Hybrid ‘superswarm’ leads to rapid divergence and establishment of populations during a biological invasion

Understanding the genetic background of invading species can be crucial information clarifying why they become invasive. Intraspecific genetic admixture among lineages separated in the native ranges may promote the rate and extent of an invasion by substantially increasing standing genetic variation. Here, we examined the genetic relationships among threespine stickleback that recently colonized Switzerland. This invasion results from several distinct genetic lineages that colonized multiple locations and have since undergone range expansions, where they coexist and admix in parts of their range. Using 17 microsatellites genotyped for 634 individuals collected from 17 Swiss and two non‐Swiss European sites, we reconstruct the invasion of stickleback and investigate the potential and extent of admixture and hybridization among the colonizing lineages from a population genetic perspective. Specifically, we test for an increase in standing genetic variation in populations where multiple lineages coexist. We find strong evidence of massive hybridization early on, followed by what appears to be recent increased genetic isolation and the formation of several new genetically distinguishable populations, consistent with a hybrid ‘superswarm’. This massive hybridization and population formation event(s) occurred over approximately 140 years and likely fuelled the successful invasion of a diverse range of habitats. The implications are that multiple colonizations coupled with hybridization can lead to the formation of new stable genetic populations potentially kick‐starting speciation and adaptive radiation over a very short timescale.     

Steady-state,Pre-steady-state,and Single-turnover Kinetic Measurement for DNA Glycosylase Activity

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization of OGG1 is undertaken to measure the rates of 8-oxoG excision and product release. When the OGG1 concentration is lower than substrate DNA, time courses of product formation are biphasic; a rapid exponential phase (i.e. burst) of product formation is followed by a linear steady-state phase. The initial burst of product formation corresponds to the concentration of enzyme properly engaged on the substrate, and the burst amplitude depends on the concentration of enzyme. The first-order rate constant of the burst corresponds to the intrinsic rate of 8-oxoG excision and the slower steady-state rate measures the rate of product release (product DNA dissociation rate constant, k_off). Here, we describe steady-state, pre-steady-state, and single-turnover approaches to isolate and measure specific steps during OGG1 catalytic cycling. A fluorescent labeled lesion-containing oligonucleotide and purified OGG1 are used to facilitate precise kinetic measurements. Since low enzyme concentrations are used to make steady-state measurements, manual mixing of reagents and quenching of the reaction can be performed to ascertain the steady-state rate (k_off). Additionally, extrapolation of the steady-state rate to a point on the ordinate at zero time indicates that a burst of product formation occurred during the first turnover (i.e. y-intercept is positive). The first-order rate constant of the exponential burst phase can be measured using a rapid mixing and quenching technique that examines the amount of product formed at short time intervals (<1 sec) before the steady-state phase and corresponds to the rate of 8-oxoG excision (i.e. chemistry). The chemical step can also be measured using a single-turnover approach where catalytic cycling is prevented by saturating substrate DNA with enzyme (E>S). These approaches can measure elementary rate constants that influence the efficiency of removal of a DNA lesion.     

唐菖蒲球茎芽的离体培养及快速繁殖

将带1-2个芽眼的唐菖蒲球茎切块接种到附加1.0mg/LBA的MS基本培养基上可诱导休眠芽萌动、无菌芽转移至附加3.0mg/LBA的培养基上可分化产生丛生芽。丛生芽的继代增殖宜采用附加1.5mg/LBA的培养基生根培养,以MS+NAA 0.1-0.5mg/L或MS+IBA 1.5mg/L效果最佳。试管苗移栽存活率可达50%左右。     

A rapid method for the determination of antibiotic resistance in bacterial pathogens within diseased specimens

A technique was developed, which permitted the rapid determination of antibiotic resistance of bacterial pathogens in diseased material. The method involved use of an antibody-based antigen capturing system, exposure to antibiotic solutions, and thence the determination of viability by reduction of thiazolyl blue.     

