonary petiole. Transcriptomic and hormone analyses show that this developmental arrest is associated with the low expression of development-related genes and accumulation of hormones that promote dormancy and confer resistance to stress. Furthermore, organ-specific cell-type mapping demonstrates that organogenesis occurs inside the cotyledonary petiole, with identifiable root and shoot meristems and their respective stem cells. The plant body emerges from the surrounding tissues with developed leaves and a complex root system that maximizes efficient nutrient and water uptake. We further show that, similar to its role in Arabidopsis (Arabidopsis thaliana), the SHORT-ROOT homolog from date palms functions in maintaining stem cell activity and promoting formative divisions in the root ground tissue. Our findings provide insight into developmental programs that confer adaptive advantages in desert plants that thrive in hostile habitats.

Taxon sampling and alternative hypotheses of relationships in the euphyllophyte plexus that gave rise to seed plants: insights from an Early Devonian radiatopsid.

An abrupt transition in the fossil record separates Early Devonian euphyllophytes with a simple structure from a broad diversity of structurally complex Middle-Late Devonian plants. Morphological evolution and phylogeny across this transition are poorly understood due to incomplete sampling of the fossil record. We document a new Early Devonian radiatopsid and integrate it in analyses addressing euphyllophyte relationships. Anatomically preserved Emsian fossils (402-394 Ma) from the Battery Point Formation (Gaspé, Quebec, Canada) are studied in serial sections. The phylogenetic analysis is based on a matrix of 31 taxa and 50 characters emphasising vegetative morphology (41 discrete, nine continuous). The new plant, Kenrickia bivena gen. et sp. nov., is one of very few structurally complex euphyllophytes documented in the Early Devonian. Inclusion of Kenrickia overturns previously established phylogenetic relationships among Radiatopses, reiterating the need for increased density of Early Devonian taxon sampling. Kenrickia is recovered as the sister lineage to all other radiatopsids, a clade in which paraphyletic Stenokoleales led to a lignophyte clade where archaeopterids and seed plants fall into sister clades. Our results shed light on early euphyllophyte relationships and evolution, indicating early exploration of structural complexity by multiple lineages and reiterating the potential of a single origin of secondary growth in euphyllophytes.

The interaction between wheat roots and soil pores in structured field soil.

Wheat (Triticum aestivum L.) root growth in the subsoil is usually constrained by soil strength, although roots can use macropores to elongate to deeper layers. The quantitative relationship between the elongation of wheat roots and the soil pore system, however, is still to be determined. We studied the depth distribution of roots of six wheat varieties and explored their relationship with soil macroporosity from samples with the field structure preserved. Undisturbed soil cores (to a depth of 100 cm) were collected from the field and then non-destructively imaged using X-ray computed tomography (at a spatial resolution of 90 µm) to quantify soil macropore structure and root number density (the number of roots cm-2 within a horizontal cross-section of a soil core). Soil macroporosity changed significantly with depth but not between the different wheat lines. There was no significant difference in root number density between wheat varieties. In the subsoil, wheat roots used macropores, especially biopores (i.e. former root or earthworm channels) to grow into deeper layers. Soil macroporosity explained 59% of the variance in root number density. Our data suggested that the development of the wheat root system in the field was more affected by the soil macropore system than by genotype. On this basis, management practices which enhance the porosity of the subsoil may therefore be an effective strategy to improve deep rooting of wheat.

Fossil evidence for a Cretaceous rise of the mahogany family.

PREMISE: The mahogany family (Meliaceae) is an angiosperm lineage comprising many species that are important elements in tropical ecosystems, and is often used as a study system to understand the evolution of tropical rainforests. While divergence time studies have estimated a Cretaceous origin for the family, no unequivocal fossils of that age have been described. Here, the first Cretaceous evidence for Meliaceae is reported, based on an exceptionally well-preserved fruit from the Upper Cretaceous (79-72 Ma, Campanian) of North America. METHODS: The fossil fruit was prepared using traditional paleobotanical techniques. Bayesian phylogenetic analyses using morphological and molecular data were conducted to assess the phylogenetic position of the Cretaceous fruit in Meliaceae and to assess the effect of morphology for inferring the overall pattern of phylogeny for the family. RESULTS: The fruit consists of a fleshy mesocarp and a woody endocarp with a hollow center, nine locules, loculicidal sutures, and one subapically attached seed per locule that has an enlarged sarcotesta near the hilum. The combination of characters in this fruit is strikingly similar to the genus Melia L. Phylogenetic analyses recover the Cretaceous fruit as being closely related to Melia and highlights the effect of fruit morphological data for inferring the overall pattern of phylogeny in Meliaceae. There are a few structural differences between the fossil fruit of this study and Melia; thus, the newly characterized Cretaceous taxon is named Manchestercarpa vancouverensis gen. et sp. nov. DISCUSSION: These results clearly confirm a Cretaceous origin for Meliaceae and that important tropical families were present prior to the development of modern tropical ecosystems in the Cenozoic.

