SlMAPK1/2/3 and Antioxidant Enzymes Are Associated with H2O2-Induced Chilling Tolerance in Tomato Plants

HvAIR12 confers aluminum tolerance in barley by H2O2-mediated activation of HvEXPA4 to facilitate aluminum detoxification and improve root growth

Aluminum (Al) toxicity is a major constraint on crop productivity in acid soils, with barley being particularly susceptible. In our previous transcriptomic analysis, we identified HvAIR12 (AUXIN INDUCED IN ROOT CULTURES), a novel gene that is specifically induced by Al in the roots of the Al-tolerant Tibetan wild barley accession XZ16. In this study, we performed comprehensive physiological, transgenic, and molecular analyses to explore the role of HvAIR12 in Al tolerance. HvAIR12 encodes a plasma membrane-bound protein and is predominantly expressed in the roots, with its expression being strongly upregulated by Al exposure. Knockdown of HvAIR12 resulted in significantly reduced root growth and increased Al accumulation, whereas overexpression of HvAIR12 elevated H2O2 levels in the apoplast and promoted root growth-effects that were reversible by H2O2 scavengers. RNA sequencing further revealed that overexpression of HvAIR12 led to the transcriptional activation of several expansin genes, including HvEXPA4 and HvEXPB2. Functional characterization of HvEXPA4 transgenic lines and gene silencing experiments in HvAIR12-overexpressing backgrounds confirmed that HvEXPA4 is an essential downstream target of HvAIR12, mitigating Al toxicity by modulating cell wall components. This study uncovers the novel role of HvAIR12 in regulating apoplastic H2O2 levels and its interaction with other Al tolerance-related genes. Our findings highlight that HvAIR12 promotes Al tolerance through H2O2-mediated activation of HvEXPA4, forming a regulatory pathway critical for Al exclusion and root elongation under Al stress. These results providing valuable molecular insights and promising target genes for breeding more resilient cereal crops for cultivation in acid soils.

Time-course transcriptome analysis reveals gene co-expression networks and transposable element responses to cold stress in cotton

BACKGROUND

Cold stress significantly challenges cotton growth and productivity, yet the genetic and molecular mechanisms underlying cold tolerance remain poorly understood.

RESULTS

We employed RNA-seq and iterative weighted gene co-expression network analysis (WGCNA) to investigate gene and transposable element (TE) expression changes at six cold stress time points (0 h, 2 h, 4 h, 6 h, 12 h, 24 h). Thousands of differentially expressed genes (DEGs) were identified, exhibiting time-specific patterns that highlight a phase-dependent transcriptional response. While the A and D subgenomes contributed comparably to DEG numbers, numerous homeologous gene pairs showed differential expression, indicating regulatory divergence. Iterative WGCNA uncovered 125 gene co-expression modules, with some enriched in specific chromosomes or chromosomal regions, suggesting localized regulatory hotspots for cold stress response. Notably, transcription factors, including MYB73, ERF017, MYB30, and OBP1, emerged as central regulators within these modules. Analysis of 11 plant hormone-related genes revealed dynamic expression, with ethylene (ETH) and cytokinins (CK) playing significant roles in stress-responsive pathways. Furthermore, we documented over 15,000 expressed TEs, with differentially expressed TEs forming five distinct clusters. TE families, such as LTR/Copia, demonstrated significant enrichment in these expression clusters, suggesting their potential role as modulators of gene expression under cold stress.

CONCLUSIONS

These findings provide valuable insights into the complex regulatory networks underlying cold stress response in cotton, highlighting key molecular components involved in cold stress regulation. This study provides potential genetic targets for breeding strategies aimed at enhancing cold tolerance in cotton.