富油脂微藻育种技术研究进展

微藻因生长迅速、光合作用效率高、分布范围广和油脂积累能力强等优势,已被认为是生产生物柴油的理想原料。诱变育种可改善野生型微藻生长缓慢、油脂含量低和环境适应能力弱等缺陷,提高了以微藻生产生物柴油的可行性。概述了物理、化学和基因工程三类诱变育种方法的研究现状,介绍了低场核磁共振和荧光激活细胞分选两种富油脂微藻筛选技术以及一种测定诱变藻株致死率的方法,讨论了三种诱变方法的应用前景,供相关研究人员参考。     

重伞灵芝线粒体基因组在灵芝种间鉴定中的应用

线粒体是“动力工厂”,能够进行氧化代谢实现能量的转化,参与三羧酸循环形成ATP。随着分子生物学和生物信息学技术的发展,担子菌灵芝属中已有几种灵芝的线粒体基因组被相继报道,但尚未有对重伞灵芝线粒体基因组的报道。本研究通过对重伞灵芝YX线粒体基因组进行组装注释,比较分析了与其他灵芝属物种的差异,根据差异序列构建分子标记对重伞灵芝菌株快速鉴定。结果显示重伞灵芝线粒体基因组大小为67 340bp的闭合环形结构,含有15个普通蛋白编码基因,28个tRNA基因,以及rRNA的大小亚基基因。共5个基因含有12个内含子,主要为IB型,部分为ID型,包含LAGLIDADG_1 superfamily、GIY-YIG_Cterm superfamily保守结构域。根据重伞灵芝线粒体cox2基因设计的特异性引物扩增结果显示：4株重伞灵芝的cox2基因片段均可准确扩增,且扩增不出其他灵芝物种的cox2基因片段。基于各灵芝菌株线粒体cox2基因序列构建系统进化树,可以将4株重伞灵芝归在同一分支上,并且同源性为98%,与ITS鉴定结果一致。可见,基于线粒体基因cox2特异性引物可以快速地对重伞灵芝进行鉴定,且只需通过观察扩增条带的有无,无需测序,省时省力。     

红花草莓的组织培养与快繁技术研究

以红花草莓叶片为外植体,通过筛选诱导愈伤组织、不定芽及壮苗、生根的培养基,建立一套实用且易推广的红花草莓组培快繁技术体系。结果表明:在愈伤组织的诱导过程中TDZ的诱导效果优于6-BA,TDZ与NAA配合使用效果优于与IBA的组合。6-BA浓度为0.5 mg·L~(-1)时不定芽诱导率高达86.6%。低浓度的6-BA和8 g·L~(-1)的琼脂更有利于壮苗培养,NAA比IBA更有利诱导生根。综上述,最适红花草莓愈伤组织的诱导培养基为MS+1.0 mg·L~(-1)TDZ+0.5 mg·L~(-1)NAA+30 g·L~(-1)蔗糖+7 g·L~(-1)琼脂;最适不定芽分化的培养基为MS+0.5 mg·L~(-1)6-BA+0.1 mg·L~(-1)NAA+30 g·L~(-1)蔗糖+7 g·L~(-1)琼脂;最适壮苗培养基为MS+0.1 mg·L~(-1)6-BA+0.1 mg·L~(-1)NAA+30 g·L~(-1)蔗糖+8g·L~(-1)琼脂;最适生根培养基为MS+0.5mg·L~(-1)NAA+30 g·L~(-1)蔗糖+8 g·L~(-1)琼脂。试管苗移栽生长20 d后,成活率高达93%,且后期草莓苗生长壮健。此体系的建立为优质红花草莓种苗大规模生产提供了科学依据和技术支持。     

桂林小花苣苔离体快速繁殖技术

对抗结核植物桂林小花苣苔(Chiritopsis repanda var. guilinensis)进行离体培养与快速繁殖技术研究。结果表明: 桂林小花苣苔叶片外植体的最适初代诱导培养基为MS+0.5 mg·L^–16-BA+0.05 mg·L^–1IBA, pH8.0; 最适继代增殖培养基为 MS+0.1 mg·L^–16-BA+0.05 mg·L^–1IBA, pH6.0, 繁殖系数7.0/35天; 最适生根培养基为1/2MS+0.2 mg·L^–1NAA, pH6.0, 生根率为93.6%。模拟桂林小花苣苔自然生境, 在春季对生根试管苗进行大棚移栽, 成活率达90%。根据上述快繁技术, 理论上每株试管苗每年可繁殖桂林小花苣苔种苗46万株。     

How Honeybees Defy Gravity with Royal Jelly to Raise Queens

1. Download high-res image (208KB)
2. Download full-size image