Decatenation checkpoint‐defective melanomas are dependent on PI3K for survival

Melanoma cell lines are commonly defective for the G2‐phase cell cycle checkpoint that responds to incomplete catenation of the replicated chromosomes. Here, we demonstrate that melanomas defective for this checkpoint response are less sensitive to genotoxic stress, suggesting that the defective cell lines compensated for the checkpoint loss by increasing their ability to cope with DNA damage. We performed an siRNA kinome screen to identify kinases responsible and identified PI3K pathway components. Checkpoint‐defective cell lines were three‐fold more sensitive to small molecule inhibitors of PI3K. The PI3K inhibitor PF‐05212384 promoted apoptosis in the checkpoint‐defective lines, and the increased sensitivity to PI3K inhibition correlated with increased levels of activated Akt. This work demonstrates that increased PI3K pathway activation is a necessary adaption for the continued viability of melanomas with a defective decatenation checkpoint.     

Golden bananas in the field: elevated fruit pro‐vitamin A from the expression of a single banana transgene

Vitamin A deficiency remains one of the world's major public health problems despite food fortification and supplements strategies. Biofortification of staple crops with enhanced levels of pro‐vitamin A (PVA) offers a sustainable alternative strategy to both food fortification and supplementation. As a proof of concept, PVA‐biofortified transgenic Cavendish bananas were generated and field trialed in Australia with the aim of achieving a target level of 20 μg/g of dry weight (dw) β‐carotene equivalent (β‐CE) in the fruit. Expression of a Fe'i banana‐derived phytoene synthase 2a (MtPsy2a) gene resulted in the generation of lines with PVA levels exceeding the target level with one line reaching 55 μg/g dw β‐CE . Expression of the maize phytoene synthase 1 (ZmPsy1) gene, used to develop ‘Golden Rice 2’, also resulted in increased fruit PVA levels although many lines displayed undesirable phenotypes. Constitutive expression of either transgene with the maize polyubiquitin promoter increased PVA accumulation from the earliest stage of fruit development. In contrast, PVA accumulation was restricted to the late stages of fruit development when either the banana 1‐aminocyclopropane‐1‐carboxylate oxidase or the expansin 1 promoters were used to drive the same transgenes. Wild‐type plants with the longest fruit development time had also the highest fruit PVA concentrations. The results from this study suggest that early activation of the rate‐limiting enzyme in the carotenoid biosynthetic pathway and extended fruit maturation time are essential factors to achieve optimal PVA concentrations in banana fruit.     

Plant Conservation in the Caribbean Island Biodiversity Hotspot

While the Caribbean is a recognized “biodiversity hotspot”, plant conservation has not received adequate attention; particularly, given the high levels of endemism in many plant groups. Besides establishing protected areas, there needs to be a sustained effort to study the taxonomy, systematics and ecology of the flora. Recent phylogenetic studies have shown high levels of endemism and conservation studies indicate a large propotion of the flora is threatened with extinction. Eight recommendations are given for plant conservation in the region.     

The yeast Apq12 protein affects nucleocytoplasmic mRNA transport

An important step in mRNA biogenesis is the export of mRNA from the nucleus to the cytoplasm. In this work, we provide evidence that the previously uncharacterized gene APQ12 functions in nucleocytoplasmic mRNA transport in Saccharomyces cerevisiae. First, apq12delta strains manifest 3' hyperadenylated mRNA similar to other previously characterized RNA export mutants. Second, bulk poly(A)+ RNA is retained in the nucleus in apq12delta cells. Third, an Apq12p-GFP chimeric protein is localized to the nuclear periphery. Fourth, mRNA in apq12delta cells is stabilized, consistent with a defect in the rate of nuclear export. Interestingly, apq12delta mutants are severely compromised for growth and display atypical cell morphology. Because this aberrant cell morphology is not seen with other viable export mutants, Apq12p must have either an additional cellular function, or preferentially impinge on the export of mRNAs regulating cell growth. Together, these findings support a role for APQ12 in nucleocytoplasmic transport of mRNA.     

An essential role for the proximal but not the distal cytoplasmic tail of glycoprotein M in murid herpesvirus 4 infection

Murid herpesvirus-4 (MuHV-4) provides a tractable model with which to define common, conserved features of gamma-herpesvirus biology. The multi-membrane spanning glycoprotein M (gM) is one of only 4 glycoproteins that are essential for MuHV-4 lytic replication. gM binds to gN and is thought to function mainly secondary envelopment and virion egress, for which several predicted trafficking motifs in its C-terminal cytoplasmic tail could be important. We tested the contribution of the gM cytoplasmic tail to MuHV-4 lytic replication by making recombinant viruses with varying C-terminal deletions. Removing an acidic cluster and a distal YXXPhi motif altered the capsid distribution somewhat in infected cells but had little effect on virus replication, either in vitro or in vivo. In contrast, removing a proximal YXXPhi motif as well completely prevented productive replication. gM was still expressed, but unlike its longer forms showed only limited colocalization with co-transfected gN, and in the context of whole virus appeared to support gN expression less well. We conclude that some elements of the gM cytoplasmic tail are dispensible for MuHV-4 replication, but the tail as a whole is not.     

