AcEXPA1, an α-expansin gene, participates in the aluminum tolerance of carpetgrass (Axonopus compressus) through root growth regulation.

KEY MESSAGE: AcEXPA1, an aluminum (Al)-inducible expansin gene, is demonstrated to be involved in carpetgrass (Axonopus compressus) root elongation under Al toxicity through analyzing composite carpetgrass plants overexpressing AcEXPA1. Aluminum (Al) toxicity is a major mineral toxicity that limits plant productivity in acidic soils by inhibiting root growth. Carpetgrass (Axonopus compressus), a dominant warm-season turfgrass widely grown in acidic tropical soils, exhibits superior adaptability to Al toxicity. However, the mechanisms underlying its Al tolerance are largely unclear, and knowledge of the functional genes involved in Al detoxification in this turfgrass is limited. In this study, phenotypic variation in Al tolerance, as indicated by relative root elongation, was observed among seventeen carpetgrass genotypes. Al-responsive genes related to cell wall modification were identified in the roots of the Al-tolerant genotype 'A58' via transcriptome analysis. Among them, a gene encoding α-expansin was cloned and designated AcEXPA1 for functional characterization. Observed Al dose effects and temporal responses revealed that Al induced AcEXPA1 expression in carpetgrass roots. Subsequently, an efficient and convenient Agrobacterium rhizogenes-mediated transformation method was established to generate composite carpetgrass plants with transgenic hairy roots for investigating AcEXPA1 involvement in carpetgrass root growth under Al toxicity. AcEXPA1 was successfully overexpressed in the transgenic hairy roots, and AcEXPA1 overexpression enhanced Al tolerance in composite carpetgrass plants through a decrease in Al-induced root growth inhibition. Taken together, these findings suggest that AcEXPA1 contributes to Al tolerance in carpetgrass via root growth regulation.

Utilizing transcriptomics and proteomics to unravel key genes and proteins of Oryza sativa seedlings mediated by selenium in response to cadmium stress.

BACKGROUND: Cadmium (Cd) pollution has declined crop yields and quality. Selenium (Se) is a beneficial mineral element that protects plants from oxidative damage, thereby improving crop tolerance to heavy metals. The molecular mechanism of Se-induced Cd tolerance in rice (Oryza sativa) is not yet understood. This study aimed to elucidate the beneficial mechanism of Se (1 mg/kg) in alleviating Cd toxicity in rice seedlings. RESULTS: Exogenous selenium addition significantly improved the toxic effect of cadmium stress on rice seedlings, increasing plant height and fresh weight by 20.53% and 34.48%, respectively, and increasing chlorophyll and carotenoid content by 16.68% and 15.26%, respectively. Moreover, the MDA, ·OH, and protein carbonyl levels induced by cadmium stress were reduced by 47.65%, 67.57%, and 56.43%, respectively. Cell wall metabolism, energy cycling, and enzymatic and non-enzymatic antioxidant systems in rice seedlings were significantly enhanced. Transcriptome analysis showed that the expressions of key functional genes psbQ, psbO, psaG, psaD, atpG, and PetH were significantly up-regulated under low-concentration Se treatment, which enhanced the energy metabolism process of photosystem I and photosystem II in rice seedlings. At the same time, the up-regulation of LHCA, LHCB family, and C4H1, PRX, and atp6 functional genes improved the ability of photon capture and heavy metal ion binding in plants. Combined with proteome analysis, the expression of functional proteins OsGSTF1, OsGSTU11, OsG6PDH4, OsDHAB1, CP29, and CabE was significantly up-regulated under Se, which enhanced photosynthesis and anti-oxidative stress mechanism in rice seedlings. At the same time, it regulates the plant hormone signal transduction pathway. It up-regulates the expression response process of IAA, ABA, and JAZ to activate the synergistic effect between each cell rapidly and jointly maintain the homeostasis balance. CONCLUSION: Our results revealed the regulation process of Se-mediated critical metabolic pathways, functional genes, and proteins in rice under cadmium stress. They provided insights into the expression rules and dynamic response process of the Se-mediated plant resistance mechanism. This study provided the theoretical basis and technical support for crop safety in cropland ecosystems and cadmium-contaminated areas.

Mitochondrial alternative oxidase pathway helps in nitrooxidative stress tolerance in germinating chickpea.

