Exogenous Application Research Articles

Rice sucrose non-fermenting related protein kinase (SnRK1) has a limited role in defense against Fall armyworm (Spodoptera frugiperda)

Sucrose non-fermenting (SNF) related protein kinase 1 (SnRK1) is a master regulator of energy deprivation signaling and has also been implicated in abiotic and biotic stress regulation. SnRK1 promotes stress tolerance through metabolic and transcriptional changes and plays important roles in innate immunity against various pathogens. However, whether it plays a role against insect herbivory is not understood. To test this, using the wild type (with SnRK1) and snrk1 mutant lines in rice, we examined the potential role of SnRK1 in rice against the ruinous pest, Fall armyworm (FAW), Spodoptera frugiperda. We also investigated the response of FAW towards these lines at different time intervals after exogenous application of plant hormone, Jasmonic acid (JA), and a JA blocker (Ibuprofen). Additional experiments by feeding FAW with leaf infused diet, fresh leaves, and a short-term exposure of FAW to the lines were also carried out. FAW mass gain, growth and development, and host ecophysiological traits were observed. In addition, we also quantified the major surface defenses- trichomes, and wax before and after herbivory. Our results show that FAW response did not vary between mutants and wild type rice. Meanwhile, we found plant hormonal application influenced the ecophysiological traits regardless of mutants and wild type rice. Collectively, we show that while defense against FAW in rice is JA mediated, SnRK1 has a limited role as observed through manipulative experiments with the wild type and snrk1 mutant rice lines.

A Zea genus-specific micropeptide controls kernel dehydration in maize.

Kernel dehydration rate (KDR) is a crucial production trait that affects mechanized harvesting and kernel quality in maize; however, the underlying mechanisms remain unclear. Here, we identified a quantitative trait locus (QTL), qKDR1, as a non-coding sequence that regulates the expression of qKDR1 REGULATED PEPTIDE GENE (RPG). RPG encodes a 31 amino acid micropeptide, microRPG1, which controls KDR by precisely modulating the expression of two genes, ZmETHYLENE-INSENSITIVE3-like 1 and 3, in the ethylene signaling pathway in the kernels after filling. microRPG1 is a Zea genus-specific micropeptide and originated de novo from a non-coding sequence. Knockouts of microRPG1 result in faster KDR in maize. By contrast, overexpression or exogenous application of the micropeptide shows the opposite effect both in maize and Arabidopsis. Our findings reveal the molecular mechanism of microRPG1 in kernel dehydration and provide an important tool for future crop breeding.

Chitosan-based NPK nanostructure for reducing synthetic NPK fertilizers and improving rice productivity and nutritional indices

Researchers have repeatedly emphasized how urgently we have to decrease the massive nitrogen fertilizer consumption to support agricultural productivity and maintain a sustainable ecosystem. Using chitosan (CS) as a carrier for slow release is considered a potential tool for reducing synthetic fertilizer and improving crop productivity. Therefore, two field experiments were arranged in a randomized complete block design to investigate the effects of seven treatments including synthetic fertilizer and exogenous application of chitosan-based NPK nano-structure (Ch/NPs-NPK) on growth, productivity, and nutrient uptake traits of rice as a worldwide strategy crop during 2022 and 2023 growing seasons. The experimental treatments were: T1 = full recommended synthetic NPK (recommended urea, superphosphate, potassium sulfate; control treatment), T2 = 70% of T1 + Ch/NPs-NPK 100 ppm, T3 = 70% of T1+ Ch/NPs-NPK 200 ppm, T4 = 70% of T1+ Ch/NPs-NPK 300 ppm, T5 = 30% of T1+ Ch/NPs-NPK 100 ppm, T6 = 30% of T1+ Ch/NPs-NPK 200 ppm, and T7 = 30% of T1 + Ch/NPs-NPK 300 ppm. The results revealed that T4 (i.e., 70% of recommended NPK+ Ch/NPs-NPK 300 ppm) and T1 (full recommended synthetic NPK) resulted in the highest and most significant growth and yield traits of rice as well as nutrient grain contents compared to other treatments. Therefore, combining 70% of recommended NPK with Ch/NPs-NPK 300 ppm as an exogenous application can be a smart choice for reducing synthetic NPK fertilizers by 30% in paddy fields without producing a significant decline in terms of growth, yield characteristics, or nutrient grain contents when applying the full recommended synthetic NPK.

