The Cys-2088-Arg mutation in the ACCase gene and enhanced metabolism confer cyhalofop-butyl resistance in Chinese sprangletop (Leptochloa chinensis).

Acetyl-CoA carboxylase (ACCase)-inhibiting herbicides are among the most commonly used herbicides to control grassy weeds, especially Leptochloa chinensis, in rice fields across China. Herein, we collected a suspected resistant (R) population of L. chinensis (HFLJ16) from Lujiang county in Anhui Province. Whole plant dose response tests showed that, compared with the susceptible (S) population, the R population showed high resistance to cyhalofop-butyl (22-fold) and displayed cross-resistance to metamifop (9.7-fold), fenoxaprop-P-ethyl (18.7-fold), quizalofop-P-ethyl (7.6-fold), clodinafop-propargyl (12-fold) and clethodim (8.4-fold). We detected an amino acid substitution (Cys-2088-Arg) in the ACCase of resistant L. chinensis. However, ACCase gene expression levels were not significantly different (P > 0.05) between R plants and S plants, without or with cyhalofop-butyl treatment. Furthermore, pretreatment with piperonyl butoxide (PBO, a cytochrome P450 monooxygenase (CYP450) inhibitor) or 4-chloro-7-nitrobenzoxadiazole (NBD-Cl, a glutathione-S-transferase (GST) inhibitor), inhibited the resistance of the R population to cyhalofop-butyl significantly (by approximately 60% and 26%, respectively). Liquid chromatography tandem mass spectrometry analysis showed that R plants metabolized cyhalofop-butyl and cyhalofop acid (its metabolite) significantly faster than S plants. Three CYP450 genes, one GST gene, and two ABC transporter genes were induced by cyhalofop-butyl and were overexpressed in the R population. Overall, GST-associated detoxification, CYP450 enhancement, and target-site gene mutation are responsible for the resistance of L. chinensis to cyhalofop-butyl.

Using sentinel-2 satellite images and machine learning algorithms to predict tropical pasture forage mass, crude protein, and fiber content.

Grasslands cover approximately 24% of the Earth's surface and are the main feed source for cattle and other ruminants. Sustainable and efficient grazing systems require regular monitoring of the quantity and nutritive value of pastures. This study demonstrates the potential of estimating pasture leaf forage mass (FM), crude protein (CP) and fiber content of tropical pastures using Sentinel-2 satellite images and machine learning algorithms. Field datasets and satellite images were assessed from an experimental area of Marandu palisade grass (Urochloa brizantha sny. Brachiaria brizantha) pastures, with or without nitrogen fertilization, and managed under continuous stocking during the pasture growing season from 2016 to 2020. Models based on support vector regression (SVR) and random forest (RF) machine-learning algorithms were developed using meteorological data, spectral reflectance, and vegetation indices (VI) as input features. In general, SVR slightly outperformed the RF models. The best predictive models to estimate FM were those with VI combined with meteorological data. For CP and fiber content, the best predictions were achieved using a combination of spectral bands and meteorological data, resulting in R2 of 0.66 and 0.57, and RMSPE of 0.03 and 0.04 g/g dry matter. Our results have promising potential to improve precision feeding technologies and decision support tools for efficient grazing management.

A rice GT61 glycosyltransferase possesses dual activities mediating 2-O-xylosyl and 2-O-arabinosyl substitutions of xylan.

