Proline Content Research Articles

A C2H2-Type Zinc Finger Protein from Mentha canadensis, McZFP1, Negatively Regulates Epidermal Cell Patterning and Salt Tolerance

C2H2-type zinc finger protein (C2H2-ZFP) transcription factors play evident roles in regulating plant growth and development and abiotic stress responses. However, the role of C2H2-ZFP from Mentha canadensis remains uncertain. We identified the multifunctional C2H2-ZFP gene McZFP1 from M. canadensis based on phylogenetic analysis. The McZFP1 gene was highly expressed in stems, responding to abiotic stress and phytohormone treatments. McZFP1 localized in the nucleus and showed no transcriptional autoactivation activity in yeast. McZFP1 overexpression in Arabidopsis thaliana significantly reduced the number of trichomes and root hairs, root hair length, and salt stress tolerance. Further study revealed that McZFP1 overexpression increased the expression of negative regulator genes and decreased that of positive regulator genes to inhibit plant trichome and root hair development. Malondialdehyde accumulation was promoted, but the proline content and catalase, superoxide dismutase, and peroxidase activities were reduced and the expression of stress response genes was inhibited in McZFP1 overexpression lines under salt treatment, thereby compromising plant salt tolerance. Overall, these results indicate that McZFP1 is a novel C2H2-ZFP transcription factor that plays negative roles in trichome and root hair development and salt stress tolerance.

Evaluating the efficacy of endophytic bacteria in controlling rice sheath blight: In vitro and In vivo studies

Rice production is highly susceptible to various pathogens, including Rhizoctonia solani, Curvularia lunata, and Epicoccum rostratum, which are major threats in Asia. Exploring biological control methods using endophytic bacteria offers promising opportunities to enhance rice resilience against these lethal diseases. Using 16S RNA sequencing, we identified four endophytic isolates of Bacillus spp. from rice roots, stems, and leaves. We evaluated the antagonistic activity of these endophytic bacterial isolates against rice pathogens both in vitro and in vivo. These isolates inhibited the growth of C. lunata by 82 %, R. solani by 79 %, and E. rostratum by 88 % in vitro. The detached leaf assay for sheath blight (ShB) disease severity in strains ranged from 10.4 % to 73.3 %. In vivo results showed that B. amyloliquefaciens (R-19) exhibited the lowest disease intensity at 7.2 % and the highest disease suppression at 78.8 %. The fungicide propiconazole at 0.1 % treatment showed the lowest disease intensity of 7.7 % and the highest disease suppression of 73.4 %, compared to the infected control. Besides biocontrol efficacy, endophytic isolates enhance plant growth parameters, including shoot height, root length, fresh and dry weights, number of tillers, and grains per tiller. Plant hormones abscisic acid (ABA) and gibberellic acids (GA3) increased by 35 % and 53 %, respectively, due to B. subtilis (R-20) and B. amyloliquefaciens (R-19), while flavonoid and indole acetic acid (IAA) concentrations surged by 30%–80 %. Similarly, chlorophyll (a, b), carotenoids, antioxidant enzymatic activity, phenolic content, carbohydrates, and proline contents were higher compared to the control. This study provides a foundation for future studies on novel and eco-friendly biocontrol agents. In addition, our study recommends the integration of endophytic bacteria into sustainable agriculture for enhancing rice production and reducing disease impacts.

Comparative Study on the Response of Hyssop (Hyssopus officinalis L.), Salvia (Salvia officinalis L.), and Oregano (Origanum vulgare L.) to Drought Stress Under Foliar Application of Selenium.

Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.