Mitochondrial alternative oxidase (AOX) is an important protein that can help in regulating reactive oxygen species and nitric oxide in plants. The role of AOX in regulation of nitro-oxidative stress in chickpea is not known. Using germinating chickpea as a model system, we investigated the role of AOX in nitro-oxidative stress tolerance. NaCl treatment was used as an inducer of nitro-oxidative stress. Treatment of germinating seeds with 150 mM NaCl led to reduced germination and radicle growth. The AOX inhibitor SHAM caused further inhibition of germination, and the AOX inducer pyruvate improved growth of the radicle under NaCl stress. Isolated mitochondria from germinated seeds under salt stress not only increased AOX capacity but also enhanced AOX protein expression. Measurement of superoxide levels revealed that AOX inhibition by SHAM can enhance superoxide levels, whereas the AOX inducer pyruvate reduced superoxide levels. Measurement of NO by gas phase chemiluminescence revealed enhanced NO generation in response to NaCl treatment. Upon NaCl treatment there was enhanced tyrosine nitration, which is an indicator of nitrosative stress response. Taken together, our results revealed that AOX induced under salinity stress in germinating chickpea can help in mitigating nitro-oxidative stress, thereby improving germination.

Seed pretreatment with brassinosteroids stimulates sunflower immunity against parasitic weed (Orobanche cumana) infection.

Broomrape (Orobanche cumana) negatively affects sunflower, causing severe yield losses, and thus, there is a need to control O. cumana infestation. Brassinosteroids (BRs) play key roles in plant growth and provide resilience to weed infection. This study aims to evaluate the mechanisms by which BRs ameliorate O. cumana infection in sunflower (Helianthus annuus). Seeds were pretreated with BRs (1, 10, and 100 nM) and O. cumana inoculation for 4 weeks under soil conditions. O. cumana infection significantly reduced plant growth traits, photosynthesis, endogenous BRs and regulated the plant defence (POX, GST), BRs signalling (BAK1, BSK1 to BSK4) and synthesis (BRI1, BR6OX2) genes. O. cumana also elevated the levels of malondialdehyde (MDA), hydroxyl radical (OH-), hydrogen peroxide (H2O2) and superoxide (O2 •-) in leaves/roots by 77/112, 63/103, 56/97 and 54/89%, as well as caused ultrastructural cellular damages in both leaves and roots. In response, plants activated a few enzymes, superoxide dismutase (SOD), peroxidase (POD) and reduced glutathione but were unable to stimulate the activity of ascorbate peroxidase (APX) and catalase (CAT) enzymes. The addition of BRs (especially at 10 nM) notably recovered the ultrastructural cellular damages, lowered the production of oxidative stress, activated the key enzymatic antioxidants and induced the phenolic and lignin contents. The downregulation in the particular genes by BRs is attributed to the increased resilience of sunflower via a susceptible reaction. In a nutshell, BRs notably enhanced the sunflower resistance to O. cumana infection by escalating the plant immunity responses, inducing systemic acquired resistance, reducing oxidative or cellular damages, and modulating the expression of BR synthesis or signalling genes.

Comparative transcriptome analysis between two different cadmium-accumulating genotypes of soybean (Glycine max) in response to cadmium stress.

BACKGROUND: Cadmium (Cd) is extremely toxic and non-essential for plants. Different soybean varieties differ greatly in their Cd accumulation ability, but little is known about the underlying molecular mechanisms. RESULTS: Here, we performed transcriptomic analysis using Illumina pair-end sequencing on root tissues from two soybean varieties (su8, high-Cd-accumulating (HAS) and su7, low Cd-accumulating (LAS)) grown with 0 or 50 µM CdSO4. A total of 18.76 million clean reads from the soybean root samples were obtained after quality assessment and data filtering. After Cd treatment, 739 differentially expressed genes (DEGs; 265 up and 474 down) were found in HAS; however, only 259 DEGs (88 up and 171 down) were found in LAS, and 64 genes were same between the two varieties. Pathway enrichment analysis suggested that after cadmium treatment, the DEGs between LAS and HAS were mainly enriched in glutathione metabolism and plant-pathogen interaction pathways. KEGG analysis showed that phenylalanine metabolism responding to cadmium stress in LAS, while ABC transporters responding to cadmium stress in HAS. Besides we found more differential expressed heavy metal transporters such as ABC transporters and zinc transporters in HAS than LAS, and there were more transcription factors differently expressed in HAS than LAS after cadmium treatment in two soybean varieties, eg. bHLH transcription factor, WRKY transcription factor and ZIP transcription factor. CONCLUSIONS: Findings from this study will shed new insights on the underlying molecular mechanisms behind the Cd accumulation in soybean.

