RESUMEN
Five new resorcylic acid lactones (RALs) hispidulactones A-E (1, 4, 5, 8, and 9), a new natural product (2), and four known ones (3, 6, 7, and 10) with different ring systems were isolated from the desert plant Chaetosphaeronema hispidulum. [corrected]. The new compounds were characterized by NMR data, CD spectra, and X-ray experiment. The new natural product (2) displayed strongly biological effects on the seedlings growth of Arabidopsis thaliana, Digitaria sanguinalis, and Echinochloa crusgalli with a dose-dependent relationship. Compounds 1, 2, and 6 were also tested cytotoxic activities against three cancer cell lines HCT116, Hela, and MCF7 and only did the new natural product (2) display biological activities with IC50 values at 54.86 ± 1.52, 4. 90 ± 0.02, and 20.04 ± 4.00 µM, respectively, whereas the IC50 values of the positive control cis-platinum were 11.36 ± 0.42, 3.54 ± 0.12, and 14.32 ± 1.01 µM, respectively.
Asunto(s)
Ascomicetos/química , Endófitos/química , Lactonas/química , Lactonas/farmacología , Arabidopsis/crecimiento & desarrollo , Arabidopsis/microbiología , Supervivencia Celular/efectos de los fármacos , Digitaria/crecimiento & desarrollo , Digitaria/microbiología , Echinochloa/crecimiento & desarrollo , Echinochloa/microbiología , Células HCT116 , Células HeLa , Humanos , Lactonas/aislamiento & purificación , Estructura MolecularRESUMEN
This study evaluates antioxidant responses and jasmonate regulation in Digitaria eriantha cv. Sudafricana plants inoculated (AM) and non-inoculated (non-AM) with Rhizophagus irregularis and subjected to drought, cold, or salinity. Stomatal conductance, photosynthetic efficiency, biomass production, hydrogen peroxide accumulation, lipid peroxidation, antioxidants enzymes activities, and jasmonate levels were determined. Stomatal conductance and photosynthetic efficiency decreased in AM and non-AM plants under all stress conditions. However, AM plants subjected to drought, salinity, or non-stress conditions showed significantly higher stomatal conductance values. AM plants subjected to drought or non-stress conditions increased their shoot/root biomass ratios, whereas salinity and cold caused a decrease in these ratios. Hydrogen peroxide accumulation, which was high in non-AM plant roots under all treatments, increased significantly in non-AM plant shoots under cold stress and in AM plants under non-stress and drought conditions. Lipid peroxidation increased in the roots of all plants under drought conditions. In shoots, although lipid peroxidation decreased in AM plants under non-stress and cold conditions, it increased under drought and salinity. AM plants consistently showed high catalase (CAT) and ascorbate peroxidase (APX) activity under all treatments. By contrast, the glutathione reductase (GR) and superoxide dismutase (SOD) activity of AM roots was lower than that of non-AM plants and increased in shoots. The endogenous levels of cis-12-oxophytodienoc acid (OPDA), jasmonic acid (JA), and 12-OH-JA showed a significant increase in AM plants as compared to non-AM plants. 11-OH-JA content only increased in AM plants subjected to drought. Results show that D. eriantha is sensitive to drought, salinity, and cold stresses and that inoculation with AM fungi regulates its physiology and performance under such conditions, with antioxidants and jasmonates being involved in this process.
