RESUMEN
Fungi in the genus Trichoderma are notorious producers of secondary metabolites with diverse applications, such as antibacterial, antifungal, and plant growth-promoting properties. Peptaibols are linear peptides produced by such fungi, with more than 440 compounds described to date, including tricholongins, longibrachins, trichobrachins, and trichovirins. Peptaibols are synthesized by non-ribosomal peptide synthetases and they have several biological activities. Our research group isolated four peptaibols (6DP2, 6DP3, 6DP4, and 6DP5) with antifungal activity against the plant pathogen Colletotrichum gloeosporioides and the proteasome (a cancer chemotherapy target) from Trichoderma sp. P8BDA1F1, an endophytic fungus from Begonia venosa. The ethyl acetate extract of this endophyte showed activity of 6.01% and 75% against C. gloeosporioides and the proteasome, respectively. The isolated compounds were identified by MS/MS and compared to literature data, suggesting the presence of trilongins BI, BII, BIII, and BIV, which are peptaibols containing 20 amino acid residues. The minimum inhibitory concentration against C. gloeosporioides was 40 µM for trilongin BI, 320 µM for trilongin BII, 160 µM for trilongin BIII, and 310 µM for trilongin BIV. BI-BIV trilongins inhibited proteasome ChTL activity, with IC50 values of 6.5 ± 2.7; 4.7 ± 1.8; 6.3 ± 2.2; and 2.7 ± 0.5 µM, respectively. The compounds were tested ex vivo against the intracellular amastigotes of Leishmania (L.) infantum but showed no selectivity. It is the first report of trilongins BI-BIV with antifungal activity against C. gloeosporioides and the proteasome target.
Asunto(s)
Antifúngicos/farmacología , Antineoplásicos/farmacología , Begoniaceae/microbiología , Peptaiboles/farmacología , Trichoderma/química , Antifúngicos/química , Antifúngicos/aislamiento & purificación , Antineoplásicos/química , Antineoplásicos/aislamiento & purificación , Colletotrichum/efectos de los fármacos , Endófitos , Concentración 50 Inhibidora , Pruebas de Sensibilidad Microbiana , Peptaiboles/química , Peptaiboles/aislamiento & purificación , Filogenia , Inhibidores de Proteasoma/farmacología , Trichoderma/clasificación , Trichoderma/genética , Trichoderma/aislamiento & purificaciónRESUMEN
Anthracnose disease, caused by Colletotrichum truncatum, affects marketable yield during preharvest production and postharvest storage of fruits and vegetables worldwide. Demethylation inhibitor (DMI) fungicides are among the very few chemical classes of single-site mode of action fungicides that are effective in controlling anthracnose disease. However, some species are inherently resistant to DMIs and more information is needed to understand this phenomenon. Isolates of C. truncatum were collected from the United States and China from peach, soybean, citrus, and begonia and sensitivity to six DMIs (difenoconazole, propiconazole, metconazole, tebuconazole, flutriafol, and fenbuconazole) was determined. Compared with DMI sensitive isolates of C. fructicola, C. siamense, and C. fioriniae (EC50 value ranging from 0.03 to 16.2 µg/ml to six DMIs), C. truncatum and C. nymphaeae were resistant to flutriafol and fenbuconazole (with EC50 values of more 50 µg/ml). Moreover, C. truncatum was resistant to tebuconazole and metconazole (with resistance factors of 27.4 and 96.0) and displayed reduced sensitivity to difenoconazole and propiconazole (with resistance factors of 5.1 and 5.2). Analysis of the Colletotrichum spp. genome revealed two potential DMI targets, CYP51A and CYP51B, that putatively encode P450 sterol 14α-demethylases. Both genes were identified and sequenced from C. truncatum and other species and no correlation between CYP51 gene expression levels and fungicide sensitivity was found. Four amino acid variations L208Y, H238R, S302A, and I366L in CYP51A, and three variations H373 N, M376L, and S511T in CYP51B correlated with the DMI resistance phenotype. CYP51A structure model analysis suggested the four alterations may reduce azole affinity. Likewise, CYP51B structure analysis suggested the H373 N and M376L variants may change the conformation of the DMI binding pocket, thereby causing differential sensitivity to DMI fungicides in C. truncatum.
