Triacontanol delivery by nano star shaped polymer promoted growth in maize.

Plant Growth Regulators (PGRs) are functional compounds known for enhancing plant growth and development. However, their environmental impact is a concern due to poor water solubility and the need for substantial organic solvents. Recently, nano-delivery systems have emerged as a solution, offering a broad range of applications for small molecule compounds. This study introduces a nano-delivery system for Triacontanol (TA), utilizing a star polymer (SPc), aimed at promoting maize growth and improving physiological indicators. The system forms nearly spherical nanoparticles through TA's hydroxyl group and SPc's tertiary amine group. The TA/SPc nano-complex notably outperforms separate TA or SPc treatments in maize, increasing biomass, chlorophyll content, and nutrient absorption. It elevates chlorophyll content by 16.4%, 10.0%, and 6.2% over water, TA, and SPc treatments, respectively, and boosts potassium and nitrate ion uptake by up to 2 and 1.6 times compared to TA alone, leading to enhanced plant height and leaf growth. qRT-PCR analysis further demonstrated that the nano-complex enhanced cellular uptake through the endocytosis pathway by up-regulating endocytosis-related gene expression. The employment of TEM to observe vesicle formation during the internalization of maize leaves furnishes corroborative evidence for the participation of the endocytosis pathway in this process. This research confirms that SPc is an effective carrier for TA, significantly enhancing biological activity and reducing TA dosage requirements.

Coronatine-treated seedlings increase the tolerance of cotton to low-temperature stress.

Coronatine, an analog of Jasmonic acid (JA), has been shown to enhance crop tolerance to abiotic stresses, including chilling stress. However, the underlying molecular mechanism remains largely unknown. In this study, we investigated the effect of Coronatine on cotton seedlings under low temperature using transcriptomic and metabolomics analysis. Twelve cDNA libraries from cotton seedlings were constructed, and pairwise comparisons revealed a total of 48,322 differentially expressed genes (DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified the involvement of these unigenes in various metabolic pathways, including Starch and sucrose metabolism, Sesquiterpenoid and triterpenoid biosynthesis, Phenylpropanoid biosynthesis, alpha-Linolenic acid metabolism, ABC transporters, and Plant hormone signal transduction. Additionally, substantial accumulations of jasmonates (JAs), abscisic acid and major cell wall metabolites were observed. Transcriptome analysis revealed differential expression of regulatory genes, and qRT-PCR analysis confirmed the expression patterns of 9 selected genes. Co-expression analysis showed that the JA-responsive genes might form a network module with ABA biosynthesis genes or cell wall biosynthesis genes, suggesting the existence of a COR-JA-cellulose and COR-JA-ABA-cellulose regulatory pathway in cotton seedlings. Collectively, our findings uncover new insights into the molecular basis of coronatine--associated cold tolerance in cotton seedlings.

A novel plant growth regulator B2 mediates drought resistance by regulating reactive oxygen species, phytohormone signaling, phenylpropanoid biosynthesis, and starch metabolism pathways in Carex breviculmis.

Drought is one of the most common environmental stressors that severely threatens plant growth, development, and productivity. B2 (2,4-dichloroformamide cyclopropane acid), a novel plant growth regulator, plays an essential role in drought adaptation, significantly enhancing the tolerance of Carex breviculmis seedlings. Its beneficial effects include improved ornamental value, sustained chlorophyll content, increased leaf dry weight, elevated relative water content, and enhanced root activity under drought conditions. B2 also directly scavenges hydrogen peroxide and superoxide anion contents while indirectly enhancing the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) to detoxify reactive oxygen species (ROS) oxidative damage. Transcriptome analysis demonstrated that B2 activates drought-responsive transcription factors (AP2/ERF-ERF, WRKY, and mTERF), leading to significant upregulation of genes associated with phenylpropanoid biosynthesis (HCT, POD, and COMT). Additionally, these transcription factors were found to suppress the degradation of starch. B2 regulates phytohormone signaling related-genes, leading to an increase in abscisic acid contents in drought-stressed plants. Collectively, these findings offer new insights into the intricate mechanisms underlying C. breviculmis' resistance to drought damage, highlighting the potential application of B2 for future turfgrass establishment and management with enhanced drought tolerance.