MAIN CONCLUSION: A member of the rice GT61 clade B is capable of transferring both 2-O-xylosyl and 2-O-arabinosyl residues onto xylan and another member specifically catalyses addition of 2-O-xylosyl residue onto xylan. Grass xylan is substituted predominantly with 3-O-arabinofuranose (Araf) as well as with some minor side chains, such as 2-O-Araf and 2-O-(methyl)glucuronic acid [(Me)GlcA]. 3-O-Arabinosylation of grass xylan has been shown to be catalysed by grass-expanded clade A members of the glycosyltransferase family 61. However, glycosyltransferases mediating 2-O-arabinosylation of grass xylan remain elusive. Here, we performed biochemical studies of two rice GT61 clade B members and found that one of them was capable of transferring both xylosyl (Xyl) and Araf residues from UDP-Xyl and UDP-Araf, respectively, onto xylooligomer acceptors, whereas the other specifically catalysed Xyl transfer onto xylooligomers, indicating that the former is a xylan xylosyl/arabinosyl transferase (named OsXXAT1 herein) and the latter is a xylan xylosyltransferase (named OsXYXT2). Structural analysis of the OsXXAT1- and OsXYXT2-catalysed reaction products revealed that the Xyl and Araf residues were transferred onto O-2 positions of xylooligomers. Furthermore, we demonstrated that OsXXAT1 and OsXYXT2 were able to substitute acetylated xylooligomers, but only OsXXAT1 could xylosylate GlcA-substituted xylooligomers. OsXXAT1 and OsXYXT2 were predicted to adopt a GT-B fold structure and molecular docking revealed candidate amino acid residues at the predicted active site involved in binding of the nucleotide sugar donor and the xylohexaose acceptor substrates. Together, our results establish that OsXXAT1 is a xylan 2-O-xylosyl/2-O-arabinosyl transferase and OsXYXT2 is a xylan 2-O-xylosyltransferase, which expands our knowledge of roles of the GT61 family in grass xylan synthesis.

Phenological characteristics of net ecosystem carbon exchange of Stipa krylovii steppe in Inner Mongolia, China and its remote sensing monitoring.

To accurately monitor the phenology of net ecosystem carbon exchange (NEE) in grasslands with remote sensing, we analyzed the variations in NEE and its phenology in the Stipa krylovii steppe and discussed the remote sensing vegetation index thresholds for NEE phenology, with the observational data from the Inner Mongolia Xilinhot National Climate Observatory's eddy covariance system and meteorological gradient observation system during 2018-2021, as well as Sentinel-2 satellite data from January 1, 2018 to December 31, 2021. Results showed that, from 2018 to 2021, NEE exhibited seasonal variations, with carbon sequestration occurring from April to October and carbon emission in other months, resulting in an overall carbon sink. The average Julian days for the start date (SCUP) and the end date (ECUP) of carbon uptake period were the 95th and 259th days, respectively, with an average carbon uptake period lasting 165 days. Photosynthetically active radiation showed a negative correlation with daily NEE, contributing to carbon absorption of grasslands. The optimal threshold for capturing SCUP was a 10% threshold of the red-edge chlorophyll index, while the normalized difference vegetation index effectively reflected ECUP with a threshold of 75%. These findings would provide a basis for remote sensing monitoring of grassland carbon source-sink dynamics.

Genome-wide analysis of the KNOX gene family in Moso bamboo: insights into their role in promoting the rapid shoot growth.

BACKGROUND: KNOTTED1-like homeobox (KNOX) genes, plant-specific homologous box transcription factors (TFs), play a central role in regulating plant growth, development, organ formation, and response to biotic and abiotic stresses. However, a comprehensive genome-wide identification of the KNOX genes in Moso bamboo (Phyllostachys edulis), the fastest growing plant, has not yet been conducted, and the specific biological functions of this family remain unknown. RESULTS: The expression profiles of 24 KNOX genes, divided into two subfamilies, were determined by integrating Moso bamboo genome and its transcriptional data. The KNOX gene promoters were found to contain several light and stress-related cis-acting elements. Synteny analysis revealed stronger similarity with rice KNOX genes than with Arabidopsis KNOX genes. Additionally, several conserved structural domains and motifs were identified in the KNOX proteins. The expansion of the KNOX gene family was primarily regulated by tandem duplications. Furthermore, the KNOX genes were responsive to naphthaleneacetic acid (NAA) and gibberellin (GA) hormones, exhibiting distinct temporal expression patterns in four different organs of Moso bamboo. Short Time-series Expression Miner (STEM) analysis and quantitative real-time PCR (qRT-PCR) assays demonstrated that PeKNOX genes may play a role in promoting rapid shoot growth. Additionally, Gene Ontology (GO) and Protein-Protein Interaction (PPI) network enrichment analyses revealed several functional annotations for PeKNOXs. By regulating downstream target genes, PeKNOXs are involved in the synthesis of AUX /IAA, ultimately affecting cell division and elongation. CONCLUSIONS: In the present study, we identified and characterized a total of 24 KNOX genes in Moso bamboo and investigated their physiological properties and conserved structural domains. To understand their functional roles, we conducted an analysis of gene expression profiles using STEM and RNA-seq data. This analysis successfully revealed regulatory networks of the KNOX genes, involving both upstream and downstream genes. Furthermore, the KNOX genes are involved in the AUX/IAA metabolic pathway, which accelerates shoot growth by influencing downstream target genes. These results provide a theoretical foundation for studying the molecular mechanisms underlying the rapid growth and establish the groundwork for future research into the functions and transcriptional regulatory networks of the KNOX gene family.

