Group AG-1 Research Articles

Secreted Glycosyltransferase RsIA_GT of Rhizoctonia solani AG-1 IA Inhibits Defense Responses in Nicotiana benthamiana

Anastomosis group AG-1 IA of Rhizoctonia solani Khün has a wide host range and threatens crop production. Various glycosyltransferases secreted by phytopathogenic fungi play an essential role in pathogenicity. Previously, we identified a glycosyltransferase RsIA_GT (AG11A_09161) as a secreted protein-encoding gene of R. solani AG-1 IA, whose expression levels increased during infection in rice. In this study, we further characterized the virulence function of RsIA_GT. It is conserved not only in Basidiomycota, including multiple anastomosis groups of R. solani, but also in other primary fungal taxonomic categories. RsIA_GT possesses a signal peptide (SP) for protein secretion, and its functionality was proven using yeast and Nicotiana benthamiana. The SP-truncated form of RsIA_GT (RsIA_GT(ΔS)) expressed in Escherichia coli-induced lesion-like phenotype in rice leaves when applied to punched leaves. However, Agrobacterium-mediated transient expressions of both the full-length RsIA_GT and RsIA_GT(ΔS) did not induce cell death in N. benthamiana leaves. Instead, only RsIA_GT(ΔS) suppressed the cell death induced by two reference cell death factors BAX and INF1 in N. benthamiana. RsIA_GT(ΔS)R154A D168A D170A, a mutant RsIA_GT(ΔS) for the glycosyltransferase catalytic domain, still suppressed the BAX- or INF1-induced cell death, suggesting that the cell death suppression activity of RsIA_GT(ΔS) would be independent from its enzymatic activity. RsIA_GT(ΔS) also suppressed the H2O2 production and callose deposition and showed an effect on the induction of defense genes associated with the expression of BAX and INF1. The transient expression of RsIA_GT(ΔS) in N. benthamiana enhanced the lesion area caused by R. solani AG-1 IA. The secreted glycosyltransferase, RsIA_GT, of R. solani AG-1 IA is likely to have a dual role in virulence inside and outside of host cells.

Effects of egg exposure to atrazine and/or glyphosate on bone development in Podocnemis unifilis (Testudines, Podocnemididae)

This study was designed to investigate skeletal changes in Podocnemis unifilis embryos derived from artificially incubated eggs exposed to different concentrations of atrazine, glyphosate or atrazine and glyphosate mixture. Forty-two eggs were randomly allocated to one of seven trays containing vermiculite treated distilled water (control group) or the following solutions: 2 or 200 μg L-1 of atrazine (groups A1 and A2 respectively); 65 or 6500 μg L-1 of glyphosate (groups G1 and G2 respectively); 2 μg L-1 and 65 μg L-1 or 200 μg L-1 and 6500 μg L-1 of atrazine and glyphosate mixture (groups AG1 and AG2 respectively). Three eggs per tray were randomly collected on days 30 and 50 of the incubation period. Embryos were submitted to soft tissue diaphanization and stained with Alizarin red S or Alcian blue for morphological analysis of bone and cartilage tissues; histological analysis was performed to confirm ossification changes. Findings were compared between groups. Morphological changes were limited to sclerotic ring features and number of ribs. Malformations rates differed significantly (p < 0.05) between embryos in the control and treated groups A2, AG1 and AG2. Concurrent exposure to atrazine and glyphosate did not affect the presence or severity of embryonic malformations and was not associated with appendicular skeleton changes in P. unifilis embryos. However, further studies focusing on the axial skeleton with particular emphasis on rib abnormalities are warranted.

The Effect of Arabic Gum on Renal Function in Reversible Unilateral Ureteric Obstruction.

Arabic gum (AG) has antioxidant and anti-inflammatory properties. However, the effect of AG in ureteric obstruction (UO) has not been investigated yet. Male rats underwent reversible left unilateral UO (UUO) for 72 h. Group AG-1 (n = 12) received AG 15 g/kg/day dissolved in drinking water starting seven days before and continuing throughout the period of the UUO, whereas group Vx-1 (n = 8) had only water. Group AG-2 (n = 12) and Vx-2 (n = 8) had similar protocols as AG-1 and Vx-1, respectively, but underwent terminal experiments to measure renal functions, six days post-UUO reversal. Arabic gum significantly attenuated the UUO-induced increase in the tissue level of malonedialdehyde and superoxide dismutase and the rise in the gene expression of TNF-α, TGF-β1, and p53 in AG-1 compared to Vx-1. It also attenuated the severity of tubular dilatation. However, AG did not affect the alterations in the renal blood flow or glomerular filtration rate. The fractional sodium excretion was lower in AG-2 but did not reach statistical significance (0.40 ± 0.11 vs 0.74 ± 0.12, p = 0.07). AG attenuated the UUO-induced rise in oxidative stress markers and proinflammatory and profibrotic cytokines and the degree of renal tubular dilatation, indicating a protective effect in obstructive nephropathy.