ABA as a downstream signal actively participates in phthalanilic acid mediated cold tolerance of common beans (Phaseolus vulgaris)

Although the reaction of plants to various stresses can be regulated by phthalanilic acid (PPA), the regulation mechanism in the cold resistance of common beans was still unclear. The study showed that the ABA content of common bean seedlings was significantly increased by PPA application under low-temperature stress, the growth of common bean seedlings was effectively protected, and the yield loss was reduced. Importantly, the regulation of PPA on cold resistance of common bean seedlings depended on ABA pathway. It was further revealed that the ABA receptor pathway was observably activated by knocking down the ABA catabolic gene CYP707As, and the cold resistance of common bean seedlings was considerably enhanced. At the same time, the regulation of PPA on the low-temperature resistance of common bean seedlings was visibly weakened, which was also proved by gene over-expression and virus induced gene silence of CYP707As. In addition, combining exogenous treatment of ABA biosynthesis inhibitor (fluridone) with endogenous gene knock-down, over-expression and virus induced gene silence of phospholipase D coding gene (PLD1), it was found that PPA could obviously enhance cold resistance of common bean seedlings by promoting phospholipase D to produce phosphatidic acid, increasing the antioxidant enzyme activity to reduce oxidative damage and improve the stability of the photosynthetic system. In summary, the molecular and physiological basis was firstly elucidated that phthalanilic acid enhanced cold resistance of common bean seedlings by phospholipid metabolism, photosynthetic system, and antioxidant status through the ABA pathway in the present study.

Tomato mitogen-activated protein kinase: mechanisms of adaptation in response to biotic and abiotic stresses

Plants live under various biotic and abiotic stress conditions, and to cope with the adversity and severity of these conditions, they have developed well-established resistance mechanisms. These mechanisms begin with the perception of stimuli, followed by molecular, biochemical, and physiological adaptive measures. Tomato (Solanum lycopersicum) is a globally significant vegetable crop that experiences several biotic and abiotic stress events that can adversely impact its quality and production. Mitogen-activated protein kinases (MAPKs) in tomato plants have crucial functions of mediating responses to environmental cues, internal signals, defense mechanisms, cellular processes, and plant development and growth. MAPK cascades respond to various environmental stress factors by modulating associated gene expression, influencing plant hormone synthesis, and facilitating interactions with other environmental stressors. Here, we review the evolutionary relationships of 16 tomato SlMAPK family members and emphasize on recent studies describing the regulatory functions of tomato SlMAPKs in both abiotic and biotic stress conditions. This review could enhance our comprehension of the MAPK regulatory network in biotic and abiotic stress conditions and provide theoretical support for breeding tomatoes with agronomic traits of excellent stress resistance.

Prediction of the postharvest quality of Boletus wild mushrooms stored with mesoporous silica nanoparticles antibacterial film using Long Short-Term Memory model combined with the Northern Goshawk Optimization (NGO-LSTM)

This study aimed to address the challenge of extending the shelf life of Boletus wild mushrooms, which are prone to environmental and microbial contamination. An antibacterial film composed of polylactic acid (PLA) and mesoporous silica nanoparticles loaded with citral (CMP film) was developed for this purpose. Fifteen quality indices were assessed, and the data were integrated using AHP and TOPSIS to evaluate the film's efficacy. The CMP film effectively maintained the quality of mushroom over time. Additionally, a Nonlinear Global Optimization-Long Short-Term Memory (NGO-LSTM) model was employed to predict storage quality, using seven highly correlated quality indicators. The model achieved a high predictive accuracy, with the R2 exceeding 0.999. This study presents a novel packaging solution and a predictive model that together enhance the storage and quality control of Boletus wild mushrooms.

Recent Insights into the Physio-Biochemical and Molecular Mechanisms of Low Temperature Stress in Tomato

Climate change has emerged as a crucial global issue that significantly threatens the survival of plants. In particular, low temperature (LT) is one of the critical environmental factors that influence plant morphological, physiological, and biochemical changes during both the vegetative and reproductive growth stages. LT, including abrupt drops in temperature, as well as winter conditions, can cause detrimental effects on the growth and development of tomato plants, ranging from sowing, transplanting, truss appearance, flowering, fertilization, flowering, fruit ripening, and yields. Therefore, it is imperative to understand the comprehensive mechanisms underlying the adaptation and acclimation of tomato plants to LT, from the morphological changes to the molecular levels. In this review, we discuss the previous and current knowledge of morphological, physiological, and biochemical changes, which contain vegetative and reproductive parameters involving the leaf length (LL), plant height (PH) stem diameter (SD), fruit set (FS), fruit ripening (FS), and fruit yield (FY), as well as photosynthetic parameters, cell membrane stability, osmolytes, and ROS homeostasis via antioxidants scavenging systems during LT stress in tomato plants. Moreover, we highlight recent advances in the understanding of molecular mechanisms, including LT perception, signaling transduction, gene regulation, and fruit ripening and epigenetic regulation. The comprehensive understanding of LT response provides a solid basis to develop the LT-resistant varieties for sustainable tomato production under the ever-changing temperature fluctuations.

