Proteomic Profiling and the Predicted Interactome of Host Proteins in Compatible and Incompatible Interactions Between Soybean and <Emphasis Type="Italic">Fusarium virguliforme</Emphasis>

Sudden death syndrome (SDS) is a complex of two diseases of soybean (Glycine max), caused by the soil borne pathogenic fungus Fusarium virguliforme. The root rot and leaf scorch diseases both result in significant yield losses worldwide. Partial SDS resistance has been demonstrated in multiple soybean cultivars. This study aimed to highlight proteomic changes in soybean roots by identifying proteins which are differentially expressed in near isogenic lines (NILs) contrasting at the Rhg1/Rfs2 locus for partial resistance or susceptibility to SDS. Two-dimensional gel electrophoresis resolved approximately 1000 spots on each gel; 12 spots with a significant (P < 0.05) difference in abundance of 1.5-fold or more were picked, trypsin-digested, and analyzed using quadruple time-of-flight tandem mass spectrometry. Several spots contained more than one protein, so that 18 distinct proteins were identified overall. A functional analysis performed to categorize the proteins depicted that the major pathways altered by fungal infection include disease resistance, stress tolerance, and metabolism. This is the first report which identifies proteins whose abundances are altered in response to fungal infection leading to SDS. The results provide valuable information about SDS resistance in soybean plants, and plant partial resistance responses in general. More importantly, several of the identified proteins could be good candidates for the development of SDS-resistant soybean plants.     

镉对植物根系的毒害作用

镉是一种毒性很强的重金属,可严重影响植物的生长。当镉对植物产生毒害作用时,首先表现在根系的形态和生理功能改变上。综述了镉胁迫下植物根系的形态学变化及生理生化改变,以及镉在植物体内的代谢过程,初步探讨了根际土壤对植物吸收镉的影响,并简单介绍了目前测定根系指标的常用方法。     

14CO2 labeling : a reliable technique for rapid measurement of total root exudation capacity and vascular sap flow in crop plants

Root release of organic compounds and rate of the vascular sap flow are important for understanding the nutrient and the source-sink dynamics in plants, however, their determination is procedurally cumbersome and time consuming. We report here a simple method involving ¹⁴C labeling for rapid and reliable measurement of root exudates and vascular sap flow rate in a variable groundnut population developed through seed gamma irradiation using a cobalt source (⁶⁰Co). An experimental hypothesis that a higher ¹⁴C level in the vascular sap would indicate a higher root release of carbon by the roots into the rhizosphere was verified.     

Understanding the inactivation process of organophosphorus herbicides: A DFT study of glyphosate metallic complexes with Zn2+, Ca2+, Mg2+, Cu2+, Co3+, Fe3+, Cr3+, and Al3+

Glyphosate is the active component of one of the top‐selling herbicides, which is also a potent EPSP synthase inhibitor. The herbicide is absorbed by living tissue and translocated via the phloem, to plant roots and rhizomes. When applied directly into the soil it has low activity, due to the high adsorption by soil constituents. Understanding the specific interactions between metals in the soil and glyphosate is the main step in understanding the low activity of the herbicide when applied directly into the ground and not pulverized. We can observe there is a stability order for both tetrahedral and octahedral complexes between glyphosate and metals: Zn>Cu>Co>Fe>Cr>Al>Ca>Mg. © 2012 Wiley Periodicals, Inc.     

Analytical challenges and solutions for performing metabolomic analysis of root exudates

Plant stress responses are mediated by the release of chemical compounds called exudates into the rhizosphere. These chemical substances include primary and secondary plant metabolites and play an important role in the plant defense mechanism. The identification, characterization and study of these compounds can open the door to numerous applications, from greener agriculture to enhanced phytoremediation. This paper critically reviews the most relevant sampling strategies, analytical methodologies, and data-mining approaches to study root exudates.Common analytical techniques are grounded in mass spectrometry or nuclear mass spectrometry, but less common biospectroscopy techniques could offer a new perspective in plant metabolomics due to the minimal sample processing they require. Finally, after analysis, the collected raw data must then be analyzed by means of different multivariate and univariate statistical approaches to test biological-response hypotheses. All in all, the assessment of root exudates calls for the development of hyphenated analytical methodologies, as well as efforts to consolidate data-preprocessing workflows.     

Flavonoids and strigolactones in root exudates as signals in symbiotic and pathogenic plant-fungus interactions

Secondary plant compounds are important signals in several symbiotic and pathogenic plant-microbe interactions. The present review is limited to two groups of secondary plant compounds, flavonoids and strigolactones, which have been reported in root exudates. Data on flavonoids as signaling compounds are available from several symbiotic and pathogenic plant-microbe interactions, whereas only recently initial data on the role of strigolactones as plant signals in the arbuscular mycorrhizal symbiosis have been reported. Data from other plant-microbe interactions and strigolactones are not available yet. In the present article we are focusing on flavonoids in plant-fungal interactions such as the arbuscular mycorrhizal (AM) association and the signaling between different Fusarium species and plants. Moreover the role of strigolactones in the AM association is discussed and new data on the effect of strigolactones on fungi, apart from arbuscular mycorrhizal fungi (AMF), are provided.     

