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Hulless Cucurbita pepo is an annual herb in the Cucurbitaceae family and is one of the main economic vegetable crops in China, and is a raw material for cosmetics and health care products. It is also called hulless pumpkin because its seeds have no seed coat, which is a rare variation of the Cucurbita. In July 2010, powdery mildew was observed on hulless Cucurbita pepo 'Tianran' in fields of Wuwei District, China(Liang et al.2010). Disease incidence when first observed was 65.67%, but increased to 100% in July 2019. Early disease symptoms appeared as circular or irregular white powdery areas on both leaf surfaces. At later infection stages, entire leavesï¼petioles, and stems were covered with white fungal mycelia that resulted in leaf yellowing and senescenceï¼but not defoliation . Fungal hyphae were septate, branched and flexuous to straigh. Conidiophores were unbranched, straight and grew vertically to the mycelium. Conidiophore foot cells of the were cylindrical with slight constriction at basal septa and followed by one to four short cells that eventually became conidia. Conidia were barrel-shaped with ends darker than the middle and measured 20 to 32 × 12 to 19µm.T Cleistothecium formed at 20 â, 70% relative humidity and light intensity of 4,400 lx. They were scattered, spherical, dark brown, with parietal cells irregularly rectangular or polygonal, and 70 to 75×90 to 95µm in diameter. Cleistothecia had four to eight appendages that were colorless to partially brown, each with three to five septa and lengths 0.5 to 3.0 times the diameter of cleistothecia. The powdery mildew fungus was tentatively identified as Podosphaera xanthii and showed characteristics similar to those reported by others (Cui et al. 2018; Choi et al. 2020). rDNA was extracted from pools of fungus conidia and the ITS region amplified using primers ITS 1:5'-TCCGTAGGT GAACCTGCGG-3'/ITS 4:5'-TCCTCCGCTTATTGATATGC-3' and then sequenced. BLASTn analysis of the 540-bp (MT250855) amplicon revealed 100% sequence identity with respective rDNA sequences of Podosphaera xanthii isolates from Momordica charantia(AB774158.1). Based on the morphological characteristics and ITS sequences, the fungal species was identified as P. xanthii .Pathogenicity of the powdery mildew fungus was tested by dusting conidia from infected hulless pumpkin leaves onto three asymptomatic plants. Three noninoculated plants was used as a controls. The Infection process of P.xanthii on pumpkins observed that the conidia began to germinate at 12h after inoculation.Twenty four to 72 h post inoculation, powdery mildew mycelia appeared on inoculated leaves. After 73 to 96 h, chains of conidia formed and these germinated to form secondary infection sites. In later stages of the disease cycle, dark brown cleistothecia formed on the yellowing plant foliage. Fungus morphology from inoculated leaves was identical to that observed on original naturally infected plants. Uninoculated plants remained healthy. Powdery mildew caused by P. xanthii is a major foliage disease that affects members of the Cucurbitaceae family worldwide. The fungus has previously been reported from China on Cucurbita moschata (DQ490752), Cucurbita maxima (DQ490759), Cucurbita pepo(DQ490750), Cucumis sativus(DQ490755)(Park et al.2010; Liang et al.2007) and Cucurbita maxima, Abelmoschus esculentus (okra), Sechium edule (mirliton, vegetable pear), and Lagenaria siceraria (bottle gourd) (Choi et al. 2020; Fan et al. 2019; Xu et al. 2020; Cui et al. 2018).To our knowledge, this is the first report on the occurrence of P. xanthii on hulless Cucurbita pepo in China.
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Autotoxicity of root exudates is one of the main reasons for consecutive monoculture problem (CMP) in cucumber under greenhouse cultivation. Rootstock grafting may improve the tolerance of cucumber plants to autotoxic stress. To verify the enhanced tolerance to autotoxic stress and illuminate relevant molecular mechanism, a transcriptomic comparative analysis was performed between rootstock grafted (RG) and non-grafted (NG) cucumber plants by a simulation of exogenous cinnamic acid (CA). The present study confirmed that relatively stable plant growth, biomass accumulation, chlorophyll content, and photosynthesis was observed in RG than NG under CA stress. We identified 3647 and 2691 differentially expressed genes (DEGs) in NG and RG cucumber plants when compared to respective control, and gene expression patterns of RNA-seq was confirmed by qRT-PCR. Functional annotations revealed that DEGs response to CA stress were enriched in pathways of plant hormone signal transduction, MAPK signaling pathway, phenylalanine metabolism, and plant-pathogen interaction. Interestingly, the significantly enriched pathway of photosynthesis-related, carbon and nitrogen metabolism only identified in NG, and most of DEGs were down-regulated. However, most of photosynthesis, Calvin cycle, glycolysis, TCA cycle, and nitrogen metabolism-related DEGs exhibited not or slightly down-regulated in RG. In addition, several stress-related transcription factor families of AP2/ERF, bHLH, bZIP, MYB. and NAC were uniquely triggered in the grafted cucumbers. Overall, the results of this study suggest that rootstock grafting improve the tolerance of cucumber plants to autotoxic stress by mediating down-regulation of photosynthesis, carbon, and nitrogen metabolism-related DEGs and activating the function of stress-related transcription factor. The transcriptome dataset provides an extensive sequence resource for further studies of autotoxic mechanism at molecular level.
