Fitness costs of gestation and lactation in wild mammals

Like a number of plants, some mammals commonly produce more progeny than they can afford to rear, terminating investment in some or even all of their offspring once the resources available for breeding are known. Adaptive interpretations of juvenile wastage rely on the argument that the costs of gestation are small compared to those of feeding offspring. Though energetic evidence supports this conclusion, it is unsafe to assume that the relative costs of gestation and lactation to the mother's survival and future reproductive success follow the same pattern because lactation commonly coincides with the period of maximum food availability. Controlling for individual variation, we show that in wild red deer (Cervus elaphus L) any costs of gestation to the mother's subsequent survival and reproductive success are slight compared to those of lactation.     

拟南芥开花时间的分子遗传调控

拟南芥开花主要受四种遗传途径调控,即:光周期途径,春化途径,自主途径和赤霉素途径。各种途径之间通过CO,FLC,FT,SOC1等主效基因的相互作用,最终调节花特异性基因AP1和LFY的表达,从而调控拟南芥的开花时间,其中各种突变体的研究揭示了相关基因的功能。这些主效基因中,CO基因对光周期途径是特异的,FLC基因对开花起抑制作用。其它因素如环境、基因染色质结构的改变、酶等对拟南芥开花时间的影响有待进一步的研究。     

A copia-like transposable element family in Arabidopsis thaliana

The fast generation time, small genome size and extensive genetic map of the crucifer Arabidopsis thaliana have made it the subject of an increasing number of studies in plant molecular genetics. As transposable elements have greatly facilitated genetic analysis in a variety of species, we have attempted to identify an endogenous A. thaliana transposable element. We report here the discovery of a family of such elements, which we refer to as Ta1 elements. Sequence analysis of one such element shows that it is closely related to retrotransposons and integrated retroviral proviruses, being bound by a direct sequence repeat and having an open reading frame with clear sequence similarity to the polyprotein of the Drosophila melanogaster retrotransposon copia. The sequence of an empty target site of a Ta1 element shows that insertion is accompanied by a five-base-pair target-site duplication and that Ta1 has transposed in the period of time since divergence of two races of A. thaliana.     

拟南芥中一个新的constans等位基因及特性

植物开花是由内外信号途径共同调控的,CONSTANS是长日照途径上控制开花的基因.在筛选拟南芥滞绿突变体的过程中筛选到一个晚花突变体,工作名称为fnc25.后来证实为一个新的constans突变体co-9.在长日照条件下该突变体植株高大,叶片呈深绿色,莲座叶数目增多,开花延迟,寿限显著延长;春化处理和外源施加赤霉素对其开花时间几乎没有响应,在短日照条件下开花时间几乎不变.测序发现co-9中CO基因编码区中有10个碱基的缺失导致了CO蛋白C末端92个氨基酸没有被合成,这其中包含一个CCT结构域.CO基因的功能缺失很可能是导致co-9晚花的原因.RT-PCR实验表明co-9中CO直接调控的基因FT的mRNA水平显著下调,而另一个调控的基因SOC1的mRNA水平和野生型相比没有改变.说明CO通过不同的结构域作用于下游目的基因,一个结构域的改变只影响下游一个目的基因的表达,导致co-9的晚花表型.     

拟南芥AHA2基因的生物信息学分析

利用生物信息学方法对拟南芥AHA2(H+-ATPase 2)基因编码蛋白的理化性质、保守结构域、疏水性/亲水性、信号肽、跨膜结构域、磷酸化修饰、二级结构和系统进化等进行了预测和分析。结果表明:AHA2属于拟南芥H+-ATPase家族成员;拟南芥AHA2基因编码的蛋白与荠菜的亲缘关系最近,具有较高的相似性。本研究的结果将为进一步研究其生物学功能提供一定的参考依据。     

Spontaneous epigenetic variation in the Arabidopsis thaliana methylome

Heritable epigenetic polymorphisms, such as differential cytosine methylation, can underlie phenotypic variation. Moreover, wild strains of the plant Arabidopsis thaliana differ in many epialleles, and these can influence the expression of nearby genes. However, to understand their role in evolution, it is imperative to ascertain the emergence rate and stability of epialleles, including those that are not due to structural variation. We have compared genome-wide DNA methylation among 10 A. thaliana lines, derived 30 generations ago from a common ancestor. Epimutations at individual positions were easily detected, and close to 30,000 cytosines in each strain were differentially methylated. In contrast, larger regions of contiguous methylation were much more stable, and the frequency of changes was in the same low range as that of DNA mutations. Like individual positions, the same regions were often affected by differential methylation in independent lines, with evidence for recurrent cycles of forward and reverse mutations. Transposable elements and short interfering RNAs have been causally linked to DNA methylation. In agreement, differentially methylated sites were farther from transposable elements and showed less association with short interfering RNA expression than invariant positions. The biased distribution and frequent reversion of epimutations have important implications for the potential contribution of sequence-independent epialleles to plant evolution.     

Defining the core Arabidopsis thaliana root microbiome

Land plants associate with a root microbiota distinct from the complex microbial community present in surrounding soil. The microbiota colonizing the rhizosphere (immediately surrounding the root) and the endophytic compartment (within the root) contribute to plant growth, productivity, carbon sequestration and phytoremediation. Colonization of the root occurs despite a sophisticated plant immune system, suggesting finely tuned discrimination of mutualists and commensals from pathogens. Genetic principles governing the derivation of host-specific endophyte communities from soil communities are poorly understood. Here we report the pyrosequencing of the bacterial 16S ribosomal RNA gene of more than 600 Arabidopsis thaliana plants to test the hypotheses that the root rhizosphere and endophytic compartment microbiota of plants grown under controlled conditions in natural soils are sufficiently dependent on the host to remain consistent across different soil types and developmental stages, and sufficiently dependent on host genotype to vary between inbred Arabidopsis accessions. We describe different bacterial communities in two geochemically distinct bulk soils and in rhizosphere and endophytic compartments prepared from roots grown in these soils. The communities in each compartment are strongly influenced by soil type. Endophytic compartments from both soils feature overlapping, low-complexity communities that are markedly enriched in Actinobacteria and specific families from other phyla, notably Proteobacteria. Some bacteria vary quantitatively between plants of different developmental stage and genotype. Our rigorous definition of an endophytic compartment microbiome should facilitate controlled dissection of plant-microbe interactions derived from complex soil communities.     

