Deciphering Aphanomyces euteiches-pea-biocontrol bacterium interactions through untargeted metabolomics.

Aphanomyces euteiches causes root rot in pea, leading to significant yield losses. However, the metabolites involved in this pathosystem have not been thoroughly studied. This study aimed to fill this gap and explore mechanisms of bacterial suppression of A. euteiches via untargeted metabolomics using pea grown in a controlled environment. Chemical isotope labeling (CIL), followed by liquid chromatography-mass spectrometry (LC-MS), was used for metabolite separation and detection. Univariate and multivariate analyses showed clear separation of metabolites from pathogen-treated pea roots and roots from other treatments. A three-tier approach positively or putatively identified 5249 peak pairs or metabolites. Of these, 403 were positively identified in tier 1; 940 were putatively identified with high confidence in tier 2. There were substantial changes in amino acid pool, and fatty acid and phenylpropanoid pathway products. More metabolites, including salicylic and jasmonic acids, were upregulated than downregulated in A. euteiches-infected roots. 1-aminocyclopropane-1-carboxylic acid and 12-oxophytodienoic acid were upregulated in A. euteiches + bacterium-treated roots compared to A. euteiches-infected roots. A great number of metabolites were up- or down-regulated in response to A. euteiches infection compared with the control and A. euteiches + bacterium-treated plants. The results of this study could facilitate improved disease management.

Genomic characterization of three bacterial isolates antagonistic to the pea root rot pathogen Aphanomyces euteiches.

Microorganisms living in soil and rhizosphere or inside plants can promote plant growth and health. Genomic characterization of beneficial microbes could shed light on their special features. Through extensive field survey across Saskatchewan, Canada, followed by in vitro and greenhouse characterization, we identified several bacterial isolates antagonistic to pea root rot pathogen Aphanomyces euteiches. In this study, the genomes of three isolates-Pseudomonas sp. rhizo 66 (PD-S66), Pseudomonas synxantha rhizo 25 (Ps-S25), and Serratia sp. root 2 (TS-R2)-were sequenced, assembled, and annotated. Genome size of PD-S66 was 6 279 416 bp with 65 contigs, 59.32% GC content, and 5653 predicted coding sequences (CDS). Genome size of Ps-S25 was 6 058 437 bp with 66 contigs, a GC content of 60.08%, and 5575 predicted CDS. The genome size of TS-R2 was 5 282 152 bp, containing 26 contigs, a GC content of 56.17%, and 4956 predicted CDS. For the identification of the isolates, digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values were determined, which confirmed PD-S66 and TS-R2 as potential new species, belonging to Pseudomonas and Serratia genera, respectively, while Ps-S25 belongs to species Pseudomonas synxantha. Biosynthetic gene clusters were predicted using antiSMASH. The genomic data provided insight into the genetics and biochemical pathways supporting the antagonistic activity against A. euteiches of these isolates.

Effects of nitrogen fertilization and a commercial arbuscular mycorrhizal fungal inoculant on root rot and agronomic production of pea and lentil crops.

In the Canadian prairies, pulse crops such as field pea (Pisum sativum L.) and lentil (Lens culinaris L.) are economically important and widely grown. However, in recent years, root rot, caused by a variety of fungal and oomycete pathogens, including Aphanomyces euteiches, has become a limiting factor on yield. In this study, we examined the impacts of nitrogen (N) fertilization and a commercial arbuscular mycorrhizal fungal (AMF) inoculant on pea and lentil plant health and agronomic production at three locations in Saskatchewan: Swift Current, Indian Head and Melfort. The AMF inoculation had no impact on root rot severity, and therefore is not considered a reliable method to manage root rot in pea and lentil. In contrast, N fertilization led to reductions in root rot in Swift Current, but not the other two sites. However, N fertilization did reduce nodulation. When both pea and lentil are considered, the abundance of A. euteiches in soil increased from pre-seeding to mid-bloom. A negative correlation between soil pH and disease severity was also observed. The high between-site variability highlights the importance of testing root rot mitigation strategies under multiple soil conditions to develop site-specific recommendations. Use of N fertilizer as a root rot management strategy merits further exploration, including investigation into its interactions with other management strategies, soil properties, and costs and benefits.

Exploring Mechanisms of Quantitative Resistance to Leptosphaeria maculans (Blackleg) in the Cotyledons of Canola (Brassica napus) Based on Transcriptomic and Microscopic Analyses.