Physiological and transcriptomic analysis reveals the coating of microcapsules embedded with bacteria can enhance wheat salt tolerance

Salt stress is one of the most important abiotic stress factors limiting crop production. Therefore, improving the stress resistance of seeds is very important for crop growth. Our previous studies have shown that using microcapsules encapsulating bacteria (Pontibacter actiniarum DSM 19842) as seed coating for wheat can alleviate salt stress. In this study, the genes and pathways involved in the response of wheat to salt stress were researched further. The results showed that compared with the control, the coating can improve osmotic stress and decrease oxidative damage by increasing the content of proline (29.1%), the activity of superoxide dismutase (SOD) (94.2%), peroxidase (POD) (45.7%) and catalase (CAT) (3.3%), reducing the content of hydrogen peroxide (H2O2) (39.8%) and malondialdehyde (MDA) (45.9%). In addition, ribonucleic acid (RNA) sequencing data showed that 7628 differentially expressed genes (DEGs) were identified, and 4426 DEGs up-regulated, 3202 down-regulated in the coated treatment. Many DEGs related to antioxidant enzymes were up-regulated, indicating that coating can promote the expression of antioxidant enzyme-related genes and alleviate oxidative damage under salt stress. The differential gene expression analysis demonstrated up-regulation of 27 genes and down-regulation of 20 genes. Transcription factor families, mostly belonging to bHLH, MYB, B3, NAC, and WRKY. Overall, this seed coating can promote the development of sustainable agriculture in saline soil.

Response mechanisms of Annual bluegrass (Poa annua) to cold, drought, combined stresses and recovery in morphology, photosynthesis, physiology and microstructure

Drought and cold stresses co-occur in nature, and significantly limited agricultural productivity in northwest China. Their effects on plant photosynthesis, physiology and biochemistry, and microstructure have been extensively studied, but their combined stress mechanisms remain unclear. Therefore, growth chamber experiments were conducted using the Annual bluegrass (Poa annua) with the ‘HZ’ and ‘ZQ’ germplasms, our goal was to clarify the responses of leaves to cold (C), drought (D), and combined (D&C) stresses in the morphology, photosynthesis, physiology and biochemistry, and microstructure. The results showed that three stress types significantly suppressed growth, reduced photosynthetic pigments, photosynthetic capacity, and photosynthetic enzyme activities, with ‘ZQ’ being more sensitive than ‘HZ’. C stress (12/36 h) improved chlorophyll fluorescence parameters in ‘HZ’ (except for photochemical quenching coefficient), while D and D&C stresses diminished these parameters of both germplasms. Under single and combined stresses, leaf thickness and cuticle thickness generally increased then decreased with stress duration, except for ‘ZQ’ under D stress. D stress increased reactive oxygen species, relative conductivity, malondialdehyde content and stomatal density, while inhibited stomatal size. Conversely, C stress exacerbated the negative effects of drought on these traits. The D&C stress enhanced antioxidant enzyme activity and proline content, which were similar to the responses to D stress, except for ‘ZQ’ under D&C stress. After 24 h of stress relief, the recoveries degree of most traits in plant under D and D&C stresses were similar, with ‘HZ’ recovering more than ‘ZQ’. This study indicated drought played a dominant role in combined stress. However, some unique responses could not be inferred from the superimposed effects of some single stresses.

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.

PpERF-CRF3 selected by transcriptomic analysis plays key roles in the regulation of ABA alleviating chilling injury in peach fruit

Abscisic acid (ABA) is widely utilized to mitigate chilling injury (CI) of fruit. However, the molecular mechanism of ABA alleviates CI in peach fruit remain unclear. Herein, 10−4 M ABA treatment significantly mitigated the CI of peach fruit by reducing relative conductivity and malondialdehyde content, while increasing proline and endogenous ABA content. Transcriptomic analysis indicated that an abundant number of differentially expressed genes were altered by ABA treatment, which primarily enriched pathways such as plant hormone signal transduction, glycerophospholipid metabolism and phenylpropanoid biosynthesis. RNA-Seq results indicate that ABA modulates the transcription of genes involved in auxin, ABA and ethylene signal transduction, as well as in cell wall degradation, antioxidant, fatty acid desaturation and proline metabolism. RT-qPCR confirmed the RNA-Seq results, ABA treatment induced the transcription of proline metabolism related genes (PpP5CR2, PpP5CS, PpP5CS1) and PpERF-CRF3. Particularly noteworthy, as a nuclear protein, PpERF-CRF3 activated the expression of PpP5CR2 and PpP5CS by directly binding to their promoters and over-expression PpERF-CRF3 increased proline content and enhanced PpP5CR2 and PpP5CS expression. Overall, these findings suggest that ABA mitigates CI in peach fruit may be by mediating these pathways, and PpERF-CRF3 potentially involves this process by stimulating the expression of genes related to proline synthesis.