拟南芥抗盐单基因突变体的诱导与筛选

用Co60-γ射线辐照野生型拟南芥种子，将诱变处理后的M一代种子温室种植，收获的M2代种子用于抗盐突变体的筛选，将在200mmol／L盐胁迫条件下筛选出的352株幼苗根仍表现向地性生长或真叶不变为褐色的植株作为可能的突变体，再将这些M2代可能的突变体移苗种植至基质中并收获M3代种子，经对M3代的抗盐性状继续进行检测，最终获得4株100％表现抗盐性状的突变体。     

拟南芥菜室内培养技术的改进

报道了室内培养拟南芥过程中的一些改进技术,在培养介质、播种、浇水、湿度、培养密度方面作了详细介绍,为研究工作者在简陋条件下进行拟南芥培养提供了经验。     

拟南芥AtJ2基因植物超量表达载体的构建

在胁迫条件下,分子伴侣可以稳定蛋白质结构,防止蛋白质凝聚变性,并修复受伤害蛋白.J蛋白是一类重要的分子伴侣.AtJ2是拟南芥(Arabidopsis thaliana)J蛋白中的一种.为研究该基因的功能,提取了拟南芥幼苗的总RNA,经过RT-PCR获得了AtJ2的全长.并将其构建入表达载体pMD中,得到重组质粒pMD/AtJ2.通过农杆菌(Agrobacterium tumefaciens)将此重组质粒转化入拟南芥,得到了转基因植株,为后续该基因的功能研究奠定基础.     

异三聚体G蛋白在拟南芥生长过程中的作用

利用拟南芥的野生型和异三聚体G蛋白α亚基基因GPA1缺失突变体(gpα1-1,gpα1-2)和超表达突变体(wGα,cGα)为材料,对植株生长发育的一些形态指标进行了观测比较．结果表明2个缺失突变体的植株高度、叶片宽度、长角果果柄长度都明显超过野生型,而超表达突变体的部分指标与野生型相比也有明显差别．实验结果表明,异三聚体G蛋白参与某些器官生长发育的调节,初步证明G蛋白α亚基在伸长生长过程中可能起负调节作用。     

培养室内拟南芥蚜虫的防治技术

拟南芥是广泛应用于遗传学研究的模式植物,生长过程中容易受到蚜虫的侵害.使用捕虫板法、喷洒药物法和综合法对蚜虫进行防治,通过效果比较,发现综合法是培养室内拟南芥蚜虫防治的理想方法.通过不同时间间隔灭杀蚜虫的效果比较,发现3 d后再次进行灭蚜处理,能够达到彻底消灭蚜虫的目的.     

SRO1 regulates heavy metal mercury stress response in Arabidopsis thaliana

Heavy metals in the environment are harmful limiting factors for the normal growth and development of plants. Here, we isolated and identified an Arabidopsis thaliana T-DNA insertion mutant, named srol-1, which showed a hyper-sensitive response to HgCl2. The SRO1 protein contains a WWE domain that mediates proteinprotein interactions. Under HgCl2 treatment, when compared with the wild-type plants, the growth of srol-1 was repressed dramatically and the number of true leaves was reduced and etiolated. The electrolyte leakage rates showed that cell membrane integrity in srol-1 was damaged more severely than in the wild type. DAB （3,5-diaminobenzidine） staining and confocal microscopy showed that Hg2＋ stress induced more hydrogen peroxide accumulation in srol-1 than in the wild type. The qRT-PCR results indicated that the expression of some abiotic stress-induced genes, such as L-ascorbate peroxidase （APX1）, was reduced under oxidative or Hg2＋ stress. Transgenic plants containing a GFP：：SRO1 fusion protein showed that SRO1 was localized in the nucleus of the cells. SRO1 was shown to be expressed in various tissues, and was most highly expressed in the vigorous tissues. Our results suggest thatSRO1 may play an important role in the stress response of A. thaliana to heavy metals.     

拟南芥类结瘤素基因At1g01070的生物信息学分析

类结瘤素基因在非结瘤植物生长发育中承担着重要的功能,但仅少数基因的功能被鉴定.本研究对拟南芥类结瘤素MtN21(Medicago truncatula NODULIN 21)家族成员At1g01070进行了生物信息学分析及亚细胞定位验证.结果表明,At1g01070有两种可变剪切体,编码两种蛋白At1g01070.1和At1g01070.2,前者比后者在N端多47个氨基酸,它们的分子量分别为40KD和35KD,等电点分别为9.2和8.9;均含有2个MtN21蛋白的特征结构域EamA(药物/代谢物转运结构域),At1g01070.1比At1g01070.2多一个PLN00411结构域,且其靠近N端的EamA结构域较后者长;三级结构均由7个α-螺旋和一些不规则卷曲组成,分别含有10个和8个疏水跨膜区,均含13个磷酸化修饰位点,亚细胞定位预测主要定位在质膜;进化上,与琴叶拟南芥(Arabidopsis lyrata)亲缘关系最近;亚细胞定位结果显示At1g01070.1定位在质膜,与预测结果一致.推测At1g01070在植物体内可能参与物质运输.