Ethylene Role in Plant Growth, Development and Senescence: Interaction with Other Phytohormones

Plasticity of Root System Architecture and Whole Transcriptome Responses Underlying Nitrogen Deficiency Tolerance Conferred by a Wild Emmer Wheat QTL

Our aim was to elucidate mechanisms underlying nitrogen (N)-deficiency tolerance in bread wheat (cultivar Ruta), conferred by a wild emmer wheat QTL (WEW; IL99). We hypothesised that the tolerance in IL99 is driven by enhanced N-uptake through modification of root system architecture (RSA) underscored by transcriptome modifications. Severe N-deficiency (0.1 N for 26 days) triggered significantly higher plasticity in IL99 compared to Ruta by modifying 16 RSA traits; nine of which were IL99-specific. The change in root growth in IL99 was collectively characterised by a transition in root orientation from shallow to steep, increased root number and length, and denser networks, enabling nutrient acquisition from a larger volume and deeper soil layers. Gene ontology and KEGG-enrichment analyses highlighted IL99-specific pathways and candidate genes elevated under N-deficiency. This included Jasmonic acid metabolism, a key hormone mediating RSA plasticity (AOS1, TIFY, MTB2, MYC2), and lignification-mediated root strengthening (CYP73A, 4CL). 'N-metabolism' was identified as a main shared pathway to IL99 and Ruta, with enhanced nitrate uptake predominant in IL99 (NRT2.4), while remobilisation was the main strategy in Ruta (NRT2.3). These findings provide novel insights into wheat plasticity response underlying tolerance to N-deficiency and demonstrate the potential of WEW for improving N-uptake under suboptimal conditions.

A review of the interaction mechanisms between jasmonic acid (JA) and various plant hormones, as well as the core regulatory role of MYC2

Jasmonic acid (JA), as a defensive plant hormone, can synergistically or antagonistically interact with common hormones such as gibberellin (GA), abscisic acid (ABA), indole-3-acetic hormone acid (IAA), and ethylene (ETH) during the plant growth process, as well as interact with hormones such as melatonin (MT), brassinolide (BR), and resveratrol to regulate plant growth and development processes such as metabolite synthesis, pest and disease defense, and organ growth. The core regulatory factor MYC2 of JA mainly mediates the signal transduction pathways of these hormone interactions by interacting with other genes or regulating transcription. This article reviews the mechanism of cross-talk between JA and hormones such as ABA, GA, and salicylic acid (SA), and discusses the role of MYC2 in hormone interactions.

Clove (Syzygium aromaticum) Pods: Revealing Their Antioxidant Potential via GC-MS Analysis and Computational Insights

Background:Syzygium aromaticum is a tree whose aromatic dried flower buds are known as cloves. When it comes to phenolic chemicals, such as flavonoids, hydroxybenzoic acids, hydroxycinnamic acids, and hydroxyphenyl propane, clove is a major plant source of these substances. Finding out how effective clove buds are as antioxidants was the driving force behind this study's GC-MS investigation and computational discoveries. Methods: This inquiry into clove pods focused on the chemical composition of clove using the GC-MS technique, as well as its antioxidant qualities and computational modeling. Results: This antioxidant may be more effective in lower doses than ascorbic acid (A.A.), butylate hydroxytoluene (BHT), and β-carotene, with 57.22 ± 0.41 mg QE/g of total phenols and flavonoids and 7.25 ± 0.12 mg GAE/g of clove extract. Phenols destroy free radicals, which boosts antioxidant activity. Flavonoids defend against ROS, which also boosts antioxidant activity. Clove pod GC-MS analysis identified 21 components, of which eugenol accounted for 58.86%. The absence of nitrogen and chlorine molecules emphasizes the composition's organic nature. Eugenol, the major component of clove oil, is a phenolic molecule that binds strongly to bacterial enzymes such as DNA gyrase and dihydrofolate reductase. Docking experiments have shown that clove chemicals interact with acetylcholinesterase, a crucial enzyme in insect larvae, paralyzing and killing them. Conclusions: This study demonstrates the immense potential of plants in providing novel therapeutic and environmental solutions. We must support further research into nature's inherent benefits. The extensive knowledge that can be gained from botany can be used to improve health, ecology, and sustainability.

Phytohormones: Heart of plants' signaling network under biotic, abiotic, and climate change stresses

Industrialization has made the world increasingly unstable, subjecting plants to various constraints. As a consequence, plants are constantly experiencing biological, environmental, and climatic constraints, necessitating defense mechanisms to ensure their survival. Plants are vulnerable to various biotic factors, including insects, pathogens (bacterial, fungal, viral, and nematodes), weeds, and herbivores. They also face different abiotic and climate change challenges such as drought (regulated by genes like GH3, DREB, ZIFL1;3, etc), salinity, heavy metals, metalloids, ultraviolet radiations (UV), ozone (O3), low and high temperature (chilling/cold/freezing/heat), carbon dioxide (CO2), chlorofluorocarbons (CFCs), and flooding/hypoxia/anoxia. Different transcriptional factors, such as KNOX1, PYK10, and NRP1, regulate these abiotic and climate change stresses. Different phytohormones such as auxin (regulated by components AUX/IAA3, PIN, indole-glucosinolate, indole-3-acetaldoxine), gibberellin (key elements involved in the synthesis and signaling such as DELLA, GA3ox, RhHB1), cytokinin (signaling through ARR5), ethylene (involved transcription factors like AP2/ERF), abscisic acid (signaling regulated through SnRK2), salicylic acid, jasmonic acid (regulated by JAZ1/TIFYIOA), brassinosteroids, nitric oxide, and strigolactones (synthetic precursor being GR24) control plants' maturation in normal and stressed conditions by regulating various metabolic and physiological plant activities. Phytohormonal interactions and their synergy are often assessed by different techniques and assays such as CRISPR/Cas9, ELISA, RIA, luciferase, GAL4, and mEmerald GFP. Their synthesis and signaling are regulated by various genes (such as YUCCA1, YUCCA5, GA3ox, etc), transporters (PIN, such as PIN, ABCB, NPF, etc), and receptors (such as PLY4, PLY5, BZR1/BES1, MYC2, etc) and have different precursors such as L-arginine, L-tryptophan, phenylalanine, linolenic acid, S-adenosylmethionine, geranylgeranyl diphosphate. This review comprehensively analyses the breakthrough in phytohormones and their signaling in regulating plants' growth and maturation. Their significance in combating the biotic, abiotic, and climate change stresses, improving stress adaptation to identify novel strategies enhancing plant resilience, sustainable agriculture, and ensuring food security.

Microbiomes in action: multifaceted benefits and challenges across academic disciplines

Microbiomes combine the species and activities of all microorganisms living together in a specific habitat. They comprise unique ecological niches with influences that scale from local to global ecosystems. Understanding the connectivity of microbiomes across academic disciplines is important to help mitigate global climate change, reduce food insecurity, control harmful diseases, and ensure environmental sustainability. However, most publications refer to individual microbiomes, and those integrating two or more related disciplines are rare. This review examines the multifaceted benefits of microbiomes across agriculture, food manufacturing and preservation, the natural environment, human health, and biocatalyst processes. Plant microbiomes, by improving plant nutrient cycling and increasing plant abiotic and biotic stress resilience, have increased crop yields by over 20%. Food microbiomes generate approximately USD 30 billion to the global economy through the fermented food industry alone. Environmental microbiomes help detoxify pollutants, absorb more than 90% of heavy metals, and facilitate carbon sequestration. For human microbiomes, an adult person can carry up to 38 trillion microbes which regulate well being, immune functionality, reproductive function, and disease prevention. Microbiomes are used to optimize biocatalyst processes which produce bioenergy and biochemicals; bioethanol production alone is valued at over USD 83 billion p.a. However, challenges, including knowledge gaps, engaging indigenous communities, technical limitations, regulatory considerations, the need for interdisciplinary collaboration, and ethical issues, must be overcome before the potential for microbiomes can be more effectively realized.

Investigation of Growth and Ginsenoside Content of Wild-Simulated Ginseng Cultivated in Different Vegetation Environments for Establishing a Plant Growth Model

Wild-simulated ginseng (WSG, Panax ginseng C.A. Meyer) is one of the most valuable medicinal plants in the world. This study aimed to investigate the correlation between growth and ginsenoside content of WSG in two different cultivation environments: coniferous and mixed forests. The results showed that air temperature, soil moisture content, and solar radiation were higher in mixed forest than in coniferous forest. Regarding soil properties, electrical conductivity, organic matter, total nitrogen, exchangeable potassium, and magnesium were higher in mixed forest than in coniferous forest. However, exchangeable sodium was lower in mixed forest than in coniferous forest. The analysis of growth characteristics revealed that the number of leaflets was significantly higher in WSG cultivated in mixed forest than in WSG cultivated in coniferous forest, whereas rhizome length, root diameter, root weight, and dry weight were significantly higher in coniferous forest. In contrast, total ginsenoside content and the content of each ginsenoside were much higher in WSG cultivated in mixed forest than in WSG cultivated in coniferous forest. The growth of WSG showed significantly positive correlations with electrical conductivity, organic matter, total nitrogen, exchangeable cations (K+, Mg2+, Na+), and cation exchange capacity. The number of leaflets per stem showed significantly positive correlations with six ginsenosides, whereas petiole length showed significantly negative correlations with mRb1, mRc, and Rb1. In conclusion, growth characteristics of WSG were higher in coniferous forest, but ginsenoside contents were higher in mixed forest. These results might be helpful for establishing the most optimal growth model of WSG, which is affected by various environmental factors.

