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Background The white-rot fungi in the genus Ganoderma interact with both living and dead angiosperm tree hosts. Two Ganoderma species, a North American taxon, G. zonatum and an Asian taxon, G. boninense , have primarily been found associated with live palm hosts. During the host plant colonization process, a massive transcriptional reorganization helps the fungus evade the host immune response and utilize plant cell wall polysaccharides. Results A publicly available transcriptome of G. boninense - oil palm interaction was surveyed to profile transcripts that were differentially expressed in planta . Ten percent of the G. boninense transcript loci had altered expression as it colonized oil palm plants one-month post inoculation. Carbohydrate active enzymes (CAZymes), particularly those with a role in lignin degradation, and auxiliary enzymes that facilitate lignin modification, like cytochrome P450s and haloacid dehalogenases, were up-regulated in planta . Several lineage specific proteins and secreted proteins that lack known functional domains were also up-regulated in planta , but their role in the interaction could not be established. A slowdown in G. boninense respiration during the interaction can be inferred from the down-regulation of proteins involved in electron transport chain and mitochondrial biogenesis. Additionally, pathogenicity related genes and chitin degradation machinery were down-regulated during the interaction indicating G. boninense may be evading detection by the host immune system. Conclusions This analysis offers an overview of the dynamic processes at play in G. boninense - oil palm interaction and provides a framework to investigate biology of Ganoderma fungi across plantations and landscape.

Background Downy mildew, the most devastating disease of spinach ( Spinacia oleracea L.), is caused by the oomycete Peronospora effusa [= P. farinosa f. sp. spinaciae ]. The P. effusa shows race specificities to the resistant host and comprises 19 reported races and many novel isolates. Sixteen new P. effusa races were identified during the past three decades, and the new pathogen races are continually overcoming the genetic resistances used in commercial cultivars. A spinach breeding population derived from the cross between cultivars Whale and Lazio was inoculated with P. effusa race 16 in an environment-controlled facility; disease response was recorded and genotyped using genotyping by sequencing (GBS). The main objective of this study was to identify resistance-associated single nucleotide polymorphism (SNP) markers from the cultivar Whale against the P. effusa race 16. Results Association analysis conducted using GBS markers identified six significant SNPs (S3_658,306, S3_692697, S3_1050601, S3_1227787, S3_1227802, S3_1231197). The downy mildew resistance locus from cultivar Whale was mapped to a 0.57 Mb region on chromosome 3, including four disease resistance candidate genes (Spo12736, Spo12784, Spo12908, and Spo12821) within 2.69–11.28 Kb of the peak SNP. Conclusions Genomewide association analysis approach was used to map the P. effusa race 16 resistance loci and identify associated SNP markers and the candidate genes. The results from this study could be valuable in understanding the genetic basis of downy mildew resistance, and the SNP marker will be useful in spinach breeding to select resistant lines.

Downy mildew, caused by the oomycete Peronospora effusa , is the most economically important disease on spinach. Fourteen new races of P. effusa have been identified in the last three decades. The frequent emergence of new races of P. effusa continually overcome the genetic resistance to the pathogen. The objectives of this research were to more clearly map the downy mildew resistance locus RPF 1 in spinach, to identify single nucleotide polymorphism (SNP) markers associated with the resistance, and to refine the candidate genes responsible for the resistance. Progeny from populations generated from crosses of cultivars resistant (due to RPF 1) to race 13 of P. effusa (Swan, T-Bird, Squirrel, and Tonga) with race 13 susceptible cultivars (Whale and Polka) were inoculated and the downy mildew disease response determined. Association analysis was performed in TASSEL, GAPIT, PLINK, and GENESIS programs using SNP markers identified from genotyping by sequencing (GBS). Association analysis mapped the race 13 resistance loci ( RPF 1) to positions 0.39, 0.69, 0.94-0.98, and 1.2 Mb of chromosome 3. The associated SNPs were within 1–7 kb of the disease resistance genes Spo12784, Spo12719, Spo12905, and Spo12821, and 11–18 Kb from Spo12903. This study extended our understanding of the genetic basis of downy mildew resistance in spinach and provided the most promising candidate genes Spo12784 and Spo12903 near the RPF 1 locus, to pursue functional validation. The SNP markers may be used to select for the resistant lines to improve genetic resistance against the downy mildew pathogen and in developing durably resistant cultivars.