RrWRKY1, a Transcription Factor, Is Involved in the Regulation of the Salt Stress Response in Rosa rugosa.

Salt stress has become a major environmental problem affecting plant growth and development. Some WRKY transcription factors have been reported to be involved in the salt stress response in plants. However, there are few studies on the involvement of WRKYs in the salt stress response in Rosa rugosa. In this study, we isolated a salt tolerance gene, RrWRKY1, from R. rugosa. RrWRKY1 was found to belong to Group I of the WRKY family, and it was specifically expressed in leaves and petals. RrWRKY1 expression was upregulated under NaCl stress in rose leaves. After silencing RrWRKY1 in R. rugosa, transgenic plants showed dry leaves and black and brown veins, indicating sensitivity to salt stress. At the same time, the transcription levels of the salt tolerance-related genes RrNHX1, RrABF2, RrRD22, RrNCED1, and RrHKT1 also changed significantly. The superoxide dismutase (SOD) and peroxidase (POD) activities decreased, the proline content decreased, and the malondialdehyde (MDA) content in the gene-silenced plants increased, indicating that RrWRKY1 regulates the salt tolerance of R. rugosa. In addition, the overexpression of RrWRKY1 in Arabidopsis thaliana improved the germination rate and the average of the main root and lateral root lengths, and the transgenic plants had a larger number of lateral roots than the WT plants under salt stress. This study provides candidate gene resources for salinity tolerance breeding and a theoretical basis for analyzing the salinity tolerance mechanism of the WRKY gene.

Effects of guanidine acetic acid supplementation from gestation to lactation on reproductive performance, colostrum quality, blood biochemistry, and intestinal microflora diversity of sows.

This experiment aimed to study the effects of guanidine acetic acid (GAA) on reproductive performance, lactation performance and blood biochemical indices of sows, as well as the performance of offspring piglets. A total of 20 sows (Landrace × Yorkshire, parity 4) were used. Half of the sows in each parity were fed a control diet (CG; basic diet, n = 10) or GAA diet (basic diet +1 g/kg GAA, n = 10) from the 85th day of gestation until weaning. The study results are presented as follows: Supplementation of GAA from late gestation to lactation did not adversely affect sow feed intake, backfat thickness, or blood routine indexes (p > 0.05). GAA supplementation showed a tendency to increase the number of healthy piglets and their birth activity (p = 0.06; p = 0.08), while significantly increasing the IUGR score of piglets (p < 0.05). GAA supplementation significantly increased colostrum protein content (p < 0.05) and tended to increase daily milk yield in sows (p = 0.07). GAA supplementation increased the level of immunoglobulin A in sow colostrum (p < 0.05) and showed a tendency to increase proline content (p = 0.10). GAA supplementation significantly decreased triglyceride content in sow cord blood (p < 0.05), with no significant effects observed on HDL-C, LDL-C, TC, and GLU (p > 0.05). GAA supplementation significantly increased eNOS levels in sow cord blood (p < 0.05), while showing no significant effects on IL-6 and IL-10 (p > 0.05). GAA supplementation did not significantly affect the α diversity of sow intestinal flora (ACE, Shannon, Chao1, Simpson, observed_otus, pielou_e, and good_cover), but PCoA analysis revealed differences in intestinal flora structure between groups. Additionally, GAA decreased the relative abundance of Sarciha and unidentified_ruminococcaceae and increased the relative abundance of Lactobacillus, Parabacteroides, and Pedobacter in the gut. GAA boosts nitric oxide synthase in sows' umbilical cord blood, enhancing placental blood vessel development. This improves piglet health and vitality, increases beneficial gut bacteria (Lactobacillus, Parabacteroides, Pedobacter), and raises colostrum protein levels and lactation volume, leading to better piglet growth and performance.