MsHDZ23, a Novel Miscanthus HD-ZIP Transcription Factor, Participates in Tolerance to Multiple Abiotic Stresses.

The homeodomain-leucine zipper (HD-ZIP) transcription factors, representing one of the largest plant-specific superfamilies, play important roles in the response to various abiotic stresses. However, the functional roles of HD-ZIPs in abiotic stress tolerance and the underlying mechanisms remain relatively limited in Miscanthus sinensis. In this study, we isolated an HD-ZIP TF gene, MsHDZ23, from Miscanthus and ectopically expressed it in Arabidopsis. Transcriptome and promoter analyses revealed that MsHDZ23 responded to salt, alkali, and drought treatments. The overexpression (OE) of MsHDZ23 in Arabidopsis conferred higher tolerance to salt and alkali stresses compared to wild-type (WT) plants. Moreover, MsHDZ23 was able to restore the hb7 mutant, the ortholog of MsHDZ23 in Arabidopsis, to the WT phenotype. Furthermore, MsHDZ23-OE lines exhibited significantly enhanced drought stress tolerance, as evidenced by higher survival rates and lower water loss rates compared to WT. The improved drought tolerance may be attributed to the significantly smaller stomatal aperture in MsHDZ23-OE lines compared to WT. Furthermore, the accumulation of the malondialdehyde (MDA) under abiotic stresses was significantly decreased, accompanied by dramatically enhanced activities in several antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the transgenic plants. Collectively, these results demonstrate that MsHDZ23 functions as a multifunctional transcription factor in enhancing plant resistance to abiotic stresses.

Interactions between Epichloë endophyte and the plant microbiome impact nitrogen responses in host Achnatherum inebrians plants.

The clavicipitaceous fungus Epichloë gansuensis forms symbiotic associations with drunken horse grass (Achnatherum inebrians), providing biotic and abiotic stress protection to its host. However, it is unclear how E. gansuensis affects the assembly of host plant-associated bacterial communities after ammonium nitrogen (NH4+-N) treatment. We examined the shoot- and root-associated bacterial microbiota and root metabolites of A. inebrians when infected (I) or uninfected (F) with E. gansuensis endophyte. The results showed more pronounced NH4+-N-induced microbial and metabolic changes in the endophyte-infected plants compared to the endophyte-free plants. E. gansuensis significantly altered bacterial community composition and ß-diversity in shoots and roots and increased bacterial α-diversity under NH4+-N treatment. The relative abundance of 117 and 157 root metabolites significantly changed with E. gansuensis infection under water and NH4+-N treatment compared to endophyte-free plants. Root bacterial community composition was significantly related to the abundance of the top 30 metabolites [variable importance in the projection (VIP) > 2 and VIP > 3] contributing to differences between I and F plants, especially alkaloids. The correlation network between root microbiome and metabolites was complex. Microorganisms in the Proteobacteria and Firmicutes phyla were significantly associated with the R00693 metabolic reaction of cysteine and methionine metabolism. Co-metabolism network analysis revealed common metabolites between host plants and microorganisms.IMPORTANCEOur results suggest that the effect of endophyte infection is sensitive to nitrogen availability. Endophyte symbiosis altered the composition of shoot and root bacterial communities, increasing bacterial diversity. There was also a change in the class and relative abundance of metabolites. We found a complex co-occurrence network between root microorganisms and metabolites, with some metabolites shared between the host plant and its microbiome. The precise ecological function of the metabolites produced in response to endophyte infection remains unknown. However, some of these compounds may facilitate plant-microbe symbiosis by increasing the uptake of beneficial soil bacteria into plant tissues. Overall, these findings advance our understanding of the interactions between the microbiome, metabolome, and endophyte symbiosis in grasses. The results provide critical insight into the mechanisms by which the plant microbiome responds to nutrient stress in the presence of fungal endophytes.