Ethylene response factor AeABR1 regulates chlorophyll degradation in post-harvest okras

Chlorophyll degradation, marked by the loss of green color, is a prominent feature of okra storage after harvest, posing challenges for its storage, transportation, and marketability. In order to investigate the regulatory mechanisms of chlorophyll degradation in okras, we isolated and characterized AeABR1, a repressor of abscisic acid (ABA) that belongs to the ethylene-responsive element-binding factor (ERF/AP2) superfamily of ERF transcription factors. The transcriptional levels of AeABR1 during storage were closely linked to the degreening of okra fruit (R-values ranging from -0.714 to -0.516, P < 0.05) and the production of ethylene (R = -0.362, P < 0.05). Subcellular localization analysis revealed that AeABR1 was mostly located in the nucleus. Functional studies demonstrated that the transient expression of AeABR1 induced rapid chlorophyll degradation in the leaves of okra and N. benthamiana. Similar results were observed in transgenic Arabidopsis seedlings expressing AeABR1, which exhibited yellowing growth phenotypes, reduced chlorophyll content, and elevated chlorophyll catabolic genes (CCGs) expression levels. AeABR1 substantially induced the activities of AeCLH1 promoters. These findings indicated that AeABR1 may act as an activator of AeCLH1 genes and an accelerator of chlorophyll degradation in post-harvest okras.

Chemical Profiling and Bioactivity of Microalgae Extracts for Enhancing Growth and Anthracnose Resistance in the Common Bean (Phaseolus vulgaris L.)

The present study aimed to chemically profile the hydroalcoholic extracts from the microalgae (MEs) Nannochloropsis oculata, Phaeodactylum tricornutum, Tetradesmus obliquus, and Tetraselmis tetrathele and evaluate their effects on the development of Colletotrichum lindemuthianum and anthracnose symptoms, as well as on the initial growth of bean plants. For this, MEs were analyzed using UPLC coupled with a mass spectrometer, allowing the identification of peaks and annotation of potential metabolites. Fungal mycelial growth was assessed seven days after inoculation, and conidial germination was measured 72 h after incubation, using ME concentrations of 0, 0.1, 0.5, and 1.0 mg·mL-1. Bean seeds of the IPR Uirapuru cultivar were sown and treated with 3 mL of extracts at four time points: at sowing and 72 h after each previous treatment. After 11 days of cultivation in a growth chamber, the plants were divided into two groups: one for anthracnose control assessment and the other for evaluating growth promotion by MEs. Plant length as well as fresh and dry weights of shoots and roots were determined, leaf pigments were quantified, and anthracnose severity was assessed using a diagrammatic scale. The UPLC analysis identified 32 compounds in the extracts of the four microalgae, belonging to different chemical and functional groups, with lipids being the most significant fraction. The extracts exhibited variability and diversity in chemical composition depending on the microalgal species. MEs did not affect mycelial growth yet increased the germination of C. lindemuthianum conidia, regardless of the dose or species used. Anthracnose severity was not affected by the microalgae extracts. Regarding growth promotion, the extracts showed varying effects but generally increased shoot and root length, fresh biomass, and leaf pigment content.

Crucial Roles of Brassinosteroids in Cell Wall Composition and Structure Across Species: New Insights and Biotechnological Applications

Brassinosteroids (BR) are steroidal phytohormones essential for plant growth, development, and stress resistance. They fulfil this role partially by modulating cell wall structure and composition through the control of gene expression involved in primary and secondary cell wall biosynthesis and metabolism. This affects the deposition of cellulose, lignin, and other components, and modifies the inner architecture of the wall, allowing it to adapt to the developmental status and environmental conditions. This review focuses on the effects that BR exerts on the main components of the cell wall, cellulose, hemicellulose, pectin and lignin, in multiple and relevant plant species. We summarize the outcomes that result from modifying cell wall components by altering BR gene expression, applying exogenous BR and utilizing natural variability in BR content and describing new roles of BR in cell wall structure. Additionally, we discuss the potential use of BR to address pressing needs, such as increasing crop yield and quality, enhancing stress resistance and improving wood production through cell wall modulation.

ACS2 and ACS6, especially ACS2 is involved in MPK6 evoked production of ethylene under Cd stress, which exacerbated Cd toxicity in Arabidopsis thaliana

As one of the heavy metal pollutants with strong biological toxicity, cadmium (Cd) is easily absorbed by plant roots, which seriously restricts the growth of plants, causes the quality of agricultural products to decline and threatens human health. Many complex signal transduction pathways are involved in the process of plant response to Cd stress. Among them, plant hormone ethylene is an important signal molecule for plant response to various environmental stresses, and its regulatory mechanism and signal transduction pathway in Cd stress response need to be further clarified. Here, we discovered that Cd stress induced a significant increment in ethylene production in Arabidopsis roots, and the amount of ethylene produced was positively correlated with the inhibition of Arabidopsis root growth and Cd accumulation. Simultaneously, Cd stress stimulated the detoxification mechanism within cells and promoted the expression of METAL TOLERANCE PROTEIN 3 (MTP3), IRON-REGULATED TRANSPORTER2 (IRT2), IRON REGULATED GENE 2 (IREG2) genes implicated in Cd vacuolar compartmentation. However, whether this is associated with ethylene signal transduction remains to be further explored. Further studies have revealed that the Cd induced ethylene burst is attributed to the up-regulation of the expression of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE (ACS) genes that mediated by MITONGEN-ACTIVATED PROTEIN KINASE 6 (MAPK6) in Arabidopsis roots, and among them, ACS2 and ACS6, especially ACS2, are involved in MAPK6-induced ethylene production under Cd stress. The results of this study provide new ideas for understanding the signal transduction pathway of plant response to Cd stress.

Mapping resistance to Sclerotinia white mold in two pinto bean recombinant inbred line populations

White mold, caused by the fungus Sclerotinia sclerotiorum (Lib.) de Bary, is a devastating disease affecting common bean (Phaseolus vulgaris L.) production worldwide. Breeding for resistance to white mold is challenging due to its quantitative inheritance and intricate genetic mechanisms. This research aimed to validate and characterize physiological resistance in the pinto dry bean market class through greenhouse straw tests under controlled conditions and field assessments under natural environments. Classical quantitative trait locus (QTL) mapping and Khufu de novo QTL-seq were employed to detect and narrow QTL intervals and identify candidate genes associated with white mold resistance in two pinto bean recombinant inbred line populations, PT9-5-6/USPT-WM-12 (P2) and PT12-37/VCP-13 (P3). Eleven QTL, five in P2 and six in P3, conditioning white mold resistance were identified. New QTL were discovered including WM1.4 and WM11.5 in P2, and WM1.5 and WM7.7 in P3. Existing major-effect QTL were validated: WM5.4 (34%-phenotypic variation explained) and WM7.4 (20%) in straw tests, and WM2.2 (15%) and WM3.1 (27%) under field conditions. QTL for avoidance traits such as resistance to lodging and late maturity overlapped WM2.2 in P2 and WM1.5, WM3.1, WM5.4, and WM7.7 in P3. WM5.4 (Pv05: 7.0-38.7 Mb) was associated with a large Phaseolus coccineus L. genome introgression in the resistant parent VCP-13. These findings offer narrowed genomic intervals and putative candidate genes for marker-assisted selection targeting white mold resistance improvement in pinto beans.

Phytohormonal Regulation of Abiotic Stress Tolerance, Leaf Senescence and Yield Response in Field Crops: A Comprehensive Review

Field crops are expected to be increasingly threatened by climate change, which will negatively impact plant development, growth and yield. Phytohormones play a crucial role in regulating specific signalling pathways to induce rapid adaptive responses to environmental stresses. Exogenous phytohormone application alters hormonal balance, thereby enhancing plant adaptation to adverse conditions. While several studies have advanced our understanding of the use of phytohormones in field crops, yield responses and species-specific application strategies remain inconsistent and rarely assessed under field conditions. The application of cytokinins (CKs), abscisic acid (ABA), and gibberellic acid (GA) has been shown to maintain prolonged photosynthetic activity, stabilize plasma membrane, and reduce lipid peroxidation and ion accumulation under salinity stress in wheat. Additionally, inhibitors of ethylene synthesis and receptors can mitigate stress symptoms under drought and heat stress, which typically accelerates senescence and shortens the grain-filling period in cereal crops. In this way, exogenous application of CKs, GA, and ethylene inhibitors can delay senescence by sustaining leaf photosynthetic activity and postponing nutrient remobilization. However, these benefits may not consistently translate into improvements in grain yield and quality. This review explores the molecular mechanisms of phytohormones in abiotic stress tolerance, delineates their specific functions and evaluates experimental findings from field applications. It also summarizes the potential of phytohormone applications in field crops, emphasizing the need for species-specific investigations on application timing and dosages under open-field conditions to optimize their agronomic potential.