Asunto(s)
Inhibidores de 14 alfa Desmetilasa/farmacología , Colletotrichum/enzimología , Farmacorresistencia Fúngica , Variación Genética , Enfermedades de las Plantas/microbiología , Esterol 14-Desmetilasa/genética , Secuencia de Aminoácidos , Azoles/farmacología , Begoniaceae/microbiología , Citrus/microbiología , Colletotrichum/efectos de los fármacos , Colletotrichum/genética , Proteínas Fúngicas/genética , Fungicidas Industriales/farmacología , Modelos Moleculares , Filogenia , Prunus persica/microbiología , Alineación de Secuencia , Glycine max/microbiologíaRESUMEN
Tropical plants represent hotspots of endophytic fungal species diversity. Based on culture-dependent methods, we evaluated the endophytic fungal communities in leaves of three plant species found in the Brazilian Atlantic Rainforest: Begonia fischeri, Begonia olsoniae, and Begonia venosa. These species are found in two distant sites: a continental region and an insular area. A total of 426 fungal endophytes in 19 genera were isolated in pure culture including Colletotrichum (51.6% of isolates) and Diaporthe (22.5%) as the most abundant, followed by Phyllosticta (3.5%), Neopestalotiopsis (1.8%), Stagonospora (1.8%), and Nigrospora (1.6%) among the genera found in minor abundance. The diversity and composition of fungal taxa differed across plant hosts. Richness and diversity of fungi were higher in B. fischeri in comparison to B. olsoniae and B. venosa. Discriminatory analysis revealed that fungal communities are structured according to hosts, which means that each plant species had its distinct endophytic communities, but dominated by common fungal taxa. This is the first study to report fungal endophytes in begonia leaves and characterize their communities.
Asunto(s)
Begoniaceae/microbiología , Endófitos/aislamiento & purificación , Hongos/aislamiento & purificación , Biodiversidad , Brasil , Endófitos/clasificación , Endófitos/genética , Hongos/clasificación , Hongos/genética , Filogenia , Bosque LluviosoRESUMEN
A nitrogen-fixing bacterium, designated strain Be17(T), was isolated from rhizosphere soil of Begonia semperflorens planted in Beijing Botanical Garden, PR China. Phylogenetic analyses based on a segment of the nifH gene sequence and a full-length 16S rRNA gene sequence revealed that strain Be17(T) was a member of the genus Paenibacillus. High levels of 16S rRNA gene sequence similarity were found between strain Be17(T) and Paenibacillus graminis RSA19(T) (97.9 %), Paenibacillus sonchi LMG 24727(T) (97.8 %), Paenibacillus riograndensis CECT 7330(T) (96.2 %) and Paenibacillus borealis DSM 13188(T) (96.1 %), respectively. Levels of 16S rRNA gene sequence similarity between strain Be17(T) and the type strains of other recognized members of the genus Paenibacillus were below 96.0 %. However, the DNA-DNA hybridization values between strain Be17(T) and P. graminis RSA19(T), P. sonchi LMG 24727(T) and P. riograndensis CECT 7330(T) were 47.9 %, 38.7 % and 37.5 %, respectively. The DNA G+C content of strain Be17(T) was 52.9 mol%. The major fatty acid component of strain Be17(T) was anteiso-branched C(15 : 0) (30.92 %). The major isoprenoid quinone was MK-7. The cell-wall peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. On the basis of its phenotypic characteristics, 16S rRNA gene sequences, DNA G+C content, DNA-DNA relatedness, chemotaxonomic properties and nifH gene sequence, strain Be17(T) represents a nitrogen-fixing strain of a novel species of the genus Paenibacillus, for which the name Paenibacillus jilunlii sp. nov. is proposed. The type strain is Be17(T) (â=âCGMCC 1.10239(T)â=âDSM 23019(T)).