Comparative analysis of POD genes and their expression under multiple hormones in Pyrus bretschenedri.

BACKGROUND: Class III peroxidase (POD) enzymes play vital roles in plant development, hormone signaling, and stress responses. Despite extensive research on POD families in various plant species, the knowledge regarding the POD family in Chinese pear (Pyrus bretschenedri) is notably limited. RESULTS: We systematically characterized 113 POD family genes, designated as PbPOD1 to PbPOD113 based on their chromosomal locations. Phylogenetic analysis categorized these genes into seven distinct subfamilies (I to VII). The segmental duplication events were identified as a prevalent mechanism driving the expansion of the POD gene family. Microsynteny analysis, involving comparisons with Pyrus bretschenedri, Fragaria vesca, Prunus avium, Prunus mume and Prunus persica, highlighted the conservation of duplicated POD regions and their persistence through purifying selection during the evolutionary process. The expression patterns of PbPOD genes were performed across various plant organs and diverse fruit development stages using transcriptomic data. Furthermore, we identified stress-related cis-acting elements within the promoters of PbPOD genes, underscoring their involvement in hormonal and environmental stress responses. Notably, qRT-PCR analyses revealed distinctive expression patterns of PbPOD genes in response to melatonin (MEL), salicylic acid (SA), abscisic acid (ABA), and methyl jasmonate (MeJA), reflecting their responsiveness to abiotic stress and their role in fruit growth and development. CONCLUSIONS: In this study, we investigated the potential functions and evolutionary dynamics of PbPOD genes in Pyrus bretschenedri, positioning them as promising candidates for further research and valuable indicators for enhancing fruit quality through molecular breeding strategies.

Integrated transcriptome and metabolome analysis reveals the regulation of phlorizin synthesis in Lithocarpus polystachyus under nitrogen fertilization.

BACKGROUND: Nitrogen (N) is essential for plant growth and development. In Lithocarpus polystachyus Rehd., a species known for its medicinal and food value, phlorizin is the major bioactive compound with pharmacological activity. Research has revealed a positive correlation between plant nitrogen (N) content and phlorizin synthesis in this species. However, no study has analyzed the effect of N fertilization on phlorizin content and elucidated the molecular mechanisms underlying phlorizin synthesis in L. polystachyus. RESULTS: A comparison of the L. polystachyus plants grown without (0 mg/plant) and with N fertilization (25, 75, 125, 175, 225, and 275 mg/plant) revealed that 75 mg N/plant fertilization resulted in the greatest seedling height, ground diameter, crown width, and total phlorizin content. Subsequent analysis of the leaves using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detected 150 metabolites, including 42 flavonoids, that were differentially accumulated between the plants grown without and with 75 mg/plant N fertilization. Transcriptomic analysis of the L. polystachyus plants via RNA sequencing revealed 162 genes involved in flavonoid biosynthesis, among which 53 significantly differed between the N-treated and untreated plants. Fertilization (75 mg N/plant) specifically upregulated the expression of the genes phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), and phlorizin synthase (PGT1) but downregulated the expression of trans-cinnamate 4-monooxygenase (C4H), shikimate O-hydroxycinnamoyltransferase (HCT), and chalcone isomerase (CHI), which are related to phlorizin synthesis. Finally, an integrated analysis of the transcriptome and metabolome revealed that the increase in phlorizin after N fertilization was consistent with the upregulation of phlorizin biosynthetic genes. Quantitative real-time PCR (qRT‒PCR) was used to validate the RNA sequencing data. Thus, our results indicated that N fertilization increased phlorizin metabolism in L. polystachyus by regulating the expression levels of the PAL, PGT1, 5-O-(4-coumaroyl)-D-quinate 3'-monooxygenase (C3'H), C4H, and HCT genes. CONCLUSIONS: Our results demonstrated that the addition of 75 mg/plant N to L. polystachyus significantly promoted the accumulation of flavonoids, including phlorizin, and the expression of flavonoid synthesis-related genes. Under these conditions, the genes PAL, 4CL, and PGT1 were positively correlated with phlorizin accumulation, while C4H, CHI, and HCT were negatively correlated with phlorizin accumulation. Therefore, we speculate that PAL, 4CL, and PGT1 participate in the phlorizin pathway under an optimal N environment, regulating phlorizin biosynthesis. These findings provide a basis for improving plant bioactive constituents and serve as a reference for further pharmacological studies.