Design, Synthesis, and Bioactivities of N-Heterocyclic Ureas as Strigolactone Response Antagonists against Parasitic-Weed Seed Germination.

The pernicious parasitism exhibited by root parasitic weeds such as Orobanche and Striga poses substantial peril to agricultural productivity and global food security. This deleterious phenomenon hinges upon the targeted induction of the signaling molecule strigolactones (SLs). Consequently, the identification of prospective SL antagonists holds significant promise in the realm of mitigating the infection of these pernicious weeds. In this study, we synthesized and characterized D12 based on a potent SL antagonist KK094. In vivo assay results demonstrated that D12 remarkably impedes the germination of Phelipanche aegyptiaca and Striga asiatica seeds, while also alleviating the inhibitory consequence of the SL analogue GR24 on hypocotyl elongation in Arabidopsis thaliana. The docking study and ITC assay indicated that D12 can interact strongly with the SL receptor protein, which may interfere with the binding of SL to the receptor protein as a result. In addition, the results of crop safety assessment tests showed that D12 had no adverse effects on rice seed germination and seedling growth and development. The outcomes obtained from the present study suggested that D12 exhibited promise as a prospective antagonist of SL receptors, thereby displaying substantial efficacy in impeding the seed germination process of root parasitic weeds, providing a promising basis for rational design and development of further Striga-specific herbicides.

Design, Synthesis and Biological Evaluation of Novel Phenyl-Substituted Naphthoic Acid Ethyl Ester Derivatives as Strigolactone Receptor Inhibitor.

Strigolactones (SLs) are plant hormones that regulate several key agronomic traits, including shoot branching, leaf senescence, and stress tolerance. The artificial regulation of SL biosynthesis and signaling has been considered as a potent strategy in regulating plant architecture and combatting the infection of parasitic weeds to help improve crop yield. DL1b is a previously reported SL receptor inhibitor molecule that significantly promotes shoot branching. Here, we synthesized 18 novel compounds based on the structure of DL1b. We performed rice tillering activity assay and selected a novel small molecule, C6, as a candidate SL receptor inhibitor. In vitro bioassays demonstrated that C6 possesses various regulatory functions as an SL inhibitor, including inhibiting germination of the root parasitic seeds Phelipanche aegyptiaca, delaying leaf senescence and promoting hypocotyl elongation of Arabidopsis. ITC analysis and molecular docking experiments further confirmed that C6 can interact with SL receptor proteins, thereby interfering with the binding of SL to its receptor. Therefore, C6 is considered a novel SL receptor inhibitor with potential applications in plant architecture control and prevention of root parasitic weed infestation.

Jasmonate mimic modulates cell elongation by regulating antagonistic bHLH transcription factors via brassinosteroid signaling.

Lodging restricts growth, development, and yield formation in maize (Zea mays L.). Shorter internode length is beneficial for lodging tolerance. However, although brassinosteroids (BRs) and jasmonic acid (JA) are known to antagonistically regulate internode growth, the underlying molecular mechanism is still unclear. In this study, application of the JA mimic coronatine (COR) inhibited basal internode elongation at the jointing stage and repressed expression of the cell wall-related gene XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE 1 (ZmXTH1), whose overexpression in maize plants promoted internode elongation. We demonstrated that the basic helix-loop-helix (bHLH) transcription factor ZmbHLH154 directly binds to the ZmXTH1 promoter and induces its expression, whereas the bHLH transcription factor ILI1 BINDING BHLH 1 (ZmIBH1) inhibits this transcriptional activation by forming a heterodimer with ZmbHLH154. Overexpressing ZmbHLH154 led to longer internodes, whereas zmbhlh154 mutants had shorter internodes than the wild type. The core JA-dependent transcription factors ZmMYC2-4 and ZmMYC2-6 interacted with BRASSINAZOLE RESISTANT 1 (ZmBZR1), a key factor in BR signaling, and these interactions eliminated the inhibitory effect of ZmBZR1 on its downstream gene ZmIBH1. Collectively, these results reveal a signaling module in which JA regulates a bHLH network by attenuating BR signaling to inhibit ZmXTH1 expression, thereby regulating cell elongation in maize.

