Clubroot in Brassica: recent advances in genomics, breeding, and disease management

Clubroot disease, caused by Plasmodiophora brassicae, affects Brassica oilseed and vegetable production worldwide. This review is focused on various aspects of clubroot disease and its management, including understanding the pathogen and resistance in the host plants. Advances in genetics, molecular biology techniques, and omics research have helped to identify several major loci, QTL, and genes from the Brassica genomes involved in the control of clubroot resistance. Transcriptomic studies have helped to extend our understanding of the mechanism of infection by the pathogen and the molecular basis of resistance/susceptibility in the host plants. A comprehensive understanding of the clubroot disease and host resistance would allow developing a better strategy by integrating the genetic resistance with cultural practices to manage this disease from a long-term perspective.

[Usefulness of combined sequencing of the mitochondrial genome and a targeted panel of nuclear genes involved in mitochondrial diseases]

The molecular study of mitochondrial diseases, essential for diagnosis, is special due to the dual genetic origin of these pathologies: mitochondrial DNA and nuclear DNA. Complete mtDNA sequencing still remains the first line diagnostic test followed if negative, by resequencing panels of several hundred mitochondrially-encoded nuclear genes. This strategy, with an initial entire mtDNA sequencing, is currently justified by the presence of nuclear mitochondrial DNA sequences (NUMTs) in the nuclear genome. We designed a resequencing panel combining the mtDNA and 135 nuclear genes which was evaluated compared to the performances of the standard mtDNA sequencing. Method validation was performed on the reading depth and reproducibility of the results. Thirty patients were analyzed by both methods. We were able to demonstrate that NUMTs did not impact the mtDNA sequencing quality, as the identified variants and mutant loads were identical with the reference mtDNA sequencing method. Reading depths were higher than the recommendations of the MitoDiag French diagnostic network, for the entire mtDNA for muscle and for 70% of the mtDNA for blood. These results highlight the usefulness of combining both mtDNA and mitochondrially nuclear-encoded genes and thus obtain more complete results and faster turnaround time for mitochondrial disease patients.

Identification of potential proteases for abdominal aortic aneurysm by weighted gene coexpression network analysis

Proteases are involved in the degradation of the extracellular matrix (ECM), which contributes to the formation of abdominal aortic aneurysm (AAA). To identify new disease targets in addition to the results of previous microarray studies, we performed next-generation sequencing (NGS) of the whole transcriptome of Angiotensin II-treated ApoE^-/- male mice (n = 4) and control mice (n = 4) to obtain differentially expressed genes (DEGs). Identified DEGs of proteases were analyzed using weighted gene coexpression network analysis (WGCNA). RT-qPCR was conducted to validate the differential expression of selected hub genes. We found that 43 DEGs were correlated with the expression of the protease profile, and most were clustered in immune response module. Among 26 hub genes, we found that Mmp16 and Mmp17 were significantly downregulated in AAA mice, while Ctsa, Ctsc, and Ctsw were upregulated. Our functional annotation analysis of genes coexpressed with the five hub genes indicated that Ctsw and Mmp17 were involved in T cell regulation and Cell adhesion molecule pathway, respectively, and that both were involved in general regulation of the cell cycle and gene expression. Overall, our data suggest that these ectopic genes are potentially crucial to AAA formation and may act as biomarkers for the diagnosis of AAA.

Time for a paradigm shift in the use of plant genetic resources

For all major crops, sizeable genebanks are maintained across the world and serve as repositories of genetic diversity and key sources of novel traits used in breeding. Although molecular markers have been used to characterize diversity in a broad sense, the most common approach to exploring these resources has been through phenotypic characterization of subsets of these large collections. With the advent of affordable large-scale genotyping technologies and the increasing body of candidate genes for traits of interest, we argue here that it is time for a paradigm shift in the way that we explore and exploit these considerable and highly useful resources. By combining dense genotypic information in and around candidate genes, it is possible to classify accessions based on their haplotype, something approximating the actual alleles at these genes of interest.

