Soil biota and exotic plant invasion

Invasive plants are an economic problem and a threat to the conservation of natural systems. Escape from natural enemies might contribute to successful invasion, with most work emphasizing the role of insect herbivores; however, microbial pathogens are attracting increased attention. Soil biota in some invaded ecosystems may promote 'exotic' invasion, and plant-soil feedback processes are also important. Thus, relatively rare species native to North America consistently demonstrate negative feedbacks with soil microbes that promote biological diversity, whereas abundant exotic and native species demonstrate positive feedbacks that reduce biological diversity. Here we report that soil microbes from the home range of the invasive exotic plant Centaurea maculosa L. have stronger inhibitory effects on its growth than soil microbes from where the weed has invaded in North America. Centaurea and soil microbes participate in different plant-soil feedback processes at home compared with outside Centaurea's home range. In native European soils, Centaurea cultivates soil biota with increasingly negative effects on the weed's growth, possibly leading to its control. But in soils from North America, Centaurea cultivates soil biota with increasingly positive effects on itself, which may contribute to the success of this exotic species in North America.     

GC/MS法追踪摇头丸杂质体系

本文运用GS/MS的总离子流法,选择离子法,对南京地区常见的几种摇头丸进行全面分析,找出与合成途径相关的痕量杂质,根据杂质情况初步确定其合成途径.     

Strain-resolved community proteomics reveals recombining genomes of acidophilic bacteria

Microbes comprise the majority of extant organisms, yet much remains to be learned about the nature and driving forces of microbial diversification. Our understanding of how microorganisms adapt and evolve can be advanced by genome-wide documentation of the patterns of genetic exchange, particularly if analyses target coexisting members of natural communities. Here we use community genomic data sets to identify, with strain specificity, expressed proteins from the dominant member of a genomically uncharacterized, natural, acidophilic biofilm. Proteomics results reveal a genome shaped by recombination involving chromosomal regions of tens to hundreds of kilobases long that are derived from two closely related bacterial populations. Inter-population genetic exchange was confirmed by multilocus sequence typing of isolates and of uncultivated natural consortia. The findings suggest that exchange of large blocks of gene variants is crucial for the adaptation to specific ecological niches within the very acidic, metal-rich environment. Mass-spectrometry-based discrimination of expressed protein products that differ by as little as a single amino acid enables us to distinguish the behaviour of closely related coexisting organisms. This is important, given that microorganisms grouped together as a single species may have quite distinct roles in natural systems and their interactions might be key to ecosystem optimization. Because proteomic data simultaneously convey information about genome type and activity, strain-resolved community proteomics is an important complement to cultivation-independent genomic (metagenomic) analysis of microorganisms in the natural environment.     

ATM controls meiotic double-strand-break formation

In many organisms, developmentally programmed double-strand breaks (DSBs) formed by the SPO11 transesterase initiate meiotic recombination, which promotes pairing and segregation of homologous chromosomes. Because every chromosome must receive a minimum number of DSBs, attention has focused on factors that support DSB formation. However, improperly repaired DSBs can cause meiotic arrest or mutation; thus, having too many DSBs is probably as deleterious as having too few. Only a small fraction of SPO11 protein ever makes a DSB in yeast or mouse and SPO11 and its accessory factors remain abundant long after most DSB formation ceases, implying the existence of mechanisms that restrain SPO11 activity to limit DSB numbers. Here we report that the number of meiotic DSBs in mouse is controlled by ATM, a kinase activated by DNA damage to trigger checkpoint signalling and promote DSB repair. Levels of SPO11-oligonucleotide complexes, by-products of meiotic DSB formation, are elevated at least tenfold in spermatocytes lacking ATM. Moreover, Atm mutation renders SPO11-oligonucleotide levels sensitive to genetic manipulations that modulate SPO11 protein levels. We propose that ATM restrains SPO11 via a negative feedback loop in which kinase activation by DSBs suppresses further DSB formation. Our findings explain previously puzzling phenotypes of Atm-null mice and provide a molecular basis for the gonadal dysgenesis observed in ataxia telangiectasia, the human syndrome caused by ATM deficiency.     

MARCKS is an actin filament crosslinking protein regulated by protein kinase C and calcium-calmodulin.

AGONISTS that stimulate protein kinase C (PKC) induce profound changes in cell morphology correlating with the reorganization of submembranous actin, but no direct connection between PKC and actin assembly has been identified. The myristoylated, alanine-rich C kinase substrate (MARCKS) binds calmodulin and is a predominant, specific substrate of PKC which is phosphorylated during macrophage and neutrophil activation , growth factor-dependent mitogenesis and neurosecretion; it is redistributed from plasma membrane to cytoplasm when phosphorylated and is involved in leukocyte motility. Here we report that MARCKS is a filamentous (F) actin crosslinking protein, with activity that is inhibited by PKC-mediated phosphorylation and by binding to calcium-calmodulin. MARCKS may be a regulated crossbridge between actin and the plasma membrane, and modulation of the actin crosslinking activity of the MARCKS protein by calmodulin and phosphorylation represents a potential convergence of the calcium-calmodulin and PKC signal transduction pathways in the regulation of the actin cytoskeleton.