Unveiling the Regulatory Role of miRNAs in Internode Elongation: Integrated Analysis of MicroRNA and mRNA Expression Profiles across Diverse Dwarfing Treatments in Maize (Zea mays L.).

MicroRNAs are crucial regulators of gene expression in maize. However, the mechanisms through which miRNAs control internode elongation remain poorly understood. This study engineered varying levels of internode elongation inhibition, revealing that dwarfing treatments diminished gibberellin levels, curtailed cell longitudinal growth, and slowed the rate of internode elongation. Comprehensive transcriptome and miRNA profiling of the internode elongation zone showed gene expression changes that paralleled the extent of the internode length reduction. We identified 543 genes and 29 miRNAs with significant correlations to internode length, predominantly within families, including miR164 and miR396. By incorporating target gene expression levels, we pinpointed nine miRNA-mRNA pairs that are significantly associated with the regulation of the internode elongation. The inhibitory effects of these miRNAs on their target genes were confirmed through dual-luciferase reporter assays. Overexpression of miR164h in maize resulted in increased internode and cell length, suggesting a novel genetic avenue for manipulating plant stature. These miRNAs may also serve as precise spatiotemporal regulators for in vitro plant development.

Melatonin-Mediated Enhancement of Photosynthetic Capacity and Photoprotection Improves Salt Tolerance in Wheat.

The role of melatonin in plant growth and response to environmental stress has been widely demonstrated. However, the physiological and molecular regulation of salt tolerance in wheat seedlings by melatonin remains unclear. In this study, we investigated changes in phenotype, physiology, photosynthetic parameters, and transcript levels in wheat seedlings to reveal the role of melatonin in the regulation of salt tolerance in wheat. The results indicate that the application of exogenous melatonin significantly alleviates growth inhibition, reactive oxygen species accumulation, and membrane oxidative damage induced by salt stress in wheat. Additionally, exogenous melatonin increased antioxidant enzyme activity and regulated photosynthetic gas exchange. Transcriptomic data showed a significant up-regulation of genes encoding light-harvesting chlorophyll protein complex proteins in photosynthesis and genes related to chlorophyll and carotenoid biosynthesis under the influence of melatonin. These results suggest that exogenous melatonin improves salt tolerance in wheat seedlings by enhancing the antioxidant, photoprotective, and photosynthesis activities.

Coronatine-Induced Maize Defense against Gibberella Stalk Rot by Activating Antioxidants and Phytohormone Signaling.

One of the most destructive diseases, Gibberella stalk rot (GSR), caused by Fusarium graminearum, reduces maize yields significantly. An induced resistance response is a potent and cost-effective plant defense against pathogen attack. The functional counterpart of JAs, coronatine (COR), has attracted a lot of interest recently due to its ability to control plant growth and stimulate secondary metabolism. Although several studies have focused on COR as a plant immune elicitor to improve plant resistance to pathogens, the effectiveness and underlying mechanisms of the suppressive ability against COR to F. graminearum in maize have been limited. We investigated the potential physiological and molecular mechanisms of COR in modulating maize resistance to F. graminearum. COR treatment strongly enhanced disease resistance and promoted stomatal closure with H2O2 accumulation, and 10 µg/mL was confirmed as the best concentration. COR treatment increased defense-related enzyme activity and decreased the malondialdehyde content with enhanced antioxidant enzyme activity. To identify candidate resistance genes and gain insight into the molecular mechanism of GSR resistance associated with COR, we integrated transcriptomic and metabolomic data to systemically explore the defense mechanisms of COR, and multiple hub genes were pinpointed using weighted gene correlation network analysis (WGCNA). We discovered 6 significant modules containing 10 candidate genes: WRKY transcription factor (LOC100279570), calcium-binding protein (LOC100382070), NBR1-like protein (LOC100275089), amino acid permease (LOC100382244), glutathione S-transferase (LOC541830), HXXXD-type acyl-transferase (LOC100191608), prolin-rich extensin-like receptor protein kinase (LOC100501564), AP2-like ethylene-responsive transcription factor (LOC100384380), basic leucine zipper (LOC100275351), and glycosyltransferase (LOC606486), which are highly correlated with the jasmonic acid-ethylene signaling pathway and antioxidants. In addition, a core set of metabolites, including alpha-linolenic acid metabolism and flavonoids biosynthesis linked to the hub genes, were identified. Taken together, our research revealed differentially expressed key genes and metabolites, as well as co-expression networks, associated with COR treatment of maize stems after F. graminearum infection. In addition, COR-treated maize had higher JA (JA-Ile and Me-JA) levels. We postulated that COR plays a positive role in maize resistance to F. graminearum by regulating antioxidant levels and the JA signaling pathway, and the flavonoid biosynthesis pathway is also involved in the resistance response against GSR.