Transcriptome analysis reveals that trehalose alleviates chilling injury of peach fruit by regulating ROS signaling pathway and enhancing antioxidant capacity.

Peach fruit is prone to chilling injury (CI) during low-temperature storage, resulting in quality deterioration and economic losses. Our previous studies have found that exogenous trehalose treatment can alleviate the CI symptoms of peach by increasing sucrose accumulation. The purpose of this study was to explore the potential molecular mechanism of trehalose treatment in alleviating CI in postharvest peach fruit. Transcriptome analysis showed that trehalose induced gene expression in pathways of plant MAPK signaling, calcium signaling, and reactive oxygen species (ROS) signaling. Furthermore, molecular docking analysis indicated that PpCDPK24 may activate the ROS signaling pathway by phosphorylating PpRBOHE. Besides, PpWRKY40 mediates the activation of PpMAPKKK2-induced ROS signaling pathway by interacting with the PpRBOHE promoter. Accordingly, trehalose treatment significantly enhanced the activities of antioxidant-related enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and gluathione reductase (GR), as well as the transcription levels AsA-GSH cycle related gene, which led to the reduction of H2O2 and malondialdehyde (MDA) content in peach during cold storage. In summary, our results suggest that the potential molecular mechanism of trehalose treatment is to enhance antioxidant capacity by activating CDPK-mediated Ca2 + -ROS signaling pathway and WRKY-mediated MAPK-WRKY-ROS signaling pathway, thereby reducing the CI in peach fruit.

Elucidating the role of exogenous melatonin in mitigating alkaline stress in soybeans across different growth stages: a transcriptomic and metabolomic approach.

BACKGROUND: Soybean (Glycine max), a vital grain and oilseed crop, serves as a primary source of plant protein and oil. Soil salinization poses a significant threat to soybean planting, highlighting the urgency to improve soybean resilience and adaptability to saline stress. Melatonin, recently identified as a key plant growth regulator, plays crucial roles in plant growth, development, and responses to environmental stress. However, the potential of melatonin to mitigate alkali stress in soybeans and the underlying mechanisms remain unclear. RESULTS: This study investigated the effects of exogenous melatonin on the soybean cultivar Zhonghuang 13 under alkaline stress. We employed physiological, biochemical, transcriptomic, and metabolomic analyses throughout both vegetative and pod-filling growth stages. Our findings demonstrate that melatonin significantly counteracts the detrimental effects of alkaline stress on soybean plants, promoting plant growth, photosynthesis, and antioxidant capacity. Transcriptomic analysis during both growth stages under alkaline stress, with and without melatonin treatment, identified 2,834 and 549 differentially expressed genes, respectively. These genes may play a vital role in regulating plant adaptation to abiotic stress. Notably, analysis of phytohormone biosynthesis pathways revealed altered expression of key genes, particularly in the ARF (auxin response factor), AUX/IAA (auxin/indole-3-acetic acid), and GH3 (Gretchen Hagen 3) families, during the early stress response. Metabolomic analysis during the pod-filling stage identified highly expressed metabolites responding to melatonin application, such as uteolin-7-O-(2''-O-rhamnosyl)rutinoside and Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside, which helped alleviate the damage caused by alkali stress. Furthermore, we identified 183 differentially expressed transcription factors, potentially playing a critical role in regulating plant adaptation to abiotic stress. Among these, the gene SoyZH13_04G073701 is particularly noteworthy as it regulates the key differentially expressed metabolite, the terpene metabolite Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside. WGCNA analysis identified this gene (SoyZH13_04G073701) as a hub gene, positively regulating the crucial differentially expressed metabolite of terpenoids, Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside. Our findings provide novel insights into how exogenous melatonin alleviates alkali stress in soybeans at different reproductive stages. CONCLUSIONS: Integrating transcriptomic and metabolomic approaches, our study elucidates the mechanisms by which exogenous melatonin ameliorates the inhibitory effects of alkaline stress on soybean growth and development. This occurs through modulation of biosynthesis pathways for key compounds, including terpenes, flavonoids, and phenolics. Our findings provide initial mechanistic insights into how melatonin mitigates alkaline stress in soybeans, offering a foundation for molecular breeding strategies to enhance salt-alkali tolerance in this crop.

