Low genetic diversity and population connectivity fuel vulnerability to climate change for the Tertiary relict pine Pinus bungeana

Endemic species are important components of regional biodiversity and hold the key to understanding local adaptation and evolutionary processes that shape species distributions. This study investigated the biogeographic history of a relict conifer Pinus bungeana Zucc. ex Endl. confined to central China. We examined genetic diversity in P. bungeana using genotyping-by-sequencing and chloroplast and mitochondrial DNA markers. We performed spatial and temporal inference of recent genetic and demographic changes, and dissected the impacts of geography and environmental gradients on population differentiation. We then projected P. bungeana's risk of decline under future climates. We found extremely low nucleotide diversity (average π 0.0014), and strong population structure (global F_ST 0.234) even at regional scales, reflecting long-term isolation in small populations. The species experienced severe bottlenecks in the early Pliocene and continued to decline in the Pleistocene in the western distribution, whereas the east expanded recently. Local adaptation played a small (8%) but significant role in population diversity. Low genetic diversity in fragmented populations makes the species highly vulnerable to climate change, particularly in marginal and relict populations. We suggest that conservation efforts should focus on enhancing gene pool and population growth through assisted migration within each genetic cluster to reduce the risk of further genetic drift and extinction.     

Systematics of Mukdenia and Oresitrophe (Saxifragaceae): Insights from genome skimming data

Oresitrophe and Mukdenia (Saxifragaceae) are epilithic sister genera used in traditional Chinese medicine. The taxonomy of Mukdenia, especially of M. acanthifolia, has been controversial. To address this, we produced plastid and mitochondrial data using genome skimming for Mukdenia acanthifolia and Mukdenia rossii, including three individuals of each species. We assembled complete plastomes, mitochondrial CDS and nuclear ribosomal ETS/ITS sequences using these data. Comparative analysis shows that the plastomes of Mukdenia and Oresitrophe are relatively conservative in terms of genome size, structure, gene content, RNA editing sites and codon usage. Five plastid regions that represent hotspots of change (trnH-psbA, psbC-trnS, trnM-atpE, petA-psbJ and ccsA-ndhD) are identified within Mukdenia, and six regions (trnH-psbA, petN-psbM, trnM-atpE, rps16-trnQ, ycf1 and ndhF) contain a higher number of species-specific parsimony-informative sites that may serve as potential DNA barcodes for species identification. To infer phylogenetic relationships between Mukdenia and Oresitrophe, we combined our data with published data based on three different datasets. The monophyly of each species (Oresitrophe rupifraga, M. acanthifolia and M. rossii) and the inferred topology ((M. rossii, M. acanthifolia), O. rupifraga) are well supported in trees reconstructed using the complete plastome sequences, but M. acanthifolia and M. rossii did not form a separate clade in the trees based on ETS + ITS data, while the mitochondrial CDS trees are not well-resolved. We found low recovery of genes in the Angiosperms353 target enrichment panel from our unenriched genome skimming data. Hybridization or incomplete lineage sorting may be the cause of discordance between trees reconstructed from organellar and nuclear data. Considering its morphological distinctiveness and our molecular phylogenetic results, we strongly recommend that M. acanthifolia be treated as a distinct species.     

First chemical synthesis of a scorpion alpha-toxin affecting sodium channels: the Aah I toxin of Androctonus australis hector.

Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.     

Ecdysteroids During Embryogenesis in Locusta migratoria

SYNOPSIS. Ovaries of Locusta migratoria synthesize large amountsof ecdysteroids at the end of oöcyte maturation. The predominantecdysteroids in mature ovaries are conjugated 2-deoxyecdysone(100 µM) and conjugated ecdysone (50 µM) which outnumberthe corresponding free compounds by 50–100 fold. Thesevarious ecdysteroids persist during ovulation and are recoveredfrom newly-laid eggs. The conjugated maternal ecdysteroids aregradually metabolized as embryonic development proceeds; theyhave disappeared as such on day 6 after oviposition, that isafter blastokinesis and shortly after dorsal closure. Concomitantlyto this metabolism of the maternal conjugated ecdysteroids,other ecdysteroid conjugates appear in the eggs which have differentchromatographic behaviors and some of which are conjugates ofecdysone metabolites formed by the embryo. The data availableso far are compatible with the hypothesis that the maternalconjugates are hydrolysed to free 2-deoxyecdysone and ecdysoneby the embryo during early stages of development and subsequentlyconjugated to inactivation compounds. During the later stagesof embryonic development however, a de novo synthesis of ecdysoneis probable, the maternal conjugates having been metabolizedduring the earlier stages.     

Isoperoxidases in Epidermal Layers of Tobacco and Changes during Organ Formation in vitro

The content and pattern of soluble isoperoxidases were determined in epidermal explants taken from different internodes of tobacco plants in the vegetative and floral states. There were qualitative and quantitative differences in the isoperoxidases, with a decrease in content and fewer bands being observed acropetally, i.e., in going from the base of the stem towards the apex. Epidermal explants from floral branches were grown in in vitro culture, with various media moditications, to form de novo floral or vegetative buds, roots or callus. Changes in soluble isoperoxidases were followed electrophoretically in relation to these varying morphogenetic pathways. In each of them, the number of bands increased on both the anodic and cathodic sides with time in culture. Compared to each other these four morphogenetic programmes were different in their peroxidase zymograms, mainly through varying kinetics in the development of activity of the isoenzymes. The changes observed during root and vegetative bud formation agree with previously published data, and the changes during floral bud formation agree with those observed in vivo.     

ZAKβ antagonizes and ameliorates the cardiac hypertrophic and apoptotic effects induced by ZAKα

ZAK (sterile alpha motif and leucine zipper containing kinase AZK), a serine/threonine kinase with multiple biochemical functions, has been associated with various cell processes, including cell proliferation, cell differentiation, and cardiac hypertrophy. In our previous reports, we found that the activation of ZAKα signaling was critical for cardiac hypertrophy. In this study, we show that the expression of ZAKα activated apoptosis through both a FAS‐dependent pathway and a mitochondria‐dependent pathway by subsequently inducing caspase‐3. ZAKβ, an isoform of ZAKα, is dramatically expressed during cardiac hypertrophy and apoptosis. The interaction between ZAKα and ZAKβ was demonstrated here using immunoprecipitation. The results show that ZAKβ has the ability to diminish the expression level of ZAKα. These findings reveal an inherent regulatory role of ZAKβ to antagonize ZAKα and to subsequently downregulate the cardiac hypertrophy and apoptosis induced by ZAKα.