The genomes of five Cochliobolus heterostrophus strains, two Cochliobolus sativus strains, three additional Cochliobolus species (Cochliobolus victoriae, Cochliobolus carbonum, Cochliobolus miyabeanus), and closely related Setosphaeria turcica were sequenced at the Joint Genome Institute (JGI). The datasets were used to identify SNPs between strains and species, unique genomic regions, core secondary metabolism genes, and small secreted protein (SSP) candidate effector encoding genes with a view towards pinpointing structural elements and gene content associated with specificity of these closely related fungi to different cereal hosts. Whole-genome alignment shows that three to five percent of each genome differs between strains of the same species, while a quarter of each genome differs between species. On average, SNP counts among field isolates of the same C. heterostrophus species are more than 25× higher than those between inbred lines and 50× lower than SNPs between Cochliobolus species. The suites of nonribosomal peptide synthetase (NRPS), polyketide synthase (PKS), and SSP-encoding genes are astoundingly diverse among species but remarkably conserved among isolates of the same species, whether inbred or field strains, except for defining examples that map to unique genomic regions. Functional analysis of several strain-unique PKSs and NRPSs reveal a strong correlation with a role in virulence.

Treatment of hematologic malignancies is a formidable challenge for hematologists and there is an urgent need to identify safe and efficacious agents either via synthesis in the laboratory or isolation from natural products. Here, we report the cytotoxicity of extracts from mushroom Gymnopilus purpureosquamulosus Høil ( G . pps ) and describe its molecular mechanisms. Using leukemia, lymphoma and multiple myeloma cell lines, 28–35 ppm G . pps extract inhibited cell proliferation by ~46–79%, which correlates with activation of apoptosis as indicated by increase in annexin V-positive cells (~5–8-fold), production of reactive oxygen species (~2–3-fold), cells in sub G0/G1 phase (~3–13-fold), caspase 3 enzymatic activity (~1.6–2.9-fold), DNA fragmentation, PARP1 cleavage and down-regulation of prosurvival proteins. Mitochondrial membrane potential decreased and leakage of pro-apoptotic factors to cytoplasm was observed, consistent with the activation of intrinsic apoptosis. Western blot analysis showed activation of the ASK1-MEK-SAPK/JNK and ASK1-P38 MAPK pathways possibly due to changes in the cellular redox status as suggested by decreased protein levels of peroxiredoxin, thioredoxin and thioredoxin reductase. Moreover, antioxidant N-acetylcysteine alleviated the cytotoxicity of G . pps . Pharmacological inhibition of SAPK/JNK and P38 alleviated the G . pps -mediated cytotoxicity. The extract activated apoptosis in leukemia and lymphoma patient cell samples but not in mononuclear cells from healthy donors further supporting the therapeutic values of G . pps for hematologic malignancies.

Downy mildew, caused by the obligate oomycete Peronospora effusa (Pfs), is the most economically important disease of spinach. In recent years, numerous new races of the pathogen have overcome the resistance used in newly released cultivars. Resistance to Pfs in spinach is predominantly governed by dominant major resistance genes (RPFs) that are widely used in commercial spinach hybrid cultivars. Currently, a labor and resource-intensive inoculation test of whole plants, in a large tray format, in a temperature-controlled growth chamber and dew chamber, is employed to evaluate the resistance of spinach germplasm and to characterize races of the downy mildew pathogen. The objective of this work was to evaluate, standardize, and validate a more efficient detached leaf inoculation method to differentiate resistant and susceptible spinach genotypes and characterize Pfs races on a standardized set of spinach differential genotypes. Detached leaves and cotyledons of standard host differentials commonly used for race differentiation were placed on water agar in closed Petri dishes and inoculated by spraying the leaves with a spore suspension of Pfs inoculum. Disease incidence and severity on detached leaves and cotyledons were compared to the response of the corresponding cultivars in the standard whole-plant assay. There was a complete match between the disease reaction on whole plants and the disease reaction on detached leaves for all three races of Pfs examined. Furthermore, the obligate pathogen could infect, sporulate, and maintain pathogenicity by propagation solely on detached leaves. The detached leaf assay could facilitate advances in breeding for Pfs by evaluating resistance, pathogen race identification, and studies on epidemiology and genetics of the pathogen as the tests are less labor, resource-intensive than the whole-plant assay format, and environmental variables can be more accurately controlled.

Golf courses have a significant environmental impact. High water demands and the intensive use of agricultural chemicals have been a concern for decades and are therefore in the focus of efforts to make golf courses more environmentally sustainable. Products based on modifying or using plant-associated microbiota are one of the fastest-growing sectors in agriculture, but their application on turfgrasses on golf courses is so far negligible. In this review, we summarize the limited knowledge on microbiomes of golf turf ecosystems and show that the lack of holistic studies addressing the structure and function of golf turf microbiomes, including their responses to intense turf management procedures, is currently the main bottleneck for development and improvement of reliable, well-functioning microbial products. We further highlight the endosphere of turfgrasses, which is easily accessible for microbial cultivation through constant mowing, as the most stable and protected micro-environment. Many grass species do possess endophytic bacteria and fungi that have been shown to improve the plants’ resistance towards microbial pathogens and insect pests, and several products using endophyte-enhanced grass varieties are commercially successful. We anticipated that this trend would tee-off on golf courses, too, once a more comprehensive understanding of golf turf microbiomes is available.