Asunto(s)
Antioxidantes/metabolismo , Ciclopentanos/metabolismo , Digitaria/microbiología , Glomeromycota/fisiología , Micorrizas/fisiología , Oxilipinas/metabolismo , Estrés Fisiológico , Simbiosis , Frío , Digitaria/fisiología , Sequías , SalinidadRESUMEN
Deciphering the genetic bases of pathogen adaptation to its host is a key question in ecology and evolution. To understand how the fungus Magnaporthe oryzae adapts to different plants, we sequenced eight M. oryzae isolates differing in host specificity (rice, foxtail millet, wheat, and goosegrass), and one Magnaporthe grisea isolate specific of crabgrass. Analysis of Magnaporthe genomes revealed small variation in genome sizes (39-43 Mb) and gene content (12,283-14,781 genes) between isolates. The whole set of Magnaporthe genes comprised 14,966 shared families, 63% of which included genes present in all the nine M. oryzae genomes. The evolutionary relationships among Magnaporthe isolates were inferred using 6,878 single-copy orthologs. The resulting genealogy was mostly bifurcating among the different host-specific lineages, but was reticulate inside the rice lineage. We detected traces of introgression from a nonrice genome in the rice reference 70-15 genome. Among M. oryzae isolates and host-specific lineages, the genome composition in terms of frequencies of genes putatively involved in pathogenicity (effectors, secondary metabolism, cazome) was conserved. However, 529 shared families were found only in nonrice lineages, whereas the rice lineage possessed 86 specific families absent from the nonrice genomes. Our results confirmed that the host specificity of M. oryzae isolates was associated with a divergence between lineages without major gene flow and that, despite the strong conservation of gene families between lineages, adaptation to different hosts, especially to rice, was associated with the presence of a small number of specific gene families. All information was gathered in a public database (http://genome.jouy.inra.fr/gemo).
Asunto(s)
Evolución Molecular , Genoma Fúngico , Magnaporthe/genética , Adaptación Biológica , Secuencia de Bases , Evolución Biológica , Burkholderia/genética , Burkholderia/aislamiento & purificación , Elementos Transponibles de ADN , Digitaria/microbiología , Proteínas Fúngicas/genética , Genes Fúngicos , Variación Genética , Magnaporthe/aislamiento & purificación , Oryza/microbiología , Enfermedades de las Plantas/microbiología , Análisis de Secuencia de ADNRESUMEN
Understanding host-pathogen evolutionary dynamics needs characterisation and quantification of processes occurring at many spatiotemporal scales. With this aim, the effects of smut on a naturally infected population of the summer annual Digitaria sanguinalis were followed for 4 years in an uncropped field. The main purpose of the study was to quantify the effects of within-population density on the infectivity and the aggressiveness of the pathogen in a range of densities that occurred naturally. The infectivity-related variable measured was the proportion of smutted plants at the end of each growing season; proportions were analysed using a generalised linear model with a binomial distribution considering the year, the density and their interaction as effects. The aggressiveness-related variables chosen were the number of smutted inflorescences per plant and per area, obtained over the last 2 years; they were analysed by means of ancova considering disease status (seeded or smutted), year, density and all the interactions between them. Although the disease is monocyclic, results showed clearly that infectivity increased with plant density. The number of inflorescences per plant was 1.5 times higher in smutted plants than in healthy plants throughout the range of densities. This variable declined when density increased, but as the infectivity increased at a higher rate, the aggressiveness also increased with density. The surprising results on infectivity are discussed in the context of current knowledge of plant-pathogen interaction dynamics, as well as neighbour effects on pathogen aggressiveness. Moreover, the results could be useful to develop weed biological control strategies.
Asunto(s)
Digitaria/microbiología , Interacciones Huésped-Patógeno , Enfermedades de las Plantas/microbiología , Ustilago/fisiología , Evolución Biológica , Modelos Lineales , Malezas , Estaciones del Año , Ustilago/patogenicidad , VirulenciaRESUMEN
Gene expression profiles of Digitaria sanguinalis infected by Curvularia eragrostidis strain QZ-2000 at two concentrations of conidia and two dew durations were analyzed by cDNA amplified fragment length polymorphisms (cDNA-AFLP). Inoculum strength was more determinant of gene expression than dew duration. A total of 256 primer combinations were used for selective amplification and 1214 transcript-derived fragments (TDFs) were selected for their differential expression. Of these, 518 up-regulated differentially expressed TDFs were identified. Forty-six differential cDNA fragments were chosen to be cloned and 35 of them were successfully cloned and sequenced, of which 25 were homologous to genes of known function according to the GenBank database. Only 6 genes were up-regulated in Curvularia eragrostidis-inoculated D. sanguinalis, with functions involved in signal transduction, energy metabolism, cell growth and development, stress responses, abscisic acid biosynthesis and response. It appears that a few pathways may be important parts of the pathogenic strategy of C. eragrostidis strain QZ-2000 on D. sanguinalis. Our study provides the fundamentals to further study the pathogenic mechanism, screen for optimal C. eragrostidis strains as potential mycoherbicide and apply this product to control D. sanguinalis.