Transcriptomic and physiological analyses of Trichoderma citrinoviride HT-1 assisted phytoremediation of Cd contaminated water by Phragmites australis.

Plant growth promoting microbe assisted phytoremediation is considered a more effective approach to rehabilitation than the single use of plants, but underlying mechanism is still unclear. In this study, we combined transcriptomic and physiological methods to explore the mechanism of plant growth promoting microbe Trichoderma citrinoviride HT-1 assisted phytoremediation of Cd contaminated water by Phragmites australis. The results show that the strain HT-1 significantly promoted P. australis growth, increased the photosynthetic rate, enhanced antioxidant enzyme activities. The chlorophyll content and the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were increased by 83.78%, 23.17%, 47.60%, 97.14% and 12.23% on average, and decreased the content of malondialdehyde (MDA) by 31.10%. At the same time, strain HT-1 improved the absorption and transport of Cd in P. australis, and the removal rate of Cd was increased by 7.56% on average. Transcriptome analysis showed that strain HT-1 induced significant up-regulated the expression of genes related to oxidative phosphorylation and ribosome pathways, and these upregulated genes promoted P. australis remediation efficiency and resistance to Cd stress. Our results provide a mechanistic understanding of plant growth promoting microbe assisted phytoremediation under Cd stress.

Enhancing phytoremediation of cadmium and arsenic in alkaline soil by Miscanthus sinensis: A study on the synergistic effect of endophytic fungi and biochar.

Endophytic fungi (Trichoderma harzianum (TH) and Paecilomyces lilacinus (PL)) showed potential in phytoremediation for soils contaminated with potentially toxic elements (PTEs (Cd and As)). However, their efficiency is limited, which can be enhanced with the assistance of biochar. This study sought to investigate the effects of TH at two application rates (T1: 4.5 g m-2; T2: 9 g m-2), PL at two application rates (P1: 4.5 g m-2; P2: 9 g m-2), in conjunction with biochar (BC) at 750 g m-2 on the phytoremediation of PTEs by Miscanthus sinensis (M. sinensis). The results showed that the integration of endophytic fungi with biochar notably enhanced the accumulation of Cd and As in M. sinensis by 59.60 %-114.38 % and 49.91 %-134.60 %, respectively. The treatments T2BC and P2BC emerged as the most effective. Specifically, the P2BC treatment significantly enhanced the soil quality index (SQI > 0.55) across all examined soil layers, markedly improving the overall soil condition. It was observed that T2BC treatment could elevate the SQI to 0.56 at the 0-15 cm depth. The combined amendment shifted the primary influences on plant PTEs accumulation from fungal diversity and soil nutrients to bacterial diversity and the availability of soil PTEs. Characteristic microorganisms identified under the combined treatments were RB41 and Pezizaceae, indicating an increase in both bacterial and fungal diversity. This combination altered the soil microbial community, influencing key metabolic pathways. The combined application of PL and biochar was superior to the TH and biochar combination for the phytoremediation of M. sinensis. This approach not only enhanced the phytoremediation potential but also positively impacted soil health and microbial community, suggesting that the synergistic use of endophytic fungi and biochar is an effective strategy for improving the condition of alkaline soils contaminated with PTEs.

Biochar loaded with root exudates of hyperaccumulator Leersia hexandra Swartz facilitated Cr(VI) reduction by shaping soil functional microbial communities.

Cr(VI) contamination is widely recognized as one of the major environmental hazards. To address the problem of remediation of soil Cr(VI) contamination and utilization of waste peanut shells, this study comprehensively investigated the effects of peanut shell-derived biochar loaded with root exudates of hyperaccumulator Leersia hexandra Swartz on Cr(VI) reduction and microbial community succession in soil. This study confirmed that root exudate-loaded peanut shell biochar reduced soil pH while simultaneously increasing DOC, sulfide, and Fe(II) concentrations, thereby facilitating the reduction of Cr(VI), achieving a reduction efficiency of 81.8%. Based on XPS and SEM elemental mapping analyses, Cr(VI) reduction occurred concurrently with the Fe and S redox cycles. Furthermore, the microbial diversity, abundance of the functional genera (Geobacter, Arthrobacter, and Desulfococcus) and the metabolic functions associated with Cr(VI) reduction were enhanced by root exudate-loaded biochar. Root exudate-loaded biochar can promote both direct Cr(VI) reduction mediated by the Cr(VI)-reducing bacteria Arthrobacter, and indirect Cr(VI) reduction through Cr/S/Fe co-transformation mediated by the sulfate-reducing bacteria Desulfococcus and Fe(III)-reducing bacteria Geobacter. This study demonstrates the effectiveness of peanut shell biochar loaded with root exudates of hyperaccumulator Leersia hexandra Swartz to promote soil Cr(VI) reduction, reveals the mechanism how root exudate-loaded biochar shapes functional microbial communities to facilitate Cr(VI) reduction, and proposes a viable strategy for Cr(VI) remediation and utilization of peanut shell.