CsSHMT3 gene enhances the growth and development in cucumber seedlings under salt stress.

Salt stress is one of the major factors limiting plant growth and productivity. Many studies have shown that serine hydroxymethyltransferase (SHMT) gene play an important role in growth, development and stress response in plants. However, to date, there have been few studies on whether SHMT3 can enhance salt tolerance in plants. Therefore, the effects of overexpression or silencing of CsSHMT3 gene on cucumber seedling growth under salt stress were investigated in this study. The results showed that overexpression of CsSHMT3 gene in cucumber seedlings resulted in a significant increase in chlorophyll content, photosynthetic rate and proline (Pro) content, and antioxidant enzyme activity under salt stress condition; whereas the content of malondialdehyde (MDA), superoxide anion (H2O2), hydrogen peroxide (O2·-) and relative conductivity were significantly decreased when CsSHMT3 gene was overexpressed. However, the content of chlorophyll and Pro, photosynthetic rate, and antioxidant enzyme activity of the silenced CsSHMT3 gene lines under salt stress were significantly reduced, while MDA, H2O2, O2·- content and relative conductivity showed higher level in the silenced CsSHMT3 gene lines. It was further found that the expression of stress-related genes SOD, CAT, SOS1, SOS2, NHX, and HKT was significantly up-regulated by overexpressing CsSHMT3 gene in cucumber seedlings; while stress-related gene expression showed significant decrease in silenced CsSHMT3 gene seedlings under salt stress. This suggests that overexpression of CsSHMT3 gene increased the salt tolerance of cucumber seedlings, while silencing of CsSHMT3 gene decreased the salt tolerance. In conclusion, CsSHMT3 gene might positively regulate salt stress tolerance in cucumber and be involved in regulating antioxidant activity, osmotic adjustment, and photosynthesis under salt stress. KEY MESSAGE: CsSHMT3 gene may positively regulate the expression of osmotic system, photosynthesis, antioxidant system and stress-related genes in cucumber.

SOS1 tonoplast neo-localization and the RGG protein SALTY are important in the extreme salinity tolerance of Salicornia bigelovii.

The identification of genes involved in salinity tolerance has primarily focused on model plants and crops. However, plants naturally adapted to highly saline environments offer valuable insights into tolerance to extreme salinity. Salicornia plants grow in coastal salt marshes, stimulated by NaCl. To understand this tolerance, we generated genome sequences of two Salicornia species and analyzed the transcriptomic and proteomic responses of Salicornia bigelovii to NaCl. Subcellular membrane proteomes reveal that SbiSOS1, a homolog of the well-known SALT-OVERLY-SENSITIVE 1 (SOS1) protein, appears to localize to the tonoplast, consistent with subcellular localization assays in tobacco. This neo-localized protein can pump Na+ into the vacuole, preventing toxicity in the cytosol. We further identify 11 proteins of interest, of which SbiSALTY, substantially improves yeast growth on saline media. Structural characterization using NMR identified it as an intrinsically disordered protein, localizing to the endoplasmic reticulum in planta, where it can interact with ribosomes and RNA, stabilizing or protecting them during salt stress.

Genome-wide analysis of bZIP transcription factors and their expression patterns in response to methyl jasmonate and low-temperature stresses in Platycodon grandiflorus.

Background: Platycodon grandiflorus belongs to the genus Platycodon and has many pharmacological effects, such as expectorant, antitussive, and anti-tumor properties. Among transcription factor families peculiar to eukaryotes, the basic leucine zipper (bZIP) family is one of the most important, which exists widely in plants and participates in many biological processes, such as plant growth, development, and stress responses. However, genomic analysis of the bZIP gene family and related stress response genes has not yet been reported in P. grandiflorus. Methods: P. grandiflorus bZIP (PgbZIP) genes were first identified here, and the phylogenetic relationships and conserved motifs in the PgbZIPs were also performed. Meanwhile, gene structures, conserved domains, and the possible protein subcellular localizations of these PgbZIPs were characterized. Most importantly, the cis-regulatory elements and expression patterns of selected genes exposed to two different stresses were analyzed to provide further information on PgbZIPs potential biological roles in P. grandiflorus upon exposure to environmental stresses. Conclusions: Forty-six PgbZIPs were identified in P. grandiflorus and divided into nine groups, as displayed in the phylogenetic tree. The results of the chromosomal location and the collinearity analysis showed that forty-six PgbZIP genes were distributed on eight chromosomes, with one tandem duplication event and eleven segmental duplication events identified. Most PgbZIPs in the same phylogenetic group have similar conserved motifs, domains, and gene structures. There are cis-regulatory elements related to the methyl jasmonate (MeJA) response, low-temperature response, abscisic acid response, auxin response, and gibberellin response. Ten PgbZIP genes were selected to study their expression patterns upon exposure to low-temperature and MeJA treatments, and all ten genes responded to these stresses. The real-time quantitative polymerase chain reaction (RT-qPCR) results suggest that the expression levels of most PgbZIPs decreased significantly within 6 h and then gradually increased to normal or above normal levels over the 90 h following MeJA treatment. The expression levels of all PgbZIPs were significantly reduced after 3 h of the low-temperature treatment. These results reveal the characteristics of the PgbZIP family genes and provide valuable information for improving P. grandiflorus's ability to cope with environmental stresses during growth and development.