Influence of Foliar Application of Nanoparticles on Low Temperature Resistance of Rice Seedlings.

Chilling stress, a common abiotic factor, adversely affects the growth and biomass of rice seedlings during the early stages, ultimately reducing the yield. Effective strategies to mitigate these negative impacts are essential for improving rice productivity. The application of nanotechnology in agriculture, particularly nanoparticles (NPs), has shown a promising effect in alleviating chilling stress in plants. This study evaluates the effects of various nanoparticles, ZnO (0, 50, 100, and 200 mg/L), Fe2O3 (0, 50, 75, and 100 mg/L), TiO2 (0, 50, 75, and 100 mg/L), and CeO2 (0, 50, 75, and 100 mg/L) on the chilling resistance with one control (a water spray) under a normal temperature. Four rice cultivars: LLY-7108 and XZX-6 (Low-temperature-tolerant), and LLY-32 and ZJZ-17 (Low-temperature-susceptible) were tested in this experiment. Rice seedlings were subjected to low temperature conditions (12 h light 14 °C/12 h dark, at 10 °C) for five days, followed by seven days of recovery. The results of this study demonstrate that NPs significantly enhanced seedling height fresh/dry weight and root length compared to untreated controls under chilling stress. NP treatment also reduced the reactive oxygen species (ROS), malondialdehyde (MDA), and proline content, while enhancing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, thereby mitigating oxidative damage. The four rice varieties exhibited clear signs of rapid growth recovery and positive physiological changes due to NPs' application. Among the tested cultivars, LLY-7108 showed the most substantial recovery and physiological responses, while ZJZ-17 exhibited the least. The findings of this study indicate that the foliar application of ZnO (100 mg/L), Fe2O3 (50 mg/L), TiO2 (50 mg/L), and CeO2 (75 mg/L) NPs effectively mitigates chilling stress in rice seedlings, likely by enhancing the antioxidant enzymatic activity while reducing the oxidative damage. This study highlights the potential of NPs as effective agents in reducing the adverse effects of chilling stress on rice.

Evaluating the effects of rice husk derived nanosilica on growth, photosynthesis, and antioxidant activity in hybrid maize

Drought stress was exacerbated by changing climatic conditions and impact the plant water relations from the cellular to whole plant level, thereby reducing the crop productivity and causing economic losses in agriculture. The present study was aimed to explore the potentials of nanosilica synthesized from rice husk in improving growth and drought stress tolerance in maize. Synthesized nanosilica from rice husk has spherical morphology, amorphous structure, siloxane bonding and higher purity (99.1 %). Soil application of varied levels of synthesized nanosilica (0, 5, 10, 15, 20, 30 and 40 mg kg−1) was tested with hybrid maize plants grown under irrigated and drought stress (100 and 50 % field capacity, respectively). The results of the study revealed that, drought stress has adverse effect on plant growth, biomass production and physiological parameters. However soil application of nanosilica has significantly improved growth, physiological and biochemical attributes of both irrigated and drought stressed plants. Nanosilica application at 20 mg kg−1 for irrigated and 30 mg kg−1 for drought stressed hybrid maize plants has recorded higher plant height, biomass, chlorophyll a, chlorophyll b, superoxide dismutase, peroxidase, phenols, soluble proteins and considerably decreased the proline, electrolyte leakage and melondialdehyde content in hybrid maize. In contrary, higher doses of nanosilica (>30 mg kg−1) caused a slight reduction in plant growth and antioxidant activity under both the water regimes. Hence, we conclude that, soil application of 20 and 30 mg kg−1 nanosilica synthesized from rice husk had a positive effect on plant growth and development besides aided in mitigating drought stress.

