胡杨叶片及韧皮部内生细菌多样性及生物学功能分析

【目的】通过分析胡杨叶片及树干内生细菌群落多样性、结构特征及生物学功能,探究内生细菌与宿主胡杨的互作机制。【方法】利用Illumina MiSeq高通量测序技术,对采集自新疆喀什地区胡杨林的3组胡杨树叶和3组树干样本的内生细菌进行Alpha、Beta多样性分析、群落组成分析以及通过比对代谢数据库进行群落功能预测,并对样品中内生细菌进行分离纯化鉴定。【结果】胡杨树叶优势菌群依次为变形菌门Proteobacteria(40.71%)、放线菌门Actinobacteria(21.76%)、拟杆菌门Bacteroidetes (14.24%)和厚壁菌门Firmicutes (13.92%);胡杨树干优势菌群为厚壁菌门Firmicutes(56.91%)、放线菌门Actinobacteria(37.01%)。PCoA分析结果表明,胡杨树叶与树干的内生细菌群落结构存在明显差异,同类型组织样本群落结构相似。功能预测发现,内生细菌丰度较高的代谢通路及酶大多与细胞壁和细胞膜、外排泵、氧化应激、相容性溶质、能量代谢等相关。并分离到可培养内生细菌44株,分属5个属,其中芽孢杆菌属占比最多。【结论】胡杨叶片中...     

低聚壳聚糖诱导的毛白杨抗病反应与ABA信号通路的关系

脱落酸(ABA)信号通路核心组分有ABA受体(PYR/PYL/RCARs)、2C型蛋白磷酸酶家族中的A亚族成员(PP2Cs)以及蔗糖非酵解型蛋白激酶2家族成员(SnRK2s)。运用BLASTP序列比对方法,在毛果杨中获得14条PtPYR、7条PtPP2C和4条PtSnRK2基因,它们分别与拟南芥AtPYR、AtPP2C和AtSnRK2基因同源。根据系统进化树分析结果,选取基因PtPYRL7、PtPYRL9、PtHAB2、PtPP2CA、PtSnRK2.3和PtSnRK2.6,设计合适的引物。以85号无性系毛白杨组培苗为材料,分别对其根部进行外源ABA和低聚壳聚糖处理,于处理3h、6h、12h和24h4个时间点取样,提取样本叶片总RNA,反转录成cDNA,进行实时荧光定量PCR分析。结果显示:ABA处理和低聚壳聚糖处理均能使PtPYRL7和PtPYRL9基因表达下调,使PtHAB2和PtPP2CA基因表达上调,使PtSnRK2.3和PtSnRK2.6基因表达先上调后下调。研究表明,ABA处理和低聚壳聚糖处理诱导毛白杨叶片中与ABA信号通路相关的基因的表达变化趋势几乎一致,说明ABA信号通路是低聚壳聚糖诱导毛白杨抗病的信号传递途径之一。     

塔里木河源流和干流胡杨年轮生长的差异性

借助树木年轮学的方法和技术手段,通过对阿克苏河、叶尔羌河和塔里木河干流不同河段胡杨年轮样本采集,分析了塔里木河两源流与干流不同河段胡杨年轮生长特征;采用单因素方差分析方法和Kendall协同系数(W)研究了塔里木河两源流和干流不同河段胡杨年轮指数的差异性;利用突变检验和小波分析方法探讨了塔河两源流、塔河干流不同河段胡杨径向生长的周期和突变性。研究结果表明:(1)1980—2010年期间,塔里木河两源流和干流不同河段年轮宽度和年轮指数均呈下降趋势。在阿克苏河、肖夹克、沙子河口3个断面胡杨年轮宽度和年轮指数下降趋势明显,而叶尔羌河和新渠满断面的胡杨年轮宽度和年轮指数下降趋势不明显。(2)塔里木河两源流和干流不同河段的胡杨年轮生长在空间上不具有一致性(W0.5),阿克苏河断面与肖夹克、沙子河口断面,叶尔羌河与肖夹克、沙子河口断面,肖夹克与新渠满断面,新渠满与沙子河口断面之间胡杨年轮指数均具有显著的差异性(P0.05)。(3)塔里木河两源流胡杨年轮指数的突变时间与河道径流量突变时间相同或者滞后,这可能与地表水转化为地下水过程有关。(4)塔里木河两源流和干流不同河段的胡杨年轮指数变化的周期均小于其地表径流变化的周期,这可能与胡杨自身的生理特点和当地气温、水分对胡杨生长综合影响有关。本研究有助于深入了解干旱区内陆河流域胡杨生长特征变化规律,同时可为该流域胡杨资源生态保育提供参考。     