Using resistant cultivars is a common approach to managing blackleg of canola/rapeseed caused by Leptosphaeria maculans (Lm). Quantitative resistance (QR), as opposed to major-gene resistance, is of interest because it is generally more durable, due to its multi-genetic basis. However, the mechanisms and genes underlying QR are mostly unknown. In this study, potential QR modes of action in "74­44 BL" was explored. This Canadian canola cultivar showed moderate but consistent race-nonspecific resistance at the cotyledon and adult-plant stages. A susceptible cultivar, "Westar", was used as a control. After inoculation, the lesions developed more slowly on the cotyledons of 74-44 BL than those of Westar. We used RNA sequencing (-RNA-seq) to identify genes and their functions, putatively related to this resistance, and found that genes involved in programmed cell death (PCD), reactive oxygen species (ROS), signal transduction or intracellular endomembrane transport were most differentially expressed. ROS production was assessed in relation to Lm hyphal growth and lesion size; it occurred beyond the tissue colonized by Lm in 74-44 BL and appeared to trigger rapid cell death, limiting cotyledon colonization by Lm. In contrast, Lm grew more rapidly in Westar, often catching up with the ring of ROS and surpassing lesion boundaries. It appears that QR in 74-44 BL cotyledons is associated with limited colonization by Lm possibly mediated via ROS. The RNA-seq data also showed a link between ROS, signal transduction, and endomembrane vesicle trafficking, as well as PCD in the resistance. These results provide a starting point for a better understanding of the mechanisms behind QR against Lm in canola.

Rapid tip-directed movement of Golgi equivalents in growing Aspergillus nidulans hyphae suggests a mechanism for delivery of growth-related materials.

Golgi equivalents (GEs) process materials in the fungal secretory pathway. Despite the importance of localized secretion in fungal tip growth, GE behaviour in living hyphae has not been documented. The distribution was monitored of an Aspergillus nidulans putative GE-associated protein, CopA, tagged with GFP (CopA-GFP). This co-localized with a Golgi body/GE marker established in other systems, alpha-2,6-sialyltransferase, tagged with red fluorescent protein (ST-RFP). CopA-GFP and ST-RFP distributions responded similarly to brefeldin A, which impairs Golgi/GE trafficking. We used a CopA-GFP, hypA1 strain to study GE distribution and behaviour in growing A. nidulans hyphae. This strain has a wild-type phenotype at 28 degrees C, can be manipulated by changing growth temperature or by use of cytoskeleton inhibitors, and its GE behaviour is consistent with that in a wild-type-morphology strain. A. nidulans GEs were more abundant at hyphal tips than subapically, and showed saltatory motility in all directions. Anterograde GE movements predominated. These were positively correlated with, but at least 10-fold faster than, hyphal growth rate, under all growth and experimental conditions investigated. The actin inhibitor latrunculin B reduced both anterograde GE movement and hyphal growth rate, whereas the microtubule (MT) depolymerizer benomyl increased anterograde GE movement and decreased hyphal growth rate. The MT stabilizer taxol increased A. nidulans GE movement but not hyphal growth rate. A. nidulans GE motility appears to have a complex dependence on both actin and MTs. We present a model for apical delivery of growth materials in which A. nidulans GEs play a role in long-distance transport.

Health beliefs of African-Caribbean people with type 2 diabetes: a qualitative study.

BACKGROUND: There is evidence that African-Caribbean people with diabetes have poorer outcomes than other individuals with diabetes. It is not fully understood why this happens. AIM: To gain an understanding of how health beliefs influence the way African-Caribbean people with diabetes manage their illness. DESIGN OF STUDY: Qualitative study using one-to-one interviews. SETTING: Inner-city Nottingham during 2003-2004. METHOD: A purposive sample of 16 African-Caribbean people with type 2 diabetes. Participants took part in semi-structured in-depth interviews which were audio-taped recorded and transcribed. Transcripts were analysed for emergent themes and validity was checked by an independent researcher and through discussion with a local community group. Data were managed using NVivo software. RESULTS: Participants were strongly influenced by memories of growing up in the Caribbean, migration to the UK, and friends' and families' accounts of diabetes, as well as their own experiences of the illness. Knowledge and understanding of diabetes was sometimes poor. There was some mistrust in the value of advice and treatment offered by professionals and a preference for natural treatments. Health professionals were generally praised but some interviewees felt that the NHS did not cater properly for black people. Insulin treatments were feared and diet- or tablet-controlled diabetes was seen by some as a mild form that did not warrant serious concern. CONCLUSIONS: These findings have implications for how some people manage their diabetes and how diabetes care is delivered to the African-Caribbean community.