Re-harvest application of 2-(3-chlorophenoxy) propionic acid on pineapple plants

The application of plant regulators such as exogenous auxin may provide effects on the translocation of carbohydrates to plant sinks, which may result in larger parthenocarpic fruits. The objective of the study was to evaluate the effects of the application of 2-(3-chlorophenoxy) propionic acid on the growth and quality of pineapple fruits. The experiment was carried out in a randomized block design. After floral induction, 2-(3-chlorophenoxy) propionic acid (CPA) was applied directly on the inflorescences at the following doses: 0 mg L-1; 40.0 mg L-1; 80.0 mg L-1; 120.0 mg L-1 and 160.0 mg L-1. Growth evaluations continued until 84 days after application, measuring fruit length (cm) with and without crown, crown length (cm), leaf D dry matter, fruit weight with and without crown (g), calculating if also, the absolute and relative growth rates. The post-harvest and quality characteristics of the fruits were also evaluated, as well as the harvest index. The application of CPA significantly reduces the length and weight of the crown of the fruits, however, the exogenous application of auxin provided an increase in the weight of the fruit. Regarding the post-harvest analysis, the application of CPA reduced the content of soluble solids in the fruit pulp.

Exogenous Hormone Treatments in Maize.

Plant hormones have key functions in plant morphology, physiology, and stress responses. Studies on the biology of hormones and their effect on plant physiology and metabolism are greatly facilitated by the exogenous application of these compounds. In general, methods for exogenous hormone application are easy and fast, and provide useful information about their effects in planta. Although hormone effects have been studied in several plant species, the used methods need to be tailored specifically to each species to get robust data. Maize is an established model for basic and applied research, and an excellent system for studying the effects of hormones on developmental and stress responses in a cereal crop. Different methods have been reported for the exogenous application of plant growth regulators in maize, including watering, spraying, immersion, and application to the apical whorl. These various methods are useful to analyze hormone responses at different developmental stages, in specific organs, and within tissues. As with all exogenous application assays, suitable experimental design and the inclusion of proper controls are critical factors in these methods, to obtain reliable and reproducible results. Here, we provide an overview of various methods for hormone exogenous application in maize, and technical considerations to get successful results.

Foliar Spray Treatment for Exogenous Application of Hormones in Maize.

Exogenous application of hormones in plants is a valuable technique for studying and manipulating plant growth, development, and responses to environmental stimuli. The foliar spray method is one of the most common approaches for the exogenous application of hormones in plants due to its ease of use on aerial organs (such as leaves and inflorescences) and the rapid absorption of the treated tissue, facilitating subsequent analyses. Here, we provide a protocol to implement this method in maize. The approach consists of preparing dilutions of the hormones or plant growth regulators (PGRs) of interest, usually in an aqueous solution and at low concentrations, followed by application by foliar spraying using a defined treatment regimen. Users can then evaluate effects by measuring different parameters, such as stem size, flowering time, seed production, or others. The foliar spray method can easily be scaled up and automated in greenhouse and field settings, and can be used to treat plants at all developmental stages.

Apical Whorl Treatment for Exogenous Application of Hormones in Maize.

Plant hormones play an essential role in both development and stress responses. These organic natural compounds have critical functions in plant-related processes, including but not limited to seed development, anther formation, root elongation, and responses to abiotic and biotic stress. One way to study the impact of hormones on these processes is by external application, followed by evaluation of parameters of interest. Here, we describe one such method for the exogenous application of hormones in maize: the apical whorl treatment approach, which is well suited for evaluating the role of these compounds in reproductive stages (e.g., when the target organ is the inflorescence meristem). This method involves direct application of a hormone solution to the apical part of the plants every 2 days until the tassel emerges, which takes 15-20 days, or until the treated plants show noticeable phenotypic changes for evaluation. This method is ideal for observing effects on the apical meristem, and it may be scaled up for analyzing large numbers of plants.