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Cucumis sativus/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Sistema de Señalización de MAP Quinasas , Proteínas de Plantas/biosíntesis , Plantones/metabolismo , Estrés Fisiológico , Cucumis sativus/genética , Proteínas de Plantas/genética , Plantones/genéticaRESUMEN
Drought stress is a major problem around the world and there is still little molecular mechanism about how fruit crops deal with moderate drought stress. Here, the physiological and phosphoproteomic responses of drought-sensitive genotype (M26) and drought-tolerant genotype (MBB) under moderate drought stress were investigated. Our results of the physiology analysis indicated that the MBB genotype could produce more osmosis-regulating substances. Furthermore, phosphoproteins from leaves of both genotypes under moderate drought stress were analyzed using the isobaric tags for relative and absolute quantification technology. A total of 595 unique phosphopeptides, 682 phosphorylated sites, and 446 phosphoproteins were quantitatively analyzed in the two genotypes. Five and thirty-five phosphoproteins with the phosphorylation levels significantly changed (PLSC) were identified in M26 and MBB, respectively. Among these, four PLSC phosphoproteins were common to both genotypes, perhaps indicating a partial overlap of the mechanisms to moderate drought stress. Gene ontology analyses revealed that the PLSC phosphoproteins represent a unique combination of metabolism, transcription, translation, and protein processing, suggesting that the response in apple to moderate drought stress encompasses a new and unique homeostasis of major cellular processes. The basic trend was an increase in protein and organic molecules abundance related to drought. These increases were higher in MBB than in M26. Our study is the first to address the phosphoproteome of apple rootstocks in response to moderate drought stress, and provide insights into the molecular regulation mechanisms of apple rootstock under moderate drought stress.
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Sequías , Genotipo , Malus/genética , Fosfoproteínas/genética , Estrés Fisiológico , Secuencia de Aminoácidos , Cromatografía Liquida , Electroforesis en Gel de Poliacrilamida , Genes de Plantas , Malus/fisiología , Fosforilación , Reacción en Cadena en Tiempo Real de la Polimerasa , Espectrometría de Masa por Ionización de Electrospray , Espectrometría de Masas en TándemRESUMEN
MAIN CONCLUSION: Exogenously applied 2% fructose is the most appropriate carbon source that enhances photosynthesis and growth of grape plantlets compared with the same concentrations of sucrose and glucose. The role of the sugars was regulated by the expression of key candidate genes related to hormones, key metabolic enzymes, and sugar metabolism of grape plantlets ( Vitis vinifera L.) grown in vitro. The addition of sugars including sucrose, glucose, and fructose is known to be very helpful for the development of grape (V. vinifera L.) plantlets in vitro. However, the mechanisms by which these sugars regulate plant development and sugar metabolism are poorly understood. In grape plantlets, sugar metabolism and hormone synthesis undergo special regulation. In the present study, transcriptomic analyses were performed on grape (V. vinifera L., cv. Red Globe) plantlets in an in vitro system, in which the plantlets were grown in 2% each of sucrose (S20), glucose (G20), and fructose (F20). The sugar metabolism and hormone synthesis of the plantlets were analyzed. In addition, 95.72-97.29% high-quality 125 bp reads were further analyzed out of which 52.65-60.80% were mapped to exonic regions, 13.13-28.38% to intronic regions, and 11.59-28.99% to intergenic regions. The F20, G20, and S20 displayed elevated sucrose synthase (SS) activities; relative chlorophyll contents; Rubisco activity; and IAA and zeatin (ZT) contents. We found F20 improved the growth and development of the plantlets better than G20 and S20. Sugar metabolism was a complex process, which depended on the balanced expression of key potential candidate genes related to hormones (TCP15, LOG3, IPT3, ETR1, HK2, HK3, CKX7, SPY, GH3s, MYBH, AGB1, MKK2, PP2C, PYL, ABF, SnRK, etc.), key metabolic enzymes (SUS, SPS, A/V-INV, and G6PDH), and sugar metabolism (BETAFRUCT4 and AMY). Moreover, sugar and starch metabolism controls the generation of plant hormone transduction pathway signaling molecules. Our dataset advances our knowledge of the genes involved in sugar metabolism and improves the understanding of complex regulatory networks involved in signal transduction in grape plantlets.