Eco-friendly extension of postharvest longevity in Alstroemeria cut flowers using melatonin and putrescine treatments

Postharvest longevity is the most important factor concerning the commercial value of cut flowers. Alstroemeria 'Amatista' is one of the most valued species for its ornamental appeal and it has been often reported to suffer from premature senescence. The present study was undertaken to establish the efficacy of melatonin (100 and 200 μM) and putrescine (1.5 and 3 mM) as enviro-friendly compounds applied into the vase solution in extending the vase life of cut flowers of Alstroemeria by assessing different physiological parameters. Results showed that melatonin at 100 and 200 μM and putrescine at 1.5 mM significantly extended the flower vase life from 12 to 13 days (control) to 20-21 days. More precisely, both melatonin and putrescine lowered electrolyte leakage (EL) and increased relative water content (RWC), relative fresh weight (RFW), and relative solution uptake (RSU) of flowers. In addition, both compounds enhanced the total anthocyanin content, phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) activities, and reduced malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content, which implies the decline in oxidative stress. These results confirm that both melatonin and putrescine act as effective and environmental-friendly exogenous applications to improve postharvest quality and extend the vase life of Alstroemeria cut flowers. The study provides important information for possible applications in the floriculture industry.

Metabolite Profiling of the Resurrection Grass Eragrostis nindensis During Desiccation and Recovery

Resurrection plants employ unique metabolic mechanisms to protect themselves against damage caused by desiccation. This study aimed to identify metabolites, using gas chromatography-mass spectrometry, which were differentially abundant in Eragrostis nindensis at different stages of dehydration and rehydration in leaves which are destined to senesce on desiccation termed "senescent tissue" (ST) and those which remain desiccation-tolerant during water deficit and are termed "non-senescent tissue" (NST). Furthermore, the study compared the shoot and root systems during extreme water deficit and recovery therefrom to unravel similarities and differences at the whole plant level in overcoming desiccation. Shoot metabolomics data showed differentially abundant metabolites in NST, including raffinose, sucrose, glutamic acid, aspartic acid, proline, alpha-ketoglutaric acid, and allantoin, which act as major drivers for plant desiccation tolerance and aid the plant post-rehydration. The metabolites which accumulated in the ST-indicated initiation of programmed cell death (PCD) leading to senescence. The roots accumulated fewer metabolites than the shoots, some exclusive to the root tissues with functions such as osmoprotection, reactive oxygen species quenching, and signaling, and thus proposed to minimize damage in leaf tissues during dehydration and desiccation. Collectively, this work gives further insight into the whole plant responses of E. nindensis to extreme dehydration conditions and could serve as a model for future improvements of drought sensitive crops.

Determining the function of ripening associated genes and biochemical changes during tomato (Solanum lycopersicum L.) fruit maturation

This article examines biochemical alterations and gene expression changes during tomato fruit physiology. The chroma index increases from mature green (41.27) to red ripe (48.36) stages, and the texture softens from mature green (43.56 N) to red ripe (24.75 N). Reducing sugar and total carotenoid levels rise at the red ripe stage. Free radical content was elevated in the early stages (7 nM) of ripening and declined at the later stages (4 nM). The specific activity of α-mannosidase and β-N-acetyl hexosaminidase was high at the breaker (0.077 & 0.075 U/mg, respectively) stages, while polygalacturonase activity was high at red ripe (1.173 U/mg) stage. qPCR experiments revealed that the α-mannosidase was upregulated during the breaker (1.2 fold) stages of tomato ripening, the β-N-acetyl Hexosaminidase was upregulated throughout the breaker (2 fold), and pink (1.2 fold) stages of tomato ripening, and the β-xylosidase was upregulated significantly during the breaker stage (3.9 fold) of tomato ripening. The current findings revealed that the α-Mannosidase (0.77), β-N-acetylhexosaminidase (0.99), xylosidase (0.85), ethylene-responsive factors (0.86), aminocylco propane carboxylic oxidase (0.90), and pectin methylesterase (0.83), were significantly associated with textural softening. Polygalacturonase (0.75) positively correlated to reducing sugar formation, aminocylco propane carboxylic synthase 4 (0.96) expression correlates with chroma changes during tomato fruit ripening. These correlations illustrate the complex interplay between gene expression and the physical and biochemical changes occurring during tomato fruit ripening.

A chromosome-level genome assembly of the Peruvian Algarrobo (Neltuma pallida) provides insights on its adaptation to its unique ecological niche

The dry forests of northern Peru are dominated by the legumous tree Neltuma pallida which is adapted to hot arid and semiarid conditions in the tropics. Despite having been successfully introduced in multiple other areas around the world, N. pallida is currently threatened in its native area, where it is invaluable for the dry forest ecosystem and human subsistence. A major tool for enhancing ecosystem conservation and understanding the adaptive properties of N. pallida to dry forest ecosystems is the construction of a reference genome sequence. Here, we report on a high-quality reference genome for N. pallida. The final genome assembly size is 403.7 Mb, consisting of 14 pseudochromosomes and 63 scaffolds with an N50 size of 26.2 Mb and a 34.3% GC content. Use of Benchmarking Universal Single Copy Orthologs revealed 99.2% complete orthologs. Long terminal repeat elements dominated the repetitive sequence content which was 51.2%. Genes were annotated using N. pallida transcripts, plant protein sequences, and ab initio predictions resulting in 22,409 protein-coding genes encoding 24,607 gene models. Comparative genomic analysis showed evidence of rapidly evolving gene families related to disease resistance, transcription factors, and signaling pathways. The chromosome-scale N. pallida reference genome will be a useful resource for understanding plant evolution in extreme and highly variable environments.

Ethylene negatively regulates cold tolerance through HbEIN3-HbICE2 regulatory module in Hevea brasiliensis

Cold stress can result in reduced growth rates, decreased latex production, and restricted areas for the Para rubber tree (Hevea brasiliensis). However, the molecular mechanisms governing the response of Hevea brasiliensis to cold stress remain elusive. Here, we found that ethylene plays a negative role in Hevea brasiliensis responses to cold stress. Treatment with the ethylene synthesis precursor 1-aminocyclopropane-1-carboxylic acid (ACC) decreased the cold tolerance of Hevea brasiliensis, while exogenous treatment with Ag+ (an ethylene signal inhibitor) had the opposite effect. Additionally, overexpressing HbEIN3 decreased cold stress tolerance in Arabidopsis and Taraxacum koksaghyz plants. Quantitative real-time PCR analysis indicated that HbEIN3-1 and HbEIN3-2 repress the expression of the cold-responsive genes HbCBF1-3 in Hevea brasiliensis. Moreover, HbEIN3-1 and HbEIN3-2 directly bind to the HbCBF1 promoter to suppress its transcription. Further investigation revealed that HbEIN3s interact with and dampen the transcriptional activity of HbICE2, a crucial transcription factor that positively regulates the cold signaling pathway, thereby attenuating the expression of HbICE2-targeted genes. Collectively, these findings indicate that HbEIN3s play a crucial role in ethylene-regulated cold tolerance through the repression of HbCBF1 expression and HbICE2 transcriptional activity.

A tomato ethylene-resistant mutant displays altered growth and higher β-carotene levels in fruit

The mutants resistant to ethylene are helpful in deciphering the role of ethylene in plant development. We isolated an ethylene-resistant tomato (Solanum lycopersicum) mutant by screening for acetylene-resistant (atr-1) seedlings. The atr-1 mutant displayed resistance to kinetin, suggesting attenuation of the ethylene sensing response. atr-1 also exhibited resistance to ABA- and glucose-mediated inhibition of seed germination. Unlike the Never-ripe (Nr) mutant seedlings that were hypersensitive to glucose, atr-1 seedlings were resistant to glucose, indicating ethylene sensing in atr-1 is compromised in a manner distinct from Nr. Metabolically, atr-1 seedlings had lower levels of amino acids but higher levels of several phytohormones, including ABA. atr-1 plants grew faster and produced more flowers, leading to a higher fruit set. However, the atr-1 fruits took a longer duration to reach the red-ripe (RR) stage. The ripened atr-1 fruits retained high β-carotene and lycopene levels post-RR stage and had longer on-vine longevity. The metabolome profiles of post-RR stage atr-1 fruits revealed increased levels of sugars. The atr-1 had a P279L mutation in the GAF domain of the ETR4, a key ethylene receptor regulating tomato ripening. The atr-1 exhibits phenotypic traits distinct from the Sletr4-1 (G154S) mutant, thus represents a new ETR4 allele named Sletr4-2. Our study highlights that novel alleles in ethylene receptors may aid in enhancing the nutritional quality of tomato.