Exogenous applications of salicylic acid, ethrel and cycocel: Synergistic effects on yield, quality and storability in Garlic (Allium sativum L.) cv. Ooty 2

Garlic (Allium sativum L.) is a valuable bulb crop, known for its rich bioactive compounds and health benefits. This study aimed to evaluate the impact of various foliar spray treatments on the growth, yield and quality of garlic cv. Ooty 2. The treatments included a control, 100 ppm, 200 ppm and 300 ppm of salicylic acid, cycocel at 1000 ppm and ethrel 200, 300 ppm sprayed at 45 and 60 days after planting. The experiment was conducted using a randomized block design with 7 treatments and 3 replications. Results revealed that salicylic acid 300 ppm increased growth traits followed by ethrel 300 ppm over the control. Cycocel 1000 ppm showed that high bulb yield and less reduction in quality characters viz., TSS (39.2 ?Brix), acidity (0.38 %), ascorbic acid (11.25 mg 100 g-1), total carbohydrate (39.82 g 100 g-1) and phenolics (4.10 mg 100 g-1) content during 3 months storage period, followed by ethrel 300 ppm. Additionally lowest levels of physiological loss in weight (17.47 %), rubbering (5.13 %), rotting (5.88 %) and total loss (23.64 %) was observed compared to all other treatments during the storage period. The results indicate that cycocel at 1000 ppm had the most beneficial effects and can be effectively used to enhance the harvest, post-harvest traits and quality and storability of garlic bulbs.

RESPONSE OF SUMMER TOMATO WITH EXOGENOUS APPLICATION OF SALICYLIC ACID AND CALCIUM

A pot experiment was carried out at Horticulture Farm, Sher-e-Bangla Agricultural University, Dhaka May to September, 2016 to evaluate the performance of summer tomato production with the supplementation of salicylic acid (SA) and calcium (Ca). The experiment consisted of two factor. Four different levels of SA (S1 = 0 mM SA, S2 = 0.3 mM SA, S3 = 0.6 mM SA, S4 = 0.8 mM SA) and three levels of Ca (C1 = 0 mM Ca, C2 = 4 mM Ca, C3 = 8 mM Ca). Both morphological traits and yield of summer tomatoes were significantly affected by the application of SA and Ca. Exogenous application of SA and Ca influenced the growth including plant height, leaf number, branch number, yield contributing characters and yield. The combined supplementation of 0.8 mM SA and 8 mM Ca resulted the highest yields (0.8 kg/plant) where lowest one (0.3 kg/plant) was recorded from the control treatment (without SA and Ca). These results suggest that SA and Ca can improve the growth and yield of tomatoes during the summer season by alleviating the detrimental effects of extreme heat in the summer.

RNA interference protocols for gene silencing in the spittlebug Philaenus spumarius, vector of Xylella fastidiosa

RNA interference (RNAi) is double stranded RNA (dsRNA)-based gene silencing mechanism. Exogenous dsRNAs application to crops has raised as a powerful tool to control agricultural pests. In particular, several sap-feeder are important plant pathogens vectors, such as Philaenus spumarius, known as main vector of Xylella fastidiosa (Xf), causal agent of olive quick decline syndrome (OQDS) in southern Italy. Here, dsATP synthase beta (dsATP), dsLaccase (dsLacc) and dsGreen Fluorescent Protein (dsGFP) as control, were provided to spittlebug adults by microinjection or to nymphs fed on dsRNA-treated plant shoots. Treated insects were collected at different time points to monitor silencing efficiency over time, describing significant reduction of transcript levels from 8 to 24 days post treatment. Downregulation of target genes ranged from 2- to 16-fold compared to the corresponding dsGFP controls, where highest silencing effects were generally noticed for ATP synthase beta. Sequencing of libraries obtained from total smallRNA (sRNA) showed the generation of dsRNA-derived sRNAs by RNAi pathway, with majority of reads mapping exclusively on the correspondent dsRNA. Also, we characterized components of a functional RNAi machinery in P. spumarius. Further research is needed to clarify such mechanism, screen effective target lethal genes to reduce vector population and improve delivery strategies.