Transcriptome analysis reveals the molecular mechanisms underlying the enhancement of salt-tolerance in Melia azedarach under salinity stress.

Melia azedarach demonstrates strong salt tolerance and thrives in harsh saline soil conditions, but the underlying mechanisms are poorly understood. In this study, we analyzed gene expression under low, medium, and high salinity conditions to gain a deeper understanding of adaptation mechanisms of M. azedarach under salt stress. The GO (gene ontology) analysis unveiled a prominent trend: as salt stress intensified, a greater number of differentially expressed genes (DEGs) became enriched in categories related to metabolic processes, catalytic activities, and membrane components. Through the analysis of the category GO:0009651 (response to salt stress), we identified four key candidate genes (CBL7, SAPK10, EDL3, and AKT1) that play a pivotal role in salt stress responses. Furthermore, the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis revealed that DEGs were significantly enriched in the plant hormone signaling pathways and starch and sucrose metabolism under both medium and high salt exposure in comparison to low salt conditions. Notably, genes involved in JAZ and MYC2 in the jasmonic acid (JA) metabolic pathway were markedly upregulated in response to high salt stress. This study offers valuable insights into the molecular mechanisms underlying M. azedarach salt tolerance and identifies potential candidate genes for enhancing salt tolerance in M. azedarach.

Physiological and transcriptomic analyses reveal the cadmium tolerance mechanism of Miscanthus lutarioriparia.

Miscanthus lutarioriparia is a promising energy crop that is used for abandoned mine soil phytoremediation because of its high biomass yield and strong tolerance to heavy metals. However, the biological mechanism of heavy metal resistance is limited, especially for applications in the soil restoration of mining areas. Here, through the investigation of soil cadmium(Cd) in different mining areas and soil potted under Cd stress, the adsorption capacity of Miscanthus lutarioriparia was analyzed. The physiological and transcriptional effects of Cd stress on M. lutarioriparia leaves and roots under hydroponic conditions were analyzed. The results showed that M. lutarioriparia could reduce the Cd content in mining soil by 29.82%. Moreover, different Cd varieties have different Cd adsorption capacities in soils with higher Cd concentration. The highest cadmium concentrations in the aboveground and belowground parts of the plants were 185.65 mg/kg and 186.8 mg/kg, respectively. The total chlorophyll content, superoxide dismutase and catalase activities all showed a trend of increasing first and then decreasing. In total, 24,372 differentially expressed genes were obtained, including 7735 unique to leaves, 7725 unique to roots, and 8912 unique to leaves and roots, which showed differences in gene expression between leaves and roots. These genes were predominantly involved in plant hormone signal transduction, glutathione metabolism, flavonoid biosynthesis, ABC transporters, photosynthesis and the metal ion transport pathway. In addition, the number of upregulated genes was greater than the number of downregulated genes at different stress intervals, which indicated that M. lutarioriparia adapted to Cd stress mainly through positive regulation. These results lay a solid foundation for breeding excellent Cd resistant M. lutarioriparia and other plants. The results also have an important theoretical significance for further understanding the detoxification mechanism of Cd stress and the remediation of heavy metal pollution in mining soil.

Azolla filiculoides extract improved salt tolerance in wheat (Triticum aestivum L.) is associated with prompting osmostasis, antioxidant potential and stress-interrelated genes.