Some of the most damaging tree pathogens can attack woody stems, causing lesions (cankers) that may be lethal. To identify the genomic determinants of wood colonization leading to canker formation, we sequenced the genomes of the poplar canker pathogen, Mycosphaerella populorum , and the closely related poplar leaf pathogen, M. populicola . A secondary metabolite cluster unique to M. populorum is fully activated following induction by poplar wood and leaves. In addition, genes encoding hemicellulose-degrading enzymes, peptidases, and metabolite transporters were more abundant and were up-regulated in M. populorum growing on poplar wood-chip medium compared with M. populicola . The secondary gene cluster and several of the carbohydrate degradation genes have the signature of horizontal transfer from ascomycete fungi associated with wood decay and from prokaryotes. Acquisition and maintenance of the gene battery necessary for growth in woody tissues and gene dosage resulting in gene expression reconfiguration appear to be responsible for the adaptation of M. populorum to infect, colonize, and cause mortality on poplar woody stems. Significance Some of the most damaging tree diseases are caused by pathogens that induce cankers, a stem deformation often lethal. To investigate the cause of this adaptation, we sequenced the genomes of poplar pathogens that do and do not cause cankers. We found a unique cluster of genes that produce secondary metabolites and are co-activated when the canker pathogen is grown on poplar wood and leaves. The gene genealogy is discordant with the species phylogeny, showing a signature of horizontal transfer from fungi associated with wood decay. Furthermore, genes encoding hemicellulose-degrading enzymes are up-regulated on poplar wood chips, with some having been acquired horizontally. We propose that adaptation to colonize poplar woody stems is the result of acquisition of these genes.

Thielaviopsis paradoxa sensu lato is a soilborne fungal pathogen that causes Thielaviopsis trunk rot and heart rot in palms. The loss of structural integrity resulting from trunk rot can cause the palm trunk to collapse suddenly and poses a serious threat to life and property. Even though rudimentary knowledge about the Thielaviopsis infection process in palms is available, nothing is known about the T. paradoxa species complex in the US. The aim of this study was to characterize T. paradoxa s. lat. isolates collected from diseased palms grown in Florida. Multi-locus phylogeny using three genes, ITS, β-tubulin, and tef1-α, revealed that the isolates separate into two distinct clades with high bootstrap support. The majority of the isolates clustered with the species T. ethacetica, while two isolates formed a separate clade, distinct from T. musarum, and might represent an undescribed Thielaviopsis species. One representative isolate from each clade, when grown on three distinct media and at four different temperatures, showed differences in gross colony morphology, as well as growth rates. The T. ethacetica isolate TP5448 and the Thielaviopsis sp. isolate PLM300 grew better at opposite ends of the temperature spectrum tested in this study, i.e., 35 °C and 10 °C, respectively. In pathogenicity assays on whole plants, the T. ethacetica isolate proved to be more aggressive than Thielaviopsis sp. isolate PLM300, as it produced larger lesions when inoculated on wounded leaflets. An unequal distribution was observed for the mating-type locus of T. ethacetica, as 12 isolates carried the MAT1-1-1 allele, while the status for four isolates remained undefined. Variation in mycelial growth in response to different fungicides was also observed between the two clades. These results demonstrate the existence of two Thielaviopsis clades that can infect palms in Florida and underscore the need for targeted sampling to help uncover the diversity of Thielaviopsis species across palm-growing regions in the US.

Turfgrass landscapes have expanded rapidly in recent decades and are a major vegetation type in urbanizing ecosystems. While turfgrass areas provide numerous ecosystem services in urban environments, ecological side effects from intensive management are raising concerns regarding their sustainability. One potentially promising approach to ameliorate the ecological impact and decrease the use of agricultural chemicals is to take advantage of naturally evolved turfgrass-associated microbes by harnessing beneficial services provided by microbiomes. Unfortunately, especially compared to agricultural crops, the microbiomes of turfgrasses are not well understood. Here, we analyzed microbial communities inhabiting the leaf and root endospheres as well as soil in two bermudagrass cultivars, ‘Latitude 36’ and ‘TifTuf’, which exhibit distinct tolerance to nematode damage, with the goal of identifying potential differences in the microbiomes that might explain their distinct phenotype. We used 16S rRNA gene V4 and ITS2 amplicon sequencing to characterize the microbiomes in combination with microbial cultivation efforts to identify potentially beneficial endophytic fungi and bacteria. Our results show that Latitude 36 and TifTuf showed markedly different fungal microbiomes, each harboring unique taxa from Ascomycota and Glomeromycota, respectively. In contrast, less difference was observed from bacterial and archaeal microbiomes, which were dominated by Bacteroidetes and Thaumarchaeota, respectively. The TifTuf microbiomes exhibited lower microbial diversity compared to Latitude 36. Many sequences could not be classified to a higher taxonomic resolution, indicating a relatively high abundance of hitherto undescribed microorganisms. Our results provide new insights into the structure and composition of turfgrass microbiomes but also raise important questions regarding the functional attributes of key taxa.