Novel candidate genes and genetic basis analysis of kernel starch content in tropical maize

BACKGROUND

Starch is the most abundant carbohydrate in maize grains, serving as a primary energy source for both humans and animals, and playing a crucial role in various industrial applications. Increasing the starch content of maize grains is beneficial for improving the grain yield and quality. To gain insight into the genetic basis of starch content in maize kernels, a multiparent population (MPP) was constructed and evaluated for starch content in three different environments.

RESULTS

The integration of QTL mapping and genome-wide association analysis (GWAS) identified two SNPs, 8_166371888 and 8_178656036, which overlapped the QTL interval of qSC8-1, identified in the tropical maize line YML46. The phenotypic variance explained (PVE) by the QTL qSC8-1 was12.17%, while the SNPs 8_166371888 and 8_178656036 explained 10.19% and 5.72% of the phenotypic variance. Combined GWAS and QTL analyses led to the identification of two candidate genes, Zm00001d012005 and Zm00001d012687 located on chromosome 8.

CONCLUSIONS

The candidate gene Zm00001d012005 encodes histidine kinase, which is known to play a role in starch accumulation in rice spikes. Related histidine kinases, such as AHK1, are involved in endosperm transfer cell development in barley, which affects grain quality. Zm00001d012687 encodes triacylglycerol lipase, which reduces seed oil content. Since oil content in cereal kernels is negatively correlated with starch content, this gene is likely involved in regulating the starch content in maize kernels. These findings provide insights into the genetic mechanisms underlying kernel starch content and establish a theoretical basis for breeding maize varieties with high starch content.

Comparative Transcriptome Analysis of Gene Expression Between Female and Monoecious Spinacia oleracea L

BACKGROUND

Spinach (Spinacia oleracea L.) is an important leafy vegetable with dioecious and occasional monoecious plants. Monoecious lines are more suitable for hybrid production than dioecious lines due to their extended flowering period. However, genetic research on the sex determination of monoecism remains limited.

METHODS

In this study, RNA-seq analysis of monoecious and female spinach plants was performed at two distinct flowering stages. In total, we identified 4586 differentially expressed genes (DEGs), which were primarily involved in biological processes such as hormone signaling, cell wall biosynthesis, photosynthesis, and flower development, based on Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

RESULTS

Among these DEGs, 354 transcription factors, including 27 genes associated with the ABCDE gene, were discovered. Furthermore, a co-expression gene regulatory network was built, identifying nine key genes that play important roles in regulating sex differentiation between female and monoecious plants.

CONCLUSIONS

Our findings provide crucial molecular insights into the mechanisms of monoecism in spinach and offer a scientific basis for future spinach breeding.

Advantage looping: Gene regulatory circuits between microRNAs and their target transcription factors in plants

The 20 to 24 nucleotide microRNAs (miRNAs) and their target transcription factors (TF) have emerged as key regulators of diverse processes in plants, including organ development and environmental resilience. In several instances, the mature miRNAs degrade the TF-encoding transcripts, while their protein products in turn bind to the promoters of the respective miRNA-encoding genes and regulate their expression, thus forming feedback loops (FBLs) or feedforward loops (FFLs). Computational analysis suggested that such miRNA-TF loops are recurrent motifs in gene regulatory networks (GRNs) in plants as well as animals. In recent years, modeling and experimental studies have suggested that plant miRNA-TF loops in GRNs play critical roles in driving organ development and abiotic stress responses. Here, we discuss the miRNA-TF FBLs and FFLs that have been identified and studied in plants over the past decade. We then provide some insights into the possible roles of such motifs within GRNs. Lastly, we provide perspectives on future directions for dissecting the functions of miRNA-centric GRNs in plants.

Unravelling soybean responses to early and late Tetranychus urticae (Acari: Tetranychidae) infestation

Soybean is a crucial source of food, protein, and oil worldwide that is facing challenges from biotic stresses. Infestation of Tetranychus urticae Koch (Acari: Tetranychidae) stands out as detrimentally affecting plant growth and grain production. Understanding soybean responses to T. urticae infestation is pivotal for unravelling the dynamics of mite-plant interactions. We evaluated the physiological and molecular responses of soybean plants to mite infestation after 5 and 21 days. We employed visual/microscopy observations of leaf damage, H2O2 accumulation, and lipid peroxidation. Additionally, the impact of mite infestation on shoot length/dry weight, chlorophyll concentration, and development stages was analysed. Proteomic analysis identified differentially abundant proteins (DAPs) after early (5 days) and late (21 days) infestation. Furthermore, GO, KEGG, and protein-protein interaction analyses were performed to understand effects on metabolic pathways. Throughout the analysed period, symptoms of leaf damage, H2O2 accumulation, and lipid peroxidation consistently increased. Mite infestation reduced shoot length/dry weight, chlorophyll concentration, and development stage duration. Proteomics revealed 185 and 266 DAPs after early and late mite infestation, respectively, indicating a complex remodelling of metabolic pathways. Photorespiration, chlorophyll synthesis, amino acid metabolism, and Krebs cycle/energy production were impacted after both early and late infestation. Additionally, specific metabolic pathways were modified only after early or late infestation. This study underscores the detrimental effects of mite infestation on soybean physiology and metabolism. DAPs offer potential in breeding programs for enhanced resistance. Overall, this research highlights the complex nature of soybean response to mite infestation, providing insights for intervention and breeding strategies.

Molecular mechanisms of plant productivity enhancement by nano fertilizers for sustainable agriculture

Essential plant nutrients encapsulated or combined with nano-dimensional adsorbents define nano fertilizers (NFs). Nanoformulation of non-essential elements enhancing plant growth and stress tolerance also comes under the umbrella of NFs. NFs have an edge over conventional chemical fertilizers, viz., higher plant biomass and yield using much lesser fertilization, thereby reducing environmental pollution. Foliar and root applications of NFs lead to their successful uptake by the plant, depending on the size, surface charge, and other physicochemical properties of NFs. Smaller NFs can pass through channels on the waxy cuticle depending on the hydrophobicity, while larger NFs pass through the stomatal conduits of leaves. Charge-based adsorption, followed by apoplastic movement and endocytosis, translocates NFs through the root, while the size of NFs influences passage into vascular tissues. Recent transcriptomic, proteomic, and metabolomic studies throw light on the molecular mechanisms of growth promotion by NFs. The expression levels of nutrient transporter genes are regulated by NFs, controlling uptake and minimizing excess nutrient toxicity. Accelerated growth by NFs is brought about by their extensive regulation of cell division, photosynthesis, carbohydrate, and nitrogen metabolism, as well as the phytohormone-dependent signaling pathways related to development, stress response, and plant defense. NFs mimic Ca,2+ eliciting second messengers and associated proteins in signaling cascades, reaching transcription factors and finally orchestrating gene expression to enhance growth and stress tolerance. Developing advanced nano fertilizers of the future must involve exploring molecular interactions with plants to reduce toxicity and improve effectiveness.

Genome-wide association study identifies key quantitative trait loci (QTL) for fruit morphometric traits in avocado (Persea spp.)

BACKGROUND

Avocado, a fruit crop renowned for its high nutritional value, has seen a steadily increasing market demand. However, breeding efforts for avocados have lagged those for other commercial fruits due to limited genomic research and germplasm resources. To address this shortfall, a genome-wide association study was conducted on 122 avocado accessions from the United States Department of Agriculture (USDA) Agricultural Research Service (ARS) Subtropical Horticultural Research Station (SHRS) germplasm collection. The study aimed to identify genetic markers and regions associated with various morphometric traits in avocado fruits, including fruit weight, length, width, diameter, seed weight, seed length, seed width, fruit seed ratio (FSR), and fruit shape index (FSI).

RESULTS

Leveraging 4,226 high-quality single nucleotide polymorphism (SNP) markers obtained from genotyping arrays, fifteen markers were identified with strong associations with these traits, utilizing Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) and Fixed and random model Circulating Probability Unification (FarmCPU) models. Gene annotation analyses within a 200-kb window in the vicinity of significant SNPs revealed several genes associated with various metabolic pathways suggesting that some of them likely determine these fruit quality traits, which needs to be verified and validated. Our results, which were conducted at one location, provide directions for conducting future studies using high-resolution genotyping and long-term multi-year and multi-location trait evaluations for precisely identifying the causal SNP(s) and genes associated with these traits.

CONCLUSIONS

These markers reported in this manuscript provide valuable tools for applying marker-assisted selection (MAS) in avocado breeding programs aimed at enhancing fruit quality and value.