CRISPR/Cas9-Mediated SlATG5 Mutagenesis Reduces the Resistance of Tomato Fruit to Botrytis cinerea

Tomato fruit is highly susceptible to infection by Botrytis cinerea (B. cinerea), a dominant pathogen, during storage. Recent studies have shown that autophagy is essential for plant defense against biotic and abiotic stresses. Autophagy-related gene 5 (ATG5) plays a key role in autophagosome completion and maturation, and is rapidly induced by B. cinerea, but the potential mechanisms of ATG5 in Solanum lycopersicum (SlATG5) in postharvest tomato fruit resistance to B. cinerea remain unclear. To elucidate the role of SlATG5 in tomato fruit resistant to B. cinerea, CRISPR/Cas9-mediated knockout of SlATG5 was used in this study. The results showed that slatg5 mutants were more vulnerable to B. cinerea and exhibited more severe disease symptoms and lower activities of disease-resistant enzymes, such as chitinase (CHI), β-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO), than the wild type (WT). Furthermore, the study observed that after inoculation with B. cinerea, the relative expression levels of genes related to salicylic acid (SA) signaling, such as SlPR1, SlEDS1, SlPAD4, and SlNPR1, were higher in slatg5 mutants than in WT. Conversely, the relative expression levels of jasmonic acid (JA) signaling-related genes SlLoxD and SlMYC2 were lower in slatg5 mutants than in WT. These findings suggested that SlATG5 positively regulated the resistance response of tomato fruit to B. cinerea by inhibiting the SA signaling pathway and activating the JA signaling pathway.

Engineering Abiotic Stress Tolerance in Crop Plants through CRISPR Genome Editing

Environmental abiotic stresses challenge food security by depressing crop yields often exceeding 50% of their annual production. Different methods, including conventional as well as genomic-assisted breeding, mutagenesis, and genetic engineering have been utilized to enhance stress resilience in several crop species. Plant breeding has been partly successful in developing crop varieties against abiotic stresses owning to the complex genetics of the traits as well as the narrow genetic base in the germplasm. Irrespective of the fact that genetic engineering can transfer gene(s) from any organism(s), transgenic crops have become controversial mainly due to the potential risk of transgene-outcrossing. Consequently, the cultivation of transgenic crops is banned in certain countries, particularly in European countries. In this scenario, the discovery of the CRISPR tool provides a platform for producing transgene-free genetically edited plants-similar to the mutagenized crops that are not extensively regulated such as genetically modified organisms (GMOs). Thus, the genome-edited plants without a transgene would likely go into the field without any restriction. Here, we focused on the deployment of CRISPR for the successful development of abiotic stress-tolerant crop plants for sustaining crop productivity under changing environments.

Biocontrol activity and action mechanism of Bacillus velezensis strain SDTB038 against Fusarium crown and root rot of tomato

Fusarium crown and root rot of tomato is a soilborne diseases that has brought serious harm and economic losses to tomato production in facilities in recent years. The disease has been reported in more than 30 countries worldwide, but there are few reports on its biological control. A Bacillus velezensis strain SDTB038 with biocontrol effects was isolated and identified in a previous study and is considered one of the most important PGPRs. Seven secondary metabolite biosynthesis gene clusters were found in strain SDTB038 by whole genome sequencing, explaining its biocontrol effects. Results indicated that different concentrations of SDTB038 fermentation broth inhibited the mycelial growth of Fusarium crown and root rot of tomato. Strain SDTB038 could generate indole acetic acid and promote healthy growth of tomatoes, while the effect of 108 CFU/ml SDTB038 concentration on promoting tomato growth was the most obvious. B. velezensis SDTB038 significantly reduced the accumulation of ROS in tomato plants, induced the up-regulation of antifreeze genes, and promoted the rapid recovery of tomato plants at low temperatures in a pot experiment. At the same time, SDTB038 had good control effect on Fusarium crown and root rot of tomato, and 108 CFU/ml SDTB038 fermentation broth had the best control effect, which was 42.98%. In summary, the strain B. velezensis SDTB038 may be a promising bacterial agent for biological control of Fusarium crown and root rot of tomato, and an important source of potential antimicrobial compounds.