Asunto(s)
Ascomicetos , Digitaria/genética , Regulación de la Expresión Génica de las Plantas , Enfermedades de las Plantas/genética , Análisis del Polimorfismo de Longitud de Fragmentos Amplificados , Digitaria/metabolismo , Digitaria/microbiología , Perfilación de la Expresión Génica , Incidencia , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/estadística & datos numéricos , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
BACKGROUND AND PURPOSE: Pangolagrass, Digitaria decumbens Stent, is a major grass for cow feeding, and may be a good substrate for protein enrichment. To improve the quality of pangolagrass for animal feeding, cellulolytic microbes were isolated from various sources and cultivated with solid state fermentation to enhance the protein content, cellulase production and in vitro digestion. The microbes, culture conditions and culture media were studied. METHODS: Cellulolytic microbes were isolated from pangolagrass and its extracts, and composts. Pangolagrass supplemented with nitrogen and minerals was used to cultivate the cellulolytic microbes with solid state fermentation. The optimal conditions for protein enrichment and cellulase activity were pangolagrass substrate at initial moisture 65-70%, initial pH 6.0-8.0, supplementation with 2.5% (NH(4))(2)SO(4), 2.5% KH(2)PO(4) and K(2)HPO(4) mixture (2:1, w/w) and 0.3% MgSO(4).7H(2)O and cultivated at 30(o)C for 6 days. RESULTS: The protein content of fermented pangolagrass increased from 5.97-6.28% to 7.09-16.96% and the in vitro digestion improved from 4.11-4.38% to 6.08-19.89% with the inoculation of cellulolytic microbes by solid state fermentation. Each 1 g of dried substrate yielded Avicelase 0.93-3.76 U, carboxymethylcellulase 1.39-4.98 U and ß-glucosidase 1.20-6.01 U. The isolate Myceliophthora lutea CL3 was the strain found to be the best at improving the quality of pangolagrass for animal feeding with solid state fermentation. CONCLUSION: Solid state fermentation of pangolagrass inoculated with appropriate microbes is a feasible process to enrich protein content, increase in vitro digestibility and improve the quality for animal feeding.
Asunto(s)
Celulasa/metabolismo , Digitaria/enzimología , Digitaria/metabolismo , Microbiología del Suelo , Sordariales/aislamiento & purificación , Sordariales/metabolismo , Alimentación Animal , Animales , Bovinos , Medios de Cultivo/química , Digestión , Digitaria/microbiología , Fermentación , Proteínas/metabolismo , Sordariales/enzimologíaRESUMEN
This study aimed at characterizing the chemical and microbiological composition of Acha (Digitaria exiliis) and Iburu (Digitaria iburua) flours and at exploiting their potential for sourdough fermentation. Both the flours had a gross composition similar to other cereals. As shown by two-dimensional electrophoresis analysis, Acha flour had a higher number of prolamins with respect to Iburu flour. The opposite was found for the number of glutelin spots. The concentration of total free amino acids of Iburu flour was higher than that of Acha flour (1348±34 vs. 100±20 mg/kg). Pediococcus pentosaceus was the dominant species in both the flours. Several isolates were used to ferment Acha or Iburu flours. After 8h fermentation at 30°C, pH ranged from 3.41 to 3.83 and from 4.20 to 4.66 for Acha and Iburu sourdoughs, respectively. The highest values of TTA and concentration of lactic acid were found in almost all Iburu sourdoughs. The synthesis of acetoin and γ-amino butyric acid (GABA) was only found in Iburu sourdoughs. Data from the kinetics of acidification, synthesis of lactic and acetic acids, acetoin, and liberation of total free amino acids were elaborated by Principal Component Analysis. Sourdoughs from Acha and Iburu flour were clearly differentiated.