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Reguladores del Crecimiento de las Plantas/metabolismo , Transducción de Señal/efectos de los fármacos , Azúcares/farmacología , Vitis/efectos de los fármacos , Clorofila/análisis , Fructosa/farmacología , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/fisiología , Glucosa/farmacología , Técnicas In Vitro , Reguladores del Crecimiento de las Plantas/fisiología , Hojas de la Planta/química , Hojas de la Planta/efectos de los fármacos , Reacción en Cadena en Tiempo Real de la Polimerasa , Análisis de Secuencia de ADN , Transducción de Señal/fisiología , Sacarosa/farmacología , Vitis/genética , Vitis/metabolismo , Vitis/fisiologíaRESUMEN
BACKGROUND: Detailed descriptions of the early development of parasitic nematodes are seldom available. The embryonic development of the plant-parasitic nematode Meloidogyne incognita was studied, focusing on the early events. RESULTS: A fixed pattern of repeated cell cleavages was observed, resulting in the appearance of the six founder cells 3 days after the first cell division. Gastrulation, characterized by the translocation of cells from the ventral side to the center of the embryo, was seen 1 day later. Approximately 10 days after the first cell division a rapidly elongating two-fold stage was reached. The fully developed second stage juvenile hatched approximately 21 days after the first cell division. CONCLUSIONS: When compared to the development of the free-living nematode Caenorhabditis elegans, the development of M. incognita occurs approximately 35 times more slowly. Furthermore, M. incognita differs from C. elegans in the order of cell divisions, and the early cleavage patterns of the germ line cells. However, cytoplasmic ruffling and nuclear migration prior to the first cell division as well as the localization of microtubules are similar between C. elegans and M. incognita.
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Desarrollo Embrionario , Raíces de Plantas/parasitología , Tylenchoidea/embriología , Animales , División Celular , Linaje de la Célula , Núcleo Celular/metabolismo , Citoesqueleto/metabolismo , ADN/metabolismo , Embrión no Mamífero/citología , Embrión no Mamífero/metabolismo , Femenino , Gastrulación , Óvulo/citología , Filogenia , Tylenchoidea/citologíaRESUMEN
Trichothecium roseum is one of the most important postharvest pathogens in arid and semiarid regions. Sodium silicate (NaSi) and environmental pH have significant inhibitory effects on fungal growth. However, no study has addressed the relationship of NaSi and pH in combination and the effects on T. roseum. In this work, we showed that spore germination, germ tube elongation, and mycelial growth of T. roseum were significantly inhibited by various NaSi concentrations, which had corresponding increasing pHs. Furthermore, these NaSi solutions showed a much greater impact than did pH treatments alone. The pathogenicity of NaSi-treated conidia on a model assay (conidia-inoculated apple fruit) was dramatically reduced, whereas no changes of pathogenicity were evident for the corresponding pH (various sodium hydroxide (NaOH) solutions) treatments. Fluorescent microscopy, using propidium iodide staining, showed damage of the plasma membranes of T. roseum conidia treated with both NaSi and NaOH, although the damage was more severe with NaSi. Leakage of proteins and sugars was significantly higher in NaSi-treated and NaOH-treated conidia than in untreated controls. In addition, serious damage was observed in the conidia exposed to NaSi for longer periods of time. Ultrastructural observations showed that treatment with either NaSi or NaOH caused a plasmolysis state and disorganized organelles. Taken together the results show that NaSi has inhibitory effects on T. roseum and that the inherent higher pH of NaSi solutions of higher concentrations simply acts as an enhancer of the inhibitory effects of NaSi.