Coupling of a Major Allergen to the Surface of Immune Cells for Use in Prophylactic Cell Therapy for the Prevention of IgE-Mediated Allergy.

Up to a third of the world's population suffers from allergies, yet the effectiveness of available preventative measures remains, at large, poor. Consequently, the development of successful prophylactic strategies for the induction of tolerance against allergens is crucial. In proof-of-concept studies, our laboratory has previously shown that the transfer of autologous hematopoietic stem cells (HSC) or autologous B cells expressing a major grass pollen allergen, Phl p 5, induces robust tolerance in mice. However, eventual clinical translation would require safe allergen expression without the need for retroviral transduction. Therefore, we aimed to chemically couple Phl p 5 to the surface of leukocytes and tested their ability to induce tolerance. Phl p 5 was coupled by two separate techniques, either by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) or by linkage via a lipophilic anchor, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol)-maleimide (DSPE-PEG-Mal). The effectiveness was assessed in fresh and cultured Phl p 5-coupled cells by flow cytometry, image cytometry, and immunofluorescence microscopy. Chemical coupling of Phl p 5 using EDC was robust but was followed by rapid apoptosis. DSPE-PEG-Mal-mediated linkage was also strong, but antigen levels declined due to antigen internalization. Cells coupled with Phl p 5 by either method were transferred into autologous mice. While administration of EDC-coupled splenocytes together with short course immunosuppression initially reduced Phl p 5-specific antibody levels to a moderate degree, both methods did not induce sustained tolerance towards Phl p 5 upon several subcutaneous immunizations with the allergen. Overall, our results demonstrate the successful chemical linkage of an allergen to leukocytes using two separate techniques, eliminating the risks of genetic modifications. More durable surface expression still needs to be achieved for use in prophylactic cell therapy protocols.

Exploring Aegilops caudata: A Comprehensive Study of the CslF6 Gene and ß-Glucan.

In the quest for sustainable and nutritious food sources, exploration of ancient grains and wild relatives of cultivated cereals has gained attention. Aegilops caudata, a wild wheatgrass species, stands out as a promising genetic resource due to its potential for crop enhancement and intriguing nutritional properties. This manuscript investigates the CslF6 gene sequence and protein structure of Aegilops caudata, employing comparative analysis with other grass species to identify potential differences impacting ß-glucan content. The study involves comprehensive isolation and characterization of the CslF6 gene in Ae. caudata, utilizing genomic sequence analysis, protein structure prediction, and comparative genomics. Comparisons with sequences from diverse monocots reveal evolutionary relationships, highlighting high identities with wheat genomes. Specific amino acid motifs in the CslF6 enzyme sequence, particularly those proximal to key catalytic motifs, exhibit variations among monocot species. These differences likely contribute to alterations in ß-glucan composition, notably impacting the DP3:DP4 ratio, which is crucial for understanding and modulating the final ß-glucan content. The study positions Ae. caudata uniquely within the evolutionary landscape of CslF6 among monocots, suggesting potential genetic divergence or unique functional adaptations within this species. Overall, this investigation enriches our understanding of ß-glucan biosynthesis, shedding light on the role of specific amino acid residues in modulating enzymatic activity and polysaccharide composition.

Balancing trade-offs: Enhanced carbon assimilation and productivity with reduced nutritional value in a well-watered C4 pasture under a warmer CO2-enriched atmosphere.