不同土壤水盐条件下多枝柽柳(Tamarix ramosissima)对胡杨(Populus euphratica)幼苗的影响

目前胡杨更新困难,种群处于退化阶段,而与其生态位高度重叠的多枝柽柳却在扩张。为探讨多枝柽柳对胡杨生长的影响,本研究设置了3个水平的水分、盐分梯度,对胡杨进行了单种和混种的盆栽控制实验,通过测定胡杨幼苗的生长和存活状况,分析不同水、盐梯度下多枝柽柳如何影响胡杨生长。结果表明：（1）多枝柽柳伴生降低当年生胡杨幼苗的存活率,随着水分条件改善,胡杨存活率提高,而盐分对存活率没有显著的影响。（2）水分、盐分和伴生模式几个因子对胡杨的生长特征的影响存在显著的交互作用（P<0.05）。各水盐条件下,多枝柽柳会不同程度降低胡杨幼苗的株高、主根长和地上地下生物量,而根冠比增大。混种条件下,胡杨幼苗对水盐的响应更为敏感。（3）相对竞争强度对水盐环境有明显的响应（P<0.05）,随水分条件改善,地上、地下相对竞争强度降低。多枝柽柳对胡杨的生长产生不良影响的机制是通过快速消耗土壤的水分,从而导致胡杨幼苗水分亏缺。土壤水分条件是胡杨和多枝柽柳幼苗共存的关键因素,在水分供给不足的情况下,对水分偏好的差异导致胡杨无法通过实生苗进行有效的更新从而加剧胡杨种群的衰退,而多枝柽柳更为耐旱的特性使其逐步占据河岸的生境。我们的研究结果强调了两个树种对环境因子的适应性差异决定了河岸带植被发育过程中植物-土壤的相互作用导致胡杨在演替过程中表现出的衰退现象。     

Species‐specific microsatellite markers to monitor gene flow between exotic poplars and their natural relatives in eastern North America

Species‐specific microsatellite markers were obtained for the unambiguous recognition of five poplar species of ecological and commercial importance to eastern North America: the native species Populus balsamifera and Populus deltoides, the exotic species Populus maximowiczii, Populus nigra, Populus trichocarpa and their interspecific hybrids. Forty‐four of 71 tested primer pairs amplified simple sequence repeat (SSR) loci for all five taxa. Six of these loci showed non‐overlapping allelic diversity between species, including fixed differences. Together, they were useful to identify unambiguously the five taxa and to validate parental contributions in a group of hybrid progeny. These markers will be invaluable to detect gene flow from plantations of exotic poplar into adjacent stands of native species and between the two potentially hybridizing native species P. balsamifera and P. deltoides.     

High tolerance against Chrysomela tremulae of transgenic poplar plants expressing a synthetic cry3Aa gene from Bacillus thuringiensis ssp tenebrionis

Hybrid poplars (Populus tremula ×Populus tremuloides) have been genetically engineered viaAgrobacterium tumefaciens, to express a syntheticcry3Aa gene derived from the native Bacillusthuringiensis subsp. tenebrionis cry3Aa gene.The presence and the expression of the transgene have been verified in fourtransgenic poplar lines, using Southern, northern and western analyses. Thetransgenic poplar's toxicity towards the phytophagous beetleChrysomela tremulae (Coleoptera, Chrysomelidae) has beenassessed on six month-old greenhouse-grown selected plants in laboratoryconditions. Laboratory experiments consisted of feeding tests of fresh detachedleaves on C. tremulae at all developmental stages. Ourresults indicate that the transgenic poplar leaves, expressing a Cry3Aa proteinamount in a range of 0.05–0.0025% of total soluble protein, weredefinitely deleterious for C. tremulae, regardless of thedevelopmental stage.     

An efficient and novel plant selectable marker based on organomercurial resistance

A selectable marker gene facilitates the detection of genetically modified plant cells during transformation experiments. So far, these marker genes are almost exclusively of two types, conferring either antibiotic resistance or herbicide tolerance. However, more selectable markers must be developed as additional transgenic traits continue to be incorporated into transgenic plants. Here, we used mercury resistance, conferred by the organomercurial lyase gene, as a selectable marker for transformation. The merB gene fromStreptococcus aureus was modified for plant expression and transferred to a hybrid poplar(Populus alba xPopulus glandulosa), using the stem segment-agrobacteria co-cultivation method. The transformed cells were selected on a callus-inducing medium containing as little as 1 μM methylmercury. Subsequent plant regeneration was done in the presence of methylmercury. Resistance to Hg was stably maintained in mature plants after two years of growth in the nursery. We suggest that this gene could serve as an excellent selectable marker for plant transformation.     

青杨雌雄株叶际微生物群落多样性和结构的差异

【目的】本论文探究了青杨雌雄株的叶际微生物的群落结构差异及其主要环境影响因素。【方法】以河北小五台山的天然青杨林为研究对象,采用基于16S rRNA/ITS1基因的MiSeq高通量测序技术,分析了青杨雌雄株叶际细菌和真菌的群落结构,并耦合分析其与叶片理化性质的相关性。【结果】测序结果表明细菌和真菌的多样性指数ACE、Chao1、Shannon、Simpson在雌雄株间都无显著性差异(P>0.05)。Metastats组间群落显著性差异分析表明,在门水平,青杨雌雄株叶际细菌和真菌都无显著差异。而在属水平,青杨雌雄株的叶际细菌Amnibacterium和Spingomonas及真菌Aureobasidium、Elmerina、Exobasidium、Endoconidioma、Monilinia和Rhodotorula的相对丰度在雌雄株叶际有显著差异(P<0.05)。基于OTUs的菌群分析表明,青杨雌株和雄株的叶际环境上都有其各自的特有菌群,如雌株的特有真菌Pringsheimia(0.15%)和细菌Chitinophaga(0.04%)。RDA冗余分析表明,叶片含水量与青杨叶际真菌的群落结构有显著相关性(P<0.05),而未发现青杨细菌群落结构与测定的叶片理化性质有显著相关。【结论】青杨雌雄株叶际微生物在属水平有显著分异的菌属,且可能受叶片理化性质影响,该结果为揭示雌雄异株植物的叶际微生物差异有重要借鉴意义。     