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Hongos Mitospóricos/efectos de los fármacos , Silicatos/farmacología , Frutas/microbiología , Proteínas Fúngicas/análisis , Concentración de Iones de Hidrógeno , Malus/microbiología , Hongos Mitospóricos/crecimiento & desarrollo , Hidróxido de Sodio/farmacología , Esporas Fúngicas/efectos de los fármacos , Esporas Fúngicas/crecimiento & desarrollo , Esporas Fúngicas/ultraestructuraRESUMEN
Several studies have reported the deleterious effects of excessive salt stress on Triticum aestivum L. seedlings. Seed pretreatment with exogenous salicylic acid (SA) enhances plants to tolerate salt stress. Herein, the present study aims to investigate the potential of plant-growth-promoting fungus Trichoderma longibrachiatum (TG1) to increase the plant growth and enhance the salicylic acid (SA) contents and antioxidants activity in wheat seedlings under different concentrations of salt stress. Wheat seeds were pretreated in TG1 spore suspension before exposure to different salt stresses. Compared with 0, 50, 100, 150 salt stresses, the TG1 and NaCl increased the wheat seeds germination rate, germination potential and germination index significantly; the shoot height and root length were increased by an average of 39.45% and 29.73%, respectively. Compared to NaCl stress across the four concentrations (0, 50, 100, and 150 mM), the TG1 treated wheat seedlings increased SA concentration and phenylalanine ammonia-lyase activity (PAL) by an average of 55.87% and 24.10% respectively. In addition, the TG1+NaCl-treated seedlings increased superoxide dismutase (SOD), peroxidases (POD), and catalase (CAT) activities in the shoot by an average of 47.68%, 23.68%, and 38.65% respectively compared to NaCl-stressed seedlings. Significantly, the genes, SOD, CAT, and POD were relatively up-regulated in the salt-tolerant TG1-treated seedlings at all NaCl concentrations in comparison to the control. Wheat seedlings treated with TG1+NaCl increased the transcript levels of SOD, POD and CAT by 1.35, 1.85 and 1.04-fold at 50 mM NaCl concentration, respectively, compared with 0 mM NaCl concentration. Our results indicated that seeds pretreatment with TG1 could increase endogenous SA of plants and promote seedling growth under salt stress by improving enzymatic antioxidant activities and gene expression.
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Antioxidantes , Plantones , Antioxidantes/metabolismo , Triticum , Ácido Salicílico/farmacología , Cloruro de Sodio/farmacología , Estrés Salino , Peroxidasas/metabolismo , Superóxido Dismutasa/genéticaRESUMEN
Lanzhou Lily(Lilium davidii) var. unicolor, which is also known as sweet lily in China, is used as a type of food. This lily is distributed in narrow regions, propagates asexually, cultivates perennially, and cultivates commonly in serious consecutive replant problems (CRPs). Soil fumigation is commonly used to control soil-borne disease to alleviate crops' consecutive replant problems (CRPs). However, due to the improper fumigation application, it is common to cause chemical hazard to crops. In this study, we designed a two-factor experiment to explore the bacterial and fungal community structure and some specific microbial groups in the lily rhizosphere soil after chemical versus bacterial fertilizer treatments, by using a metagenomic analysis of the treated soils. The results showed that metham-sodium soil fumigation (SMF treatment) significantly decreased plant growth, as well as it significantly decreased both soil fungal diversity and abundance at the OTUs levels, while Special 8™ microbial fertilizer supplement (MF treatment) significantly improved plant growth and increased fungal diversity and abundance. Under FM treatment, Chao1 richness and Shannon's diversity increased by 6.70% and 35.09% compared to CK (no treatment). However, the bacterial diversity and abundance were not significantly changed among these treatments. The fungal and bacterial community structure were different in all treatments. In SMF treatment, the pathogenic fungal species Fusarium oxysporum increased compared to CK, but it significantly decreased in MF treatment; in MF and MMF treatments, some beneficial bacteria groups such as the bacterial phylum Proteobacteria and its member genus Sphingomonas, as well as the fungal genus Mortierella, increased compared to CK and SFM treatments, but the harmful bacterial genera Gemmatimona was decreased, as well as the harmful fungal genus Cryptococcus. Thus, we concluded that under chemical fumigation conditions, both fungal diversity loss and overall microorganism reduction, which impair multiple ecosystem function, in conjunction with the increase of harmful fungal species such as Fusarium oxysporum, are causes for soil degradation. On the other hand, under microbial fertilizer supplement, it was the fungal diversity increase, as well as these beneficial microorganisms groups' accumulation, together with those harmful groups' depletion, played important roles in restoring and improving soil health that suffered from the chemical fumigant hazard. In addition, the bacterial phylum Proteobacteria and its member genus Sphingomonas are involved in soil health recovery and promotion. The results also emphasized that whether soil is chemically fumigated or not, beneficial microorganism supplementary is effective in ensuring soil productivity.