The concentration of atmospheric CO2 and temperature are pivotal components of ecosystem productivity, carbon balance, and food security. In this study, we investigated the impacts of a warmer climate (+2 °C above ambient temperature) and an atmosphere enriched with CO2 (600 ppm) on gas exchange, antioxidant enzymatic system, growth, nutritive value, and digestibility of a well-watered, managed pasture of Megathyrsus maximus, a tropical C4 forage grass, under field conditions. Elevated [CO2] (eC) improved photosynthesis and reduced stomatal conductance, resulting in increased water use efficiency and plant C content. Under eC, stem biomass production increased without a corresponding increase in leaf biomass, leading to a smaller leaf/stem ratio. Additionally, eC had negative impacts on forage nutritive value and digestibility. Elevated temperature (eT) increased photosynthetic gains, as well as stem and leaf biomass production. However, it reduced P and K concentration, forage nutritive value, and digestibility. Under the combined conditions of eC and eT (eCeT), eT completely offset the effects of eC on the leaf/stem ratio. However, eT intensified the effects of eC on photosynthesis, leaf C concentration, biomass accumulation, and nutritive value. This resulted in a forage with 12% more acid detergent fiber content and 28% more lignin. Additionally, there was a decrease of 19% in crude protein leading to a 15% decrease in forage digestibility. These changes could potentially affect animal feeding efficiency and feedback climate change, as ruminants may experience an amplification in methane emissions. Our results highlight the critical significance of conducting multifactorial field studies when evaluating plant responses to climate change variables.

Review: Nitrogen acquisition, assimilation, and seasonal cycling in perennial grasses.

Perennial grasses seasonal nitrogen (N) cycle extends the residence and reuse time of N within the plant system, thereby enhancing N use efficiency. Currently, the mechanism of N metabolism has been extensively examined in model plants and annual grasses, and although perennial grasses exhibit similarities, they also possess distinct characteristics. Apart from assimilating and utilizing N throughout the growing season, perennial grasses also translocate N from aerial parts to perennial tissues, such as rhizomes, after autumn senescence. Subsequently, they remobilize the N from these perennial tissues to support new growth in the subsequent year, thereby ensuring their persistence. Previous studies indicate that the seasonal storage and remobilization of N in perennial grasses are not significantly associated with winter survival despite some amino acids and proteins associated with low temperature tolerance accumulating, but primarily with regrowth during the subsequent spring green-up stage. Further investigation can be conducted in perennial grasses to explore the correlation between stored N and dormant bud outgrowth in perennial tissues, such as rhizomes, during the spring green-up stage, building upon previous research on the relationship between N and axillary bud outgrowth in annual grasses. This exploration on seasonal N cycling in perennial grasses can offer valuable theoretical insights for new perennial grasses varieties with high N use efficiency through the application of gene editing and other advanced technologies.

Physiological and biochemical responses of Leersia hexandra Swartz to nickel stress: Insights into antioxidant defense mechanisms and metal detoxification strategies.

Phytoremediation is widely considered as a cost-effective method for managing heavy metal soil pollution. Leersia hexandra Swartz shows a promising potential for the remediation of heavy metals pollution, including chromium (Cr), copper (Cu), and nickel (Ni). It is vital to understand the physiological and biochemical responses of L. hexandra to Ni stress to elucidate the mechanisms underlying Ni tolerance and accumulation. Here, we examined the metabolic and transcriptomic responses of L. hexandra exposed to 40 mg/L Ni for 24 h and 14 d. After 24-h Ni stress, gene expression of glutathione metabolic cycle (GSTF1, GSTU1 and MDAR4) and superoxide dismutase (SODCC2) was significantly increased in plant leaves. Furthermore, after 14-d Ni stress, the ascorbate peroxidase (APX7), superoxide dismutase (SODCP and SOD1), and catalase (CAT) gene expression was significantly upregulated, but that of glutathione metabolic cycle (EMB2360, GSTU1, GSTU6, GSH2, GPX6, and MDAR2) was downregulated. After 24-h Ni stress, the differentially expressed metabolites (DEMs) were mainly flavonoids (45%) and flavones (20%). However, after 14-d Ni stress, the DEMs were mainly carbohydrates and their derivatives (34%), amino acids and derivatives (15%), and organic acids and derivatives (8%). Results suggest that L. hexandra adopt distinct time-dependent antioxidant and metal detoxification strategies likely associated with intracellular reduction-oxidation balance. Novel insights into the molecular mechanisms responsible for Ni tolerance in plants are presented.

Mapping the global distribution of C4 vegetation using observations and optimality theory.