Cretaceous asterid evolution: fruits of Eydeia jerseyensis sp. nov. (Cornales) from the upper Turonian of eastern North America.

BACKGROUND AND AIMS: The asterids (>80 000 extant species) appear in the fossil record with considerable diversity near the Turonian-Coniacian boundary (~90 Ma; Late Cretaceous) and are strongly represented in the earliest diverging lineage, Cornales. These early asterid representatives have so far been reported from western North America and eastern Asia. In this study, we characterize a new cornalean taxon based on charcoalified fruits from the upper Turonian of eastern North America, a separate landmass from western North America at the time, and identify early palaeobiogeographical patterns of Cornales during the Cretaceous. METHODS: Fossils were studied and imaged using scanning electron microscopy and micro-computed tomography (micro-CT) scanning. To assess the systematic affinities of the fossils, phylogenetic analyses were conducted using maximum parsimony. KEY RESULTS: The charcoalified fruits are represented by tri-locular woody endocarps with dorsal apically opening germination valves. Three septa intersect to form a robust central axis. Endocarp ground tissue consists of two zones: an outer endocarp composed of isodiametric sclereids and an inner endocarp containing circum-locular fibres. Central vasculature is absent; however, there are several small vascular bundles scattered within the septa. Phylogenetic analysis places the new taxon within the extinct genus Eydeia. DISCUSSION: Thick-walled endocarps with apically opening germination valves, no central vascular bundle and one seed per locule are indicative of the order Cornales. Comparative analysis suggests that the fossils represent a new species, Eydeia jerseyensis sp. nov. This new taxon is the first evidence of Cornales in eastern North America during the Cretaceous and provides insights into the palaeobiogeography and initial diversification of the order.

The critical role of fossils in inferring deep-node phylogenetic relationships and macroevolutionary patterns in Cornales.

PREMISE OF THE STUDY: The basal asterid order, Cornales, experienced a rapid radiation during the Cretaceous, which has made it difficult to elucidate the early evolution of the order using extant taxa only. Recent paleobotanical studies, however, have begun to shed light on the early diversification of Cornales. Herein, fossils are directly incorporated in phylogenetic and quantitative morphological analyses to reconstruct early cornalean evolution. METHODS: A morphological matrix of 77 fruit characters and 58 taxa (24 extinct) was assembled. Parsimony analyses including and excluding fossils were conducted. A fossil inclusive tree was time-scaled to visualize the timing of the initial cornalean radiation. Disparity analyses were utilized to infer the morphological evolution of cornaleans with drupaceous fruits. KEY RESULTS: Fossil inclusive and exclusive parsimony analyses resulted in well-resolved deep-node relationships within Cornales. Resolution in the fossil inclusive analysis is substantially higher, revealing a basal grade including Loasaceae, Hydrangeaceae, Hydrostachyaceae, Grubbiaceae, a Hironoia+Amersinia clade, and Curtisiaceae, respectively, that leads to a "core" group containing a clade comprising a Cretaceous grade leading to clade of Nyssaceae, Mastixiaceae, and Davidiaceae that is sister to a Cornaceae+Alangiaceae clade. The time-scaled tree indicates that the initial cornalean diversification occurred before 89.8 Ma. Disparity analyses suggest the morphological diversity of Cornales peaked during the Paleogene. CONCLUSIONS: Phylogenetic analyses clearly demonstrate that novel character mosaics of Cretaceous cornaleans play a critical role in resolving deep-node relationships within Cornales. The post-Cretaceous increase of cornalean disparity is associated with a shift in morphospace occupation, which can be explained from ecological and developmental perspectives.

Roots-eye view: Using microdialysis and microCT to non-destructively map root nutrient depletion and accumulation zones.