CRISPR/Cas9 Technique for Temperature, Drought, and Salinity Stress Responses

Global warming and climate change have severely affected plant growth and food production. Therefore, minimizing these effects is required for sustainable crop yields. Understanding the molecular mechanisms in response to abiotic stresses and improving agricultural traits to make crops tolerant to abiotic stresses have been going on unceasingly. To generate desirable varieties of crops, traditional and molecular breeding techniques have been tried, but both approaches are time-consuming. Clustered regularly interspaced short palindromic repeat/Cas9 (CRISPR/Cas9) and transcription activator-like effector nucleases (TALENs) are genome-editing technologies that have recently attracted the attention of plant breeders for genetic modification. These technologies are powerful tools in the basic and applied sciences for understanding gene function, as well as in the field of crop breeding. In this review, we focus on the application of genome-editing systems in plants to understand gene function in response to abiotic stresses and to improve tolerance to abiotic stresses, such as temperature, drought, and salinity stresses.

MAPK5 and MAPK10 overexpression influences strawberry fruit ripening, antioxidant capacity and resistance to Botrytis cinerea

FaMAPK5 and FaMAPK10 genes were involved in ABA-mediated strawberry fruit ripening and could enhance the antioxidant capacity by increasing non-enzymatic components and enzymatic antioxidants. Mitogen-activated protein kinases (MAPKs) are the key proteins involved in plant stress response by activating an antioxidant defense system, which cooperates with plant hormones. However, the involvement of MAPKs in the regulation of strawberry fruit ripening and resistance is unclear. In this study, two genes, FaMAPK5 and FaMAPK10, were isolated, and their expression pattern and function analysis were conducted. The results showed FaMAPK5 and FaMAPK10 were expressed in all tested tissue/organ types and reached the highest expression level at the white stage during strawberry fruit development and ripening. Transient overexpression of FaMAPK5 and FaMAPK10 increased the fruit anthocyanin, abscisic acid (ABA), total sugar, and glucose contents. ABA and especially hydrogen peroxide (H₂O₂) treatment induced the production of large amounts of H₂O₂ and noticeably increased the expression levels of FaMAPK5 and FaMAPK10 in strawberry fruit, while the reduced glutathione (GSH) had the opposite effect. The level of total phenol and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) significantly increased in FaMAPK5 overexpression fruit, and increased activities of SOD and CAT were observed in FaMAPK10 overexpression fruit. In addition, Botrytis cinerea treatment showed that overexpression of FaMAPK5 conferred retarded disease symptom development and enhanced fruit disease resistance. Our research revealed that FaMAPK5 and FaMAPK10 might participate in ABA-mediated H₂O₂ signaling in regulating strawberry fruit ripening and resistance.

Knockout of SlNPR1 enhances tomato plants resistance against Botrytis cinerea by modulating ROS homeostasis and JA/ET signaling pathways

Tomato is one of the most popular horticultural crops, and many commercial tomato cultivars are particularly susceptible to Botrytis cinerea. Non-expressor of pathogenesis-related gene 1 (NPR1) is a critical component of the plant defense mechanisms. However, our understanding of how SlNPR1 influences disease resistance in tomato is still limited. In this study, two independent slnpr1 mutants were used to study the role of SlNPR1 in tomato resistance against B. cinerea. Compared to (WT), slnpr1 leaves exhibited enhanced resistance against B. cinerea with smaller lesion sizes, higher activities of chitinase (CHI), β-1, 3-glucanases (GLU) and phenylalanine ammonia-lyase (PAL), and significantly increased expressions of pathogenesis-related genes (PRs). The increased activities of peroxidase (POD), ascorbate peroxidase (APX) and decreased catalase (CAT) activities collectively regulated reactive oxygen species (ROS) homeostasis in slnpr1 mutants. The integrity of the cell wall in slnpr1 mutants was maintained. Moreover, the enhanced resistance was further reflected by induction of defense genes involved in jasmonic acid (JA) and ethylene (ET) signaling pathways. Taken together, these findings revealed that knocking out SlNPR1 resulted in increased activities of defense enzymes, changes in ROS homeostasis and integrity of cell walls, and activation of JA and ET pathways, which confers resistance against B. cinerea in tomato plants.