The growth and productivity of crop plants are negatively affected by salinity-induced ionic and oxidative stresses. This study aimed to provide insight into the interaction of NaCl-induced salinity with Azolla aqueous extract (AAE) regarding growth, antioxidant balance, and stress-responsive genes expression in wheat seedlings. In a pot experiment, wheat kernels were primed for 21 h with either deionized water or 0.1% AAE. Water-primed seedlings received either tap water, 250 mM NaCl, AAE spray, or AAE spray + NaCl. The AAE-primed seedlings received either tap water or 250 mM NaCl. Salinity lowered growth rate, chlorophyll level, and protein and amino acids pool. However, carotenoids, stress indicators (EL, MDA, and H2O2), osmomodulators (sugars, and proline), antioxidant enzymes (CAT, POD, APX, and PPO), and the expression of some stress-responsive genes (POD, PPO and PAL, PCS, and TLP) were significantly increased. However, administering AAE contributed to increased growth, balanced leaf pigments and assimilation efficacy, diminished stress indicators, rebalanced osmomodulators and antioxidant enzymes, and down-regulation of stress-induced genes in NaCl-stressed plants, with priming surpassing spray in most cases. In conclusion, AAE can be used as a green approach for sustaining regular growth and metabolism and remodelling the physio-chemical status of wheat seedlings thriving in salt-affected soils.

BR regulates wheat root salt tolerance by maintaining ROS homeostasis.

MAIN CONCLUSION: Trace amounts of epibrassinolide (EpiBL) could partially rescue wheat root length inhibition in salt-stressed situation by scavenging ROS, and ectopic expression of TaDWF4 or TaBAK1 enhances root salt tolerance in Arabidopsis by balancing ROS level. Salt stress often leads to ion toxicity and oxidative stress, causing cell structure damage and root development inhibition in plants. While prior research indicated the involvement of exogenous brassinosteroid (BR) in plant responses to salt stress, the precise cytological role and the function of BR in wheat root development under salt stress remain elusive. Our study demonstrates that 100 mM NaCl solution inhibits wheat root development, but 5 nM EpiBL partially rescues root length inhibition by decreasing H2O2 content, oxygen free radical (OFR) content, along with increasing the peroxidase (POD) and catalase (CAT) activities in salt-stressed roots. The qRT-PCR experiment also shows that expression of the ROS-scavenging genes (GPX2 and CAT2) increased in roots after applying BR, especially during salt stress situation. Transcriptional analysis reveals decreased expression of BR synthesis and root meristem development genes under salt stress in wheat roots. Differential expression gene (DEG) enrichment analysis highlights the significant impact of salt stress on various biological processes, particularly "hydrogen peroxide catabolic process" and "response to oxidative stress". Additionally, the BR biosynthesis pathway is enriched under salt stress conditions. Therefore, we investigated the involvement of wheat BR synthesis gene TaDWF4 and BR signaling gene TaBAK1 in salt stress responses in roots. Our results demonstrate that ectopic expression of TaDWF4 or TaBAK1 enhances salt tolerance in Arabidopsis by balancing ROS (Reactive oxygen species) levels in roots.

Unravelling the biostimulant activity of a protein hydrolysate in lettuce plants under optimal and low N availability: a multi-omics approach.

The application of protein hydrolysates (PH) biostimulants is considered a promising approach to promote crop growth and resilience against abiotic stresses. Nevertheless, PHs bioactivity depends on both the raw material used for their preparation and the molecular fraction applied. The present research aimed at investigating the molecular mechanisms triggered by applying a PH and its fractions on plants subjected to nitrogen limitations. To this objective, an integrated transcriptomic-metabolomic approach was used to assess lettuce plants grown under different nitrogen levels and treated with either the commercial PH Vegamin® or its molecular fractions PH1(>10 kDa), PH2 (1-10 kDa) and PH3 (<1 kDa). Regardless of nitrogen provision, biostimulant application enhanced lettuce biomass, likely through a hormone-like activity. This was confirmed by the modulation of genes involved in auxin and cytokinin synthesis, mirrored by an increase in the metabolic levels of these hormones. Consistently, PH and PH3 upregulated genes involved in cell wall growth and plasticity. Furthermore, the accumulation of specific metabolites suggested the activation of a multifaceted antioxidant machinery. Notwithstanding, the modulation of stress-response transcription factors and genes involved in detoxification processes was observed. The coordinated action of these molecular entities might underpin the increased resilience of lettuce plants against nitrogen-limiting conditions. In conclusion, integrating omics techniques allowed the elucidation of mechanistic aspects underlying PH bioactivity in crops. Most importantly, the comparison of PH with its fraction PH3 showed that, except for a few peculiarities, the effects induced were equivalent, suggesting that the highest bioactivity was ascribable to the lightest molecular fraction.