Improvement in fertilizer use efficiency is a key aspect for achieving sustainable agriculture in order to minimize costs, greenhouse gas emissions, and pollution from nutrient run-off. To optimize root architecture for nutrient uptake and efficiency, we need to understand what the roots encounter in their environment. Traditional methods of nutrient sampling, such as salt extractions can only be done at the end of an experiment, are impractical for sampling locations precisely and give total nutrient values that can overestimate the nutrients available to the roots. In contrast, microdialysis provides a non-invasive, continuous method for sampling available nutrients in the soil. Here, for the first time, we have used microCT imaging to position microdialysis probes at known distances from the roots and then measured the available nitrate and ammonium. We found that nitrate accumulated close to roots whereas ammonium was depleted demonstrating that this combination of complementary techniques provides a unique ability to measure root-available nutrients non-destructively and in almost real time.

Anatomically preserved fossil cornalean fruits from the Upper Cretaceous of Hokkaido: Eydeia hokkaidoensis gen. et sp. nov.

PREMISE OF THE STUDY: The basal asterid clade Cornales radiated during the Late Cretaceous. However, our understanding of early evolutionary patterns and relationships remain obscure. New data from five permineralized fruits in calcareous concretions from the Upper Cretaceous (Coniacian-Santonian) Haborogawa Formation, Hokkaido, Japan provide anatomical details that aid our knowledge of the group. METHODS: Specimens were studied from cellulose acetate peels, and three-dimensional reconstructions were rendered using AVIZO. KEY RESULTS: Fruits are drupaceous, roughly pyriform, 2.9-4.3 mm in diameter, with a fleshy mesocarp, transition sclereids, and a stony endocarp of four to five locules, with the septa forming a cross or star-like pattern in transverse section, distinct germination valves, and one apically attached anatropous seed per locule. Vascular tissue occurs in zones between the mesocarp and exocarp, in two rows within the septa, and prominent seed bundles can be traced throughout the fruit sections. Seeds have a single integumentary layer of radially flattened square to rectangular cells and copious cellular endosperm. A fully formed, straight, cellular dicotyledonous embryo, with closely appressed, spathulate cotyledons, is present within each seed. CONCLUSIONS: The unique combination of characters shown by these fruits is found in Cornaceae, Curtisiaceae, and Davidiaceae and allows us to describe a new taxon of Cornales, Eydeia hokkaidoensis gen. et sp. nov., with many similarities to extant Davidia involucrata. These fossils underscore the phylogenetic diversification of Cornales that was underway during the Late Cretaceous and support the hypothesis that a Davidia-like fruit morphology is plesiomorphic within Cornales.

Hughmillerites vancouverensis sp. nov. and the Cretaceous diversification of Cupressaceae.

UNLABELLED: • PREMISE OF THE STUDY: Two ovulate conifer cones, one of which is attached terminally to a short leafy shoot, reveal the presence of a new species of Hughmillerites in the Early Cretaceous Apple Bay flora of Vancouver Island, British Columbia, Canada. This ancient conifer expands the diversity of Cupressaceae in the Mesozoic and reveals details about the evolution of Subfamily: Cunninghamioideae.• METHODS: Specimens were studied from anatomical sections prepared using the cellulose acetate peel technique.• KEY RESULTS: Vegetative shoots have helically arranged leaves that are Cunninghamia-like. Seed cones have many helically arranged bract/scale complexes in which the bract is larger than the ovuliferous scale. Each ovuliferous scale has three free tips that separate from the bract immediately distal to an inverted seed. Several ovuliferous scales show interseminal ridges between seeds.• CONCLUSIONS: This study documents a new extinct species of cunninghamioid conifers, Hughmillerites vancouverensis, expanding the record of the genus from the Late Jurassic to the Early Cretaceous. This new extinct species emphasizes the important role that conifers from subfamily Cunninghamioideae played in the initial evolutionary radiation of Cupressaceae. In light of recent findings in conifer regulatory genetics, we use H. vancouverensis to hypothesize that variations of expression in certain gene homologues played an important role in the evolution of the cupressaceous ovuliferous scale.

New insights into pesticide occurrence and multicompartmental monitoring strategies in stream ecosystems using periphyton and suspended sediment.