Peanut-Colonized Piriformospora indica Enhanced Drought Tolerance by Modulating the Enzymes and Expression of Drought-Related Genes.

Peanut (Arachis hypogaea L.) is an important cash and oil seed crop, mostly distributed in arid and semi-arid areas. In recent years, due to the influence of atmospheric circulation anomalies and other factors, drought has become frequent and increasingly serious in China. This has posed serious challenges to peanut production. The objective of this study was to investigate the potential of the endophytic fungus Piriformospora indica to form a symbiotic relationship with peanut plants and to evaluate the drought tolerance of P. indica-colonized peanut plants subjected to a simulated drought stress treatment using 20% polyethylene glycol 6000 (PEG6000). The endophytic fungus P. indica affected the physiological characteristics of the host plant by colonizing the plant roots, thereby conferring greater resistance to drought stress. This fungus strongly colonized the roots of peanuts and was found to enhance root activity after 24 h of P. indica colonization under PEG6000. Catalase (CAT) and peroxidase (POD) activities were increased at 24 h in peanut leaves colonized with P. indica. Expression of drought-related genes, such as AhNCED1, AhP5CS, and DREB2A was upregulated at 24 h of P. indica colonization. In addition, after PEG6000 treatment, proline, soluble protein, and abscisic acid (ABA) concentrations in plants were increased, while the accumulation of malondialdehyde (MDA), and hydrogen peroxide (H2O2) was decreased in P. indica colonized peanut. In conclusion, P. indica mediated peanut plant protection against the detrimental effects of drought resulted from enhanced antioxidant enzyme activities, and the upregulated expression of drought-related genes for lower membrane damage.

Combining Ability and Gene Action for Grain Yield and Attributing Traits in Maize (Zea mays L.) Subjected to Drought Stress

Background: Maize production is subdued by many impediments that cause yield minimization. Among various biotic and abiotic stress factors, one significant cause of yield reduction in maize is drought stress. Methods: A set of 15 inbreds which were crossed with 3 narrow base testers in line × tester mating design, and resulting 45 F1s along with the parent inbreds and 3 commercial checks were then, in RCBD, subjected to drought stressed and well-watered conditions to assess their genetic worth during spring 2021. Result: The ANOVA unraveled significant mean sum of squares due to lines, testers and line × tester in pooled analysis for all the ten traits. The inbred EI-2188-2 followed by EI-2448 and EI-03-3 contained fair per se performance and significant high GCA effects over the environments for grain yield/plant, proline content and cob length whereas the cross EI-2448-1 × EI-2156 was found most promising hybrid with significant and high SCA effects across the environments regarding grain yield/plant, proline content and cob girth. Prevalence of non-additive type of genetic variance in governing most of the traits suggests adoption of heterosis breeding will be rewarding for improving yield and drought tolerance. Heterotic pooling of the highlighted inbreds and utilization of the superlative hybrids in further breeding programmes for drought tolerance is proposed.