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Toxic stress caused by autotoxins is a common phenomenon for cucumber under monoculture condition. A previous study demonstrated that grafting could enhance the resistance of cucumber to cinnamic acid (CA) stress, but the underlying mechanism behind this enhanced resistance is still unclear. In the present study, we reconfirmed the stronger resistance of grafted rootstock (RG) compared to the non-grafted (NG) cucumber as measured though plant biomass accumulation. In addition, we focused on the phenolic and other aromatic acids metabolism in hydroponic culture model system using a combination of qRT-PCR (to measure gene expression of relevant genes) and HPLC (to detect the presence of phenolic and other aromatic acids). The results showed that the exogenous CA lead to the expression of four enzymes involved in phenolic and other aromatic acids biosynthesis, and a larger increase was observed in grafted rootstock (RG). Specifically, expression of six genes, involved in phenolic and other aromatic acids biosynthesis (PAL, PAL1, C4H, 4CL1, 4CL2 and COMT), with the exception of 4CL2, were significantly up-regulated in RG but down-regulated in NG when exposed to CA. Furthermore, six kinds of phenolic and other aromatic acids were detected in leaves and roots of NG and RG cucumber, while only benzoic acid and cinnamic acid were detected in root exudate of all samples. The CA treatment resulted in an increase of p-hydroxybenzonic acid, benzoic acid and cinnamic acid contents in RG cucumber, but decrease of p-coumaric acid and sinapic acid contents in NG cucumber. Surprisingly, the type and amount of phenolic and other aromatic acids in root exudate was improved by exogenous CA, particularly for RG cucumber. These results suggest that a possible mechanism for the stronger resistance to CA of RG than NG cucumber could involve the up-regulation of key genes involved in phenolic and other aromatic acids metabolism, and that the excessive phenolic compounds released to surroundings is a result of the accumulation of phenolic compounds in a short time by the plant under stress.
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Cucumis sativus , Cucumis sativus/genética , Cinamatos/metabolismo , Fenoles/toxicidad , Ácido Benzoico/metabolismoRESUMEN
A series of 30 organic chlacones and 33 ferrocenyl (Fc) chalcones were synthesized and characterized by melting point, elemental analysis, spectroscopy ((1)H NMR and FTIR) and, in two cases, by X-ray crystallography. The biological activity of each compound (10(-4)M in DMSO) against the model nematode Caenorhabditis elegans was examined in terms of % mortality (percent nematodes that died) and % fecundity (percent nematodes that reproduced) and compared to that obtained for the control medium (1% DMSO) over a 14-day period. Detailed conformational analyses for two Fc-chalcones (studied also by X-ray crystallography) were performed via molecular modeling studies. In general, the organic chalcones were found to be less polar than their Fc analogs. Some structure-activity relationships (SARs) were determined: (a) The nematocidal activities of the organic chalcones in this series were found to be much greater than those of their ferrocenyl analogs. (b) The position of the carbonyl group played a central role in the biological activity of both classes of chalcones studied. (c) For both classes of chalcones, lipophilicity of a compound seemed to play a significant role in its nematocidal activity. (d) The planarity of a ferrocenyl-chlacone seems to play a role in its activity.
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Antinematodos/química , Chalconas/química , Compuestos Ferrosos/química , Animales , Antinematodos/síntesis química , Antinematodos/farmacología , Caenorhabditis elegans/efectos de los fármacos , Chalconas/síntesis química , Chalconas/farmacología , Cristalografía por Rayos X , Metalocenos , Conformación Molecular , Relación Estructura-ActividadRESUMEN
Salinity is abiotic stress that inhibits seed germination and suppresses plant growth and root development in a dose-dependent manner. Fusarium pseudograminearum (Fg) is a plant pathogen that causes wheat crown rot. Chemical control methods against Fg are toxic to the environment and resistance has been observed in wheat crops. Therefore, an alternative approach is needed to manage this devastating disease and the effects of salinity. Our research focused on the mycoparasitic mechanisms of Trichoderma longibrachiatum (TG1) on Fg and the induction of defenses in wheat seedlings under salt and Fg stress at physiological, biochemical and molecular levels. The average inhibition rate of TG1 against Fg was 33.86%, 36.32%, 44.59%, and 46.62%, respectively, in the four NaCl treatments (0, 50, 100, and 150 mM). The mycoparasitic mechanisms of TG1 against Fg were coiling, penetration, and wrapping of Fg hyphae. In response to inoculation of TG1 with Fg, significant upregulation of cell wall degrading enzymes (CWDEs) was observed. The expression of ß-1, 6-glucan synthase (PP4), endochitinase precursor (PH-1), and chitinase (chi18-15) increased by 1. 6, 1. 9, and 1.3-fold on day 14 compared with day 3. Wheat seedlings with combined TG1 + Fg treatments under different NaCl stress levels decreased disease index by an average of 51.89%; increased the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity by an average of 38%, 61%, and 24.96%, respectively; and decreased malondialdehyde (MDA) and hydrogen peroxide (H2O2) content by an average of 44.07% and 41.75% respectively, compared with Fg treated seedlings. The combined TG1 + Fg treatment induced the transcription level of plant defense-related genes resulting in an increase in tyrosin-protein kinase (PR2), chitinase class I (CHIA1), and pathogenesis-related protein (PR1-2) by an average of 1.15, 1.35, and 1.37-fold, respectively compared to Fg treatment. However, the expression levels of phenylalanine ammonia-lyase (PAL) increased 3.40-fold under various NaCl stresses. Our results suggest that TG1 enhances wheat seedling growth and controls wheat crown rot disease by strengthening the plant defense system and upregulating the expression of pathogenesis-related genes under both Fg and salt stress.