Incidence of Wolbachia in aquatic insects

Wolbachia is a genus of intracellular bacteria typically found within the reproductive systems of insects that manipulates those systems of their hosts. While current estimates of Wolbachia incidence suggest that it infects approximately half of all arthropod species, these estimates are based almost entirely on terrestrial insects. No systematic survey of Wolbachia in aquatic insects has been performed. To estimate Wolbachia incidence among aquatic insect species, we combined field‐collected samples from the Missouri River (251 samples from 58 species) with a global database from previously published surveys. The final database contained 5,598 samples of 2,687 total species (228 aquatic and 2,459 terrestrial). We estimate that 52% (95% CrIs: 44%–60%) of aquatic insect species carry Wolbachia, compared to 60% (58%–63%) of terrestrial insects. Among aquatic insects, infected orders included Odonata, Coleoptera, Trichoptera, Ephemeroptera, Diptera, Hemiptera, and Plecoptera. Incidence was highest within aquatic Diptera and Hemiptera (69%), Odonata (50%), and Coleoptera (53%), and was lowest within Ephemeroptera (13%). These results indicate that Wolbachia is common among aquatic insects, but incidence varies widely across orders and is especially uncertain in those orders with low sample sizes such as Ephemeroptera, Plecoptera, and Trichoptera.     

Salvaging Pyrococcus furiosus Protein Targets at SECSG

Proteins derived from the coding regions of Pyrococcus furiosus are targets for three-dimensional X-ray and NMR structure determination by the Southeast Collaboratory for Structural Genomics (SECSG). Of the 2200 open reading frames (ORFs) in this organism, 220 protein targets were cloned and expressed in a high-throughput (HT) recombinant system for crystallographic studies. However, only 96 of the expressed proteins could be crystallized and, of these, only 15 have led to structures. To address this issue, SECSG has recently developed a two-tier approach to protein production and crystallization. In this approach, tier-1 efforts are focused on producing protein for new Pfu(italics?) targets using a high-throughput approach. Tier-2 protein production efforts support tier-1 activities by (1) producing additional protein for further crystallization trials, (2) producing modified protein (further purification, methylation, tag removal, selenium labeling, etc) as required and (3) serving as a salvaging pathway for failed tier-1 proteins. In a recent study using this two-tiered approach, nine structures were determined from a set of 50 Pfu proteins, which failed to produce crystals suitable for X-ray diffraction analysis. These results validate this approach and suggest that it has application to other HT crystal structure determination applications.     

Molecular mapping of QTLs for resistance to Gibberella ear rot, in corn, caused by Fusarium graminearum.

Gibberella ear rot, caused by the fungus Fusarium graminearum Schwabe, is a serious disease of corn (Zea mays) grown in northern climates. Infected corn is lower yielding and contains toxins that are dangerous to livestock and humans. Resistance to ear rot in corn is quantitative, specific to the mode of fungal entry (silk channels or kernel wounds), and highly influenced by the environment. Evaluations of ear rot resistance are complex and subjective; and they need to be repeated over several years. All of these factors have hampered attempts to develop F. graminearum resistant corn varieties. The aim of this study was to identify molecular markers linked to the genes for resistance to Gibberella ear rot. A recombinant inbred (RI) population, produced from a cross between a Gibberella ear rot resistant line (CO387) and a susceptible line (CG62), was field-inoculated and scored for Gibberella ear rot symptoms in the F4, F6, and F7 generations. The distributions of disease scores were continuous, indicating that resistance is probably conditioned by multiple loci. A molecular linkage map, based on segregation in the F5 RI population, contained 162 markers distributed over 10 linkage groups and had a total length of 2237 cM with an average distance between markers of 13.8 cM. Composite interval mapping identified 11 quantitative trait loci (QTLs) for Gibberella ear rot resistance following silk inoculation and 18 QTLs following kernel inoculation in 4 environments that accounted for 6.7%-35% of the total phenotypic variation. Only 2 QTLs (on linkage group 7) were detected in more than 1 test for silk resistance, and only 1 QTL (on linkage group 5) was detected in more than 1 test for kernel resistance, confirming the strong influence of the environment on these traits. The majority of the favorable alleles were derived from the resistant parent (CO387). The germplasm and markers for QTLs with significant phenotypic effects may be useful for marker-assisted selection to incorporate Gibberella ear rot resistance into commercial corn cultivars.     

Comparing Effects of Nutrients on Algal Biomass in Streams in Two Regions with Different Disturbance Regimes and with Applications for Developing Nutrient Criteria

Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams with repeated sampling at each site over a 2−month period. Many measures of algal biomass and nutrient availability were positively correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in either region. Chl a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations. Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic algal biomass occurred in nutrient concentrations between 10 and 30 μg TP l⁻¹ and between 400 and 1000 μg TN l⁻¹.