Biological Acclimatization of Micropropagated Al-Taif Rose (Rosa damascena f. trigintipetala (Diek) R. Keller) Plants Using Arbuscular Mycorrhizal Fungi Rhizophagus fasciculatus

Tissue culture is used to multiply Al-Taif rose (Rosa damascena f. trigintipetala (Diek) R. Keller) plants in order to meet the demands of the fragrance, cosmetic, and floriculture industries. The use of arbuscular mycorrhizal fungus (AMF) could potentially improve plant growth and acclimatization performance to ex vitro conditions. Thus, in the current study, we investigated how AMF Rhizophagus fasciculatus influences the growth, establishment, and physiological performance of micropropagated Al-Taif rose plants during the acclimatization stage. The growth and physiological parameters of the AMF-treated plants were evaluated after a 12 week growth period in the growth chambers. The plants treated with AMF exhibited greater height (25.53 cm) and biomass growth values for both shoot fresh weight (0.93 g/plant) and dry weight (0.030 g/plant), more leaves (11.3/plant), more leaf area (66.15 cm2), longer main roots (15.05 cm/plant), total root length (172.16 cm/plant), total root area (64.36 cm2/plant), and biomass from both fresh weight (383 mg/plant) and dry weight (80.00 mg/plant) of the plants. The plants treated with AMF also exhibited increased rates of net CO2 assimilation, stomatal conductance, and transpiration compared to the control plants. The proline content in the leaves and roots was significantly lower in the AMF-treated plants than untreated plants. The Fv/Fm ratio, which serves as an indicator of the intrinsic or maximal efficacy of Photosystem II (PSII) demonstrated a notable decline in the untreated Al-Taif rose plants. These results elucidate the advantageous impact of AMF colonization on micropropagated Al-Taif rose plants, thereby enhancing their resilience against adverse ex vitro conditions.

Analysis of the Physiological Parameters of Cold Resistance in Core Winter and Spring Wheat Cultivars

We selected 46 core winter–spring wheat cultivars from China’s main wheat-producing areas as experimental materials to clarify the differences in the physiological parameters of their cold resistance and provide a theoretical basis and high-quality germplasm for cold resistance breeding. We investigated differences in their cold resistance under field conditions for two consecutive years, and determined the physiological parameters of the cold resistance, yield, and quality indicators of different winter–spring wheat cultivars. Our results showed that the cold resistance of winter wheat cultivars was higher than that of spring wheat cultivars. The chlorophyll (Chl), soluble sugar (SS), soluble protein (SP), and free proline (Pro) contents of different winter–spring wheat cultivars were positively correlated with cold resistance, and malondialdehyde (MDA) content was negatively correlated with cold resistance. The five physiological parameters can be used as physiological indicators for the breeding of cold-resistant cultivars. The cold resistance, yield, and quality indicators of different spring and winter wheat cultivars were comprehensively evaluated by using the average membership value and comprehensive score. It was found that the average membership value and comprehensive score of winter wheat cultivars were higher than those of spring wheat cultivars. Through classification using the K-means method, the cold-resistant, high-yield, and high-quality cultivars were screened out, namely, Jimai23 (JM23), Jimai44 (JM44), Shannong57 (SN57), and Jinmai 919 (JM919).

AtZAT10/STZ1 improves drought tolerance and increases fiber yield in cotton.

Drought poses a significant challenge to global crop productivity, necessitating innovative approaches to bolster plant resilience. Leveraging transgenic technology to bolster drought tolerance in crops emerges as a promising strategy for addressing the demands of a rapidly growing global populace. AtZAT10/STZ1, a C2H2-type zinc finger protein transcription factor has shown to significantly improve Arabidopsis' tolerance to various abiotic stresses. In this study, we reports that AtSTZ1 confers notable drought resistance in upland cotton (Gossypium hirsutum), amplifying cotton fiber yield under varying conditions, including irrigated and water-limited environments, in field trials. Notably, AtSTZ1-overexpressing transgenic cotton showcases enhanced drought resilience across critical growth stages, including seed germination, seedling establishment, and reproductive phases. Morphological analysis reveals an expanded root system characterized by an elongated taproot system, increased lateral roots, augmented root biomass, and enlarged cell dimensions from transgenic cotton plants. Additionally, higher contents of proline, chlorophyll, soluble sugars, and enhanced ROS-scavenging enzyme activities are observed in leaves of transgenic plants subjected to drought, underscoring improved physiological adaptations. Furthermore, transgenic lines exhibit heightened photosynthetic rate, increased water use efficiency, and larger stomatal and epidermal cell sizes, coupled with a decline in leaf stomatal conductance and density, as well as diminished transpiration rates compared to the wild type counterparts. Transcriptome profiling unveils 106 differentially expressed genes in transgenic cotton leaves post-drought treatment, including protein kinases, transcription factors, aquaporins, and heat shock proteins, indicative of an orchestrated stress response. Collectively, these findings underscore the capacity of AtSTZ1 to augment the expression of abiotic stress-related genes in cotton following drought conditions, thus presenting a compelling candidate for genetic manipulation aimed at enhancing crop resilience.