γ-Aminobutyric Acid Alleviates Salinity-Induced Impairments in Rice Plants by Improving Photosynthesis and Upregulating Osmoprotectants and Antioxidants

Salt stress is a significant abiotic stress that hinders the growth of rice (Oryza sativa L.) and reduces their yield. Previous research has examined the synthesis of γ-aminobutyric acid (GABA) and its role in plant resistance under various abiotic stresses. However, the synthesis of GABA and its ability to mitigate damage caused by salt stress—particularly its effects on osmotic adjustment, antioxidant defense, photosynthesis, and overall plant growth throughout the entire rice lifecycle—remains unclear. Therefore, we conducted two experiments using salt-tolerant rice cultivar Lianjian 5 (J-5) and salt-susceptible cultivar Lianjing 7 (L-7). In Experiment I, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. In Experiment II, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. Therefore, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. Subsequently, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. We measured the activities of superoxide dismutase, peroxidase, and catalase, as well as photosynthetic characteristics such as photosynthesis, transpiration, chlorophyll content, stomatal density and size, and leaf anatomical features. The RNA-seq analysis revealed that GABA production is enhanced via the glutamate decarboxylase (GAD) gene (LOC4333932) in the salt-resistant rice cultivar. Exogenous GABA application improves salt-stress tolerance by increasing endogenous ABA and GABA contents, which enhance osmotic adjustment, boost antioxidant defenses, and regulate ion balance. These combined effects help maintain photosynthetic efficiency and support overall plant growth under salt-stressed environments. Additionally, the increased proportion of mesophyll cell periphery covered by chloroplasts (Sc/Sm) indicated enhanced mesophyll conductance. These helped maintain photosynthesis under saline conditions while reducing water consumption.

Functions of exogenous strigolactone application and strigolactone biosynthesis genes GhMAX3/GhMAX4b in response to drought tolerance in cotton (Gossypium hirsutum L.)

BackgroundDrought stress markedly constrains plant growth and diminishes crop productivity. Strigolactones (SLs) exert a beneficial influence on plant resilience to drought conditions. Nevertheless, the specific function of SLs in modulating cotton’s response to drought stress remains to be elucidated.ResultsIn this study, we assess the impact of exogenous SL (rac-GR24) administration at various concentrations (0, 1, 5, 10, 20 µM) on cotton growth during drought stress. The findings reveal that cotton seedlings treated with 5 µM exogenous SL exhibit optimal mitigation of growth suppression induced by drought stress. Treatment with 5 µM exogenous SL under drought stress conditions enhances drought tolerance in cotton seedlings by augmenting photosynthetic efficiency, facilitating stomatal closure, diminishing reactive oxygen species (ROS) generation, alleviating membrane lipid peroxidation, enhancing the activity of antioxidant enzymes, elevating the levels of osmoregulatory compounds, and upregulating the expression of drought-responsive genes. The suppression of cotton SL biosynthesis genes, MORE AXILLARY GROWTH 3 (GhMAX3) and GhMAX4b, impairs the drought tolerance of cotton. Conversely, overexpression of GhMAX3 and GhMAX4b in respective Arabidopsis mutants ameliorates the drought-sensitive phenotype in these mutants.ConclusionThese observations underscore that SLs significantly bolster cotton’s resistance to drought stress.

Enhancing salt tolerance in rice genotypes through exogenous melatonin application by modulating growth patterns and antistress agents

Melatonin is a bioactive molecule with an important role in plants responding to various abiotic and biotic stresses. This study aims to determine the role of melatonin in rice under salt stress. This study used a factorial completely randomized design. The first factor was local rice varieties (IR64 and Silaun), and the second factor was plant treatments (control, 1 µM melatonin, 150 mM NaCl, 150 mM NaCl + 1µM melatonin). This study shows that exogenous melatonin can increase plant growth, such as plant height, root length, stem length, leaf length, leaf area, and plant biomass under salt stress compared to treatment without melatonin. Exogenous melatonin can increase the total chlorophyll content, relative water content, and proline content, reduce the total sodium content, and increase potassium absorption under conditions of salinity stress. Melatonin is also able to scavenge ROS in plants, resulted the decrease in ROS and MDA content. In terms of gene expression, OsAPX1 and cytosolic APX exhibited the highest expression in IR64 under combined salt and melatonin treatment, while GPOD, Mn-SOD, and Cu/Zn-SOD were upregulated under various conditions in both varieties. Additionally, OsLEA showed high expression in both varieties under control conditions, and CAT was significantly upregulated under salt stress. Our findings indicate that exogenous melatonin has the potential to enhance various factors under salt stress and helping in the recovery of rice plants from sodium (Na+) damage.

