Distinct physiological and metabolic reprogramming by highbush blueberry (Vaccinium corymbosum) cultivars revealed during long‐term UV‐B radiation

Despite the Montreal protocol and the eventual recovery of the ozone layer over Antarctica, there are still concerns about increased levels of ultraviolet‐B (UV‐B) radiation in the Southern Hemisphere. UV‐B induces physiological, biochemical and morphological stress responses in plants, which are species‐specific and different even for closely related cultivars. In woody plant species, understanding of long‐term mechanisms to cope with UV‐B‐induced stress is limited. Therefore, a greenhouse UV‐B daily course simulation was performed for 21 days with two blueberry cultivars (Legacy and Bluegold) under UV‐B_BE irradiance doses of 0, 0.07 and 0.19 W m^?2. Morphological changes, photosynthetic performance, antioxidants, lipid peroxidation and metabolic features were evaluated. We found that both cultivars behaved differently under UV‐B exposure, with Legacy being a UV‐B‐resistant cultivar. Interestingly, Legacy used a combined strategy: initially, in the first week of exposure its photoprotective compounds increased, coping with the intake of UV‐B radiation (avoidance strategy), and then, increasing its antioxidant capacity. These strategies proved to be UV‐B radiation dose dependent. The avoidance strategy is triggered early under high UV‐B radiation in Legacy. Moreover, the rapid metabolic reprogramming capacity of this cultivar, in contrast to Bluegold, seems to be the most relevant contribution to its UV‐B stress‐coping strategy.     

Nanomaterial enabled sensors for environmental contaminants

The need and desire to understand the environment, especially the quality of one’s local water and air, has continued to expand with the emergence of the digital age. The bottleneck in understanding the environment has switched from being able to store all of the data collected to collecting enough data on a broad range of contaminants of environmental concern. Nanomaterial enabled sensors represent a suite of technologies developed over the last 15 years for the highly specific and sensitive detection of environmental contaminants. With the promise of facile, low cost, field-deployable technology, the ability to quantitatively understand nature in a systematic way will soon be a reality. In this review, we first introduce nanosensor design before exploring the application of nanosensors for the detection of three classes of environmental contaminants: pesticides, heavy metals, and pathogens.     

Elevated SNAP-25 is associated with fatty acid-induced impairment of mouse islet function

The role of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in insulin secretion following chronic exposure to non-esterified fatty acids (NEFAs) has not been extensively investigated. Here, we show that synaptosome-associated protein of 25 kDa (SNAP-25) levels were predominantly elevated in the soluble fraction of mouse islets exposed to palmitate. This coincided with an impairment of insulin secretion to glucose and non-glucose secretagogues, consistent with a defect at a distal regulatory step in exocytosis. Removal of palmitate from the media restored both SNAP-25 protein levels and insulin secretion to control levels. We conclude that increased expression of SNAP-25 is associated with NEFA-induced impairment of insulin secretion in mouse islets.     

Human genetic disease caused by de novo mitochondrial-nuclear DNA transfer

Transfer of nucleic acid from cytoplasmic organelles to the nuclear genome is a well-established mechanism of evolutionary change in eukaryotes. Such transfers have occurred throughout evolution, but so far, none has been shown unequivocally to occur de novo to cause a heritable human disease. We have characterized a patient with a de novo nucleic acid transfer from the mitochondrial to the nuclear genome, a transfer that is responsible for a sporadic case of Pallister-Hall syndrome, a condition usually inherited in an autosomal dominant fashion. This mutation, a 72-bp insertion into exon 14 of the GLI3 gene, creates a premature stop codon and predicts a truncated protein product. Both the mechanism and the cause of the mitochondrial-nuclear transfer are unknown. Although the conception of this patient was temporally and geographically associated with high-level radioactive contamination following the Chernobyl accident, this case cannot, on its own, be used to establish a causal relationship between radiation exposure and this rare type of mutation. Thus, for the time being, it must be considered as an intriguing coincidence. Nevertheless, these data serve to demonstrate that de novo mitochondrial-nuclear transfer of nucleic acid is a novel mechanism of human inherited disease.     