Web blight (Thanatephorus cucumeris): a new disease on leaves of okra plants

ABSTRACT: In an experiment on organic production of okra (Abelmoschus esculentus (L.) Moench) that was carried out from September 2013 to January 2014, in Manaus, Amazonas state, Brazil, we observed large chlorotic, necrotic, helical, discontinuous, dark or light-brown lesions with partial detachment of the injured area on the adaxial surface of leaves located in the median and basal portions of the plants. A whitish mycelium mantle covers the lesions on the leaves at the abaxial surface at high moisture conditions. Using morphological characteristics, Koch’s postulates, and phylogenetic analyses of the ITS-5.8S rDNA region, we identified that the fungus causing the lesions on the okra leaves was Thanatephorus cucumeris (Frank) Donk (asexual stage of Rhizoctonia solani Kuhn of the anastomosis group AG-1 ID). This is the first report of T. cucumeris causing web blight on okra in Brazil, and probably in the world. So far, T. cucumeris was described on okra only on post-harvest pods rotting and seedlings’ damping off.

Pathogenicity and Fungicide Sensitivity of Rhizoctonia solani and R. cerealis Isolates

The Rhizoctonia solani species consists of multinucleate isolates that belong to anastomosis groups AG1–AG3 and differ in virulence and host affinity. R. cerealis is a binucleate species of anastomosis group AG-D which causes sharp eyespot, a common plant disease in Poland. Rhizoctonia spp. is a ubiquitous soil pathogen that poses a significant threat for global crop production due to the absence of effective crop protection products. The aim of this study was to determine the virulence of R. solani and R. cerealis isolates towards Beta vulgaris, Zea mays, Triticum spelta and T. aestivum seedlings, to confirm the presence of endopolygalacturonase genes pg1 and pg5 in the genomes of the tested isolates and to evaluate the tested isolates’ sensitivity to triazole, strobilurin, imidazole and carboxamide fungicides. All tested isolates infected B. vulgaris seedlings. but none of them were virulent against Z. mays plants. R. solani isolates AG4 PL and AG2-2IIIB PL were characterized by the highest virulence (average infestation score of 2.37 and 2.53 points on a scale of 0–3 points) against sugar beet seedlings. The prevalence of infections caused by most of the analysed isolates (in particular R. solani AG4 J—11.8, and R. cerealis RC2—0.78) was higher in spelt than in bread wheat. The virulence of the analysed isolates was not correlated with the presence of pg1 and pg5 genes. The efficacy of the tested fungicides in controlling Rhizoctonia spp. infections was estimated at 100% (propiconazole + cyproconazole), 98.8% (penthiopyrad), 95.4% (tebuconazole) and 78.3% (azoxystrobin).

Evidência de que o fungo Rhizoctonia solani AG-1 IA adaptado à Urochloa na Colômbia mantém ampla gama de hospedeiros incluindo o milho

RESUMO O fungo Rhizoctonia solani grupo de anastomose AG-1 IA emergiu como patógeno importante associado à queima foliar, podridão do coleto e morte de pastagens do gênero Urochloa (braquiária) na América do Sul. Neste estudo objetivou-se determinar se a adaptação de R. solani AG-1 IA à Urochloa spp. na Colômbia promoveu diferenças fenotípicas de agressividade a hospedeiros distintos. Testou-se a hipótese de que as populações do patógeno adaptadas à Urochloa não são hospedeiro-especializadas e, desta forma, não estão geneticamente isoladas, mantendo assim ampla gama de hospedeiros, incluindo as fabáceas feijão caupi e soja. Determinou-se, também, se dois grupos de isolados obtidos de populações de R. solani AG-1 IA amostradas de Urochloa na Colômbia tinham potencial adaptativo para emergir como patógeno do milho. Além do nível de agressividade da doença em diferentes hospedeiros, determinou-se os componentes de evolutibilidade como o coeficiente de variância genotípica (IG), de variância ambiental (IE) e a herdabilidade (h2). Concluiu-se que: i) A adaptação de R. solani AG-1 IA à Urochloa spp. não promoveu diferenças fenotípicas de agressividade em hospedeiros distintos e, desta forma, o patógeno mantêm ampla gama de hospedeiros; ii) A população de R. solani AG-1 IA de Urochloa híbrido Mulato da Colômbia tem potencial adaptativo para emergir como patógeno do milho.

Rhizoctonia solani Identified as the Disease Causing Agent of Peanut Leaf Rot in China.

