Culture Independent Diversity of Bacterial Communities Indigenous to Lower Altitude at Laohugou Glacial Environment

Abstract

High-throughput sequencing approach of the 16S rRNA gene was employed to evaluate the bacterial diversity inhabit in melted water, snow, soil, and rocks samples at the lower altitudes of the Laohugou glacial environment. Bioinformatics tools were used to process millions of Illumina reads for alpha and beta diversities of bacterial communities. The diversity indices such as Chao, Shannon, and Simpson were different in the collected samples and solid samples (soil and rocks) showed higher taxon richness and evenness. Taxonomic diversity was unexpectedly higher and the major portion of sequences was assigned to Proteobacteria, Actinobacteria, and Acidobacteria. Higher variation in community structure was reported at the class level and Alphaproteobacteria was dominant. The solid niches were occupied by a higher number of phyla compared with liquid. The physicochemical variables acted as spatial gradients and associated with the bacterial structural communities of the glacial ecosystem. Findings showed that both Proteobacteria and Actinobacteria in solid samples influenced the bacterial community structure in downstream liquid samples. Interestingly, the metagenomic biomarkers were higher in liquid samples. This study provides precious datasets to understand the bacterial community in a better way under the influence of spatial, physical and environmental factors.     

Achene morphology of Saussurea species (Asteraceae,Cardueae) in Korea and its systematic implications

Achene size and shape, surface sculpturing, and pericarp and testa wall structure of 23 Korean Saussurea spp. were investigated using scanning electron microscopy (SEM) and light microscopy to evaluate the infrageneric relationships and assess their systematic significance. Achene size categories and thickness of the testa epidermis were distinguished using biometric measurements. Four basic types of surface pattern were observed: (1) lineate; (2) striate; (3) reticulate; and (4) colliculate. Saussurea rorinsanensis was found to have some unique achene characteristics, such as a fusiform achene, uniform pappus, presence of epidermal hairs and tangentially elongated, narrow testa epidermal cells. The characteristic achene features for species were found to be achene size and shape, hilum position, surface sculpture, pappus composition, morphology of the pericarp wall and thickness of the testa epidermis. Based on 16 morphological and achene characters, a cladistic analysis resolved three well‐supported clades, with S. eriophylla as the first‐branching taxon. Saussurea pulchella and S. japonica, both belonging to Saussurea subgenus Theodorea, were distant from each other in the 50% majority rule consensus tree and the character distribution cladogram. This cladistic analysis of achene morphology and anatomy should be regarded as giving us a tentative picture of the phylogenetics of Saussurea, and this study may serve as a reference for future hypotheses and studies on the characterization and classification of Saussurea spp. in Korea.     

Morphological changes and increase of resistance to oxidative stress by overexpression of the <Emphasis Type="Italic">LebZIP2</Emphasis> gene in <Emphasis Type="Italic">Nicotiana benthamiana</Emphasis>

The tomato bZIP2-encoding gene was inserted into the Nicotiana benthamiana genome using Agrobacterium-mediated transformation to characterize resistance to oxidative stress and two herbicides, glyphosate and paraquat. We produced transgenic tobacco plants using the LebZIP2 gene, which were then utilized to examine salt stress and herbicide resistance through oxidative mechanisms. Transgenic LebZIP2-overexpressing plants were examined using specific primers for selection marker genes (PCR using genomic DNA) and target genes (RT-PCR). Based on microscopic examination, we observed an increase in leaf thickness and cell number in transgenic plants. The electrolyte leakage of leaves suggested that LebZIP2-overexpressing lines were weak tolerant to NaCl stress and resistant to methyl viologen. During our analysis, transgenic lines were exposed to different herbicides. Transgenic plants showed an increased tolerance based on visual injury, as well as an increased biomass. Based on these results, the LebZIP2 gene may be involved in oxidative stress tolerance and cell development in plants.     