[Benefits of Molecular Analyses in Thyroid Carcinoma]

Benefits of Molecular Analyses in Thyroid Carcinoma Abstract. The widespread access to neck ultrasonography has led to high detection rates of thyroid nodules, whose vast majority will remain clinically silent. In daily practice it is a challenge to filter out the thyroid nodules that require medical attention. This is usually achieved by a combination of sonomorphologic criteria and fine-needle aspiration cytology. In recent years, there is a trend toward deescalation in diagnostic and therapeutic measures for thyroid nodules. Some authors even advocate active surveillance instead of surgical approaches for very low-risk thyroid carcinoma. This approach requires an accurate assessment of the malignant potential of each thyroid nodule. As recent studies have allowed better understanding of molecular pathogenesis of thyroid cancer, the mutational profile of thyroid nodules has emerged as a new tool for assessment of thyroid nodules. Its exact clinical application in daily routine remains, however, unclear.

Degenerate ITS7 primer enhances oomycete community coverage and PCR sensitivity to Aphanomyces species, economically important plant pathogens

Metagenomic analysis of oomycetes through deep amplicon sequencing has been conducted primarily using the ITS6-ITS7 primer set that targets the ITS1 region. While this primer set shows a perfect match to most oomycete taxa, ITS7 contains 3 mismatches to the corresponding binding site of plant pathogens within the genus Aphanomyces. Polymerase chain reaction (PCR) efficiency differs for taxa with uneven primer matching characteristics, which may explain why previous studies have detected this genus at low abundance. To overcome the impact of these mismatches on PCR sensitivity, the mismatched nucleotides were replaced with degenerate nucleotides. Oomycete communities from 35 soil samples collected from asymptomatic and root rot diseased sites in pea fields across Alberta were analyzed simultaneously using ITS6-ITS7 and ITS6-ITS7-a.e. (modified version of ITS7) primer sets on 1 Illumina MiSeq run. The number of high-quality reads obtained by ITS6-ITS7-a.e. was more than twice that of ITS6-ITS7. The relative abundance of Pythium spp. was reduced and Aphanomyces spp. increased. Aphanomyces cf. cladogamus and Aphanomyces euteiches were the second and third most abundant species, respectively, in the pea rhizosphere using the ITS7-a.e. primer, but were rare using the ITS7 primer. These results indicate that use of ITS7-a.e. provides a more accurate picture of oomycete communities than ITS7 by enhancing PCR sensitivity to Aphanomyces.

Phytohormone and genome variations in Vitis amurensis resistant to downy mildew

Downy mildew (DM) resistance is a highly desirable agronomic trait in grape breeding. High variation in Plasmopara viticola resistance was found in Vitis cultivars. Some accessions show high P. viticola resistance even under conditions highly conducive to DM. Here, leaf disc inoculation experiments revealed that Vitis amurensis 'Zuoshaner' exhibited DM resistance with necrotic spots, whereas the V. amurensis × V. vinifera hybrid cultivar 'Zuoyouhong' was susceptible. Changes in plant hormones accumulation profiles differed between the cultivars. To investigate the genetic mechanisms related to DM resistance, we performed genome-wide sequencing of 'Zuoshaner' and 'Zuoyouhong' and identified cultivar-specific single-nucleotide polymorphisms, insertions/deletions (indels), structural variations (SVs), and copy number variations (CNVs), identifying 5399 SVs and 191 CNVs specific for 'Zuoshaner'. Genes affected by these genetic variations were enriched in biological processes, including defense response and response to stress and stimulation, and were associated with sesquiterpenoid and triterpenoid biosynthesis, ABC transporters, and phenylalanine metabolism pathways. Additionally, indels and SVs were detected in six NBS-LRR disease resistance genes, and a CNV was mapped to the Rpv8 locus responsible for downy mildew resistance. These findings further our understanding of the genetic mechanisms underlying grape mildew resistance, and will facilitate genomic marker-assisted breeding for improved V. amurensis cultivars.