Peanut (Arachis hypogaea L.) is one of the most economically important oil crops in the world. Since the 1990s, the peanut industry has developed rapidly in China. However, because of the use of high-yield varieties and increased plant density, a peanut leaf rot disease occurred in Laixi Experimental Fields in Shandong Province, China in 2007. Leaves had nearly circular, brown lesions that enlarged quickly developing yellow-brown halos at the edges of the lesions. High relative humidity under field conditions led to complete necrosis of the leaves with cotton wool-like mycelia observed followed by the development of sclerotia on the leaf surface. Symptomatic plants were observed between 2007 and 2010, and symptomatic leaf tissue was collected from the Laixi Experimental Fields. An isolate (designated YF-1) from symptomatic peanut leaves was isolated and purified on potato dextrose agar (PDA) and water agar (WA) medium. On PDA, the colony appeared initially as colorless and grew to the diameter of a 9-cm petri dish within 3 days. As the mycelium aged, the colony color gradually became light brown, and sclerotia developed on the surface of the colony. YF-1 was identified as Rhizoctonia solani Kühn based on the number of nuclei per cell ranging from 4 to 13 (average 6.1), hyphal diameter being 7.5 to 12.9 μm (average 8.3 μm), branching at right angles, a septum was present near each hyphal branch with a slight constriction, and no clamp connection structures or conidia were ever observed (4). To further confirm the identity of isolate YF-1, genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Shanghai Leifeng Biotechnol. Co., Ltd.), and the complete internal transcribed spacer (ITS) region of ribosomal DNA was amplified and sequenced with a pair of primers ITS1/ITS4 (2). A GenBank BLAST search produced an exact match for the sequences of R. solani (AY154301), with 100% sequence similarity. To estimate the mode of anastomosis, YF-1 was paired on WA medium with each reference strain belonging to anastomosis groups (AGs) 1 through 8 (provided by Shandong Agriculture University) (1,3). The results indicated that YF-1 belonged to group AG-1, subgroup AG-1-IA of R. solani. Pathogenicity tests were conducted by inoculating 10 peanut leaves using a colonized paper disc method (filter paper 1 cm in diameter suspended in the mycelia suspension). Ten control leaves received paper discs without mycelium. Inoculated and non-inoculated plants were kept in humid chambers for 24 h at 25°C. Three days after inoculation, the leaves developed typical brown lesions that were similar to those of naturally diseased plants. Koch's postulates were fulfilled by reisolation of R. solani from symptomatic leaves. No symptoms were observed on control leaves. To our knowledge, this is the first report of peanut leaf rot caused by R. solani. Occurrence of the disease in China is a new threat to the health of peanut.

Highly polymorphic microsatellite loci in the rice‐ and maize‐infecting fungal pathogen Rhizoctonia solani anastomosis group 1 IA

Ten polymorphic microsatellite loci were isolated and characterized from the rice- and maize-infecting Basidiomycete fungus Rhizoctonia solani anastomosis group AG-1 IA. All loci were polymorphic in two populations from Louisiana in USA and Venezuela. The total number of alleles per locus ranged from four to eight. All 10 loci were also useful for genotyping soybean-infecting R. solani AG-1 isolates from Brazil and USA. One locus, TC06, amplified across two other AG groups representing different species, showing species-specific repeat length polymorphism. This marker suite will be used to determine the global population structure of this important pathogenic fungus.

Antimicrobial activity and induction of systemic resistance in rice by leaf extract of Datura metel against Rhizoctonia solani and Xanthomonas oryzae pv. oryzae

The leaf extracts of Datura metel significantly reduced the in vitro growth of Rhizoctonia solani (RS7, Anastomosis group AG1) and Xanthomonas oryzae pv. o ryzae ( Xoo). Methanol extract exhibited the best control of the pathogens recording 10–35% more toxicity than aqueous extract. Foliar application of leaf extracts effectively reduced the incidence of sheath blight and bacterial blight diseases of rice under greenhouse condition. Pre-inoculation applications of leaf extract were found better than post-inoculation applications. Induction of systemic resistance as evident from the increased accumulation of pathogenesis related (PR) proteins and other defense related compounds was observed in rice plants following application of leaf extract of D. metel and challenge inoculation with either R. solani or Xoo. The methanol extract of D. metel when subjected to thin layer chromatography (TLC) showed a spot with relative front (Rf) value of 0.705. Well pronounced antibacterial activity against Xoo was demonstrated by the compound eluted from the region corresponding to this spot. The molecular ion peak and the fragmentation peaks of the eluted compound analyzed by mass spectrometry correspond to the already published mass spectrum of daturilin (Siddiqui et al., Phytochemistry 26: 2641-2643, 1987), a withanolide compound from D. metel.