Constitutive expression of cucumber CsACS2 in Arabidopsis Thaliana disrupts anther dehiscence through ethylene signaling and DNA methylation pathways

KEY MESSAGE

Constitutive expression of cucumber CsACS2 in Arabidopsis disrupts anther dehiscence and male fertility via ethylene signaling and DNA methylation, revealing new avenues for enhancing crop reproductive traits. The cucumber gene CsACS2, encoding ACC (1-aminocyclopropane-1-carboxylic acid) synthase, plays a pivotal role in ethylene biosynthesis and sex determination. This study investigates the effects of constitutive CsACS2 expression in Arabidopsis thaliana on anther development and male fertility. Transgenic Arabidopsis plants overexpressing CsACS2 exhibited male sterility due to inhibited anther dehiscence, which was linked to suppressed secondary cell wall thickening. RNA-Seq analysis revealed upregulation of ethylene signaling pathway genes and downregulation of secondary cell wall biosynthesis genes, with gene set enrichment analysis indicating the involvement of DNA methylation. Rescue experiments demonstrated that silver nitrate (AgNO₃) effectively restored fertility, while 5-azacytidine (5-az) partially restored it, highlighting the roles of ethylene signaling and DNA methylation in this process. Constitutive CsACS2 expression in Arabidopsis disrupts anther development through ethylene signaling and DNA methylation pathways, providing new insights into the role of ethylene in plant reproductive development and potential applications in crop improvement.

Harnessing Pseudomonas spp. for sustainable plant crop protection

This review examines the role of Pseudomonas spp. bacteria as biocontrol agents against crop diseases, focusing on their mechanisms of action, efficacy, and potential applications in sustainable agriculture. Pseudomonas spp., ubiquitous in soil ecosystems and root microbiomes, have attracted attention for their ability to suppress phytopathogens and enhance plant health through various mechanisms. These include direct competition for nutrients, production of antimicrobial compounds and volatile organic compounds, competition using type VI secretion systems, and indirect induction of systemic resistance. Our review shows that Pseudomonas strains effectively control a wide range of diseases across diverse plant species, with some strains demonstrating efficacy comparable to chemical fungicides. However, the review also highlights challenges in achieving consistent performance when using Pseudomonas inoculants under field conditions due to various biotic and abiotic factors. Strategies to optimize biocontrol potential, such as formulation techniques, application methods, and integration with other management practices, are discussed. The advantages of Pseudomonas-based biocontrol for sustainable agriculture include reduced reliance on chemical pesticides, enhanced crop productivity, and improved environmental sustainability. Future research directions should focus on understanding the complex interactions within the plant microbiome, optimizing delivery systems, and addressing regulatory hurdles for commercial deployment. This review underscores the significant potential of Pseudomonas spp. in sustainable crop protection while acknowledging the need for further research to fully harness their capabilities in agricultural systems.

Ethylene-mediated stomatal responses to dehydration and rehydration in seed plants

Ethylene, a plant hormone that significantly influences both plant growth and response to stress, plays a well-established role in stress signaling. However, its impact on stomatal opening and closure during dehydration and rehydration remains relatively unexplored and is still debated. Exogenous ethylene has been proven to induce stomatal closure through a series of signaling pathways, including the accumulation of reactive oxygen species, subsequent synthesis of nitric oxide and hydrogen sulfide, and SLOW ANION CHANNEL-ASSOCIATED 1 activation. Thus, it has been suggested that ethylene might function to induce stomatal closure synergistically with abscisic acid (ABA). Furthermore, it has also been shown that increased ethylene can inhibit ABA- and jasmonic acid-induced stomatal closure, thus hindering drought-induced closure during dehydration. Simultaneously, other stresses, such as chilling, ozone pollution, and K+ deficiency, inhibit drought- and ABA-induced stomatal closure in an ethylene synthesis-dependent manner. However, ethylene has been shown to take on an opposing role during rehydration, preventing stomatal opening in the absence of ABA through its own signaling pathway. These findings offer novel insights into the function of ethylene in stomatal regulation during dehydration and rehydration, giving a better understanding of the mechanisms underlying ethylene-induced stomatal movement in seed plants.

Nano/micro flexible fiber and paper-based advanced functional packaging materials

Recently, fiber-based and functional paper food packaging has garnered significant attention for its versatility, excellent performance, and potential to provide sustainable solutions to the food packaging industry. Fiber-based food packaging is characterized by its large surface area, adjustable porosity and customizability, while functional paper-based food packaging typically exhibits good mechanical strength and barrier properties. This review summarizes the latest research progress on food packaging based on fibers and functional paper. Firstly, the raw materials used for preparing fiber and functional paper, along with their physical and chemical properties and roles in food packaging, were discussed. Subsequently, the latest advancements in the application of fiber and paper materials in food packaging were introduced. This paper also discusses future research directions and potential areas for improvement in fiber and functional paper food packaging to further enhance their effectiveness in ensuring food safety, quality, and sustainability.

Effects of chitosan on plant growth under stress conditions: similarities with plant growth promoting bacteria

The agricultural use of synthetic pesticides, fertilizers, and growth regulators may represent a serious public health and environmental problem worldwide. All this has prompted the exploration of alternative chemical compounds, leading to exploring the potential of chitosan and PGPB in agricultural systems as a potential biotechnological solution to establish novel agricultural production practices that not only result in fewer adverse impacts on health and the environment but also improve the resilience and growth of the plants. In this work, an analysis of the impact of plant growth-promoting bacteria (PGPB) and chitosan on plant growth and protection has been conducted, emphasizing the crucial bioactivities of the resistance of the plants to both biotic and abiotic stressors. These include inducing phytohormone production, mobilization of insoluble soil nutrients, biological nitrogen fixation, ethylene level regulation, controlling soil phytopathogens, etc. Moreover, some relevant aspects of chitin and chitosan are discussed, including their chemical structures, sources, and how their physical properties are related to beneficial effects on agricultural applications and mechanisms of action. The effects of PGPB and chitosan on photosynthesis, germination, root development, and protection against plant diseases have been compared, emphasizing the intriguing similarities and synergistic effects observed in some of these aspects. Although currently there are limited studies focused on the combined application of PGPB and chitosan, it would be important to consider the similarities highlighted in this work, and those that may emerge in future studies or through well-designed investigations, because these could permit advancing towards a greater knowledge of these systems and to obtain better formulations by combining these bioproducts, especially for use in the new contexts of sustainable agriculture. Thus, it seems feasible to augur a promising near future for these combinations, considering the wide range of possibilities offered by chitinous biomaterials for the development of innovative formulations, as well as allowing different application methods. Likewise, the studies related to the PGPB effects on plant growth appear to be expanding due to ongoing research to test on plants the impacts of microorganisms derived from different environments, whether known or recently discovered, making it a very exciting field of research.

Probing ozone effects on European hornbeam (Carpinus betulus L. and Ostrya carpinifolia Scop.) leaf water content through THz imaging and dynamic stomatal response

We investigated the impact of ozone exposure on Hornbeam using a novel dual approach based on Terahertz (THz) imaging in a free-air ozone exposure experiment (three ozone levels: ambient; 1.5 times ambient; twice ambient). The research aims at unraveling the physiological responses induced by elevated ozone levels on water dynamics. THz imaging unveiled dynamic changes in leaf water content, providing a non-invasive approach to leaf water monitoring. Leaf gas exchange measurements assessed stomatal responses to light variation. Our findings showcase a compelling correlation between elevated ozone levels and reduction in photosynthetic rate and impairment of stomatal function, i.e. "stomatal sluggishness", indicative of nuanced regulatory mechanism. Stomatal sluggishness was particularly evident in Carpinus betulus (CB) compared to Ostrya carpinifolia (OC) and was linked to reduction in photosynthetic capacity. THz-based imaging techniques confirmed this result indicating a negative effect of O3 on leaf-level total water content. In addition, spatial analysis of leaf water status using these techniques also highlighted that the negative effect of O3 on water status was progressing even in less sensitive OC plants though visible foliar injury was not detected. In fact, OC showed a relative dry area of 1.6 ± 1.6 % in the control group and 3.8 ± 1.3 % under high ozone levels. THz-based imaging techniques provided a deep understanding of O3 behavior in plants and may be recommended for precision biosensing in the early detection of O3-induced damage. The integration of THz imaging and physiological analysis resulted in comprehensive understanding of Hornbeam acclimation response to ozone exposure.

New piperidinium surfactants with carbamate fragments as effective adjuvants in insecticide compositions based on imidacloprid

BACKGROUND

Surfactants, particularly non-ionic ones, are widely used as adjuvants in pesticide formulations due to their ability to maintain pesticide effectiveness without changing solution properties, such as pH. While non-ionic surfactants are generally low-toxic, stable, and excellent dispersants with high solubilization capabilities, they may be less effective than cationic surfactants, which offer superior surface activity, transport properties, and antimicrobial action. This study investigates the efficacy of new piperidinium surfactants with carbamate fragments as adjuvants in insecticide formulations containing imidacloprid. The efficacy of these formulations is being assessed against greenhouse whitefly, a pest known to harm cultivated and ornamental flowering plants.

RESULTS

The aggregation behavior of piperidinium surfactants containing carbamate fragments was investigated, and their wetting effect was evaluated. Synthesized surfactants have lower CMC values compared to their methylpiperidinium analogue. The effect of piperidinium surfactants on the insecticide concentration on the surface and inside tomato leaves was assessed using spectrophotometric methods. It was found that the introduction of piperidinium surfactants with carbamate fragment at a concentration of 0.1% wt. allows for decrease in lethal concentration of imidacloprid up to 10 times, thereby testifying the marked increase in the effectiveness of imidacloprid against the greenhouse whitefly insect pest (Trialeurodes vaporariorum). It was shown that the main factors responsible for the enhanced efficacy of the insecticide were the ability of the surfactant to increase the concentration of imidacloprid on the leaf surfaces and improve their penetration into the plant.