Streams are susceptible to pesticide pollutants which are transported outside of the intended area of application from surrounding agricultural fields. It is essential to monitor the occurrence and levels of pesticides in aquatic ecosystems to comprehend their effects on the aquatic environment. The common sampling strategy used for monitoring pesticides in stream ecosystems is through the collection and analysis of grab water samples. However, grab water sampling may not effectively monitor pesticides due to its limited ability to capture temporal and spatial variability, potentially missing fluctuations and uneven distribution of pesticides in aquatic environments. Monitoring using periphyton and sediment sampling may offer a more comprehensive approach by accounting for accumulative processes and temporal variations. Periphyton are a collective of microorganisms that grow on hard surfaces in aquatic ecosystems. They are responsive to chemical and biological changes in the environment, and therefore have the potential to act as a cost-effective, integrated sampling tool to monitor pesticide exposures in aquatic ecosystems. The objective of this study was to assess pesticides detected through periphyton, suspended sediment, and conventional grab water sampling methods and identify the matrix that offers a more comprehensive characterization of a stream's pesticide exposure profile. Ten streams across Southern Ontario were sampled in 2021 and 2022. At each stream site, water, sediment and periphyton, colonizing both artificial and natural substrates, were collected and analyzed for the presence of ~500 pesticides. Each of the three matrices detected distinctive pesticide exposure profiles. The frequency of detection in periphyton, sediment and water matrices were related to pesticides' log Kow and log Koc (P < 0.05). In addition, periphyton bioconcentrated 22 pesticides above levels observed in the ambient water. The bioconcentration factors of pesticides in periphyton can be predicted from their log Kow (simple linear regressions, P < 0.05). The results demonstrate that sediment and periphyton accumulate pesticides in stream environments. This highlights the importance of monitoring pesticide exposure using these matrices to ensure a complete and comprehensive characterization of exposure in stream ecosystems.

ERFVII action and modulation through oxygen-sensing in Arabidopsis thaliana.

Oxygen is a key signalling component of plant biology, and whilst an oxygen-sensing mechanism was previously described in Arabidopsis thaliana, key features of the associated PLANT CYSTEINE OXIDASE (PCO) N-degron pathway and Group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factor substrates remain untested or unknown. We demonstrate that ERFVIIs show non-autonomous activation of root hypoxia tolerance and are essential for root development and survival under oxygen limiting conditions in soil. We determine the combined effects of ERFVIIs in controlling gene expression and define genetic and environmental components required for proteasome-dependent oxygen-regulated stability of ERFVIIs through the PCO N-degron pathway. Using a plant extract, unexpected amino-terminal cysteine sulphonic acid oxidation level of ERFVIIs was observed, suggesting a requirement for additional enzymatic activity within the pathway. Our results provide a holistic understanding of the properties, functions and readouts of this oxygen-sensing mechanism defined through its role in modulating ERFVII stability.

An Assessment of the Toxicity of Pesticide Mixtures in Periphyton from Agricultural Streams to the Mayfly Neocloeon triangulifer.

Residual concentrations of pesticides are commonly found outside the intended area of application in Ontario's surface waters. Periphyton are a vital dietary component for grazing organisms in aquatic ecosystems but can also accumulate substantial levels of pesticides from the surrounding water. Consequently, grazing aquatic organisms are likely subjected to pesticide exposure through the consumption of pesticide-contaminated periphyton. The objectives of the present study were to determine if pesticides partition into periphyton in riverine environments across southern Ontario and, if so, to determine the toxicity of pesticides in periphyton when fed to the grazing mayfly Neocloeon triangulifer. Sites with low, medium, and high pesticide exposure based on historic water quality monitoring data were selected to incorporate a pesticide exposure gradient into the study design. Artificial substrate samplers were utilized to colonize periphyton in situ, which were then analyzed for the presence of approximately 500 pesticides. The results demonstrate that periphyton are capable of accumulating pesticides in agricultural streams. A novel 7-day toxicity test method was created to investigate the effects of pesticides partitioned into periphyton when fed to N. triangulifer. Periphyton collected from the field sites were fed to N. triangulifer and survival and biomass production recorded. Survival and biomass production significantly decreased when fed periphyton colonized in streams with catchments dominated by agricultural land use (p < 0.05). However, the relationship between pesticide concentration and survival or biomass production was not consistent. Using field-colonized periphyton allowed us to assess the dietary toxicity of environmentally relevant concentrations of pesticide mixtures; however, nutrition and taxonomic composition of the periphyton may vary between sites. Environ Toxicol Chem 2023;42:2143-2157. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.