Differential beta-arrestin binding of AT1 and AT2 angiotensin receptors

Agonist stimulation of G protein-coupled receptors causes receptor activation, phosphorylation, beta-arrestin binding and receptor internalization. Angiotensin II (AngII) causes rapid internalization of the AT1 receptors, whereas AngII-bound AT2 receptors do not internalize. Although the activation of the rat AT1A receptor with AngII causes translocation of beta-arrestin2 to the receptor, no association of this molecule with the AT2 receptor can be detected after AngII treatment with confocal microscopy or bioluminescence resonance energy transfer. These data demonstrate that the two subtypes of angiotensin receptors have different mechanisms of regulation.     

A subset of chemosensory genes differs between two populations of a specialized leaf beetle after host plant shift

Due to its fundamental role in shaping host selection behavior, we have analyzed the chemosensory repertoire of Chrysomela lapponica. This specialized leaf beetle evolved distinct populations which shifted from the ancestral host plant, willow (Salix sp., Salicaceae), to birch (Betula rotundifolia, Betulaceae). We identified 114 chemosensory candidate genes in adult C. lapponica: 41 olfactory receptors (ORs), eight gustatory receptors, 17 ionotropic receptors, four sensory neuron membrane proteins, 32 odorant binding proteins (OBPs), and 12 chemosensory proteins (CSP) by RNA‐seq. Differential expression analyses in the antennae revealed significant upregulation of one minus‐C OBP (ClapOBP27) and one CSP (ClapCSP12) in the willow feeders. In contrast, one OR (ClapOR17), four minus‐C OBPs (ClapOBP02, 07, 13, 20), and one plus‐C OBP (ClapOBP32) were significantly upregulated in birch feeders. The differential expression pattern in the legs was more complex. To narrow down putative ligands acting as cues for host discrimination, the relative abundance and diversity of volatiles of the two host plant species were analyzed. In addition to salicylaldehyde (willow‐specific), both plant species differed mainly in their emission rate of terpenoids such as (E,E)‐α‐farnesene (high in willow) or 4,8‐dimethylnona‐1,3,7‐triene (high in birch). Qualitatively, the volatiles were similar between willow and birch leaves constituting an “olfactory bridge” for the beetles. Subsequent structural modeling of the three most differentially expressed OBPs and docking studies using 22 host volatiles indicated that ligands bind with varying affinity. We suggest that the evolution of particularly minus‐C OBPs and ORs in C. lapponica facilitated its host plant shift via chemosensation of the phytochemicals from birch as novel host plant.     

Molecular characterization influencing metal resistance in the Cupriavidus/Ralstonia genomes

Our environment is stressed with a load of heavy and toxic metals. Microbes, abundant in our environment, are found to adapt well to this metal-stressed condition. A comparative study among five Cupriavidus/Ralstonia genomes can offer a better perception of their evolutionary mechanisms to adapt to these conditions. We have studied codon usage among 1051 genes common to all these organisms and identified 15 optimal codons frequently used in highly expressed genes present within 1051 genes. We found the core genes of Cupriavidus metallidurans CH34 have a different optimal codon choice for arginine, glycine and alanine in comparison with the other four bacteria. We also found that the synonymous codon usage bias within these 1051 core genes is highly correlated with their gene expression. This supports that translational selection drives synonymous codon usage in the core genes of these genomes. Synonymous codon usage is highly conserved in the core genes of these five genomes. The only exception among them is C. metallidurans CH34. This genomewide shift in synonymous codon choice in C. metallidurans CH34 may have taken place due to the insertion of new genes in its genomes facilitating them to survive in heavy metal containing environment and the co-evolution of the other genes in its genome to achieve a balance in gene expression. Structural studies indicated the presence of a longer N-terminal region containing a copper-binding domain in the cupC proteins of C. metallidurans CH3 that helps it to attain higher binding efficacy with copper in comparison with its orthologs.     

