Coxsackieviruses Undergo Intercellular Transmission as Pools of Sibling Viral Genomes Associated to Membranes

Some viruses are released from cells as pools of membrane-associated virions. By increasing the multiplicity of infection, this type of collective dispersal could favor viral cooperation, but also the emergence of cheater-like viruses, such as defective interfering particles. To better understand this process, we examined the genetic diversity of membrane-associated coxsackievirus infectious units. We found that infected cells released large membranous structures containing 8–21 infectious particles on average, including vesicles. However, in most cases (62–93%), these structures did not promote the co-transmission of different viral genetic variants present in a cell. Furthermore, collective dispersal had no effect on viral population sequence diversity. Our results indicate that membrane-associated collective infectious units typically contain viral particles derived from the same parental genome. Hence, if cooperation occurred, it should probably involve sibling viral particles rather than different variants. As shown by social evolution theory, cooperation among siblings should be robust against cheater invasion.

Hsp90 dictates viral sequence space by balancing the evolutionary tradeoffs between protein stability, aggregation and translation rate

Acquisition of mutations is central to evolution but the detrimental effects of most mutations on protein folding and stability limit protein evolvability. Molecular chaperones, which suppress aggregation and facilitate polypeptide folding, are proposed to promote sequence diversification by buffering destabilizing mutations. However, whether and how chaperones directly control protein evolution remains poorly understood. Here, we examine the effect of reducing the activity of the key eukaryotic chaperone Hsp90 on poliovirus evolution. Contrary to predictions of a buffering model, inhibiting Hsp90 increases population sequence diversity and promotes accumulation of mutations reducing protein stability. Explaining this counterintuitive observation, we find that Hsp90 offsets the evolutionary tradeoff between protein stability and aggregation. Lower chaperone levels favor sequence variants of reduced hydrophobicity, thus decreasing protein aggregation propensity but at a cost to protein stability. Notably, reducing Hsp90 activity also promotes clusters of codon-deoptimized synonymous mutations at inter-domain boundaries, likely to promote local ribosomal slowdown to facilitate cotranslational domain folding. Our results reveal how a chaperone can shape the sequence landscape at both the protein and RNA levels to harmonize the competing constraints posed by protein stability, aggregation propensity and translation rate on successful protein biogenesis.

Genomic Rearrangements Considered as Quantitative Traits

To understand the population genetics of structural variants (SVs), and their effects on phenotypes, we developed an approach to mapping SVs, particularly transpositions, segregating in a sequenced population, and which avoids calling SVs directly. The evidence for a potential SV at a locus is indicated by variation in the counts of short-reads that map anomalously to the locus. These SV traits are treated as quantitative traits and mapped genetically, analogously to a gene expression study. Association between an SV trait at one locus and genotypes at a distant locus indicate the origin and target of a transposition. Using ultra-low-coverage (0.3x) population sequence data from 488 recombinant inbred Arabidopsis genomes, we identified 6,502 segregating SVs. Remarkably, 25% of these were transpositions. Whilst many SVs cannot be delineated precisely, PCR validated 83% of 44 predicted transposition breakpoints. We show that specific SVs may be causative for quantitative trait loci for germination, fungal disease resistance and other phenotypes. Further we show that the phenotypic heritability attributable to sequence anomalies differs from, and in the case of time to germination and bolting, exceeds that due to standard genetic variation. Gene expression within SVs is also more likely to be silenced or dysregulated. This approach is generally applicable to large populations sequenced at low-coverage, and complements the prevalent strategy of SV discovery in fewer individuals sequenced at high coverage.

Glyphosate Resistance in Tall Waterhemp (Amaranthus tuberculatus) from Mississippi is due to both Altered Target-Site and Nontarget-Site Mechanisms

A tall waterhemp population from Missisippi was suspected to be resistant to glyphosate. Glyphosate dose response experiments resulted in GR50(dose required to reduce plant growth by 50%) values of 1.28 and 0.28 kg ae ha−1glyphosate for the glyphosate-resistant (GR) and -susceptible (GS) populations, respectively, indicating a five-fold resistance. The absorption pattern of14C-glyphosate between the GR and GS populations was similar up to 24 h after treatment (HAT). Thereafter, the susceptible population absorbed more glyphosate (55 and 49% of applied) compared to the resistant population (41 and 40% of applied) by 48 and 72 HAT, respectively. Treatment of a single leaf in individual plants with glyphosate at 0.84 kg ha−1, in the form of 10 1-µl droplets, provided greater control (85 vs. 29%) and shoot fresh weight reduction (73 vs. 34% of nontreated control) of the GS plants compared to the GR plants, possibly indicating a reduced movement of glyphosate in the GR plants. The amount of14C-glyphosate that translocated out of the treated leaves of GR plants (20% of absorbed at 24 HAT and 23% of absorbed at 48 HAT) was significantly lower than the GS plants (31% of absorbed at 24 HAT and 32% of absorbed at 48 HAT). A potential difference in shikimate accumulation between GR and GS populations at different concentrations of glyphosate was also studied in vitro. The IC50(glyphosate concentration required to cause shikimate accumulation at 50% of peak levels measured) values for the GR and GS populations were 480 and 140 µM of glyphosate, respectively, resulting in more shikimate accumulation in the GS than the GR population. Sequence analysis of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the target site of glyphosate, from GR and GS plants identified a consistent single nucleotide polymorphism (T/C, thymine/cytosine) between GR/GS plants, resulting in a proline to serine amino acid substitution at position 106 in the GR population. The GR and GS plants contained equal genomic copy number ofEPSPS, which was positively correlated withEPSPSgene expression. Thus, glyphosate resistance in the tall waterhemp population from Mississippi is due to both altered target site and nontarget site mechanisms. This is the first report of an alteredEPSPS-based resistance in a dicot weed species that has evolved resistance to glyphosate.

Aplicaciones infográficas en yacimientos neolíticos y calcolíticos: Huecas (Toledo)

<p>Archaeological researches developed by the University of Alcalá de Henares in Huecas (Toledo) have provided interesting conclusions about the population sequence and socioeconomic transformations in the inner zone of Iberian Peninsula during Neolithic and Chalcolithic periods. Burial mounds, artificial caves and spectaculars archaeological materials have been recupered in succesive seasons of excavation. The construction of a collector and a puryfing plant for the village of Huecas allowed the intensification of the investigations and the drawing of several pictures to present some relevant archaeological data. This paper shows the 3D interpretation of some archaeological data from Huecas.</p>