Sex pheromone evolution is associated with differential regulation of the same desaturase gene in two genera of leafroller moths

Chemical signals are prevalent in sexual communication systems. Mate recognition has been extensively studied within the Lepidoptera, where the production and recognition of species-specific sex pheromone signals are typically the defining character. While the specific blend of compounds that makes up the sex pheromones of many species has been characterized, the molecular mechanisms underpinning the evolution of pheromone-based mate recognition systems remain largely unknown. We have focused on two sets of sibling species within the leafroller moth genera Ctenopseustis and Planotortrix that have rapidly evolved the use of distinct sex pheromone blends. The compounds within these blends differ almost exclusively in the relative position of double bonds that are introduced by desaturase enzymes. Of the six desaturase orthologs isolated from all four species, functional analyses in yeast and gene expression in pheromone glands implicate three in pheromone biosynthesis, two Δ9-desaturases, and a Δ10-desaturase, while the remaining three desaturases include a Δ6-desaturase, a terminal desaturase, and a non-functional desaturase. Comparative quantitative real-time PCR reveals that the Δ10-desaturase is differentially expressed in the pheromone glands of the two sets of sibling species, consistent with differences in the pheromone blend in both species pairs. In the pheromone glands of species that utilize (Z)-8-tetradecenyl acetate as sex pheromone component (Ctenopseustis obliquana and Planotortrix octo), the expression levels of the Δ10-desaturase are significantly higher than in the pheromone glands of their respective sibling species (C. herana and P. excessana). Our results demonstrate that interspecific sex pheromone differences are associated with differential regulation of the same desaturase gene in two genera of moths. We suggest that differential gene regulation among members of a multigene family may be an important mechanism of molecular innovation in sex pheromone evolution and speciation.     

The nuclear genome of the phytoseiid <Emphasis Type="Italic">Metaseiulus occidentalis</Emphasis> (Acari: Phytoseiidae) is among the smallest known in arthropods

The genome size of the phytoseiid Metaseiulus (=Typhlodromus or Galendromus) occidentalis (Nesbitt) needs to be estimated before the whole nuclear genome can be sequenced. Two different procedures were used to estimate the genome size of M. occidentalis; (1) flow cytometry (Marescalchi et al. in Genome 33:789–793, 1990) and (2) quantitative real-time PCR (qRT-PCR) (Wilhelm et al. in Nucleic Acids Res 31:e56, 2003). Fluorescence intensity of propidium iodide-stained nuclei of M. occidentalis was measured by flow cytometry using females, males, and eggs. Only the eggs yielded peaks, which ranged in size from 35 to 160 Mb, with a tall peak of 140 Mb in 1-day-old eggs and 65 Mb in 2-day-old eggs, respectively. However, the peaks are broad and do not provide an accurate estimate. The qRT-PCR procedure required single-copy nuclear gene sequences from this phytoseiid. This was accomplished by designing degenerate primers, amplifying the Actin and EF1α sequences from M. occidentalis, and then designing M. occidentalis-specific primers that amplified a unique sequence. The standard qRT-PCR protocol was inefficient and amplification failed frequently, so we developed a high-fidelity qRT-PCR protocol, which utilizes a mix of two DNA polymerases (Taq and a proof-reading Tgo or ACCUZYME) to consistently amplify sequences. This allowed us to estimate the nuclear genome size of M. occidentalis as 88–90 ± 5 Mb. When compared to other arthropod genomes, this appears to be very small.     

Regulation of alternative splicing by the ATP-dependent DEAD-box RNA helicase p72

Although a number of ATP-dependent RNA helicases are important for constitutive RNA splicing, no helicases have been implicated in alternative RNA splicing. Here, we show that the abundant DEAD-box RNA helicase p72, but not its close relative p68, affects the splicing of alternative exons containing AC-rich exon enhancer elements. The effect of p72 was tested by using mini-genes that undergo different types of alternative splicing. When the concentration of p72 was increased in transient transfections, the inclusion of enhancer-containing CD44 alternative exons v4 and v5 increased using a mini-gene that contained these exons and their flanking introns inserted into a beta-globin gene. Other types of alternative splicing were not impacted by altering p72 concentrations. Mutation of the p72 helicase ATP-binding site or deletion of the carboxy-terminal region of the protein reduced the ability of the transfected protein to affect CD44 variable exon splicing. Use of in vitro extracts overexpressing p72 indicated that p72 becomes associated with complexes containing precursor RNA. Helicases have been implicated both in altering RNA-RNA interactions and in remodeling RNA-protein complexes. CD44 exon v4 contains a potential internal secondary structure element that base pairs the 5' splice site with a region inside the exon located between enhancer elements. Mutations that destroyed this complementarity modestly increased inclusion in the absence of p72 but still responded to increasing p72 concentration like the wild-type exon, suggesting that p72 might have effects on protein-RNA interactions. In agreement with this hypothesis, p72 was not able to restore the inclusion of an exon mutated for its major enhancer element. Our results suggest that RNA helicases may be important alternative splicing regulatory factors.