Effect of Sodium Selenite Foliar Treatment on the Nutritional Quality of Cyclocarya paliurus (Batalin) Iljinsk

Cyclocarya paliurus (Batalin) Iljinskaja is a rare, endemic tree species in China. The leaves of C. paliurus contain a high concentration of biologically active compounds, and they are often used to make herbal tea. Exogenous selenium (Se) enrichment can promote the levels of active ingredients in C. paliurus. To explore the effects of exogenous Se enrichment, this study applied different concentrations of sodium selenite solution on the leaves (0, 40, 80, 120, 160, and 300 mg/L) and measured the changes in Se, secondary metabolites, soluble sugar, soluble protein, starch, and trace elements in the leaves at different treatment times. The results showed that with the increase in the concentration of sodium selenite spray, the selenium content in the leaves of C. paliurus gradually increased, and high selenium concentrations could cause seedling burning to the leaf surface (>160 mg/kg). When the selenium treatment concentration was 80 mg/kg, the selenium content reached the maximum value of the selenium-rich tea standard (4 mg/kg). The content of polyphenols and most elements reached their maxima under the treatment of 40 mg/L Na2SeO3, except for Mg and Mn, which peaked at 300 mg/L. The content of soluble sugars (38.1 mg/g) and starch reached their maxima under relatively high selenium treatment concentrations, whereas soluble protein (10.63 mg/g) exhibited its maximum value in the control group. The optimal harvest time was mainly concentrated in the 10–20 day treatment period. The objective of this research is to investigate the effects of exogenous selenium application on the nutritional quality of C. paliurus leaves. The findings will provide guidance for the effective cultivation of selenium-enriched Poria cocos as a medicinal and health-promoting product.

Using Nanomaterials and Arbuscular mycorrhizas to Alleviate Saline–Alkali Stress in Cyperus esculentus (L.)

Saline–alkali (SA) stress is an abiotic stress that exists widely in the natural environment, seriously affecting the growth and development of crops. Tiger nut (Cyperus esculentus L.), a perennial herb of Cyperus in Cyperaceae, is considered a pioneer crop for growing and improving SA land due to its excellent adaptability and SA tolerance. This study is the first to evaluate the SA tolerance of tiger nut and the alleviative effects of nanomaterials (nano-selenium and multi-walled carbon nanotubes) and arbuscular mycorrhizas (AMs) on SA stress. The results showed that the seedling fresh weight of tiger nut was the most suitable parameter to describe the dose–response effect of plant growth with increased SA concentration. Based on the log-logistic dose–response curve, the GR50 values of NaCl and NaHCO3 (the concentrations causing a 50% reduction in seedling fresh weight) were determined to be 163 mmol L−1 and 63 mmol L−1, respectively. Under these stresses, the exogenous application of MWCNTs at 100 mg L−1 or Nano-Se at 10 mg L−1 showed that the effect of SA on tiger nut was alleviated. Field evaluation further showed that the exogenous application of MWCNTs, Nano-Se, or AMs could effectively alleviate SA stress on tiger nut. Compared to the untreated control, the application of these substances significantly improved the plant photosynthesis-related parameter, antioxidant enzyme activity, plant height (height: 66.0–69.9 cm), tuber yield (yield: 23.4–27.4 g plant−1), and oil quality of tiger nut under SA stress. The results of this study indicate that the application of MWCNTs, Nano-Se, or AMs, to tiger nut can alleviate SA stress and maintain seed yield, providing the possibility of using these nanoparticles to improve the SA tolerance of tiger nut in agricultural practice.

Maize DLR1/NHX7 Is Required for Root Development Under Potassium Deficiency.

Root System Architecture (RSA) is a crucial plant trait that governs a plant's ability to absorb water and nutrients. In this study, we describe a mutant with nutrient-dependent defects in root development, affecting both the primary root and lateral roots (LRs). This mutant, identified through a screen for defects in LR development, has been designated dlr1-1. The dlr1-1 mutant exhibits impaired LR emergence rather than defects in the LR primordium (LRP) formation, particularly under potassium (K+)-deprivation conditions. This impairment likely stems from inhibited cell proliferation caused by the dlr1-1 mutation. K+ deprivation specifically leads to the accumulation of salicylic acid (SA) in the dlr1-1 mutant, consistent with the upregulation of SA biosynthesis genes. Moreover, exogenous application of SA to wild-type plants (B73) mimics the dlr1-1 phenotype. Conversely, treatment of the dlr1-1 mutant with 2-aminoindane-2-phosphonic acid, an SA biosynthesis inhibitor, partially restores LR emergence, indicating that elevated SA levels may be responsible for the mutant's developmental defects. MutMap analysis and allelism tests confirmed that the phenotypes of the dlr1-1 mutant results from the loss of the Na+/H+ antiporter, ZmNHX7. Additionally, the application of NaCl exacerbates the dlr1-1 mutant phenotype, suggesting that the root defects in dlr1-1 mutant depend on ion homoeostasis. In conclusion, our findings demonstrate that maize DLR1/NHX7 is essential for root development under potassium deprivation.