VvBAP1, a Grape C2 Domain Protein, Plays a Positive Regulatory Role Under Heat Stress

Temperature is considered one of the critical factors directly influencing grapevine during the three primary growth and development stages: sprout, flowering, and fruit-coloring, which is strongly correlated to the yield and quality of the grape. The grapevine is frequently exposed to high-temperature conditions that are detrimental to growth. However, the mechanisms of the heat stress response and adaptation in grapevine are not adequately studied. The Arabidopsis copine gene AtBON1 encodes a highly conserved protein containing two C2 domains at the amino terminus, participation in cell death regulation and defense responses. Previously, we showed that a BON1 association protein from the grapevine, VvBAP1, plays a positive role in cold tolerance. Similarly, the involvement of VvBAP1 in the resistance to heat stress was also found in the present study. The results indicated VvBAP1 was significantly induced by high temperature, and the elevated expression of VvBAP1 was significantly higher in the resistant cultivars than the sensitive cultivars under heat stress. Seed germination and phenotypic analysis results indicated that overexpression of VvBAP1 improved Arabidopsis thermoresistance. Compared with the wild type, the chlorophyll content and net photosynthetic rate in VvBAP1 overexpressing Arabidopsis plants were markedly increased under heat stress. At high temperatures, overexpression of VvBAP1 also enhanced antioxidant enzyme activity as well as their corresponding gene transcription levels, to reduce the accumulation of reactive oxygen species and lipid peroxidation. Besides, the transcriptional activities of HSP70, HSP101, HSFA2, and HSFB1 in VvBAP1 overexpressing Arabidopsis plants were significantly up-regulated compare to the wild type. In summary, we propose that VvBAP1 may play a potential important role in enhanced grapevine thermoresistance, primarily through the enhancement of antioxidant enzyme activity and promoted heat stress response genes expression.

Tomato GLR3.3 and GLR3.5 mediate cold acclimation-induced chilling tolerance by regulating apoplastic H2 O2 production and redox homeostasis

Plant glutamate receptor-like (GLR) genes play important roles in plant development and immune response. However, the functions of GLRs in abiotic stress response remain unclear. Here we show that cold acclimation at 12°C induced the transcripts of GLR3.3 and GLR3.5 with increased tolerance against a subsequent chilling at 4 °C. Silencing of GLR3.3 or/and GLR3.5 or application of the antagonist of ionotropic glutamate receptor 6,7-dinitroquinoxaline-2,3-dione (DNQX), all compromised the acclimation-induced increases in the transcripts of respiratory burst oxidase homolog1 (RBOH1), activity of NADPH oxidase, the accumulation of apoplastic H₂ O₂ and the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG), resulting in an attenuated chilling tolerance; the effect, however, was rescued by foliar application of H₂ O₂ or GSH. Both RBOH1-silenced and glutathione biosynthesis genes, γ- glutamylcysteine synthetase (GSH1)- and glutathione synthetase (GSH2)-cosilenced plants had decreased chilling tolerance with reduced GSH/GSSG ratio. Moreover, application of DNQX had little effects on the GSH/GSSG ratio and the tolerance in RBOH1-silenced plants and GSH1- and GSH2-cosilenced plants. These findings unmasked the functional hierarchy of GLR-H₂ O₂ -glutathione cascade and shed new light on cold response pathway in tomato plants.