Plants with the C4 photosynthesis pathway typically respond to climate change differently from more common C3-type plants, due to their distinct anatomical and biochemical characteristics. These different responses are expected to drive changes in global C4 and C3 vegetation distributions. However, current C4 vegetation distribution models may not predict this response as they do not capture multiple interacting factors and often lack observational constraints. Here, we used global observations of plant photosynthetic pathways, satellite remote sensing, and photosynthetic optimality theory to produce an observation-constrained global map of C4 vegetation. We find that global C4 vegetation coverage decreased from 17.7% to 17.1% of the land surface during 2001 to 2019. This was the net result of a reduction in C4 natural grass cover due to elevated CO2 favoring C3-type photosynthesis, and an increase in C4 crop cover, mainly from corn (maize) expansion. Using an emergent constraint approach, we estimated that C4 vegetation contributed 19.5% of global photosynthetic carbon assimilation, a value within the range of previous estimates (18-23%) but higher than the ensemble mean of dynamic global vegetation models (14 ± 13%; mean ± one standard deviation). Our study sheds insight on the critical and underappreciated role of C4 plants in the contemporary global carbon cycle.

Anti-herbivory defences delivered by Epichloë fungal endophytes: a quantitative review of alkaloid concentration variation among hosts and plant parts.

BACKGROUND AND AIMS: In the subfamily Poöideae (Poaceae), certain grass species possess anti-herbivore alkaloids synthesized by fungal endophytes that belong to the genus Epichloë (Clavicipitaceae). The protective role of these symbiotic endophytes can vary, depending on alkaloid concentrations within specific plant-endophyte associations and plant parts. METHODS: We conducted a literature review to identify articles containing alkaloid concentration data for various plant parts in six important pasture species, Lolium arundinaceum, Lolium perenne, Lolium pratense, Lolium multiflorum|Lolium rigidum and Festuca rubra, associated with their common endophytes. We considered the alkaloids lolines (1-aminopyrrolizidines), peramine (pyrrolopyrazines), ergovaline (ergot alkaloids) and lolitrem B (indole-diterpenes). While all these alkaloids have shown bioactivity against insect herbivores, ergovaline and lolitrem B are harmful for mammals. KEY RESULTS: Loline alkaloid levels were higher in the perennial grasses L. pratense and L. arundinaceum compared to the annual species L. multiflorum and L. rigidum, and higher in reproductive tissues than in vegetative structures. This is probably due to the greater biomass accumulation in perennial species that can result in higher endophyte mycelial biomass. Peramine concentrations were higher in L. perenne than in L. arundinaceum and not affected by plant part. This can be attributed to the high within-plant mobility of peramine. Ergovaline and lolitrem B, both hydrophobic compounds, were associated with plant parts where fungal mycelium is usually present, and their concentrations were higher in plant reproductive tissues. Only loline alkaloid data were sufficient for below-ground tissue analyses and concentrations were lower than in above-ground parts. CONCLUSIONS: Our study provides a comprehensive synthesis of fungal alkaloid variation across host grasses and plant parts, essential for understanding the endophyte-conferred defence extent. The patterns can be understood by considering endophyte growth within the plant and alkaloid mobility. Our study identifies research gaps, including the limited documentation of alkaloid presence in roots and the need to investigate the influence of different environmental conditions.

Non-additive effects on biodegradation of moso bamboo litter- and broadleaf tree litter-leached dissolved organic matter mixtures in a subtropical forest of southern China.