The first complete mitochondrial genome of Carex (C. breviculmis): a significantly expanded genome with highly structural variations.

MAIN CONCLUSION: The first complete mitochondrial genome of Carex (C. breviculmis) was sequenced and assembled, and its genomic signature was analyzed and the possible conformations of its mitochondrial genome were validated. Carex breviculmis is a very adaptable grass that is highly resistant to environmental stresses such as drought and low light. It is also admired as a landscape plant with high development prospects and scientific research value. In this study, the mitochondrial genome of C. breviculmis was assembled using Pacbio and Illumina sequencing data. We detected 267 pairs of repeats and found that three pairs of repeats could mediate the recombination of its mitochondrial genome and formed four possible conformations, of which we verified the two conformations mediated by the shortest pair of repeats using PCR amplification and Sanger sequencing. The major conformation of the C. breviculmis mitochondrial genome is a 1,414,795 bp long circular molecule with 33 annotated protein-coding genes, 15 tRNA genes, and three rRNA genes. We detected a total of 25 homologous sequences between the chloroplast and mitochondrial genomes, corresponding to 0.40% of the mitochondrial genome. Combined with the low GC content (41.24%), we conclude that the reduction in RNA editing sites in the C. breviculmis mitochondrial genome may be due to an accumulation of point mutations in C-to-T or retroprocessing events within the genome. The relatively low number of RNA editing sites in its mitochondrial genome could serve as important material for subsequent studies on the selection pressure of RNA editing in angiosperms. A maximum likelihood analysis based on 23 conserved mitochondrial genes from 28 species reflects an accurate evolutionary and taxonomic position of C. breviculmis. This research provided us with a comprehensive understanding of the mitochondrial genome of Carex and also provided important information for its molecular breeding.

Ethylene enhanced waterlogging tolerance by changing root architecture and inducing aerenchyma formation in maize seedlings.

Waterlogging negatively affects maize growth and yield. In this study, we found that ethylene played a vital role in plant adaptation to waterlogging. ET promotes better growth in seedlings under waterlogging conditions by altering root architecture and increasing lateral root formation by 42.1%. What's more, plants with high endogenous ethylene levels exhibited reduced sensitivity to waterlogging stress. ET also induced the formation of aerenchyma, a specialized tissue that facilitates gas exchange, in a different pattern compared to aerenchyma formed under waterlogging. Aerenchyma induced by ET was mainly located in the medial cortex of the roots and was not prone to decay. ethylene inhibited root elongation under normal conditions, but this inhibition was not alleviated under waterlogging stress. Upon activation of the ET signaling pathway, the transcription factor EREB90 promoted aerenchyma formation by enhancing the programmed cell death process. Overexpression of EREB90 resulted in increased waterlogging tolerance compared to wild type plants. Our findings suggest that pre-treatment of maize seedlings with ET before waterlogging stress can trigger the programmed cell death process and induce aerenchyma formation, thus improving waterlogging resistance.

Discovery of Novel Hybrid-Type Strigolactone Mimics Derived from Cinnamic Amide.

Strigolactones (SLs) are a class of plant hormones and rhizosphere communication signals of great interest. They perform diverse biological functions including the stimulation of parasitic seed germination and phytohormonal activity. However, their practical use is limited by their low abundance and complex structure, which requires simpler SL analogues and mimics with maintained biological function. Here, new, hybrid-type SL mimics were designed, derived from Cinnamic amide, a new potential plant growth regulator with good germination and rooting-promoting activities. Bioassay results indicated that compound 6 not only displayed good germination activity against the parasitic weed O. aegyptiaca with an EC50 value of 2.36 × 10-8 M, but also exhibited significant inhibitory activity against Arabidopsis root growth and lateral root formation, as well as promoting root hair elongation, similar to the action of GR24. Further morphological experiments on Arabidopsis max2-1 mutants revealed that 6 possessed SL-like physiological functions. Furthermore, molecular docking studies indicated that the binding mode of 6 was similar to that of GR24 in the active site of OsD14. This work provides valuable clues for the discovery of novel SL mimics.