Metabolic profile analysis and identification of key metabolites during rice seed germination under low-temperature stress

The metabolic profile of rice (Oryza sativa) during germination under low temperature (LT) has not been reported. In this study, the rice varieties 02428 (japonica) and YZX (indica) were subjected to experiments consisting of treatments including LT, normal temperature (NT) and a transition from LT to NT, and tissues were sampled at different time points during germination. A total of 730 metabolites were detected by a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based widely targeted metabolomics method. On the basis of the screening criteria of increased contents under LT and decreased contents under NT, we identified 35 different metabolites that responded to LT stress among the 730 metabolites. Furthermore, the content differences of the 35 metabolites were compared when the samples were transferred from LT to NT. According to a fold change <0.5 or a variable importance in projection (VIP) score>1 at the transition point, 7 out of the 35 metabolites responded significantly to LT stress and were defined as key metabolites. A partial least squares (PLS) regression model of seven key metabolites with seedling length (SL), seedling area (SSA), and seedling volume (SV) was constructed, and the fitting effect was good. These seven key metabolites participate in the biosynthesis of amino acids and phenylpropanoids and in the metabolism of glutathione and inositol phosphate. This study laid a foundation for an improved understanding of the LT-germination mechanism of rice seeds.

Deciphering hydrogen peroxide-induced signalling towards stress tolerance in plants

Plants encounter a variety of adverse environmental conditions, such as high salinity, drought, extreme heat/cold and heavy metals contamination (abiotic stress) or attack of various pathogens (biotic stress). These detrimental environmental factors enhanced the ROS production such as singlet oxygen (¹O₂), superoxide (O₂ ^•-), hydrogen peroxide (H₂O₂) and hydroxyl radicals (OH^•). ROS are highly reactive and directly target several cellular molecules and metabolites, which lead to severe cellular dysfunction. Plants respond to oxidative damages by activating antioxidant machinery to trigger signalling cascades for stress tolerance. H₂O₂ signalling balances the plant metabolism through cross-talk with other signals and plant hormones during growth, development and stress responses. H₂O₂ facilitates the regulation of different stress-responsive transcription factors (TFs) including NAC, Zinc finger, WRKY, ERF, MYB, DREB and bZIP as both upstream and downstream events during stress signalling. The present review focuses on the biological synthesis of the H₂O₂ and its effect on the upregulation of kinase genes and stress related TFs for imparting stress tolerance.

Knockout of SlMAPK3 enhances tolerance to heat stress involving ROS homeostasis in tomato plants

BACKGROUND

High temperature is a major environmental stress that limits plant growth and agriculture productivity. Mitogen-activated protein kinases (MAPKs) are highly conserved serine and threonine protein kinases that participate in response to diverse environmental stresses in plants. A total of 16 putative SlMAPK genes are identified in tomato, and SlMAPK3 is one of the most extensively studied SlMAPKs. However, the role of SlMAPK3 in response to heat stress is not clearly understood in tomato plants. In this study, we performed functional analysis of SlMAPK3 for its possible role in response to heat stress.

RESULTS

qRT-PCR analyses revealed that SlMAPK3 relative expression was depressed by heat stress. Here, wild-type (WT) tomato plants and CRISPR/Cas9-mediated slmapk3 mutant lines (L8 and L13) were used to investigate the function of SlMAPK3 in response to heat stress. Compared with WT plants, slmapk3 mutants exhibited less severe wilting and less membrane damage, showed lower reactive oxygen species (ROS) contents, and presented higher both activities and transcript levels of antioxidant enzymes, as well as elevated expressions of genes encoding heat stress transcription factors (HSFs) and heat shock proteins (HSPs).

CONCLUSIONS

CRISPR/Cas9-mediated slmapk3 mutants exhibited more tolerance to heat stress than WT plants, suggesting that SlMAPK3 was a negative regulator of thermotolerance. Moreover, antioxidant enzymes and HSPs/HSFs genes expression were involved in SlMAPK3-mediated heat stress response in tomato plants.