Large carbon release legacy from bark beetle outbreaks across Western United States

Warmer conditions over the past two decades have contributed to rapid expansion of bark beetle outbreaks killing millions of trees over a large fraction of western United States (US) forests. These outbreaks reduce plant productivity by killing trees and transfer carbon from live to dead pools where carbon is slowly emitted to the atmosphere via heterotrophic respiration which subsequently feeds back to climate change. Recent studies have begun to examine the local impacts of bark beetle outbreaks in individual stands, but the full regional carbon consequences remain undocumented for the western US. In this study, we quantify the regional carbon impacts of the bark beetle outbreaks taking place in western US forests. The work relies on a combination of postdisturbance forest regrowth trajectories derived from forest inventory data and a process‐based carbon cycle model tracking decomposition, as well as aerial detection survey (ADS) data documenting the regional extent and severity of recent outbreaks. We find that biomass killed by bark beetle attacks across beetle‐affected areas in western US forests from 2000 to 2009 ranges from 5 to 15 Tg C yr^?1 and caused a reduction of net ecosystem productivity (NEP) of about 6.1–9.3 Tg C y^?1 by 2009. Uncertainties result largely from a lack of detailed surveys of the extent and severity of outbreaks, calling out a need for improved characterization across western US forests. The carbon flux legacy of 2000–2009 outbreaks will continue decades into the future (e.g., 2040–2060) as committed emissions from heterotrophic respiration of beetle‐killed biomass are balanced by forest regrowth and accumulation.     

Methyl Jasmonate Increases the Tropane Alkaloid Scopolamine and Reduces Natural Herbivory in Brugmansia suaveolens: Is Scopolamine Responsible for Plant Resistance?

The tropane alkaloid (TA) scopolamine is suggested to protect Brugmansia suaveolens (Solanaceae) against herbivorous insects. To test this prediction in a natural environment, scopolamine was induced by methyl jasmonate (MJ) in potted plants which were left 10?days in the field. MJ-treated plants increased their scopolamine concentration in leaves and herbivory decreased. These findings suggest a cause?Ceffect relationship. However, experiments in laboratory showed that scopolamine affect differently the performance of the specialist larvae of the ithomiine butterfly Placidina euryanassa (C. Felder & R. Felder) and the generalist fall armyworm Spodoptera frugiperda (J. E. Smith): the specialist that sequester this TA from B. suaveolens leaves was not negatively affected, but the generalist was. Therefore, scopolamine probably acts only against insects that are not adapted to TAs. Other compounds that are MJ elicited may also play a role in plant resistance against herbivory by generalist and specialist insects, and deserve future investigations.     

The influence of spin-labeled fluorene compounds on the assembly and toxicity of the aβ peptide

Background

The deposition and oligomerization of amyloid β (Aβ) peptide plays a key role in the pathogenesis of Alzheimer''s disease (AD). Aβ peptide arises from cleavage of the membrane-associated domain of the amyloid precursor protein (APP) by β and γ secretases. Several lines of evidence point to the soluble Aβ oligomer (AβO) as the primary neurotoxic species in the etiology of AD. Recently, we have demonstrated that a class of fluorene molecules specifically disrupts the AβO species.

Methodology/Principal Findings

To achieve a better understanding of the mechanism of action of this disruptive ability, we extend the application of electron paramagnetic resonance (EPR) spectroscopy of site-directed spin labels in the Aβ peptide to investigate the binding and influence of fluorene compounds on AβO structure and dynamics. In addition, we have synthesized a spin-labeled fluorene (SLF) containing a pyrroline nitroxide group that provides both increased cell protection against AβO toxicity and a route to directly observe the binding of the fluorene to the AβO assembly. We also evaluate the ability of fluorenes to target multiple pathological processes involved in the neurodegenerative cascade, such as their ability to block AβO toxicity, scavenge free radicals and diminish the formation of intracellular AβO species.

Conclusions

Fluorene modified with pyrroline nitroxide may be especially useful in counteracting Aβ peptide toxicity, because they posses both antioxidant properties and the ability to disrupt AβO species.     

Identification of a cryptic type III polyketide synthase (1,3,6,8-tetrahydroxynaphthalene synthase) from Streptomyces peucetius ATCC 27952

We identified a 1,134-bp putative type III polyketide synthase from the sequence analysis of Streptomyces peucetius ATCC 27952, named Sp-RppA, which is characterized as 1,3,6,8-tetrahydroxynaphthalene synthase and shares 33% identity with SCO1206 from S. coelicolor A3(2) and 32% identity with RppA from S. griseus. The 1,3,6,8-tetrahydroxynaphthalene synthase is known to catalyze the sequential decarboxylative condensation, intramolecular cyclization, and aromatization of an oligoketide derived from five units of malonyl-CoA to give 1,3,6,8-tetrahydroxynaphthalene, which spontaneously oxidizes to form 2,5,7-trihydroxy-1,4-naphthoquinone (flaviolin). In this study, we report the in vivo expression and in vitro synthesis of flaviolin from purified gene product (Sp-RppA).