CONCLUSION

The presented work employed a comprehensive approach, which significantly increases the generalizability of the results obtained and provides the ability to predict the effect and target selection of adjuvants. © 2024 Society of Chemical Industry.

Diverse functional interactions between ABA and ethylene in plant development and responses to stress

Abscisic acid (ABA) and ethylene are two essential hormones that play crucial roles throughout the entire plant life cycle and in their tolerance to abiotic or biotic stress. In recent decades, increasing research has revealed that, in addition to their individual roles, these two hormones are more likely to function through their interactions, forming a complex regulatory network. More importantly, their functions change and their interactions vary from synergistic to antagonistic depending on the specific plant organ and development stage, which is less focused, compared and systematically summarized. In this review, we first introduce the general synthesis and action signaling pathways of these two plant hormones individually and their interactions in relation to seed dormancy and germination, primary root growth, shoot development, fruit ripening, leaf senescence and abscission, and stomatal movement regulation under both normal and stress conditions. A better understanding of the complex interactions between ABA and ethylene will enhance our knowledge of how plant hormones regulate development and respond to stress and may facilitate the development of crops with higher yields and greater tolerance to stressful environments through tissue-specific genetic modifications in the future.

Transcriptomic Analysis of the Combined Effects of Methyl Jasmonate and Wounding on Flavonoid and Anthraquinone Biosynthesis in Senna tora

Jasmonates, including jasmonic acid (JA) and its derivatives such as methyl jasmonate (MeJA) or jasmonly isoleucine (JA-Ile), regulate plant responses to various biotic and abiotic stresses. In this study, we applied exogenous MeJA onto Senna tora leaves subjected to wounding and conducted a transcriptome deep sequencing analysis at 1 (T1), 3 (T3), 6 (T6), and 24 (T24) h after MeJA induction, along with the pretreatment control at 0 h (T0). Out of 18,883 mapped genes, we identified 10,048 differentially expressed genes (DEGs) between the T0 time point and at least one of the four treatment times. We detected the most DEGs at T3, followed by T6, T1, and T24. We observed the upregulation of genes related to JA biosynthesis upon exogenous MeJA application. Similarly, transcript levels of genes related to flavonoid biosynthesis increased after MeJA application and tended to reach their maximum at T6. In agreement, the flavonols kaempferol and quercetin reached their highest accumulation at T24, whereas the levels of the anthraquinones aloe-emodin, emodin, and citreorosein remained constant until T24. This study highlights an increase in flavonoid biosynthesis following both MeJA application and mechanical wounding, whereas no significant influence is observed on anthraquinone biosynthesis. These results provide insights into the distinct regulatory pathways of flavonoid and anthraquinone biosynthesis in response to MeJA and mechanical wounding.

Physiological and molecular mechanisms associated with potato tuber dormancy

Tuber dormancy is an important physiological trait that impacts post-harvest storage and end-use qualities of potatoes. Overall, dormancy regulation of potato tubers is a complex process driven by genetic as well as environmental factors. Elucidation of the molecular and physiological mechanisms that influence different dormancy stages of tubers has wider potato breeding and industry-relevant implications. Therefore, the primary objective of this review is to present current knowledge of the diversity in tuber dormancy traits among wild relatives of potatoes and discuss how genetic and epigenetic factors contribute to tuber dormancy. Advancements in understanding of key physiological mechanisms involved in tuber dormancy regulation, such as apical dominance, phytohormone metabolism, and oxidative stress responses, are also discussed. This review highlights the impacts of common sprout suppressors on the molecular and physiological mechanisms associated with tuber dormancy and other storage qualities. Collectively, the literature suggests that significant changes in expression of genes associated with the cell cycle, phytohormone metabolism, and oxidative stress response influence initiation, maintenance, and termination of dormancy in potato tubers. Commercial sprout suppressors mainly alter the expression of genes associated with the cell cycle and stress responses and suppress sprout growth rather than prolonging tuber dormancy.

Enhancing the medicinal properties and phytochemical content of bitter melon (Momordica charantia L.) through elicitation with brassinosteroid, ethrel, and carrageenan

Bitter melon (Momordica charantia L.) is well-known for its high protein, steroid, alkaloid, mineral, lipid, triterpene, and phenolic compound content, as well as its medicinal properties, particularly its anti-diabetic effects. To investigate the impact of elicitors on the morphology and phytochemical characteristics of bitter melon (Jounpouri cultivar) over two consecutive years (2018 and 2019), we conducted a field experiment. The study aimed to determine the effects of Ethrel, brassinosteroids (BRs), and k-carrageenan on yield and the production of anti-diabetic agents in M. charantia farm crops. The elicitors included ten levels, ranging from a control group to Ethrel (100, 300, and 600 mg l- 1), brassinosteroids (BRs) (0.1, 0.5, and 1 mg l- 1), and k-carrageenan (200, 400, and 600 mg l- 1). These characteristics included leaf area, leaf length, leaf width, fruit parameters, carbohydrate content, total phenols and flavonoid accumulation, antioxidant activity, total acid, ascorbic acid, momordicine, and charantin. Across both years, we observed the highest flavonoid accumulation and antioxidant activity in the Ethrel treatment group. Specifically, applying 0.5 mg l- 1 BRs and 300 mg l- 1 Ethrel led to an 18.8% and 14.8% increase in momordicine content, respectively. All elicitor treatments, particularly at 0.1 mg l- 1 BRs, significantly increased leaf area, leaf length, and leaf width compared to the control group in both cropping years. Additionally, the application of all elicitors resulted in increased fruit weight, dimensions, and yield over the two consecutive years. Notably, in 2018, 600 mg l- 1 Ethrel contributed to enhanced fruit weight and yield, while in 2019, 0.5 mg l- 1 BRs exhibited the same effect. Metabolic and physiological changes in bitter squash induced by employed elicitors over two different years (2018-2019) are strongly dependent on a variety of environmental factors such as temperature and rainfall. In conclusion, using BRs as an elicitor has the potential to optimize the health benefits of bitter melon by increasing the content of two bioactive molecules, momordicine and charantin.

The roles of nitric oxide in improving postharvest fruits quality: Crosstalk with phytohormones

Nowadays, improving the quality of postharvest fruits has become a hot research topic. Nitric oxide (NO) is often regarded as a signaling molecule that delays the postharvest senescence of fruits. Moreover, phytohormones affect the postharvest senescence of fruits. This review mainly describes how NO improves the postharvest quality of fruits by delaying postharvest fruit senescence, mitigating fruit cold damage and controlling postharvest diseases. Furthermore, the crosstalk of NO and multiple plant hormones effectively delays the postharvest senescence of fruits, and the major crosstalk mechanisms include (1) mediating phytohormone signaling. (2) inhibiting ETH production. (3) stimulating antioxidant enzyme activity. (4) decreasing membrane lipid peroxidation. (5) maintaining membrane integrity. (6) inhibiting respiration rate. (7) regulating gene expression related to fruit senescence. This review concluded the roles and mechanisms of NO in delaying postharvest fruit senescence. In addition, the crosstalk mechanisms between NO and various phytohormones on the regulation of postharvest fruit quality are also highlighted, which provides new ideas for the subsequent research.

Transcriptome profiling of two rice varieties reveals their molecular responses under high night-time temperature

High night-time temperatures (HNT) pose a threat to the sustainability of crop production, including rice. HNT can affect crop productivity and quality by influencing plant physiology, morphology, and phenology. The ethylene perception inhibitor, 1-methylcyclopropene (1-MCP), can minimize HNT-induced damage to plant membranes, thereby preventing decrease in rice yield. In this study, we employed a transcriptome approach to investigate the effects of HNT, 1-MCP, and their interaction on two Texas rice varieties, Antonio and Colorado. The plants were exposed to temperatures of 25°C (ambient night-time temperature, ANT) and 30°C (HNT) using an infrared heating system from the booting stage until harvest, while 1-MCP was applied at the booting stage of rice development. Several physiological and agronomical traits were evaluated under each condition to assess plant responses. Leaf tissues were collected from the plants grown in the ANT and HNT conditions after the heat stress and 1-MCP treatments. Based on agronomic performance, Colorado was less negatively affected than Antonio under HNT, showing a slight reduction in spikelet fertility and leaf photosynthetic rate but no significant reduction in yield. The application of 1-MCP significantly mitigated the adverse effects of HNT in Antonio. However, no significant differences were observed in yield and leaf photosynthetic rate in Colorado. Furthermore, transcriptomic data revealed distinct responsive mechanisms in Antonio and Colorado in response to both HNT and 1-MCP. Several ethylene and senescence-related transcription factors (TFs) were identified only in Antonio, suggesting that 1-MCP affected the ethylene signaling pathway in Antonio but not in Colorado. These findings contribute to our understanding of the physiological differences between varieties exhibiting susceptible and tolerant responses to high night-time temperatures, as well as their response to 1-MCP and ethylene regulation under 1-MCP.