ABA signaling rather than ABA metabolism is involved in trehalose-induced drought tolerance in tomato plants

Trehalose increased drought tolerance of tomato plants, accompanied by reduced water loss and closed stomata, which was associated with the upregulated ABA signaling-related genes expression, but not in ABA accumulation. Drought is one of the principal abiotic stresses that negatively influence the growth of plant and yield. Trehalose has great agronomic potential to improve the stress tolerance of plants. However, little information is available on the role of ABA and its signaling components in trehalose-induced drought tolerance. The aim of this study is to elucidate the potential mechanism by which trehalose regulates ABA in response to drought stress. In this study, 6-week-old tomato (Solanum lycopersicum cv. Ailsa Craig) plants were treated with 0 or 15.0 mM trehalose solution. Results showed that trehalose treatment significantly enhanced drought tolerance of tomato plants, accompanied by encouraged stomatal closure and protected chloroplast ultrastructure. Compared with controls, trehalose-treated plants showed lower hydrogen peroxide content and higher antioxidant enzymes activities, which contributed to alleviate oxidative damage caused by drought. Moreover, trehalose treatment decreased ABA content, which was followed by the downregulation of ABA biosynthesis genes expression and the upregulation of ABA catabolism genes expression. In contrast, exogenous trehalose upregulated transcript levels of ABA signaling-related genes, including SlPYL1/3/4/5/6/7/9, SlSnRK2.3/4, SlAREB1/2, and SlDREB1. These results suggested that trehalose treatment enhanced drought tolerance of tomato plants, and it's ABA signaling rather than ABA metabolism that was involved in trehalose-induced drought tolerance in tomato plants. These findings provide evidence for the physiological role of trehalose and bring about a new understanding of the possible relationship between trehalose and ABA.

Overexpression of Solanum habrochaites microRNA319d (sha-miR319d) confers chilling and heat stress tolerance in tomato (S. lycopersicum)

BACKGROUND

MicroRNA319 (miR319) acts as an essential regulator of gene expression during plant development and under stress conditions. Although the role of miR319a in regulating leaf development has been well studied in tomato (Solanum lycopersicum), the function of the recently discovered wild tomato Solanum habrochaites miRNA319d (sha-miR319d) remains poorly understood. In this study, we overexpressed sha-miR319d in cultivated tomato 'Micro-Tom' to further investigate its role in tomato temperature stress responses.

RESULTS

Under chilling or heat stress, sha-miR319d-overexpressing plants showed enhanced stress tolerance, including lower relative electrolyte leakage (REL), malondialdehyde (MDA) concentration, O₂^- generation and H₂O₂ concentration and higher chlorophyll contents and Fv/Fm values than wild-type (WT) plants. Overexpression of sha-miR319d enhanced the activities of superoxide dismutase (SOD) and catalase (CAT), with possible correlation with elevated expression levels of the genes FeSOD, CuZnSOD and CAT. Moreover, different expression levels of key genes involved in chilling (MYB83 and CBF1), heat (HsfA1a, HsfA1b and Hsp90), and reactive oxygen species (ROS) (ZAT12 and ZAT10) signaling in transgenic plants and WT were determined, suggesting a role for sha-miR319d in regulating tomato temperature stress via chilling, heat and ROS signaling. Silencing GAMYB-like1 increased tomato chilling tolerance as well as the expression levels of CBF1, CuZnSOD, CAT, APX1, APX2, ZAT12 and ZAT10. Additionally, overexpression of sha-miR319d in tomato caused plant leaf crinkling and reduced height.

CONCLUSIONS

Overexpression of sha-miR319d confers chilling and heat stress tolerance in tomato. Sha-miR319d regulates tomato chilling tolerance, possibly by inhibiting expression of GAMYB-like1 and further alters chilling, heat and ROS signal transduction. Our research provides insight for further study of the role of sha-miR319d in tomato growth and stress regulation and lays a foundation for the genetic improvement of tomato.

Phytoremediation through Bidens pilosa L., a nonhazardous approach for uranium remediation of contaminated water