International Barcode of Life: Evolution of a global research community

The 6th International Barcode of Life Conference (Guelph, Canada, 18-21 August 2015), themed Barcodes to Biomes, showcases the latest developments in DNA barcoding research and its diverse applications. The meeting also provides a venue for a global research community to share ideas and to initiate collaborations. All plenary and contributed abstracts are being published as an open-access special issue of Genome. Here, I use a comparison with the 3rd Conference (Mexico City, 2009) to highlight 10 recent and emerging trends that are apparent among the contributed abstracts. One of the outstanding trends is the rising proportion of abstracts that focus upon multiple socio-economically important applications of DNA barcoding, including studies of agricultural pests, quarantine and invasive species, wildlife forensics, disease vectors, biomonitoring of ecosystem health, and marketplace surveys evaluating the authenticity of seafood products and medicinal plants. Other key movements include the use of barcoding and metabarcoding approaches for dietary analyses-and for studies of food webs spanning three or more trophic levels-as well as the spread of next-generation sequencing methods in multiple contexts. In combination with the rising taxonomic and geographic scope of many barcoding iniatives, these developments suggest that several important questions in biology are becoming tractable. "What is this specimen on an agricultural shipment?", "Who eats whom in this whole food web?", and even "How many species are there?" are questions that may be answered in time periods ranging from a few years to one or a few decades. The next phases of DNA barcoding may expand yet further into prediction of community shifts with climate change and improved management of biological resources.

A genomic investigation of the putative contact zone between divergent Brown Creeper (Certhia americana) lineages: chromosomal patterns of genetic differentiation

Sky islands, or montane forest separated by different lowland habitats, are highly fragmented regions that potentially limit gene flow between isolated populations. In the sky islands of the Madrean Archipelago (Arizona, USA), various taxa display different phylogeographic patterns, from unrestricted gene flow among sky islands to complex patterns with multiple distinct lineages. Using genomic-level approaches allows the investigation of differential patterns of gene flow, selection, and genetic differentiation among chromosomes and specific genomic regions between sky island populations. Here, we used thousands of SNPs to investigate the putative contact zone of divergent Brown Creeper (Certhia americana) lineages in the Madrean Archipelago sky islands. We found the two lineages to be completely allopatric (during the breeding season) with a lack of hybridization and gene flow between lineages and no genetic structure among sky islands within lineages. Additionally, the two lineages inhabit different climatic and ecosystem conditions and have many local primary song dialects in the southern Arizona mountain ranges. We identified a positive relationship between genetic differentiation and chromosome size, but the sex chromosome (Z) was not found to be an outlier. Differential patterns of genetic differentiation per chromosome may be explained by genetic drift--possibly in conjunction with non-random mating and non-random gene flow--due to variance in recombination rates among chromosomes.

Draft genome sequence of the silver pomfret fish, Pampus argenteus

Silver pomfret, Pampus argenteus, is a fish species from coastal waters. Despite its high commercial value, this edible fish has not been sequenced. Hence, its genetic and genomic studies have been limited. We report the first draft genome sequence of the silver pomfret obtained using a Next Generation Sequencing (NGS) technology. We assembled 38.7 Gb of nucleotides into scaffolds of 350 Mb with N50 of about 1.5 kb, using high quality paired end reads. These scaffolds represent 63.7% of the estimated silver pomfret genome length. The newly sequenced and assembled genome has 11.06% repetitive DNA regions, and this percentage is comparable to that of the tilapia genome. The genome analysis predicted 16 322 genes. About 91% of these genes showed homology with known proteins. Many gene clusters were annotated to protein and fatty-acid metabolism pathways that may be important in the context of the meat texture and immune system developmental processes. The reference genome can pave the way for the identification of many other genomic features that could improve breeding and population-management strategies, and it can also help characterize the genetic diversity of P. argenteus.