The case for sporadic cyanogenic glycoside evolution in plants

Cyanogenic glycosides are α-hydroxynitrile glucosides present in approximately 3000 different plant species. Upon tissue disruption, cyanogenic glycosides are hydrolyzed to release toxic hydrogen cyanide as a means of chemical defense. Over 100 different cyanogenic glycosides have been reported, with structural diversity dependent on the precursor amino acid, and subsequent modifications. Cyanogenic glycosides represent a prime example of sporadic metabolite evolution, with the metabolic trait arising multiple times throughout the plant lineage as evidenced by recruitment of different enzyme families for biosynthesis. Here, we review the latest developments within cyanogenic glycoside biosynthesis, and argue possible factors driving sporadic evolution including shared intermediates and crossovers with other metabolic pathways crossovers, and metabolite multifunctionality beyond chemical defense.

Cadmium toxicity promotes hormonal imbalance and induces the expression of genes involved in systemic resistances in barley

Cadmium (Cd) is a widely distributed pollutant that adversely affects plants' metabolism and productivity. Phytohormones play a vital role in the acclimation of plants to metal stress. On the other hand, phytohormones trigger systemic resistances, including systemic acquired resistance (SAR) and induced systemic resistance (ISR), in plants in response to biotic interactions. The present study aimed to investigate the possible induction of SAR and ISR pathways in relation to the hormonal alteration of barley seedlings in response to Cd stress. Barley seedlings were exposed to 1.5 mg g-1 Cd in the soil for three days. The nutrient content, oxidative status, phytohormones profile, and expression of genes involved in SAR and ISR pathways of barley seedlings were examined. Cd accumulation resulted in a reduction in the nutrient content of barley seedlings. The specific activity of superoxide dismutase and the hydrogen peroxide content significantly increased in response to Cd toxicity. Abscisic acid, jasmonic acid, and ethylene content increased under Cd exposure. Cd treatment resulted in the upregulation of NPR1, PR3, and PR13 genes in SAR pathways. The transcripts of PAL1 and LOX2.2 genes in the ISR pathway were also significantly increased in response to Cd treatment. These findings suggest that hormonal-activated systemic resistances are involved in the response of barley to Cd stress.

Arinole, a novel auxin-stimulating benzoxazole, affects root growth and promotes adventitious root formation

The triple response phenotype is characteristic for seedlings treated with the phytohormone ethylene or its direct precursor 1-aminocyclopropane-carboxylic acid, and is often employed to find novel chemical tools to probe ethylene responses. We identified a benzoxazole-urea derivative (B2) partially mimicking ethylene effects in a triple response bioassay. A phenotypic analysis demonstrated that B2 and its closest analogue arinole (ARI) induced phenotypic responses reminiscent of seedlings with elevated levels of auxin, including impaired hook development and inhibition of seedling growth. Specifically, ARI reduced longitudinal cell elongation in roots, while promoting cell division. In contrast to other natural or synthetic auxins, ARI mostly acts as an inducer of adventitious root development, with only limited effects on lateral root development. Quantification of free auxins and auxin biosynthetic precursors as well as auxin-related gene expression demonstrated that ARI boosts global auxin levels. In addition, analyses of auxin reporter lines and mutants, together with pharmacological assays with auxin-related inhibitors, confirmed that ARI effects are facilitated by TRYPTOPHAN AMINOTRANSFERASE1 (TAA1)-mediated auxin synthesis. ARI treatment in an array of species, including Arabidopsis, pea, tomato, poplar, and lavender, resulted in adventitious root formation, which is a desirable trait in both agriculture and horticulture.

PGPR: Key to Enhancing Crop Productivity and Achieving Sustainable Agriculture

Due to the burgeoning global population and the advancement of economies, coupled with human activities leading to the degradation of soil ecosystems and the depletion of non-renewable resources, concerns have arisen regarding food security and human survival. In order to address these adverse impacts, the spotlight has been cast upon plant growth-promoting rhizobacteria (PGPR), driven by a strong environmental consciousness. PGPR possesses the capability to foster plant growth and amplify crop yield through both direct and indirect mechanisms. By expediting plant growth, augmenting nutrient assimilation, heightening crop yield and caliber, and fortifying stress resilience, the application of PGPR can mitigate reliance on chemical fertilizers and pesticides while diminishing ecological perils. This exposition delves into the function of PGPR in modulating plant hormones, fostering nutrient solubilization, and fortifying plant resistance against biotic and abiotic stressors. This review offers valuable insights into the intricate interplay between PGPR and plants, elucidating uncertainties ripe for further investigation. Profound comprehension and judicious utilization of PGPR are indispensable for attaining sustainable agricultural progression, making substantial contributions to resolving the conundrums of global food security and environmental conservation.

The underlying molecular mechanisms of hormonal regulation of fruit color in fruit-bearing plants

Fruit color is a key feature of fruit quality, primarily influenced by anthocyanin or carotenoid accumulation or chlorophyll degradation. Adapting the pigment content is crucial to improve the fruit's nutritional and commercial value. Genetic factors along with other environmental components (i.e., light, temperature, nutrition, etc.) regulate fruit coloration. The fruit coloration process is influenced by plant hormones, which also play a vital role in various physiological and biochemical metabolic processes. Additionally, phytohormones play a role in the regulation of a highly conserved transcription factor complex, called MBW (MYB-bHLH-WD40). The MBW complex, which consists of myeloblastosis (MYB), basic helix-loop-helix (bHLH), and WD40 repeat (WDR) proteins, coordinates the expression of downstream structural genes associated with anthocyanin formation. In fruit production, the application of plant hormones may be important for promoting coloration. However, concerns such as improper concentration or application time must be addressed. This article explores the molecular processes underlying pigment formation and how they are influenced by various plant hormones. The ABA, jasmonate, and brassinosteroid increase anthocyanin and carotenoid formation, but ethylene, auxin, cytokinin, and gibberellin have positive as well as negative effects on anthocyanin formation. This article establishes the necessary groundwork for future studies into the molecular mechanisms of plant hormones regulating fruit color, ultimately aiding in their effective and scientific application towards fruit coloration.

Ethylene, a Signaling Compound Involved in Seed Germination and Dormancy

The present review is focused on current findings on the involvement of ethylene in seed biology. The responsiveness of seeds to ethylene depends on the species and the dormancy status, improving concentrations ranging from 0.1 to 200 μL L-1. The signaling pathway of ethylene starts with its binding to five membrane-anchored receptors, which results in the deactivation of Constitutive Triple Response 1 (CTR1, a protein kinase) that does not exert its inhibitory effect on Ethylene Insensitive 2 (EIN2) by phosphorylating its cytosolic C-terminal domain. An analysis of germination in the presence of inhibitors of ethylene synthesis or action, and using seeds from mutant lines altered in terms of the genes involved in ethylene synthesis (acs) and the signaling pathway (etr1, ein2, ein4, ctr1 and erf1), demonstrates the involvement of ethylene in the regulation of seed dormancy. The promoting effect of ethylene is also regulated through crosstalk with abscisic acid (ABA) and gibberellins (GAs), essential hormones involved in seed germination and dormancy, and Reactive Oxygen Species (ROS). Using a mutant of the proteolytic N-degron pathway, Proteolysis (PRT6), the Ethylene Response Factors (ERFs) from group VII (HRE1, HRE2, RAP 2.2, RAP2.3 and RAP 2.12) have also been identified as being involved in seed insensitivity to ethylene. This review highlights the key roles of EIN2 and EIN3 in the ethylene signaling pathway and in interactions with different hormones and discusses the responsiveness of seeds to ethylene, depending on the species and the dormancy status.

The crosstalk interaction of ethylene, gibberellins, and arbuscular mycorrhiza improves growth in salinized tomato plants by modulating the hormonal balance

Ethylene (ET) and gibberellins (GAs) play key roles in controlling the biotic and abiotic interactions between plants and environment. To gain insights about the role of ET and GAs interactions in the mycorrization and response to salinity of tomato (Solanum lycopersicum L.) plants, the ET-insensitive (Never-ripe, Nr), and the ET-overproducer (Epinastic, Epi) mutants and their wild type cv. Micro-Tom (MT), were inoculated or not with the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis and exposed to control (0 mM NaCl) and salinity (100 mM NaCl) conditions, with and without gibberellic acid (10-6 M GA3) application during four weeks. Exogenous GA3 enhanced plant growth irrespective of the genotype, AMF, and salinity conditions, while an additional effect on growth by AMF was only found in the ET-overproducer (Epi) mutant under control and salinity conditions. Epi almost doubled the AMF colonization level under both conditions but was the most affected by salinity and GA3 application compared to MT and Nr. In contrast, Nr registered the lowest AMF colonization level, but GA3 produced a positive effect, particularly under salinity, with the highest leaf growth recovery. Foliar GA3 application increased the endogenous concentration of GA1, GA3, and total GAs, more intensively in AMF-Epi plants, where induced levels of the ET-precursor ACC were also found. Interestingly, GA4 which is associated with AMF colonization, registered the strongest genotype x GA x AMF × salinity interactions. The different growth responses in relation to those interactions are discussed.