A few plant species are recognized for uranium bioaccumulation, particularly as upper accumulator. Uranium has a dynamic impact on the physiological, biochemical, and photochemical reactions. Therefore, the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), soluble sugar, protein, photochemical reactions, and accumulation of uranium characteristics were studied in Bidens pilosa L. while applying altered concentrations of uranium in the form of C₄H₆O₆U. It was done to measure the capacity of B. pilosa L. to remediate uranium from wastewater. In this study, the results showed that B. pilosa L. not only has the ability of uranium accumulation but it can accumulate in the upper parts i.e. leaves and stem. Overall it can accumulate as much as 1538 mg/kg on a dry weight basis. Uranium accumulation is a complex process which changes both physiological and biochemical index in plant species under different treatments. SOD decreased in leaves and stem in response to all treatments whereas POD and CAT increased at treatment 3 and 72 h up to 1335 μ/g-FW and 47 μ/g-FW at 72 h, respectively. This increase was followed by a downward trend. The correlation coefficient between fluorescence ratio F_v/F_m and the concentrations of uranium treatment were significantly negative i.e. -0.928. The Fourier transform infrared spectroscopy (FTIR) analysis also highlighted that uranium does not change the basic chemical composition of B. pilosa L., but has an effect on the contents of chemical constituents. From the study, it is concluded that B. Pilosa L. has shown a capacity for uranium enrichment, especially as an upper accumulator.

Knockout of SlMAPK3 Reduced Disease Resistance to Botrytis cinerea in Tomato Plants

Mitogen-activated protein kinases (MAPKs) play an important role in defense responses to biotic and abiotic stresses. In order to investigate the role of SlMAPK3 in tomato plant resistance to Botrytis cinerea, two lines of slmapk3 mutants and wild-type (WT) tomato plants were used. The results showed that slmapk3 mutants were more susceptible to B. cinerea and that knockout of SlMAPK3 reduced the activities of defense enzymes and enhanced the accumulation of reactive oxygen species (ROS). Furthermore, we detected the expressions of salicylic acid (SA) and jasmonic acid (JA) signaling-related genes and found that knockout of SlMAPK3 enhanced the expressions of SlPR1, SlPAD4 and SlEDS1, whereas reduced the expressions of SlLoxC, SlPI I and SlPI II and enhanced the expressions of SlJAZ1 and SlMYC2. We postulate that SlMAPK3 plays a positive role in tomato plant resistance to B. cinerea through regulating ROS accumulation and SA and JA defense signaling pathways.

Reduction of Tomato-Plant Chilling Tolerance by CRISPR-Cas9-Mediated SlCBF1 Mutagenesis

Chilling stress is the main constraint in tomato ( Solanum lycopersicum) production, as this is a chilling-sensitive horticultural crop. The highly conserved C-repeat binding factors (CBFs) are cold-response-system components found in many species. In this study, we generated slcbf1 mutants using the CRISPR-Cas9 system and investigated the role of SlCBF1 in tomato-plant chilling tolerances. The slcbf1 mutants exhibited more severe chilling-injury symptoms with higher electrolyte leakage and malondialdehyde levels than wild-type (WT) plants. Additionally, slcbf1 mutants showed lower proline and protein contents and higher hydrogen peroxide contents and activities of antioxidant enzymes than WT plants. Knockout of SlCBF1 significantly increased indole acetic acid contents but decreased methyl jasmonate, abscisic acid, and zeatin riboside contents. The reduced chilling tolerance of the slcbf1 mutants was further reflected by the down-regulation of CBF-related genes. These results contribute to a better understanding of the molecular basis underlying SlCBF1 mediation of tomato chilling sensitivity.

Compound Synthesis or Growth and Development of Roots/Stomata Regulate Plant Drought Tolerance or Water Use Efficiency/Water Uptake Efficiency

Water is crucial to plant growth and development because it serves as a medium for all cellular functions. Thus, the improvement of plant drought tolerance or water use efficiency/water uptake efficiency is important in modern agriculture. In this review, we mainly focus on new genetic factors for ameliorating drought tolerance or water use efficiency/water uptake efficiency of plants and explore the involvement of these genetic factors in the regulation of improving plant drought tolerance or water use efficiency/water uptake efficiency, which is a result of altered stomata density and improving root systems (primary root length, hair root growth, and lateral root number) and enhanced production of osmotic protectants, which is caused by transcription factors, proteinases, and phosphatases and protein kinases. These results will help guide the synthesis of a model for predicting how the signals of genetic and environmental stress are integrated at a few genetic determinants to control the establishment of either water use efficiency or water uptake efficiency. Collectively, these insights into the molecular mechanism underpinning the control of plant drought tolerance or water use efficiency/water uptake efficiency may aid future breeding or design strategies to increase crop yield.