番茄复三螺旋基因响应外源激素和非生物胁迫的研究

复三螺旋(double trihelix)基因在植物形态建成和植株抗逆性方面发挥关键作用。该研究以番茄自交品种AC⁺⁺为试验材料,运用生物信息学方法与qRT PCR技术对5个复三螺旋成员(SlGTL1~SlGTL5)在番茄体内不同器官的表达模式、以及基因对激素与非生物胁迫的响应进行表达分析,以探讨番茄复三螺旋基因的功能。结果表明：(1)生物信息学分析显示,番茄中含有5个复三螺旋基因(SlGTL1~SlGTL5);进化树分析表明,番茄复三螺旋基因具有物种特异性。(2)qRT PCR分析显示,番茄SlGTL3基因在根和茎中特异表达,其他4个基因均在果实中较高表达,表明不同番茄复三螺旋基因的表达具有组织特异性。(3)激素诱导表达结果显示,SlGTL1只响应ABA(1种)激素,而SlGTL5基因可响应4种激素,且速度较快。(4)非生物胁迫诱导证实,SlGTL3、SlGTL5基因可响应盐胁迫,SlGTL3~SlGTL5基因可响应极端温度,SlGTL3和SlGTL4基因可响应机械损伤;SlGTL1、SlGTL4和SlGTL5可响应脱水胁迫。研究认为,SlGTL3的功能可能与植株形态建成和非生物胁迫有关,其他4个基因的功能可能与果实的发育有关;推测SlGTL1可能与ABA信号途径有关,SlGTL5快速响应多种激素,可能位于信息传递的节点,其功能可能与信号传递有关。     

Disentangling the roles of history and local selection in shaping clinal variation of allele frequencies and gene expression in Norway spruce (Picea abies)

Understanding the genetic basis of local adaptation is challenging due to the subtle balance among conflicting evolutionary forces that are involved in its establishment and maintenance. One system with which to tease apart these difficulties is clines in adaptive characters. Here we analyzed genetic and phenotypic variation in bud set, a highly heritable and adaptive trait, among 18 populations of Norway spruce (Picea abies), arrayed along a latitudinal gradient ranging from 47°N to 68°N. We confirmed that variation in bud set is strongly clinal, using a subset of five populations. Genotypes for 137 single-nucleotide polymorphisms (SNPs) chosen from 18 candidate genes putatively affecting bud set and 308 control SNPs chosen from 264 random genes were analyzed for patterns of genetic structure and correlation to environment. Population genetic structure was low (F(ST) = 0.05), but latitudinal patterns were apparent among Scandinavian populations. Hence, part of the observed clinal variation should be attributable to population demography. Conditional on patterns of genetic structure, there was enrichment of SNPs within candidate genes for correlations with latitude. Twenty-nine SNPs were also outliers with respect to F(ST). The enrichment for clinal variation at SNPs within candidate genes (i.e., SNPs in PaGI, PaPhyP, PaPhyN, PaPRR7, and PaFTL2) indicated that local selection in the 18 populations, and/or selection in the ancestral populations from which they were recently derived, shaped the observed cline. Validation of these genes using expression studies also revealed that PaFTL2 expression is significantly associated with latitude, thereby confirming the central role played by this gene in the control of phenology in plants.     

GENOME‐WIDE INVESTIGATION OF REPRODUCTIVE ISOLATION IN EXPERIMENTAL LINEAGES AND NATURAL SPECIES OF NEUROSPORA: IDENTIFYING CANDIDATE REGIONS BY MICROARRAY‐BASED GENOTYPING AND MAPPING

Inherent incompatibilities between genetic components from genomes of different species may cause intrinsic reproductive isolation. In evolution experiments designed to instigate speciation in laboratory populations of the filamentous fungus Neurospora, we previously discovered a pair of incompatibility loci (dfe and dma) that interact negatively to cause severe defects in sexual reproduction. Here we show that the dfe‐dma incompatibility also is a significant cause of genetic isolation between two naturally occurring species of Neurospora (N. crassa and N. intermedia). The strong incompatibility interaction has a simple genetic basis (two biallelic loci) and antagonistic epistasis occurs between heterospecific alleles only, consistent with the Dobzhansky–Muller model of genic incompatibility. We developed microarray‐based, restriction‐site associated DNA (RAD) markers that identified ～1500 polymorphisms between the genomes of the two species, and constructed the first interspecific physical map of Neurospora. With this new mapping resource, the approximate genomic locations of the incompatibility loci were determined using three different approaches: genome scanning, bulk‐segregant analyses, and introgression. These population, quantitative, and classical genetics methods concordantly identified two candidate regions, narrowing the search for each incompatibility locus to only ～2% of the nuclear genome. This study demonstrates how advances in high‐throughput, genome‐wide genotyping can be applied to mapping reproductive isolation genes and speciation research.