Phyllostachys pubescens (moso bamboo) has extensively expanded to subtropical broadleaf forests. However, how moso bamboo expansion influences litter-leached dissolved organic matter (DOM) biodegradation is unclear. In this study, we collected fresh leaf litter of moso bamboo and 10 broadleaf tree species from a subtropical forest in southern China and extracted litter-leached dissolved organic carbon (DOC), dissolved total nitrogen (DTN), and dissolved total phosphorus (DTP). Then, using a 42-day incubation experiment, we measured litter-leached DOM biodegradation of the selected 11 species and assessed the relative mixing effects on biodegradation of bamboo litter- and broadleaf tree litter-leached DOM mixtures with volume mixing ratios of 1:3, 1:1, and 3:1. In the litter leachates, bamboo had lower DOC:DTN ratio, DOC:DTP ratio, and DOM aromaticity (i.e., lower SUVA254 and SUVA350 values) than most broadleaf tree species. Litter-leached DOM biodegradation did not differ among bamboo, Liquidambar formosana, Vernicia fordii, and Cyclobalanopsis glauca, but was greater for bamboo than for the other seven broadleaf tree species. Leaf litter-leached DOM biodegradation correlated negatively with DOC:DTN and DOC:DTP ratios, but exhibited no significant relationship with DOM aromaticity. Regardless of volume mixing ratios, antagonistic effects were observed when bamboo litter-leached DOM was mixed with broadleaf tree litter-leached DOM with comparable biodegradation, whereas synergistic effects occurred when bamboo litter-leached DOM was mixed with broadleaf tree litter-leached DOM with lower biodegradation. The relative mixing effects on DOM biodegradation increased linearly with elevated interspecific difference in litter-leached DOM biodegradation between bamboo and broadleaf tree species across the incubation periods. These findings indicate that moso bamboo expansion will substantially alter litter-leached DOM biodegradation by improving substrate quality and changing species interactions, and the magnitudes of such changing trends are dependent on the native tree litter-leached DOM biodegradation in subtropical broadleaf forests.

Carbon and phosphorus exchange rates in arbuscular mycorrhizas depend on environmental context and differ among co-occurring plants.

Phosphorus (P) for carbon (C) exchange is the pivotal function of arbuscular mycorrhiza (AM), but how this exchange varies with soil P availability and among co-occurring plants in complex communities is still largely unknown. We collected intact plant communities in two regions differing c. 10-fold in labile inorganic P. After a 2-month glasshouse incubation, we measured 32P transfer from AM fungi (AMF) to shoots and 13C transfer from shoots to AMF using an AMF-specific fatty acid. AMF communities were assessed using molecular methods. AMF delivered a larger proportion of total shoot P in communities from high-P soils despite similar 13C allocation to AMF in roots and soil. Within communities, 13C concentration in AMF was consistently higher in grass than in blanketflower (Gaillardia aristata Pursh) roots, that is P appeared more costly for grasses. This coincided with differences in AMF taxa composition and a trend of more vesicles (storage structures) but fewer arbuscules (exchange structures) in grass roots. Additionally, 32P-for-13C exchange ratios increased with soil P for blanketflower but not grasses. Contrary to predictions, AMF transferred proportionally more P to plants in communities from high-P soils. However, the 32P-for-13C exchange differed among co-occurring plants, suggesting differential regulation of the AM symbiosis.

Differential capacity of phragmites ecotypes in remediation of inorganic contaminants in coastal ecosystems: Implications for climate change.

Remediating inorganic pollutants is an important part of protecting coastal ecosystems, which are especially at risk from the effects of climate change. Different Phragmites karka (Retz) Trin. ex Steud ecotypes were gathered from a variety of environments, and their abilities to remove inorganic contaminants from coastal wetlands were assessed. The goal is to learn how these ecotypes process innovation might help reduce the negative impacts of climate change on coastal environments. The Phragmites karka ecotype E1, found in a coastal environment in Ichkera that was impacted by residential wastewater, has higher biomass production and photosynthetic pigment content than the Phragmites karka ecotypes E2 (Kalsh) and E3 (Gatwala). Osmoprotectant accumulation was similar across ecotypes, suggesting that all were able to successfully adapt to polluted marine environments. The levels of both total soluble sugars and proteins were highest in E2. The amount of glycine betaine (GB) rose across the board, with the highest levels being found in the E3 ecotype. The study also demonstrated that differing coastal habitats significantly influenced the antioxidant activity of all ecotypes, with E1 displaying the lowest superoxide dismutase (SOD) activity, while E2 exhibited the lowest peroxidase (POD) and catalase (CAT) activities. Significant morphological changes were evident in E3, such as an expansion of the phloem, vascular bundle, and metaxylem cell areas. When compared to the E3 ecotype, the E1 and E2 ecotypes showed striking improvements across the board in leaf anatomy. Mechanistic links between architectural and physio-biochemical alterations are crucial to the ecological survival of different ecotypes of Phragmites karka in coastal environments affected by climate change. Their robustness and capacity to reduce pollution can help coastal ecosystems endure in the face of persistent climate change.