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The mechanisms involved in adventitious root formation reflect the adaptability of plants to the environment. Moreover, the rooting process is regulated by endogenous hormone signals. Ethylene, a signaling hormone molecule, has been shown to play an essential role in the process of root development. In the present study, in order to explore the relationship between the ethylene-induced adventitious rooting process and photosynthesis and energy metabolism, the iTRAQ technique and proteomic analysis were employed to ascertain the expression of different proteins that occur during adventitious rooting in cucumber (Cucumis sativus L.) seedlings. Out of the 5,014 differentially expressed proteins (DEPs), there were 115 identified DEPs, among which 24 were considered related to adventitious root development. Most of the identified proteins were related to carbon and energy metabolism, photosynthesis, transcription, translation and amino acid metabolism. Subsequently, we focused on S-adenosylmethionine synthase (SAMS) and ATP synthase subunit a (AtpA). Our findings suggest that the key enzyme, SAMS, upstream of ethylene synthesis, is directly involved in adventitious root development in cucumber. Meanwhile, AtpA may be positively correlated with photosynthetic capacity during adventitious root development. Moreover, endogenous ethylene synthesis, photosynthesis, carbon assimilation capacity, and energy material metabolism were enhanced by exogenous ethylene application during adventitious rooting. In conclusion, endogenous ethylene synthesis can be improved by exogenous ethylene additions to stimulate the induction and formation of adventitious roots. Moreover, photosynthesis and starch degradation were enhanced by ethylene treatment to provide more energy and carbon sources for the rooting process.
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Antibiotic and herbicide resistance genes are the most common marker genes for plant transformation to improve crop yield and food quality. However, there is public concern about the use of resistance marker genes in food crops due to the risk of potential gene flow from transgenic plants to compatible weedy relatives, leading to the possible development of "superweeds" and antibiotic resistance. Several selectable marker genes such as aph, nptII, aaC3, aadA, pat, bar, epsp and gat, which have been synthesized to generate transgenic plants by genetic transformation, have shown some limitations. These marker genes, which confer antibiotic or herbicide resistance and are introduced into crops along with economically valuable genes, have three main problems: selective agents have negative effects on plant cell proliferation and differentiation, uncertainty about the environmental effects of many selectable marker genes, and difficulty in performing recurrent transformations with the same selectable marker to pyramid desired genes. Recently, a simple, novel, and affordable method was presented for plant cells to convert non-metabolizable phosphite (Phi) to an important phosphate (Pi) for developing cells by gene expression encoding a phosphite oxidoreductase (PTXD) enzyme. The ptxD gene, in combination with a selection medium containing Phi as the sole phosphorus (P) source, can serve as an effective and efficient system for selecting transformed cells. The selection system adds nutrients to transgenic plants without potential risks to the environment. The ptxD/Phi system has been shown to be a promising transgenic selection system with several advantages in cost and safety compared to other antibiotic-based selection systems. In this review, we have summarized the development of selection markers for genetic transformation and the potential use of the ptxD/Phi scheme as an alternative selection marker system to minimize the future use of antibiotic and herbicide marker genes.
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Soil salinity causes damage to plants and a reduction in output. A natural plant growth regulator, 5-aminolevulinic acid (ALA), has been shown to promote plant growth under abiotic stress conditions. In the present study, we assessed the effects of exogenously applied ALA (25 mg L-1) on the root architecture and Na+ distribution of cucumber (Cucumis sativus L.) seedlings under moderate NaCl stress (50 mmol L-1). The results showed that exogenous ALA improved root length, root volume, root surface area, and cell activity in the root tips, which were inhibited under salt stress. In addition, although salinity stress increased the subcellular Na+ contents, such as those of the cell wall, nucleus, plastid, and mitochondria, ALA treatment reduced these Na+ contents, except the soluble fraction. Molecular biological analysis revealed that ALA application upregulated both the SOS1 and HA3 transcriptional and translational levels, which suggested that the excretion of Na+ into the cytoplasm cloud was promoted by exogenous ALA. Meanwhile, exogenously applied ALA also upregulated the gene and protein expression of NHX1 and VHA-A under salinity stress, which suggested that the compartmentalization of Na+ to the vacuole was enhanced. Overall, exogenous ALA mitigated the damage caused by NaCl in cucumber by enhancing Na+ redistribution and increasing the cytoactivity of root cells.