Deciphering transcriptional mechanisms of maize internodal elongation by regulatory network analysis.

The lengths of the basal internodes is an important factor for lodging resistance of maize (Zea mays). In this study, foliar application of coronatine (COR) to 10 cultivars at the V8 growth stage had different suppression effects on the length of the eighth internode, with three being categorized as strong-inhibition cultivars (SC), five as moderate (MC), and two as weak (WC). RNA-sequencing of the eighth internode of the cultivars revealed a total of 7895 internode elongation-regulating genes, including 777 transcription factors (TFs). Genes related to the hormones cytokinin, gibberellin, auxin, and ethylene in the SC group were significantly down-regulated compared to WC, and more cell-cycle regulatory factors and cell wall-related genes showed significant changes, which severely inhibited internode elongation. In addition, we used EMSAs to explore the direct regulatory relationship between two important TFs, ZmABI7 and ZmMYB117, which regulate the cell cycle and cell wall modification by directly binding to the promoters of their target genes ZmCYC1, ZmCYC3, ZmCYC7, and ZmCPP1. The transcriptome reported in this study will provide a useful resource for studying maize internode development, with potential use for targeted genetic control of internode length to improve the lodging resistance of maize.

Coronatine-Based Gene Expression Changes Impart Partial Resistance to Fall Armyworm (Spodoptera frugiperda) in Seedling Maize.

In recent years, Spodoptera frugiperda (S. frugiperda, Smith) has invaded China, seriously threatening maize production. To explore an effective method to curb the further expansion of the harm of the S. frugiperda, this experiment used maize seedlings of the Zhengdan 958 three-leaf stage (V3) of maize as the material to study the effect of coronatine (COR) on the ability of maize to resist insects (S. frugiperda) at the seedling stage. The results showed that when maize was sprayed with 0.05 µM COR, the newly incubated larvae of S. frugiperda had the least leaf feeding. It was found that 0.05 µM COR significantly increased the contents of abscisic acid (ABA) and jasmonate (JA) in maize leaves through the determination of hormone content. Moreover, transcriptome sequencing revealed that the expression of six genes (ZmBX1, ZmBX2, ZmBX3, ZmBX4, ZmBX5 and ZmBX6), which are associated with the synthesis of benzoxazinoid, were upregulated. Nine genes (ZmZIM3, ZmZIM4, ZmZIM10, ZmZIM13, ZmZIM18, ZmZIM23, ZmZIM27, ZmZIM28 and ZmZIM38) of JA-Zim Domain (JAZ) protein in the JA signal pathway, and seven genes (ZmPRH19, ZmPRH18, Zm00001d024732, Zm00001d034109, Zm00001d026269, Zm00001d028574 and Zm00001d013220) of ABA downstream response protein Group A Type 2C Protein Phosphatase (PP2C) were downregulated. These results demonstrated that COR could induce anti-insect factors and significantly improve insect resistance in seedling maize, which laid a theoretical foundation for further study of the mechanism of COR improving insect resistance in seedling maize, and provided data references for the use of COR as an environmentally friendly pest control method.

Chloroplast genomes of four Carex species: Long repetitive sequences trigger dramatic changes in chloroplast genome structure.