Exogenous Application of Chitosan Mitigates the Inhibitory Effects of Zinc on the Growth of Wheat Seedlings by Modulating Zn Transport and ROS Scavenging

Exogenous Application of Chitosan Mitigates the Inhibitory Effects of Zinc on the Growth of Wheat Seedlings by Modulating Zn Transport and ROS Scavenging

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.

Competitive control of CsNCED1-1 by CsLOB1 and CsbZIP40 triggers susceptibility to citrus canker.

Pustule formation is pivotal for the development of the Xanthomonas citri subsp. citri (Xcc)-induced citrus canker disease (CCD). Although our previous study demonstrated that the exogenous application of abscisic acid (ABA) facilitated pustule formation induced by Xcc, the precise mechanism remains elusive. The 9-cis-epoxycarotenoid dioxygenase (NCED) is a crucial enzyme in ABA biosynthesis. This study explored the role of citrus CsNCED1-1 in CCD resistance through overexpression and RNA interference of CsNCED1-1 in Wanjincheng orange (Citrus sinensis). Our findings indicated that CsNCED1-1 negatively modulated CCD resistance by fostering ABA accumulation, concomitant with an increase in jasmonic acid (JA) and a decrease in salicylic acid (SA). Plants overexpressing CsNCED1-1 displayed shortened leaves with smaller and denser stomata along with irregular and increased palisade cells. CsLOB1 is a known susceptibility gene for CCD, and CsbZIP40 positively influences resistance to this disease. We further confirmed that CsLOB1 promoted and CsbZIP40 suppressed the transcription of CsNCED1-1 by directly binding to the CsNCED1-1 promoter. Notably, CsbZIP40 and CsLOB1 showed a competitive relationship in the regulation of CsNCED1-1 expression, with CsbZIP40 exhibiting greater competitiveness. Overall, our findings highlight that CsNCED1-1 promotes susceptibility to citrus canker by disrupting JA- and SA-mediated defense mechanisms and triggering the proliferation and remodeling of palisade cells, thereby facilitating pathogen colonization and pustule formation. This study offers novel insights into the regulatory mechanisms underlying citrus canker resistance and the role of CsNCED1-1 in citrus.

Exogenous glucose irrigation alleviates cold stress by regulating soluble sugars, ABA and photosynthesis in melon seedlings

Melon (Cucumis melo L.) is an important economic crop and widely planted around the world. Cold stress severely limits its development and yield. Carbohydrates play multiple roles in plant cold tolerance. However, little is known in melon. Based on the metabolome analysis, a total of 635 metabolites were identified upon cold stress in melon seedlings. KEGG analysis shows that differential metabolites were mainly enriched in the glycolysis/gluconeogenesis pathway and pentose phosphate pathway, with glucose being one of the most prominent metabolites. To further investigate the role of glucose in cold tolerance of melon seedlings. We found that root irrigation was more effective than foliar spraying for exogenous glucose application, with optimal concentrations of 0.5% and 1% for cold-tolerant and cold-sensitive genotypes, respectively. Glucose irrigation mainly promoted soluble sugar accumulation to reduce cold damage in melon seedlings. For cold-sensitive genotype, only the sucrose content could be increased, while for cold-tolerant genotype, sucrose, fructose and glucose content could be simultaneously increased. Meanwhile, glucose irrigation recruited ABA not antioxidant enzyme system to cope with cold stress. Hence, glucose watering could improve the maximum photochemical efficiency of seedling photosystem II (Fv/Fm), alleviate physiological drought, reduce the accumulation of malondialdehyde, and accelerated the photosynthetic efficiency of melon seedlings. Based on coefficient of variation and principal component analysis, it was confirmed again that glucose irrigation did alter the strategies for withstanding cold stress and enhance the cold tolerance of melon seedlings. Thus, the results would provide a theoretical basis and feasible measures to protect melon seedings from cold damage.