Asunto(s)
Bacterias/metabolismo , Digitaria/química , Fermentación , Harina/análisis , Bacterias/genética , Bacterias/aislamiento & purificación , Pan/análisis , Pan/microbiología , Digitaria/metabolismo , Digitaria/microbiología , Harina/microbiologíaRESUMEN
Common wheat cultivars are resistant to Magnaporthe grisea, a crabgrass (Digitaria sanguinalis)-specific species of the blast fungus. To dissect the genetic basis of this "nonhost" type of resistance, we need an exceptional cultivar that is susceptible to M. grisea. A screening under various conditions revealed that Triticum aestivum 'Chinese Spring' (CS) was susceptible to M. grisea isolate Dig41 when incubated at high temperature (26 degrees C) after inoculation. By contrast, T. aestivum 'P168', 'Shin-chunaga' (Sch), 'Norin 4' (N4), 'Norin 26' (N26), 'Norin 29' (N29), 'Red Egyptian' (RE), and 'Salmon' (Slm) and Triticum compactum 'No. 44' (Cmp) were highly resistant even at the high temperature. When F2 seedlings derived from crosses between the resistant cultivars and CS were inoculated with Dig41, they segregated in a 3:1 ratio of resistant to susceptible, suggesting that the resistance of each cultivar is controlled by one major gene. Crosses of N4 with P168, Sch, N26, N29, and Cmp yielded no susceptible F2 seedlings, suggesting that these six cultivars share the same gene. Similarly, a cross between RE and Slm yielded no susceptible F2 seedlings, suggesting that these two cultivars share the same gene. On the other hand, crosses between the N4 group and the RE group produced resistant and susceptible seedlings in a 15:1 ratio, indicating that these two groups carry different genes inherited independently. The gene in N4 was located on chromosome 4A by a monosomic analysis and designated Rmg4, while the gene in RE was located on chromosome 6D using a series of chromosome substitution lines and designated Rmg5. These results suggest that the resistance of common wheat to M. grisea, an inappropriate species of the blast fungus, is under a simple genetic control.
Asunto(s)
Magnaporthe/patogenicidad , Enfermedades de las Plantas/genética , Triticum/genética , Mapeo Cromosómico , Cruzamientos Genéticos , Digitaria/microbiología , Genes de Plantas/genética , Inmunidad Innata/genética , Magnaporthe/clasificación , Enfermedades de las Plantas/microbiología , Especificidad de la Especie , Temperatura , Triticum/clasificación , Triticum/microbiologíaRESUMEN
Rice blast disease, caused by the fungus Magnoporthe grisea is responsible for considerable damages on rice and leaf spot on some weeds in Iran and in other parts of the world. Infected samples were collected from rice and weeds including Digitaria sanguinalis (crabgrass), Setaria italica (foxtail millet), Echinochloa crus-galli (barnyard millet), and some unknown weeds during 1997-2005 and were preserved in collection of Mycology at the University of Tehran, Iran. In this study, genetic diversity of Magnaporthe grisea species complex isolates was studied based on DNA fingerprinting by rep-PCR, using of two primers including ERIC and BOX. The total DNA of 75 isolates was extracted and DNA fragments were amplified in a thermal cycler program using mentioned primers. Therefore, DNA fragments from 400 bp to 3000 bp were amplified. Based on cluster analysis for two primers (ERIC and BOX), eight fingerprinting groups (ctonal lineages) and sixty haplotypes were identified. "A" clonal lineage was containing the highest number of isolates and became dominant clonal lineages with 35 isolates from rice and 3 isolates from S. italica, whereas the highest number of isolates obtained from D. sanguinalis belonged to "E" clonal lineage and was the second largest clonal lineage. Approximately all of the M. grisea species complex isolates from crabgrass and some of unknown weeds were separated from other isolates in 42% similarity. As a result, asexual fertility causes low diversity in populations of M. grisea species complex and speciation could be one of the reasons of differentiation between isolates from D. sanguinalis with other isolates. Overall, these data indicated a low level of genetic diversity in the Iranian M. grisea species complex population similar to that reported in other countries.
