Extensive chloroplast genome rearrangement amongst three closely related Halamphora spp. (Bacillariophyceae), and evidence for rapid evolution as compared to land plants

Diatoms are the most diverse lineage of algae, but the diversity of their chloroplast genomes, particularly within a genus, has not been well documented. Herein, we present three chloroplast genomes from the genus Halamphora (H. americana, H. calidilacuna, and H. coffeaeformis), the first pennate diatom genus to be represented by more than one species. Halamphora chloroplast genomes ranged in size from ~120 to 150 kb, representing a 24% size difference within the genus. Differences in genome size were due to changes in the length of the inverted repeat region, length of intergenic regions, and the variable presence of ORFs that appear to encode as-yet-undescribed proteins. All three species shared a set of 161 core features but differed in the presence of two genes, serC and tyrC of foreign and unknown origin, respectively. A comparison of these data to three previously published chloroplast genomes in the non-pennate genus Cyclotella (Thalassiosirales) revealed that Halamphora has undergone extensive chloroplast genome rearrangement compared to other genera, as well as containing variation within the genus. Finally, a comparison of Halamphora chloroplast genomes to those of land plants indicates diatom chloroplast genomes within this genus may be evolving at least ~4&ndash;7 times faster than those of land plants. Studies such as these provide deeper insights into diatom chloroplast evolution and important genetic resources for future analyses.</p

Genome streamlining via complete loss of introns has occurred multiple times in lichenized fungal mitochondria.

Reductions in genome size and complexity are a hallmark of obligate symbioses. The mitochondrial genome displays clear examples of these reductions, with the ancestral alpha-proteobacterial genome size and gene number having been reduced by orders of magnitude in most descendent modern mitochondrial genomes. Here, we examine patterns of mitochondrial evolution specifically looking at intron size, number, and position across 58 species from 21 genera of lichenized Ascomycete fungi, representing a broad range of fungal diversity and niches. Our results show that th

Whole Genome Shotgun Sequencing Detects Greater Lichen Fungal Diversity Than Amplicon-Based Methods in Environmental Samples

In this study we demonstrate the utility of whole genome shotgun (WGS) metagenomics in study organisms with small genomes to improve upon amplicon-based estimates of biodiversity and microbial diversity in environmental samples for the purpose of understanding ecological and evolutionary processes. We generated a database of full-length and near-full-length ribosomal DNA sequence complexes from 273 lichenized fungal species and used this database to facilitate fungal species identification in the southern Appalachian Mountains using low coverage WGS at higher resolution and without the biases of amplicon-based approaches. Using this new database and methods herein developed, we detected between 2.8 and 11 times as many species from lichen fungal propagules by aligning reads from WGS-sequenced environmental samples compared to a traditional amplicon-based approach. We then conducted complete taxonomic diversity inventories of the lichens in each one-hectare plot to assess overlap between standing taxonomic diversity and diversity detected based on propagules present in environmental samples (i.e., the &ldquo;potential&rdquo; of diversity). From the environmental samples, we detected 94 species not observed in organism-level sampling in these ecosystems with high confidence using both WGS and amplicon-based methods. This study highlights the utility of WGS sequence-based approaches in detecting hidden species diversity and demonstrates that amplicon-based methods likely miss important components of fungal diversity. We suggest that the adoption of this method will not only improve understanding of biotic constraints on the distributions of biodiversity but will also help to inform important environmental policy.</p

Extensive chloroplast genome rearrangement amongst three closely related Halamphora spp. (Bacillariophyceae), and evidence for rapid evolution as compared to land plants.

Diatoms are the most diverse lineage of algae, but the diversity of their chloroplast genomes, particularly within a genus, has not been well documented. Herein, we present three chloroplast genomes from the genus Halamphora (H. americana, H. calidilacuna, and H. coffeaeformis), the first pennate diatom genus to be represented by more than one species. Halamphora chloroplast genomes ranged in size from ~120 to 150 kb, representing a 24% size difference within the genus. Differences in genome size were due to changes in the length of the inverted repeat region, length of intergenic regions, and the variable presence of ORFs that appear to encode as-yet-undescribed proteins. All three species shared a set of 161 core features but differed in the presence of two genes, serC and tyrC of foreign and unknown origin, respectively. A comparison of these data to three previously published chloroplast genomes in the non-pennate genus Cyclotella (Thalassiosirales) revealed that Halamphora has undergone extensive chloroplast genome rearrangement compared to other genera, as well as containing variation within the genus. Finally, a comparison of Halamphora chloroplast genomes to those of land plants indicates diatom chloroplast genomes within this genus may be evolving at least ~4-7 times faster than those of land plants. Studies such as these provide deeper insights into diatom chloroplast evolution and important genetic resources for future analyses

Genetic Architecture of Capitate Glandular Trichome Density in Florets of Domesticated Sunflower (Helianthus annuus L.)

