Mutual interplay between phytopathogenic powdery mildew fungi and other microorganisms

Powdery mildew is a common and widespread plant disease of considerable agronomic relevance. It is caused by obligate biotrophic fungal pathogens which, in most cases, epiphytically colonize aboveground plant tissues. The disease has been typically studied as a binary interaction of the fungal pathogen with its plant hosts, neglecting, for the most part, the mutual interplay with the wealth of other microorganisms residing in the phyllo- and/or rhizosphere and roots. However, the establishment of powdery mildew disease can be impacted by the presence/absence of host-associated microbiota (epi- and endophytes) and, conversely, plant colonization by powdery mildew fungi might disturb indigenous microbial community structures. In addition, other (foliar) phytopathogens could interact with powdery mildews, and mycoparasites may affect the outcome of plant–powdery mildew interactions. In this review, we discuss the current knowledge regarding the intricate and multifaceted interplay of powdery mildew fungi, host plants and other microorganisms, and outline current gaps in our knowledge, thereby setting the basis for potential future research directions.     

Threshold response of Madagascar's littoral forest to sea-level rise

Aim Coastal biodiversity hotspots are globally threatened by sea‐level rise. As such it is important to understand how ecosystems resist, respond and adapt to sea‐level rise. Using pollen, geochemistry, charcoal and diatom records in conjunction with previously published palaeoclimatic records, we investigated the mechanism, interactions and ecosystem response and resilience of Madagascar's littoral forest to late Holocene sea‐level rise. Location Sediment sequences were collected along the south‐east coast of Madagascar in two adjacent habitats in Mandena; the highly diverse littoral forest fragment and species‐poor Erica‐matrix. Methods We used a multi‐proxy approach to investigate the relative influence of environmental changes on the littoral ecosystem. We reconstructed past vegetation and fire dynamics over the past 6500 years at two sites in the littoral forest using fossil pollen and macrofossil charcoal contained in sedimentary sequences. Alongside these records we reconstructed past marine transgressions from the same sedimentary sequences using geochemical analyses, and a salinity and drought index through the analysis of fossil diatoms. Results Our findings indicated that it was the synergistic effect of sea‐level rise coupled with rainfall deficits that triggered a threshold event with a switch from two types of littoral forest (an open Uapaca forest and a closed littoral forest fragment) to an Erica–Myrica heath/grassland occurring in approximately less than 100 years. Resilience to sea‐level rise differed in the two adjacent habitats, suggesting that the littoral forest fragment was more resilient to the impacts of sea‐level change and aridity than the open Uapaca woodland. Conclusions We demonstrated that the littoral ecosystem was influenced by late Holocene sea‐level rise and climatic desiccation. While climate change‐integrated conservation strategies address the effects of climate change on species distribution and dispersal, our work suggests that more attention should be paid to the impacts of interactive climatic variables that affect ecosystem thresholds.     

Association of the colistin resistance gene mcr-1 with faecal pollution in water environments in Hanoi,Vietnam

Colistin is one of the antibiotics of last resort for human health. However, the dissemination of the plasmid-mediated colistin resistance gene mcr-1 is of great concern globally. In the One Health framework, the environment is an important component for managing antimicrobial resistance. However, little information is available concerning the prevalence of mcr-1 in water environments. We aimed to reveal the prevalence of mcr-1 in different water environments in Hanoi, Vietnam. Quantitative PCR was applied to detect mcr-1 in four urban drainages receiving untreated domestic wastewater, three rivers, five lakes and two groundwater samples. Urban drainages contained higher concentrations of mcr-1, suggesting that urban residents carry the gene. The class 1 integron-integrase gene was identified as a good surrogate of antibiotic resistance genes including mcr-1. A significant correlation was found between the levels of mcr-1 and the human-specific cross-assembly phage, which is an indicator of human faecal pollution. These results indicated that the primary source of mcr-1 in urban water environments is human faeces, which is consistent with the fact that most domestic wastewater is untreated in Hanoi. The control of untreated wastewater is critical for alleviating the spread of mcr-1 in water environments in Vietnam.     

Targeted amplification and MinION nanopore sequencing of key azole and echinocandin resistance determinants of clinically relevant Candida spp. from blood culture bottles

The objective of the study was to evaluate the use of targeted multiplex Nanopore MinION amplicon re-sequencing of key Candida spp. from blood culture bottles to identify azole and echinocandin resistance associated SNPs. Targeted PCR amplification of azole (ERG11 and ERG3) and echinocandin (FKS) resistance-associated loci was performed on positive blood culture media. Sequencing was performed using MinION nanopore device with R9.4.1 Flow Cells. Twenty-eight spiked blood cultures (ATCC strains and clinical isolates) and 12 prospectively collected positive blood cultures with candidaemia were included. Isolate species included Candida albicans, Candida glabrata, Candida krusei, Candida parapsilosis, Candida tropicalis and Candida auris. SNPs that were identified on ERG and FKS genes using Snippy tool and CLC Genomic Workbench were correlated with phenotypic testing by broth microdilution (YeastOne™ Sensititre). Illumina whole-genome-sequencing and Sanger-sequencing were also performed as confirmatory testing of the mutations identified from nanopore sequencing data. There was a perfect agreement of the resistance-associated mutations detected by MinION-nanopore-sequencing compared to phenotypic testing for acquired resistance (16 with azole resistance; 3 with echinocandin resistance), and perfect concordance of the nanopore sequence mutations to Illumina and Sanger data. Mutations with no known association with phenotypic drug resistance and novel mutations were also detected.     