Integrative analysis of transcriptome and metabolome reveals how ethylene increases natural rubber yield in Hevea brasiliensis

Hevea brasiliensis is an important cash crop with the product named natural rubber (NR) for markets. Ethylene (ET) is the most effective yield stimulant in NR production but the molecular mechanism remains incomplete. Here, latex properties analysis, transcriptome analysis, and metabolic profiling were performed to investigate the mechanism of NR yield increase in four consecutive tappings after ET stimulation. The results revealed that sucrose and inorganic phosphate content correlated positively with dry-rubber yield and were induced upon ET stimulation. Stimulation with ET also led to significant changes in gene expression and metabolite content. Genes involved in phytohormone biosynthesis and general signal transduction as well as 51 transcription factors potentially involved in the ET response were also identified. Additionally, KEGG annotation of differentially accumulated metabolites suggested that metabolites involved in secondary metabolites, amino-acid biosynthesis, ABC transporters, and galactose metabolism were accumulated in response to ET. Integrative analysis of the data collected by transcriptomics and metabolomics identified those differentially expressed genes and differentially accumulated metabolites are mainly involved in amino-acid biosynthesis and carbohydrate metabolism. Correlation analysis of genes and metabolites showed a strong correlation between amino-acid biosynthesis during ET stimulation. These findings provide new insights into the molecular mechanism underlying the ET-induced increase in rubber yield and further our understanding of the regulatory mechanism of ethylene signaling in rubber biosynthesis.

How Do Plant Growth-Promoting Bacteria Use Plant Hormones to Regulate Stress Reactions?

Phytohormones play a crucial role in regulating growth, productivity, and development while also aiding in the response to diverse environmental changes, encompassing both biotic and abiotic factors. Phytohormone levels in soil and plant tissues are influenced by specific soil bacteria, leading to direct effects on plant growth, development, and stress tolerance. Specific plant growth-promoting bacteria can either synthesize or degrade specific plant phytohormones. Moreover, a wide range of volatile organic compounds synthesized by plant growth-promoting bacteria have been found to influence the expression of phytohormones. Bacteria-plant interactions become more significant under conditions of abiotic stress such as saline soils, drought, and heavy metal pollution. Phytohormones function in a synergistic or antagonistic manner rather than in isolation. The study of plant growth-promoting bacteria involves a range of approaches, such as identifying singular substances or hormones, comparing mutant and non-mutant bacterial strains, screening for individual gene presence, and utilizing omics approaches for analysis. Each approach uncovers the concealed aspects concerning the effects of plant growth-promoting bacteria on plants. Publications that prioritize the comprehensive examination of the private aspects of PGPB and cultivated plant interactions are of utmost significance and crucial for advancing the practical application of microbial biofertilizers. This review explores the potential of PGPB-plant interactions in promoting sustainable agriculture. We summarize the interactions, focusing on the mechanisms through which plant growth-promoting bacteria have a beneficial effect on plant growth and development via phytohormones, with particular emphasis on detecting the synthesis of phytohormones by plant growth-promoting bacteria.

Integrated metabolomic and transcriptomic analysis reveals biosynthesis mechanism of flavone and caffeoylquinic acid in chrysanthemum

BACKGROUND

Chrysanthemum morifolium 'HangBaiJu', a popular medicinal and edible plant, exerts its biological activities primarily through the presence of flavones and caffeoylquinic acids (CQAs). However, the regulatory mechanism of flavone and CQA biosynthesis in the chrysanthemum capitulum remains unclear.

RESULTS

In this study, the content of flavones and CQAs during the development of chrysanthemum capitulum was determined by HPLC, revealing an accumulation pattern with higher levels at S1 and S2 and a gradual decrease at S3 to S5. Transcriptomic analysis revealed that CmPAL1/2, CmCHS1/2, CmFNS, CmHQT, and CmHCT were key structural genes in flavones and CQAs biosynthesis. Furthermore, weighted gene co-expression correlation network analysis (WGCNA), k-means clustering, correlation analysis and protein interaction prediction were carried out in this study to identify transcription factors (TFs) associated with flavone and CQA biosynthesis, including MYB, bHLH, AP2/ERF, and MADS-box families. The TFs CmERF/PTI6 and CmCMD77 were proposed to act as upstream regulators of CmMYB3 and CmbHLH143, while CmMYB3 and CmbHLH143 might form a complex to directly regulate the structural genes CmPAL1/2, CmCHS1/2, CmFNS, CmHQT, and CmHCT, thereby controlling flavone and CQA biosynthesis.

CONCLUSIONS

Overall, these findings provide initial insights into the TF regulatory network underlying flavones and CQAs accumulation in the chrysanthemum capitulum, which laid a theoretical foundation for the quality improvement of C. morifolium 'HangBaiJu' and the high-quality development of the industry.

Discovery of candidate genes involved in ethylene biosynthesis and signal transduction pathways related to peach bud cold resistance

Background: Low temperature pose significant challenges to peach cultivation, causing severe damage to peach buds and restricting production and distribution. Ethylene, an important phytohormone, plays a critical role in enhancing plant cold resistance. Structural genes and transcription factors involved in ethylene biosynthesis and signal transduction pathways are associated with cold resistance. However, no research has specifically addressed their roles in peach cold resistance. Methods: In this study, we aimed for cold-resistance gene discovery in cold-sensitive peach cultivar "21Shiji" (21SJ) and cold-resistance cultivar "Shijizhixing" (SJZX) using RNA-seq and gas chromatography. Results: The findings revealed that under cold stress conditions, ethylene biosynthesis in "SJZX" was significantly induced. Subsequently, a structural gene, PpACO1-1, involved in ethylene biosynthesis in peach buds was significantly upregulated and showed a higher correlation with ethylene release rate. To identify potential transcription factors associated with PpACO1-1 expression and ethylene signal transduction, weighted gene co-expression network analysis was conducted using RNA-seq data. Four transcription factors: PpERF2, PpNAC078, PpWRKY65 and PpbHLH112, were identified. Conclusion: These findings provide valuable theoretical insights for investigating the regulatory mechanisms of peach cold resistance and guiding breeding strategies.

High expression of ethylene response factor BcERF98 delays the flowering time of non-heading Chinese cabbage

MAIN CONCLUSION

BcERF98 is induced by ethylene signaling and inhibits the expression of BcFT by interacting with BcNF-YA2 and BcEIP9, thereby inhibiting plant flowering. Several stresses trigger the accumulation of ethylene, which then transmits the signal to ethylene response factors (ERFs) to participate in the regulation of plant development to adapt to the environment. This study clarifies the function of BcERF98, a homolog of AtERF98, in the regulation of plant flowering time mediated by high concentrations of ethylene. Results indicate that BcERF98 is a nuclear and the cell membrane-localized transcription factor and highly responsive to ethylene signaling. BcERF98 inhibits the expression of BcFT by interacting with BcEIP9 and BcNF-YA2, which are related to flowering time regulation, thereby participating in ethylene-mediated plant late flowering regulation. The results have enriched the theoretical knowledge of flowering regulation in non-heading Chinese cabbage (NHCC), providing the scientific basis and gene reserves for cultivating new varieties of NHCC with different flowering times.

Transcriptomic and metabolomic profiling reveals molecular regulatory network involved in flower development and phenotypic changes in two Lonicera macranthoides varieties

Due to the medicinal importance of the flowers of Xianglei type (XL) Lonicera macranthoides, it is important to understand the molecular mechanisms that underlie their development. In this study, we elucidated the transcriptomic and metabolomic mechanisms that underlie the flower development mechanism of two L. macranthoides varieties. In this study, 3435 common differentially expressed unigenes (DEGs) and 1138 metabolites were identified. These common DEGs were mainly enriched in plant hormone signal transduction pathways. Metabolomic analysis showed that amino acids were the main metabolites of differential accumulation in wild-type (WT) L. macranthoides, whereas in XL, they were flavonoids and phenylalanine metabolites. Genes and transcription factors (TFs), such as MYB340, histone deacetylase 1 (HDT1), small auxin-up RNA 32 (SAUR32), auxin response factor 6 (ARF6), PIN-LIKES 7 (PILS7), and WRKY6, likely drive metabolite accumulation. Plant hormone signals, especially auxin signals, and various TFs induce downstream flower organ recognition genes, resulting in a differentiation of the two L. macranthoides varieties in terms of their developmental trajectories. In addition, photoperiodic, autonomous, and plant hormone pathways jointly regulated the L. macranthoides corolla opening. SAUR32, Arabidopsis response regulator 9 (ARR9), Gibberellin receptor (GID1B), and Constans-like 10 (COL10) were closely related to the unfolding of the L. macranthoides corolla. These findings offer valuable understanding of the flower growth process of L. macranthoides and the excellent XL phenotypes at the molecular level.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04019-1.