Genetic diversity and virulence of Rhizoctonia species associated with plantings of Lotus corniculatus

Species of Rhizoctonia cause a blight of Lotus corniculatus, a perennial forage legume. We characterized genetic variation and virulence in populations of R. solani and binucleate Rhizoctonia's associated with diseased L. corniculatus in field plantings over several years. Isolates of anastomosis groups AG-1 and AG-4 accounted for the R. solani recovered from diseased leaf and shoot tissues. Isolates of binucleate Rhizoctonia were recovered predominantly from soil and associated plant debris. Isolates of R. solani were more virulent on leaves and shoots of L. corniculatus than were binucleate Rhizoctonia isolates. Numerous unique DNA restriction patterns were observed among binucleate isolates and anastomosis groups of R. solani. Variation in restriction patterns was greater among isolates of AG-1 from the lower plant canopy than from the upper canopy. No restriction pattern was shared by any isolate from AG-1 and AG-4. Allelic and genotypic heterogeneity of AG-1 isolates were also greater in the lower plant canopy. Binucleate isolates exhibited greater heterogeneity than AG-1 isolates from either canopy region. L. corniculatus offers significant opportunities for investigating temporal and spatial dynamics of genetic structure of Rhizoctonia populations in perennial plant systems.

Análise de proteínas e isoenzimas de isolados de Rhizoctonia spp. patogênicos a Eucalyptus

Objetivou-se caracterizar isolados de Rhizoctonia solani AG1 e AG4 e isolados binucleados de Rhizoctonia spp. patogênicos a Eucalyptus, por meio de eletroforese de proteínas, em gel de poliacrilamida, e de isoenzimas (ACP, 6-PGDH, LAP, SOD, MDH e IDH), em gel de amido. Para comparação, incluíram-se alguns isolados brasileiros de outros hospedeiros e isolados-padrões de R. solani AG1, procedentes do Japão. Observaram-se diferenças nos padrões gerais de proteínas e nos fenótipos isoenzimáticos entre isolados binucleados e multinucleados e entre isolados de diferentes grupos e subgrupos de anastomose. Isolados de R. solani AG1, procedentes do Brasil e Japão, apresentaram baixa similaridade nos padrões de proteínas e de isoenzimas. Isolados brasileiros morfologicamente semelhantes a R. solani AG1-IB (microesclerodiais) apresentaram padrões de proteínas similares e um maior número de fenótipos isoenzimáticos idênticos entre si. Esta tendência foi independente do hospedeiro e da origem geográfica. Variações nos padrões de proteínas e de isoenzimas foram também observadas dentre isolados brasileiros de R. solani AG4. Discute-se o uso da eletroforese de proteínas e isoenzimas na caracterização de isolados de Rhizoctonia spp. e em estudos genéticos e filogenéticos de fungos deste gênero.

Gender related differences in the effect of aging on blood amino acid compartmentation☆

This work has been focused on the study of the variations in blood amino acid compartmentation (plasma and blood cells) with aging, both in men and women. Aging is a situation which, under the influence of gender, involves a decline in body weight functions and variations in energy metabolism with a deterioration of muscular metabolism leading to changes in amino acid handling. We determined the blood levels of individual amino acids in whole blood, plasma compartment and blood cell compartment of 51 men and 51 women. Subjects were classified in three age groups—AG1 (18 to 35 y), AG2 (35–50 y) and AG3 (more than 50 y). Aging was accompanied by significant changes in blood levels of amino acids showing gender-linked differences which were distinct for both blood compartments (plasma and blood cells). In men, aging was accompanied by a drop in blood levels of several amino acids, due mainly to the plasma compartment, whereas in women aging brought about a rise in blood levels of various amino acids mainly in blood cell compartment. This paper contributes to enhancing the physiological importance of the blood cell pool in the handling of amino acids.

Influence of herbicides on growth and sclerotia production inRhizoctonia solani

Abstract This study was conducted to determine the effects of three commonly applied soybean (Glycine max) herbicides (glyphosate, imazethapyr, and pendimethalin) on the mycelial growth, sclerotial production, and viability of Rhizoctonia solani isolates [anastomosis groups AG-1, AG-2-2, and AG-4] under controlled conditions. Pendimethalin significantly reduced mycelial growth of all three R. solani isolates investigated, whereas effects of the herbicides imazethapyr and glyphosate were not significant. Sclerotial production was affected differently by the three herbicides. Isolates AG-1 and AG-2-2 produced sclerotia both in vitro and in vivo, whereas isolate AG-4 did not produce sclerotia in vitro. In vitro AG-1 isolate showed a decrease, and AG-2-2 isolate showed an increase in sclerotial production in the presence of herbicide. In contrast, both AG-1 and AG-2-2 isolates showed reduction in sclerotial production in vivo compared to AG-4 isolate, which showed an increase in sclerotial production in the p...