The chloroplast genomes of angiosperms usually have a stable circular quadripartite structure that exhibits high consistency in genome size and gene order. As one of the most diverse genera of angiosperms, Carex is of great value for the study of evolutionary relationships and speciation within its genus, but the study of the structure of its chloroplast genome is limited due to its highly expanded and restructured genome with a large number of repeats. In this study, we provided a more detailed account of the chloroplast genomes of Carex using a hybrid assembly of second- and third-generation sequencing and examined structural variation within this genus. The study revealed that chloroplast genomes of four Carex species are significantly longer than that of most angiosperms and are characterized by high sequence rearrangement rates, low GC content and gene density, and increased repetitive sequences. The location of chloroplast genome structural variation in the species of Carex studied is closely related to the positions of long repeat sequences; this genus provides a typical example of chloroplast structural variation and expansion caused by long repeats. Phylogenetic relationships constructed based on the chloroplast protein-coding genes support the latest taxonomic system of Carex, while revealing that structural variation in the chloroplast genome of Carex may have some phylogenetic significance. Moreover, this study demonstrated a hybrid assembly approach based on long and short reads to analyze complex chloroplast genome assembly and also provided an important reference for the analysis of structural rearrangements of chloroplast genomes in other taxa.

Transcriptomic Analysis of Resistant and Wild-Type Botrytis cinerea Isolates Revealed Fludioxonil-Resistance Mechanisms.

Botrytis cinerea, the causal agent of gray mold, is one of the most destructive pathogens of cherry tomatoes, causing fruit decay and economic loss. Fludioxonil is an effective fungicide widely used for crop protection and is effective against tomato gray mold. The emergence of fungicide-resistant strains has made the control of B. cinerea more difficult. While the genome of B. cinerea is available, there are few reports regarding the large-scale functional annotation of the genome using expressed genes derived from transcriptomes, and the mechanism(s) underlying such fludioxonil resistance remain unclear. The present study prepared RNA-sequencing (RNA-seq) libraries for three B. cinerea strains (two highly resistant (LR and FR) versus one highly sensitive (S) to fludioxonil), with and without fludioxonil treatment, to identify fludioxonil responsive genes that associated to fungicide resistance. Functional enrichment analysis identified nine resistance related DEGs in the fludioxonil-induced LR and FR transcriptome that were simultaneously up-regulated, and seven resistance related DEGs down-regulated. These included adenosine triphosphate (ATP)-binding cassette (ABC) transporter-encoding genes, major facilitator superfamily (MFS) transporter-encoding genes, and the high-osmolarity glycerol (HOG) pathway homologues or related genes. The expression patterns of twelve out of the sixteen fludioxonil-responsive genes, obtained from the RNA-sequence data sets, were validated using quantitative real-time PCR (qRT-PCR). Based on RNA-sequence analysis, it was found that hybrid histidine kinase, fungal HHKs, such as BOS1, BcHHK2, and BcHHK17, probably involved in the fludioxonil resistance of B. cinerea, in addition, a number of ABC and MFS transporter genes that were not reported before, such as BcATRO, BMR1, BMR3, BcNMT1, BcAMF1, BcTOP1, BcVBA2, and BcYHK8, were differentially expressed in the fludioxonil-resistant strains, indicating that overexpression of these efflux transporters located in the plasma membranes may associate with the fludioxonil resistance mechanism of B. cinerea. All together, these lines of evidence allowed us to draw a general portrait of the anti-fludioxonil mechanisms for B. cinerea, and the assembled and annotated transcriptome data provide valuable genomic resources for further study of the molecular mechanisms of B. cinerea resistance to fludioxonil.

Coronatine promotes maize water uptake by directly binding to the aquaporin ZmPIP2;5 and enhancing its activity.

Water uptake is crucial for crop growth and development and drought stress tolerance. The water channel aquaporins (AQP) play important roles in plant water uptake. Here, we discovered that a jasmonic acid analog, coronatine (COR), enhanced maize (Zea mays) root water uptake capacity under artificial water deficiency conditions. COR treatment induced the expression of the AQP gene Plasma membrane intrinsic protein 2;5 (ZmPIP2;5). In vivo and in vitro experiments indicated that COR also directly acts on ZmPIP2;5 to improve water uptake in maize and Xenopus oocytes. The leaf water potential and hydraulic conductivity of roots growing under hyperosmotic conditions were higher in ZmPIP2;5-overexpression lines and lower in the zmpip2;5 knockout mutant, compared to wild-type plants. Based on a comparison between ZmPIP2;5 and other PIP2s, we predicted that COR may bind to the functional site in loop E of ZmPIP2;5. We confirmed this prediction by surface plasmon resonance technology and a microscale thermophoresis assay, and showed that deleting the binding motif greatly reduced COR binding. We identified the N241 residue as the COR-specific binding site, which may activate the channel of the AQP tetramer and increase water transport activity, which may facilitate water uptake under hyperosmotic stress.