Charged particle activation analysis at RIKEN: Past,present and future

To study the effect of rhizosphere pH condition on the cadmium uptake movement, ¹⁰⁹Cd, was applied as a radioisotope tracer to a soybean plant grown in a water culture at pH 4.5 or pH 6.5. The distribution of ¹⁰⁹Cd in the soybean plant was observed radiographically with an imaging plate (IP). The amount of Cd transported from the root to the upper part of the plant at pH 4.5 was approximately two times higher than that at pH 6.5. However, the movement of Cd in the upper part of the plant was similar under both pH conditions. The distribution of Cd inside the internodes at pH 4.5 also showed similar pattern to that at pH 6.5, suggesting that once Cd reached to the vessel of the root, the movement of Cd was not dependent on rhizosphere pH conditions.     

Reproducibility of the high-performance liquid chromatographic fingerprints obtained from two soybean cultivars and a selected progeny

Roots from soybean cultivars Williams 82 and Hartwig along with one of their progeny 14a, were extracted with non-polar, moderately polar, and highly polar solvent systems. Extracts were compared by thin-layer chromatography and by HPLC. Methanol extractions conducted at ambient temperature coupled with analysis by reversed-phase HPLC using UV detection provided the most representative sets of reproducible fingerprints. Further optimization of the overall protocol should allow for the profiling of different soybean cultivars when their roots are exposed to various environments and insults during early growth.     

Insights to Sequence Information of Polyphenol Oxidase Enzyme from Different Source Organisms

Polyphenol oxidases (PPOs) are widely distributed enzymes among animals, plants, bacteria, and fungi. PPOs often have significant role in many biologically essential functions including pigmentation, sclerotization, primary immune response, and host defense mechanisms. In the present study, forty-seven full-length amino acid sequences of PPO from bacteria, fungi, and plants were collected and subjected to multiple sequence alignment (MSA), domain identification, and phylogenetic tree construction. MSA revealed that six histidine, two phenylalanine, two arginine, and two aspartic acid residues were highly conserved in all the analyzed species, while a single cysteine residue was conserved in all the plant and fungal PPOs. Two major sequence clusters were constructed by phylogenetic analysis. One cluster was of the plant origin, whereas the other one was of the fungal and bacterial origin. Motif GGGMMGDVPTANDPIFWLHHCNVDRLWAVWQ was found in all the species of bacterial and fungus sources. In addition, seven new motifs which were unique for their group were also identified.     

Bioenergetics and bioremediation of contaminated soil

The microbial biodegradation of xenobiotic compounds in soil and ground water is constrained by the laws of thermodynamics. Bioremediation is being investigated in a rhizosphere environment in which higher plants provide carbon and energy to sustain the microbial population. Toluene, phenol, trichloroethylene and trichloroethane have been fed in separate experiments to a pilot scale system with alfalfa growing in sandy soil containing less than 10% of silt. It is well known that microbial populations are numerous in the root zone of healthy vegetation. Root exudates can stimulate aerobic microbial biodegradation of compounds which by themselves support growth poorly or not at all. Polynuclear aromatic compounds such as phenanthrene, anthracene, and pyrene, which are not very soluble in water, and chlorinated aliphatic hydrocarbons such as trichloroethylene are examples of compounds that can be biodegraded in the rhizosphere when root exudates are present to enhance and sustain microbial activity. Solar driven transport processes such as water and solute movements due to evapotranspiration increase the likelihood that the contaminants will come into contact with the microorganisms and be degraded. The thermodynamic and bioenergetic aspects of transport and biodegradation in the rhizosphere are examined through a review of the literature and the analysis of experimental data collected in the pilot scale system.     

Aquaphotomics Research of Cold Stress in Soybean Cultivars with Different Stress Tolerance Ability: Early Detection of Cold Stress Response

The development of non-destructive methods for early detection of cold stress of plants and the identification of cold-tolerant cultivars is highly needed in crop breeding programs. Current methods are either destructive, time-consuming or imprecise. In this study, soybean leaves’ spectra were acquired in the near infrared (NIR) range (588–1025 nm) from five cultivars genetically engineered to have different levels of cold stress tolerance. The spectra were acquired at the optimal growing temperature 27 °C and when the temperature was decreased to 22 °C. In this paper, we report the results of the aquaphotomics analysis performed with the objective of understanding the role of the water molecular system in the early cold stress response of all cultivars. The raw spectra and the results of Principal Component Analysis, Soft Independent Modeling of Class Analogies and aquagrams showed consistent evidence of huge differences in the NIR spectral profiles of all cultivars under normal and mild cold stress conditions. The SIMCA discrimination between the plants before and after stress was achieved with 100% accuracy. The interpretation of spectral patterns before and after cold stress revealed major changes in the water molecular structure of the soybean leaves, altered carbohydrate and oxidative metabolism. Specific water molecular structures in the leaves of soybean cultivars were found to be highly sensitive to the temperature, showing their crucial role in the cold stress response. The results also indicated the existence of differences in the cold stress response of different cultivars, which will be a topic of further research.     