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Edible lily (Lilium davidii var. unicolor) has economic value in China, particularly in Gansu Province, due to its uses as food and in gardening. Edible lily is usually cultivated in a long-term continuous monoculture resulting in the so-called consecutive replant problem (CRP), which is associated with severe soil degradation and significant yield and quality losses. This study was conducted to investigate the fungal community structure and specific fungal members related to lily's CRPs using metabarcoding analysis. Fungal diversity of rhizosphere soil was analyzed by high-throughput DNA sequencing (Miseq) of samples collected in fields at 0, 3, 6, and 9 replant years (L0, L3, L6, and L9, respectively). The results show that long-term replanting significantly decreased both soil fungal diversity and abundance at the OTUs levels. Furthermore, replanting altered the soil microbial communities, where 4 to 5 years of replanting is a key transition period for substantial change of fungal community structure, resulting in new fungal community structures in L6 and L9 compared to in L0 and L3. The fungal diversity loss and fungal community structure simplification contributes to the negative effect of replanting in lily, and after 6 years of replanting, accumulation of highly abundant pathogenic fungal genera and depletion of the putative plant-beneficial fungal genera exacerbate the lily CRP. In addition, changes in the soil physiochemical properties strongly contributes to the new structure of fungal communities, and the genera Cryptococcus and Guehomyces could be regarded as potential indicators to monitor and manage sustainable soil health in the lily cropping system.
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Cadmium (Cd2 +) is among the toxic non-essential heavy metals that adversely affect plants metabolic processes and the safety of produce. However, plant hormones can improve plant's tolerance to various stresses. This study investigated the effect of exogenous abscisic acid (ABA) on the biochemical and physiological processes and food safety of cadmium (Cd2 +)-sensitive lettuce genotype (Lüsu). Seedlings were subjected to five treatments: [(i) Control (untreated plants), (ii) 100 µM CdCl2, (iii) 100 µM CdCl2+10 µg L-1 ABA (iv) 10 µg L-1 ABA, and (v) 0.01 g L-1 ABA-inhibitor (fluridone)] for fourteen days in hydroponic system. The 100 µM CdCl2 increased the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA), decreased photosynthesis and plant biomass. Moreover, it decreased the contents of essential nutrients (except copper) in the leaves but increased the contents of toxic Cd2 + in the leaves and roots of the plants. Foliar application of fluridone (0.01 g L-1) also caused oxidative stress by increasing the contents of H2O2 and MDA. It also decreased the contents of nutrient elements in the leaves of the plants. However, exogenous ABA (10 µg L-1) mitigated the Cd2 +-induced stress, increased antioxidant enzymes activities, photosynthesis and plant biomass under CdCl2 treatment. Remarkably, exogenous ABA increased the contents of essential nutrient elements but decreased the Cd2 + content in leaves under the CdCl2 treatment. Our results have demonstrated that foliar application of ABA mitigates Cd2 + stress and increases the nutritional quality and food safety of Cd2 +-sensitive lettuce genotype under CdCl2 treatment.
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Optimal plant growth in many species is achieved when the two major forms of N are supplied at a particular ratio. In this pot experiment, the effects of five different ammonium:nitrate ratios (ANRs) (0:100, 12.5:87.5, 25:75, 37.5:62.5, and 50:50) on photosynthesis efficiency in chilli pepper (Capsicum annuum L.) plants were evaluated. The results showed that an ANR of 25:75 increased the contents of chl a, leaf area and dry matter, whereas chl b content was not affected by the ANRs. Regarding chlorophyll fluorescence, an ANR of 25:75 also enhanced the actual photochemical efficiency, photochemical quenching and maximum photosynthetic rate. However, the 0:100 and 50:50 ANRs resulted in higher values for nonphotochemical quenching. An inhibition of maximal photochemical efficiency was found when 50% NH4+ was supplied at the later stage of plant growth. The addition of 25% or 37.5% NH4+ was beneficial for gas exchange parameters and the 25% NH4+ optimised the thylakoid of chloroplasts. Compared with nitrate alone, 12.550% NH4+ upregulated glutamate dehydrogenase (GDH), the large subunit and the small subunit of Rubisco. It can be concluded that the 25:75 ANR accelerated N assimilation through active GDH, which provides a material basis for chloroplast and Rubisco formation, resulting in the increased photosynthetic rate and enhanced growth in chilli pepper.