Capitate glandular trichomes (CGT), one type of glandular trichomes, are most common in Asteraceae species. CGT can produce various secondary metabolites such as sesquiterpene lactones (STLs) and provide durable resistance to insect pests. In sunflower, CGT-based host resistance is effective to combat the specialist pest, sunflower moth. However, the genetic basis of CGT density is not well understood in sunflower. In this study, we identified two major QTL controlling CGT density in sunflower florets by using a F4 mapping population derived from the cross HA 300 × RHA 464 with a genetic linkage map constructed from genotyping-by-sequencing data and composed of 2121 SNP markers. One major QTL is located on chromosome 5, which explained 11.61% of the observed phenotypic variation, and the second QTL is located on chromosome 6, which explained 14.06% of the observed phenotypic variation. The QTL effects and the association between CGT density and QTL support interval were confirmed in a validation population which included 39 sunflower inbred lines with diverse genetic backgrounds. We also identified two strong candidate genes in the QTL support intervals, and the functions of their orthologs in other plant species suggested their potential roles in regulating capitate glandular trichome density in sunflower. Our results provide valuable information to sunflower breeding community for developing host resistance to sunflower insect pests

Comparative analysis of the mitochondrial genomes of six newly sequenced diatoms reveals group II introns in the barcoding region of <i>cox1</i>

<p>Diatoms are the most diverse lineage of algae and at the base of most aquatic food webs, but only 11 of their mitochondrial genomes have been described. Herein, we present the mitochondrial genomes of six diatom species, including: <i>Melosira undulata</i>, <i>Nitzschia alba</i>, <i>Surirella</i> sp., <i>Entomoneis</i> sp., <i>Halamphora coffeaeformis</i>, and <i>Halamphora calidilacuna.</i> Comparison of these six genomes to the 11 currently published diatom mitochondrial genomes revealed a novel ubiquitous feature block consisting of <i>tatC</i>-<i>orf157</i>-<i>rps11.</i> The presence of intronic retrotransposable elements in the barcoding region of <i>cox1</i> in the <i>Halamphora</i> genomes may explain historic difficulty (especially PCR) with <i>cox1</i> as a universal barcode for diatoms. Our analysis suggests that high rates of variability in number and position of introns, in many commonly used coding sequences, prevent these from being universally viable as barcodes for diatoms. Therefore, we suggest researchers examine the chloroplast and/or nuclear genomes for universal barcoding markers.</p

Immunizing against Anogenital Cancer: HPV Vaccines

Most of us are familiar with foot and hand warts caused by the skin tropic human papillomaviruses (HPV). However, it is less well recognized that infection with HPV types that replicate in the anogenital mucosa is the most prevalent sexually transmitted disease in the world. Indeed, a recent estimate suggests that 80%–90% of the sexually active population is exposed during their lifetime to mucosal HPV [1]. Of the more than 40 genotypes of mucosal HPV, most result in benign and transient disease, such as genital warts caused by HPV types 6 and 11. However, 15 HPV genotypes (e.g., HPV types 16 and 18) are classified as high-risk because they are causal agents of human cancers [2]. Almost all of the half million cervical cancer cases that occur worldwide each year are related to infection with high-risk HPV (hrHPV) [4]. High-risk HPVs, most especially HPV16, are also implicated in the development of some anal, oropharyngeal, vaginal, vulval, and penile cancers. Within a given population, the most prevalent hrHPV genotype varies with geographical location [1–3]. Combined, all of the hrHPVs are responsible for approximately 5% of all cancers worldwide (10% in women) [1–3]. HPV infection is a significant health burden on the United States economy, costing approximately US$7.6 billion per year for screening (Pap smear) and cervical cancer treatment [4]. Recommendations for the current vaccines are for routine inoculation of females 13–26 years of age as well as males 13–21 years of age. The vaccines are most effective when administered prior to potential virus exposure (i.e., before commencement of sexual activity) [5]. Vaccination is the most effective strategy to prevent these cancers and associated morbidities [3–5]