Peculiarity of the early metabolomic response in tomato after urea, ammonium or nitrate supply.

Nitrogen (N) is the nutrient most applied in agriculture as fertilizer (as nitrate, Nit; ammonium, A; and/or urea, U, forms) and its availability strongly constrains the crop growth and yield. To investigate the early response (24 h) of N-deficient tomato plants to these three N forms, a physiological and molecular study was performed. In comparison to N-deficient plants, significant changes in the transcriptional, metabolomic and ionomic profiles were observed. As a probable consequence of N mobility in plants, a wide metabolic modulation occurred in old leaves rather than in young leaves. The metabolic profile of U and A-treated plants was more similar than Nit-treated plant profile, which in turn presented the lowest metabolic modulation with respect to N-deficient condition. Urea and A forms induced some changes at the biosynthesis of secondary metabolites, amino acids and phytohormones. Interestingly, a specific up-regulation by U and down-regulation by A of carbon synthesis occurred in roots. Along with the gene expression, data suggest that the specific N form influences the activation of metabolic pathways for its assimilation (cytosolic GS/AS and/or plastidial GS/GOGAT cycle). Urea induced an up-concentration of Cu and Mn in leaves and Zn in whole plant. This study highlights a metabolic reprogramming depending on the N form applied, and it also provide evidence of a direct relationship between urea nutrition and Zn concentration. The understanding of the metabolic pathways activated by the different N forms represents a milestone in improving the efficiency of urea fertilization in crops.

Genome wide identification and expression profiling of ATP binding cassette (ABC) transporters gene family in lentil (Lens culinaris Medikus) under aluminium stress condition.

Adenosine triphosphate-binding cassette transporters (ABC transporters) are involved in regulating plant growth, development and tolerance to environmental stresses. In this study, a total of 138 ABC transporter genes were identified in the lentil genome that were classified into eight subfamilies. Four lentil ABC transporters from subfamily B and I were clustered together with the previously characterized ABC transporter proteins related to aluminium (Al) detoxification. Lentil ABC transporter genes were distributed across the chromosomes. Tandem duplication was the main driving force for expansion of the ABC gene family. Collinearity of lentil with soybean indicated that ABC gene family is closely linked to Glycine max. ABC genes in the same subfamily showed similar gene structure and conserved motifs. The ABC promoter regions harboured a large number of plant hormones and multiple stress responsive cis-regulatory elements. The qRT-PCR showed that ABC genes had varied expression in roots of lentil at different time points under Al stress. This is the first report on genome wide identification and expression analyses of genes encoding ABC transporter genes in lentil which has provided in-depth insight for future research on evolution and elucidation of molecular mechanisms for aluminium tolerance.

Physiological response and molecular mechanism of Quercus variabilis under cadmium stress.

Heavy metal pollution is a global environmental problem, and Quercus variabilis has a stronger tolerance to Cd stress than do other species. We aimed to explore the physiological response and molecular mechanisms of Q. variabilis to Cd stress. In this study, the antioxidant enzyme activities of leaves were determined, while the photosynthetic parameters of leaves were measured using Handy PEA, and ion fluxes and DEGs in the roots were investigated using noninvasive microtest technology (NMT) and RNA sequencing techniques, respectively. Cd stress at different concentrations and for different durations affected the uptake patterns of Cd2+ and H+ by Q. variabilis and affected the photosynthetic efficiency of leaves. Moreover, there was a positive relationship between antioxidant enzyme (CAT and POD) activity and Cd concentration. Transcriptome analysis revealed that many genes, including genes related to the cell wall, glutathione metabolism, ion uptake and transport, were significantly upregulated in response to cadmium stress in Q. variabilis roots. WGCNA showed that these DEGs could be divided into eight modules. The turquoise and blue modules exhibited the strongest correlations, and the most significantly enriched pathways were the phytohormone signaling pathway and the phenylpropanoid biosynthesis pathway, respectively. These findings suggest that Q. variabilis can bolster plant tolerance by modulating signal transduction and increasing the synthesis of compounds, such as lignin, under Cd stress. In summary, Q. variabilis can adapt to Cd stress by increasing the activity of antioxidant enzymes, and regulating the fluxes of Cd2+ and H+ ions and the expression of Cd stress-related genes.