Total Synthesis and Biological Evaluation of Zealactone 1a/b

Strigolactones are plant hormones, which play pivotal roles in plant growth and development with potential application in sustainable agriculture. Recently, zealactone 1a/b has been identified as the major strigolactone from the root exudates of corn. Although zealactone is a promising molecule affecting signaling in the rhizosphere as well as in planta, evaluating its biological activities has been hampered by its low natural abundance and its relative chemical instability. Herein, we present the total synthesis of zealactone 1a/b based on our studies employing a [2+2]-cycloaddition strategy and a chemoselective Baeyer-Villiger oxidation to forge the γ-butyrolactone fragment. Furthermore, we disclose the biological activities of zealactone 1a/b on corn and in soil in comparison with related synthetic analogues.     

On the resilience of nitrogen assimilation by intact roots under starvation,as revealed by isotopic and metabolomic techniques

The response of root metabolism to variations in carbon source availability is critical for whole‐plant nitrogen (N) assimilation and growth. However, the effect of changes in the carbohydrate input to intact roots is currently not well understood and, for example, both smaller and larger values of root:shoot ratios or root N uptake have been observed so far under elevated CO₂. In addition, previous studies on sugar starvation mainly focused on senescent or excised organs while an increasing body of data suggests that intact roots may behave differently with, for example, little protein remobilization. Here, we investigated the carbon and nitrogen primary metabolism in intact roots of French bean (Phaseolus vulgaris L.) plants maintained under continuous darkness for 4 days. We combined natural isotopic ¹⁵N/¹⁴N measurements, metabolomic and ¹³C‐labeling data and show that intact roots continued nitrate assimilation to glutamate for at least 3 days while the respiration rate decreased. The activity of the tricarboxylic acid cycle diminished so that glutamate synthesis was sustained by the anaplerotic phosphoenolpyruvate carboxylase fixation. Presumably, the pentose phosphate pathway contributed to provide reducing power for nitrate reduction. All the biosynthetic metabolic fluxes were nevertheless down‐regulated and, consequently, the concentration of all amino acids decreased. This is the case of asparagine, strongly suggesting that, as opposed to excised root tips, protein remobilization in intact roots remained very low for 3 days in spite of the restriction of respiratory substrates. Copyright © 2009 John Wiley & Sons, Ltd.     

Technologies Employed in the Treatment of Water Contaminated with Glyphosate: A Review

Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide with several commercial formulations that are used generally in agriculture for the control of various weeds. It is the most used pesticide in the world and comprises multiple constituents (coadjutants, salts, and others) that help to effectively reach the action’s mechanism in plants. Due to its extensive and inadequate use, this herbicide has been frequently detected in water, principally in surface and groundwater nearest to agricultural areas. Its presence in the aquatic environment poses chronic and remote hazards to human health and the environment. Therefore, it becomes necessary to develop treatment processes to remediate aquatic environments polluted with glyphosate, its metabolites, and/or coadjutants. This review is focused on conventional and non-conventional water treatment processes developed for water polluted with glyphosate herbicide; it describes the fundamental mechanism of water treatment processes and their applications are summarized. It addressed biological processes (bacterial and fungi degradation), physicochemical processes (adsorption, membrane filtration), advanced oxidation processes—AOPs (photocatalysis, electrochemical oxidation, photo-electrocatalysis, among others) and combined water treatment processes. Finally, the main operating parameters and the effectiveness of treatment processes are analyzed, ending with an analysis of the challenges in this field of research.     

Glyphosate and aminomethylphosphonic acid in human hair quantified by an LC-MS/MS method

An LC-MS/MS method for hair testing of glyphosate and aminomethylphosphonic acid (AMPA), its main biodegradation product, has been developed. After decontamination, 50 mg of hair was ground and sonicated in water for 2 h. The method was fully validated in the 5–500 pg/mg range for glyphosate and 10–500 pg/mg for AMPA, and the limits of detection were 2 and 5 pg/mg, respectively. Matrix effect for glyphosate and AMPA was compensated by an isotope-labeled internal standard. Hair samples from four farmers who regularly used glyphosate and one farmer who used glyphosate but not his wife and 14 hair samples from nonoccupationally exposed subjects were tested. Glyphosate was found in head hair of three farmers, with concentration in the range 14–188 pg/mg. The fourth was found negative but with hair colored in red. Glyphosate was detected in 10 of 14 hair samples from nonoccupationally exposed subjects at concentrations of 11.5 pg/mg or lower and only in one segment (0–3 cm) of the farmer's spouse (6 pg/mg). AMPA was detected in five subjects, above the limit of quantification only in two of three occupationally exposed subjects with positive glyphosate. Further studies should be conducted to validate this potential new biomarker that could be useful for assessing long-term exposure to glyphosate.     