Asunto(s)
Compuestos de Amonio , Capsicum , Compuestos de Amonio/metabolismo , Cloroplastos/metabolismo , Fotosíntesis , Hojas de la PlantaRESUMEN
Optimal plant growth in many species is achieved when the two major forms of N are supplied at a particular ratio. In this pot experiment, the effects of five different ammonium:nitrate ratios (ANRs) (0:100, 12.5:87.5, 25:75, 37.5:62.5, and 50:50) on photosynthesis efficiency in chilli pepper (Capsicum annuum L.) plants were evaluated. The results showed that an ANR of 25:75 increased the contents of chl a, leaf area and dry matter, whereas chl b content was not affected by the ANRs. Regarding chlorophyll fluorescence, an ANR of 25:75 also enhanced the actual photochemical efficiency, photochemical quenching and maximum photosynthetic rate. However, the 0:100 and 50:50 ANRs resulted in higher values for nonphotochemical quenching. An inhibition of maximal photochemical efficiency was found when 50% NH4+ was supplied at the later stage of plant growth. The addition of 25% or 37.5% NH4+ was beneficial for gas exchange parameters and the 25% NH4+ optimised the thylakoid of chloroplasts. Compared with nitrate alone, 12.5-50% NH4+ upregulated glutamate dehydrogenase (GDH), the large subunit and the small subunit of Rubisco. It can be concluded that the 25:75 ANR accelerated N assimilation through active GDH, which provides a material basis for chloroplast and Rubisco formation, resulting in the increased photosynthetic rate and enhanced growth in chilli pepper.
RESUMEN
This study was conducted to determine the root tolerance and biochemical responses of four Chinese Lactuca sativa L. genotypes (Lüsu, Lümeng, Yidali and Anyan) to cadmium (Cd2+) stress. Twenty-eight days old seedlings were exposed to Hoagland's nutrient solution supplied with or without 100 µM CdCl2 and monitored for seven days in a climate controlled room. The 100 µM CdCl2 significantly (P < 0.001) decreased all the root morphological indexes of the four genotypes. However, Yidali, which possessed the smallest root system, exhibited greater root tolerance to Cd2+ by having the highest tolerance indexes for root volume (46%), surface area (61%), projected area (74%) and numbers of root forks (63%) and root tips (58%). Moreover, Cd2+ stress also caused increases in H2O2 contents in the roots but the increase was least in Yidali which showed greater root tolerance to Cd2+stress. The effect of Cd2+ stress on the contents of hormones in the roots depended on the genotypes. Under Cd2+ stress, abscisic acid correlated positively with indole-3-acetic acid (r = 0.669*), gibberellic acid (r = 0.630*) and cytokinin (r = 0.785**). The antioxidant enzyme activities and proline responses of the four genotypes to Cd2+ stress were similar. The SOD activity was decreased whiles the CAT and POD activities, as well as the contents of proline increased in all the genotypes under the stress condition. These results suggest that lettuce genotypes with smaller root systems could be more tolerant to Cd2+ stress compared to those with larger root systems.
RESUMEN
Low light intensity is common in northern China due to fog or haze, and causes stress for crop plants. To solve the problem of low light intensity stress on the growth and development of vegetable crops in China, new cropping strategies must be developed. We previously showed that an appropriate ratio of ammonium and nitrate (NH4+:NO3-) can alleviate the effect of low light stress on plants, although it is not clear what mechanism is involved in this alleviation. We propose the hypothesis that an appropriate ammonium/nitrate ratio (10:90) can induce NO synthesis to regulate the AsA-GSH cycle in mini Chinese cabbage seedlings under low light intensity. To test the hypothesis, we conducted a series of hydroponic experiments. The results indicated that, under low light intensity conditions, appropriate NH4+:NO3- (N, NH4+:NO3- = 10:90) decreased the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2-) in leaves compared with nitrate treatment. Exogenous nitric oxide (SNP) had the same effects on MDA, H2O2, and O2-. However, with the addition of a NO scavenger (hemoglobin, Hb) and NO inhibitors (N-nitro-l-arginine methyl ester, L-NAME), NaN3 (NR inhibitor) significantly increased the contents of MDA, H2O2, and O2-. The application of N solution enhanced the AsA-GSH cycle by increasing the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and ascorbate oxidase (AAO), compared with control (NH4+:NO3- = 0:100). Meanwhile, exogenous SNP significantly increased the above indicators. All these effects of N on AsA-GSH cycle were inhibited by the addition of Hb, L-NAME and NaN3 in N solution. The results also revealed that the N and SNP treatments upregulated the relative expression level of GR, MDHAR1, APXT, DHAR2, and AAO gene in mini Chinese cabbage leaves under low light stress. These results demonstrated that the appropriate NH4+:NO3- (10:90) induced NO synthesis which regulates the AsA-GSH cycle in mini Chinese cabbage seedlings under low light stress.