Asunto(s)
Variación Genética , Magnaporthe/genética , Oryza/microbiología , Dermatoglifia del ADN , ADN de Hongos/genética , Digitaria/microbiología , Irán , Magnaporthe/clasificación , Magnaporthe/patogenicidad , Enfermedades de las Plantas/microbiología , Reacción en Cadena de la Polimerasa/métodos , Setaria (Planta)/microbiologíaRESUMEN
The best characterized form of resistance is gene-for-gene resistance. Less well characterized is nonhost resistance in which an entire plant species is resistant to an entire pathogen species. Here, different rice genotypes were inoculated with host and nonhost strains of Magnaporthe isolated from rice, wheat and crabgrass. The different types of interactions were characterized at a cytological level using a 3,3'-diaminobenzidine (DAB) stain to investigate the occurrence of reactive oxygen intermediates or by observing the occurrence of cellular autofluorescence. Gene expression of a set of selected PR-genes was analysed using quantitative real-time polymerase chain reaction. Inoculation with the isolate from crabgrass resulted in a lack of penetration. The wheat isolate induced a hypersensitive response with varying degrees of pathogen growth inside the invaded cell according to the rice genotype. Expression analysis of our PR-gene set revealed clear differences between the different types of interactions in both kinetic and magnitude of gene induction. Our integrated study opens the way to the dissection of molecular components leading to nonhost reactions to Magnaporthe grisea in rice and points to novel sources of durable resistance to fungal plant pathogens in other cereal crops.
Asunto(s)
Interacciones Huésped-Patógeno/genética , Magnaporthe/patogenicidad , Oryza/microbiología , Enfermedades de las Plantas/microbiología , Digitaria/microbiología , Fluorescencia , Perfilación de la Expresión Génica , Interacciones Huésped-Patógeno/fisiología , Magnaporthe/clasificación , Oryza/genética , Oryza/fisiología , Enfermedades de las Plantas/genética , Hojas de la Planta/citología , Triticum/microbiologíaRESUMEN
We analyzed host-species specificity of Magnaporthe grisea on rice using 110 F1 progeny derived from a cross between the Oryza isolate CH87 (pathogenic to rice) and the Digitaria isolate 6023 (pathogenic to crabgrass). To elucidate the genetic mechanisms controlling species specificity in M. grisea, we performed a genetic analysis of species-specific avirulence on this rice population. Avirulent and virulent progeny segregated in a 1:1 ratio on the 2 rice cultivars 'Lijiangxintuanheigu' (LTH) and 'Shin2', suggesting that a single locus, designated PRE1, was involved in the specificity. In a combination between 'Kusabue' and 'Tsuyuake', the segregation of the 4 possible phenotypes of F1 progeny was significantly different from the expected 3:1:3:1 and instead fit a ratio of 2:0:1:1. This indicated that 2 loci, PRE1 and AVR2, were involved in specific parasitism on rice. These results suggest that the species specificity of M. grisea on rice is governed by species-dependent genetic mechanisms that are similar to the gene-for-gene interactions controlling cultivar specificity. Pathogenicity tests with various plant species revealed that the Digitaria isolate 6023 was exclusively parasitic on crabgrass. Genetic linkage analysis showed that PRE1 was mapped on chromosome 3 with respect to RAPD and SSR markers. RAPD marker S361 was linked to the avirulence gene at a distance of ~6.4 cM. Two SSR markers, m677-678 and m77-78, were linked to the PRE1 gene on M. grisea chromosome 3 at distances of 5.9 and 7.1 cM, respectively. Our results will facilitate positional cloning and functional studies of this gene.