Potential toxicity and dietary risk of tricyclazole to Chinese mitten crab (Eriocheir sinensis) in the rice-crab co-culture model.

Tricyclazole is used as a common fungicide to control rice blast. However, studies on the toxicity of tricyclazole to crabs in the rice-crab co-culture system are still extremely rare. Here, the environmental dissipation of tricyclazole was monitored in this model, and the potential toxicity of tricyclazole to E. sinensis at environmental concentrations as well as the dietary risk was evaluated. The results showed that tricyclazole had no significant acute toxicity to E. sinensis (LC50 > 100 mg/L), while it promoted body weight gain. Tricyclazole in the hepatopancreas had a higher persistent bioaccumulation risk than in the muscle. Tricyclazole suppressed the immune response of E. sinensis under prolonged exposure and there should be gender differences, with females being more sensitive. Lipid metabolism enzymes were also significantly inhibited. While tricyclazole stimulated males molting but prolonged molting duration, both molting and duration of females were also disturbed. The dietary risk assessment indicated that tricyclazole intake from current crab consumption was low risk. This evidence demonstrated that tricyclazole may have potential risks to individual development, nutritional quality, and economic value on E. sinensis and should be used with caution in rice-crab co-culture system whenever possible.

Effects of triazole plant growth regulators on molting mechanism in Chinese mitten crab (Eriocheir sinensis).

Rice crab co-culture is a new integrated farming model in China. The application of triazole plant growth regulators (PRGs) is often used as an advantageous option to combat rice lodging. However, there is still a gap regarding the toxicity of these PRGs on the growth and development of the Chinese mitten crab (Eriocheir sinensis, E. sinensis). Here the effect of triazoles (paclobutrazol and uniconazole) on the molting mechanism of E. sinensis was investigated. Monitoring of regulatory genes associated with molting showed that the two PRGs were found to inhibit the expression of ecdysteroid hormone (EH), ecdysteroid receptors gene (EcR), and retinoid X receptors gene (RXR) and induce secretion of molt-inhibiting hormone (MIH) gene. In addition, the activities of chitinase (CHIA) and N-acetyl-ß-d-aminoglucosidase (ß-NAGase) were also inhibited by exposure to PRGs. Exposure to PRGs also elevated the mRNA expression of the growth-related myostatin gene (MSTN). These results revealed that there is a long-term risk of exposure to triazoles PRGs that may inhibit molting and affect normal development and immune system of E. sinensis.

B2, an abscisic acid mimic, improves salinity tolerance in winter wheat seedlings via improving activity of antioxidant enzymes.

Salinity severely inhibits growth and reduces yield of salt-sensitive plants like wheat, and this effect can be alleviated by plant growth regulators and phytohormones, among which abscisic acid (ABA) plays a central role in response to various stressful environments. ABA is highly photosensitive to light disruption, which this limits its application. Here, based on pyrabactin (a synthetic ABA agonist), we designed and synthesized a functional analog of ABA and named B2, then evaluated its role in salt resistance using winter wheat seedlings. The phenotypes showed that B2 significantly improved the salt tolerance of winter wheat seedlings by elevating the biomass. The physiological analysis found that B2 treatment reduced the generation rate of O2 -, electrolyte leakage, the content of proline, and the accumulation of malonaldehyde (MDA) and H2O2 and also significantly increased the contents of endogenous hormones zeatin riboside (ZA) and gibberellic acid (GA). Further biochemical analysis revealed that the activities of various antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), were enhanced by B2, and the activities of antioxidase isozymes SOD3, POD1/2, and APX1/2 were particularly increased, largely resembling ABA treatment. The abiotic stress response-related gene TaSOS1 was significantly upregulated by B2, while the TaTIP2;2 gene was suppressed. In conclusion, an ABA analog B2 was capable to enhance salt stress tolerance in winter wheat seedlings by stimulating the antioxidant system, providing a novel regulator for better survival of crops in saline soils and improving crop yield.