Cerium Oxide Nanoparticles (CeO2 NPs) Enhance Salt Tolerance in Spearmint (Mentha spicata L.) by Boosting the Antioxidant System and Increasing Essential Oil Composition

Salinity represents a considerable environmental risk, exerting deleterious effects on horticultural crops. Nanotechnology has recently emerged as a promising avenue for enhancing plant tolerance to abiotic stress. Among nanoparticles, cerium oxide nanoparticles (CeO2 NPs) have been demonstrated to mitigate certain stress effects, including salinity. In the present study, the impact of CeO2 NPs (0, 25, and 100 mg L−1) on various morphological traits, photosynthetic pigments, biochemical parameters, and the essential oil profile of spearmint plants under moderate (50 mM NaCl) and severe (100 mM NaCl) salinity stress conditions was examined. As expected, salinity reduced morphological parameters, including plant height, number of leaves, fresh and dry weight of leaves and shoots, as well as photosynthetic pigments, in comparison to control. Conversely, it led to an increase in the content of proline, total phenols, malondialdehyde (MDA), hydrogen peroxide (H2O2), and antioxidant enzyme activities. In terms of CeO2 NP applications, they improved the salinity tolerance of spearmint plants by increasing chlorophyll and carotenoid content, enhancing antioxidant enzyme activities, and lowering MDA and H2O2 levels. However, CeO2 NPs at 100 mg L−1 had adverse effects on certain physiological parameters, highlighting the need for careful consideration of the applied concentration of CeO2 NPs. Considering the response of essential oil compounds, combination of salinity stress and CeO2 treatments led to an increase in the concentrations of L-menthone, pulegone, and 1,8-cineole, which are the predominant compounds in spearmint essential oil. In summary, foliar application of CeO2 NPs strengthened the resilience of spearmint plants against salinity stress, offering new insights into the potential use of CeO2 NP treatments to enhance crop stress tolerance.

Elevated CO2 Concentration Enhances Drought Tolerance by Mitigating Oxidative Stress and Enhancing Carbon Assimilation in Foxtail Millet (Setaria italica)

ABSTRACTElevated CO2 concentration (eCO2) can modulate the response of crop plants to drought stress (DS). This study aimed to investigate the response of leaf gas exchange, chlorophyll fluorescence, antioxidant activities, osmotic adjustment substance, phytohormone and signal transduction regulatory enzymes, as well as related genes in foxtail millet to DS (water stress for 10 days), ambient condition (aCO2, 400 μmol mol−1) and eCO2 (600 μmol mol−1). eCO2 significantly increased the net photosynthetic rate, maximum net photosynthetic rate, chlorophyll a content, transpiration rate and stomatal conductance, but did not affect leaf instantaneous water‐use efficiency under DS. eCO2 also significantly enhanced the quantum yield of Photosystem II (PSII), photosynthetic electron transport, and proportion of open PSII reaction centers under DS. Moreover, eCO2 significantly increased abscisic acid (ABA) content, proline content, and the activities of peroxidase, superoxide dismutase, and calcium‐dependent protein kinase under DS, leading to a significant reduction in malondialdehyde content. eCO2 significantly increased the expressions of gene encoding ABA‐, stress‐ and ripening‐induced proteins and ABA‐responsive element binding factor under DS. Our results clearly demonstrated the vital role of eCO2 in mitigating the drought‐induced damage over ambient CO2 grown foxtail millet.