Resistance to the tyrosine kinase inhibitor axitinib is associated with increased glucose metabolism in pancreatic adenocarcinoma

Alterations in energy (glucose) metabolism are key events in the development and progression of cancer. In pancreatic adenocarcinoma (PDAC) cells, we investigated changes in glucose metabolism induced by resistance to the receptor tyrosine kinase inhibitor (RTKI) axitinib. Here, we show that human cell lines and mouse PDAC cell lines obtained from the spontaneous pancreatic cancer mouse model (Kras^G12DPdx1-cre) were sensitive to axitinib. The anti-proliferative effect was due to a G2/M block resulting in loss of 70–75% cell viability in the most sensitive PDAC cell line. However, a surviving sub-population showed a 2- to 3-fold increase in [C-14]deoxyglucose ([C-14]DG) uptake. This was sustained in axitinib-resistant cell lines, which were derived from parental PDAC. In addition to the axitinib-induced increase in [C-14]DG uptake, we observed a translocation of glucose transporter-1 (Glut-1) transporters from cytosolic pools to the cell surface membrane and a 2-fold increase in glycolysis rates measured by the extracellular acidification rate (ECAR). We demonstrated an axitinib-induced increase in phosphorylated Protein Kinase B (pAkt) and by blocking pAkt with a phosphatidylinositol-3 kinase (PI3K) inhibitor we reversed the Glut-1 translocation and restored sensitivity to axitinib treatment. Combination treatment with both axitinib and Akt inhibitor in parental pancreatic cell line resulted in a decrease in cell viability beyond that conferred by single therapy alone. Our study shows that PDAC resistance to axitinib results in increased glucose metabolism mediated by activated Akt. Combining axitinib and an Akt inhibitor may improve treatment in PDAC.     

MITOCHONDRIA: Are mitochondria accessory to metastasis?

Since the nineteenth century the importance of mitochondria in cellular physiology has been growing steadily. Not only the organelle harbors the main systems for ATP generation, but also buffers the redox potential in the cytosol and is one of the protagonists of the intrinsic pathway for apoptosis. In tumor cells, mitochondria went from being dysfunctional compartments to playing a supportive or perhaps even a triggering part in metastasis. This “Organelle In Focus” article discusses the classical metabolic events that occur in mitochondria and why these pathways could be essential for the onset of the malignant phenotype. Finally, we propose that the oxidative metabolism of tumor cells in conjunction with the inactivation of anoikis may have been coopted through a non-adaptive evolutionary process.     

Farmer knowledge,attitude and practice on cotton (Gossypium hirsutum L.) pest resistance management strategies in Zimbabwe

Cotton is an important cash crop and a means of survival for Zimbabwe’s smallholder farmers who are located in the semi-arid areas. However, it is plagued by a wide variety of pests. The cotton industry in Zimbabwe came up with sustainable pest management strategies which include within the season rotation of bollworm pesticides, a closed season and acaricide rotation scheme. The land reform programme brought new players in the cotton industry and it was critical to determine their knowledge on the pest management strategies. A survey was conducted to determine farmer knowledge, practice and perception on the resistance management strategy. Responses indicated that both communal and new farmers based their spray on egg counts. Communal farmers knew when to use pyrethroids compared to new farmers. Farmers observed the acaricide rotation scheme although they use some non acaricide pesticides. More than half of the new farmers could not say which acaricides were in the acaricide scheme. The majority of the farmers reported that they adhered to the closed season although field observation revealed otherwise. A significantly higher number of new farmers knew when to slash cotton compared to communal farmers. Knowledge of acaricides was not common among farmers. Use of pyrethroids was not limited to 1 February onwards as stipulated in the cotton pest resistance management strategy. The results suggest the need for training among the cotton farmers especially the new farmers or refresher courses among the communal farmers.     

Establishment of an in vitro sciarid fly larvae assay to study plant resistance

Mechanisms underlying natural plant resistance to herbivorous invertebrates are still poorly understood in comparison with bacterial or fungal interactions. One reason is the difficulty in reliably and reproducibly assessing the effects under controlled conditions. This article describes a newly developed in vitro biological assay system that enables the interactions between sciarid larvae and plants, whose roots they feed on, to be studied under highly controlled conditions. The bioassay eliminates the problems created by the often variable environmental factors by providing an aseptic arena where experimental plants can be germinated and grown on agar within a Petri dish. Sciarid fly eggs are then collected, sterilised and added to the Petri dish. The system allows the eggs to hatch and the larvae to feed on the plant roots. A range of developmental parameters can then be recorded over time which can then be correlated with the experimental plant type. This assay system also allows a simultaneous comparison or 'choice chamber' between two (or more) different genotypes. The assay should greatly help to facilitate the identification of new components involved in insect resistance mediated pathway via the characterisation of mutant plants.