Total synthesis and antifungal activity of a carbohydrate ring-expanded pyranosyl nucleoside analogue of nikkomycin B

In a study aimed at investigating an as yet unknown structure-activity relationship of the nikkomycin family of antifungal peptidyl nucleoside antibiotics, the present research reports the synthesis and antifungal evaluation of a carbohydrate ring-expanded pyranosyl nucleoside analogue of nikkomycin B. Employing a convergent synthetic route, independent synthesis of the N-terminal amino acid side chain and a stereoselective de novo construction of the desired pyranosyl nucleoside amino acid fragment was followed by peptidic coupling of the two components, leading to the first synthesis of a carbohydrate ring-enlarged pyranosyl nikkomycin B analogue. In vitro biological evaluation of the above analogue against a variety of human pathogenic fungi demonstrated significant antifungal activity against several fungal strains of clinical significance.     

Expression Analysis of Rice Pathogenesis-related Proteins Involved in Stress Response and Endophytic Colonization Properties of gfp-tagged Bacillus subtilis CB-R05

Bacillus subtilis CB-R05, possessing antagonistic effects against several fungal pathogens, is a diazotrophic plant growth-promoting bacteria marked with the green fluorescent protein (gfp) gene. To confirm the expression level of the pathogenesis-related (PR) proteins in rice inoculated with CB-R05, the expressions of four pathogenesis-related (PR) proteins (PR2, PR6, PR15, and PR16) were examined in the rice leaves treated with wounding stress over a time period. The PR proteins were generally more strongly expressed in the rice leaves inoculated with CB-R05 compared with the untreated control. The marked gfp-tagged B. subtilis CB-R05 strain was inoculated onto the rice seedlings under axenic conditions. Under the confocal laser scanning microscope (CLSM), the gfp-tagged CB-R05 bacterial cells were observed to penetrate the rhizoplane, especially in the elongation and differentiation zones of the rice roots, and colonize the root intracellularly. The bacteria, 24 h after the gfp-tagged CB-R05 inoculation, were seen to penetrate into the cell wall, cortex, xylem, and concentrate mainly in the vascular bundle. Numerous bacteria were observed within the intercellular spaces, root cortical cells, and xylem vessels. Over time, these bacteria dispersed to the lateral root junctions and propagated slowly from the roots to the stems and leaves. The B. subtilis CB-R05 population in the rice root rhizosphere was also monitored. These results show a very widespread colonization of the B. subtilis CB-R05 in the rice rhizosphere. Further attempts are under way to investigate the competition between the CB-R05 bacteria and the fungal pathogen in vivo.     

Strigolactones,from Plants to Human Health: Achievements and Challenges

Strigolactones (SLs) are a class of sesquiterpenoid plant hormones that play a role in the response of plants to various biotic and abiotic stresses. When released into the rhizosphere, they are perceived by both beneficial symbiotic mycorrhizal fungi and parasitic plants. Due to their multiple roles, SLs are potentially interesting agricultural targets. Indeed, the use of SLs as agrochemicals can favor sustainable agriculture via multiple mechanisms, including shaping root architecture, promoting ideal branching, stimulating nutrient assimilation, controlling parasitic weeds, mitigating drought and enhancing mycorrhization. Moreover, over the last few years, a number of studies have shed light onto the effects exerted by SLs on human cells and on their possible applications in medicine. For example, SLs have been demonstrated to play a key role in the control of pathways related to apoptosis and inflammation. The elucidation of the molecular mechanisms behind their action has inspired further investigations into their effects on human cells and their possible uses as anti-cancer and antimicrobial agents.     

Peagol and peagoldione, two new strigolactone-like metabolites isolated from pea root exudates

Two new strigolactone-like metabolites, named peagol and peagoldione, with germinative activity for root parasitic plants, were isolated from pea root exudates and were characterized by spectroscopic methods. Peagol was more active on Orobanche foetida and Phelipanche aegyptiaca seeds, while peagoldione was active on P. aegyptiaca only. Low activity was found on Orobanche crenata and Orobanche minor. Stimulatory activity of peagol on O. foetida seeds is most relevant as this species does not respond to the synthetic strigolactone analogue GR24, usually used as Orobanche germination standard.