Root physiological and morphology processes co-regulate the growth of Chinese-fir saplings in response to warming and precipitation reduction in the sub-tropical regions

Subtropical China is projected to experience elevated temperature greater than the mean global temperature increase and is accompanied by reduced precipitation. The plasticity of roots to changing environment strongly influences ecosystem feedbacks to climate change. However, knowledge gaps on the individual and combined effects of warming and precipitation reduction on root systems hinder our ability to accurately predict the growth and adaptability of forests under future climate change. To examine the effects of warming (W) and precipitation reduction (P) on roots physiology and morphology of Chinese-fir saplings, we used a randomized complete block design with factorial soil warming (ambient, ambient + 5℃) and precipitation reduction (ambient, ambient-50 %) treatments. A full excavation method was adopted to obtain roots, then we measured the root physiology (osmoregulatory substances, oxidant substances, protective enzymes, endogenous hormones), morphology (specific root length, SRL; surface root area, SRA; root tissue density, RTD). The content of carbon and nitrogen, isotopes (δ13C and δ15N); soil temperature, soil moisture and sapling growth were also measured. We found that compared with the control, W decreased the abscisic acid (IAA) content; P increased the contents of hydrogen peroxide (H2O2) and proline (Pro), and decreased the contents of IAA and cytokinin (CTK); warming plus precipitation reduction (WP) increased the Pro content, and decreased the contents of IAA and CTK. In addition, the effects of W and P on root morphology varied with soil depth and root diameter class. W, P, and WP all increased fine root SRL and SRA in deep soil. Warming and precipitation reduction could affect physiological traits (e.g. non-enzymatic substances and antioxidant enzymes) and subsequently morphological traits via influencing soil environment and root tissue chemistry. Collectively, the results indicated that Chinese-fir saplings responded to warming and precipitation reduction by comprehensive regulation of the non-enzymatic substances (e.g., osmotic substances and endogenous hormones) of fine roots and changing root morphological characteristics in deep soil.

Exogenous 5-aminolevulinic acid enhanced saline-alkali tolerance in pepper seedlings by regulating photosynthesis, oxidative damage, and glutathione metabolism.

A plant growth regulator, 5-aminolevulinic acid, enhanced the saline-alkali tolerance via photosynthetic, oxidative-reduction, and glutathione metabolism pathways in pepper seedlings. Saline-alkali stress is a prominent environmental problem, hindering growth and development of pepper. 5-Aminolevulinic acid (ALA) application effectively improves plant growth status under various abiotic stresses. Here, we evaluated morphological, physiological, and transcriptomic differences in saline-alkali-stressed pepper seedlings after ALA application to explore the impact of ALA on saline-alkali stress. The results indicated that saline-alkali stress inhibited plant growth, decreased biomass and photosynthesis, altered the osmolyte content and antioxidant system, and increased reactive oxygen species (ROS) accumulation and proline content in pepper seedlings. Conversely, the application of exogenous ALA alleviated this damage by increasing the photosynthetic rate, osmolyte content, antioxidant enzyme activity, and antioxidants, including superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase, and reducing glutathione to reduce ROS accumulation and malonaldehyde content. Moreover, the transcriptomic analysis revealed the differentially expressed genes were mainly associated with photosynthesis, oxidation-reduction process, and glutathione metabolism in saline-alkali stress + ALA treatment compared to saline-alkali treatment. Among them, the change in expression level in CaGST, CaGR, and CaGPX was close to the variation of corresponding enzyme activity. Collectively, our findings revealed the alleviating effect of ALA on saline-alkali stress in pepper seedlings, broadening the application of ALA and providing a feasible strategy for utilize saline-alkali soil.