Thaumatin-like proteins are differentially expressed and localized in phloem tissues of hybrid poplar

Background  

Two thaumatin-like proteins (TLPs) were previously identified in phloem exudate of hybrid poplar (Populus trichocarpa × P. deltoides) using proteomics methods, and their sieve element localization confirmed by immunofluorescence. In the current study, we analyzed different tissues to further understand TLP expression and localization in poplar, and used immunogold labelling to determine intracellular localization.     

新疆叶尔羌河流域胡杨林时空格局特征

叶尔羌河流域胡杨林对保障我国新疆南疆地区生态安全有着重要的功能,到目前对该区胡杨林时空格局特征规律的研究极少。基于1995—2015年Landsat TM/OLI长时间序列遥感监测数据,通过土地利用程度变化指数、转移矩阵以及景观指数对叶尔羌河流域胡杨林时空格局变化进行动态监测与分析。结果表明:(1)胡杨林面积从1995年的1916.15 km~2减少到2015年的1652.25 km~2,面积减少了263.90 km~2。永安坝至夏河林场段,耕地向河道扩张,胡杨林转为耕地;而夏河林场至三河口段,水资源匮乏,胡杨林被迫向河道收缩,转为未利用地。(2)胡杨林动态度和空间动态度降低,而胡杨林变化状态指数、斑块密度、最大斑块指数和散布与并列指数增加,斑块结合度指数高,胡杨林空间分布逐渐集中、破碎度降低、连通性增加。流域景观要素连接性逐渐减弱,破碎化程度较高,优势度斑块类型比例逐渐下降,景观类型向复杂化方向发展。(3)1995—2005年胡杨林受气候变化和人类活动的干扰,胡杨林面积减少较快,景观格局变化剧烈,而2005—2015年胡杨林保护措施的实施、区域产业结构的调整以及生态安全输水区域的扩大等,胡杨林面积减少速度减缓,但形势仍较为严峻。在叶尔羌河流域合理利用水资源,统筹协调生活、生产和生态用水、强化水资源管理力度,以及调整产业结构、控制人口增长速度等是该区胡杨林生态系统恢复的有效手段和途径。研究可以为叶尔羌河流域生态系统恢复以及胡杨林保护提供参考。     

欧美杂种山杨微扦插不定根发生过程的解剖学研究

采用石蜡切片技术,以欧美杂种山杨插穗基部茎段为实验材料,连续解剖观察插穗不定根发生发育过程,分析根原基发生部位与扦插生根的关系。结果显示:欧美杂种山杨插穗不定根的发生过程分为4个时期,为根原基诱导期,不定根起始期、表达期和伸长生长期。根原基诱导期维管形成层产生具有分生组织特点的薄壁细胞;不定根起始期,维管形成层及附近的薄壁细胞脱分化,形成不定根原基发端细胞;不定根表达期,根原基发端细胞不断分裂成具有方向性的根原基,根原基穿过韧皮射线和皮层,向皮孔方向发展;不定根伸长生长期,根原基从皮孔伸出,其内部的维管系统开始发育,形成不定根。研究认为,欧美杂种山杨为皮部诱导生根类型,不定根原基起源于维管形成层区,起源部位单一,扦插难生根。     

Element content and expression of genes of interest in guard cells are connected to spatiotemporal variations in stomatal conductance

Element content and expression of genes of interest on single cell types, such as stomata, provide valuable insights into their specific physiology, improving our understanding of leaf gas exchange regulation. We investigated how far differences in stomatal conductance (g_s) can be ascribed to changes in guard cells functioning in amphistomateous leaves. g_s was measured during the day on both leaf sides, on well-watered and drought-stressed trees (two Populus euramericana Moench and two Populus nigra L. genotypes). In parallel, guard cells were dissected for element content and gene expressions analyses. Both were strongly arranged according to genotype, and drought had the lowest impact overall. Normalizing the data by genotype highlighted a structure on the basis of leaf sides and time of day both for element content and gene expression. Guard cells magnesium, phosphorus, and chlorine were the most abundant on the abaxial side in the morning, where g_s was at the highest. In contrast, genes encoding H⁺-ATPase and aquaporins were usually more abundant in the afternoon, whereas genes encoding Ca²⁺-vacuolar antiporters, K⁺ channels, and ABA-related genes were in general more abundant on the adaxial side. Our work highlights the unique physiology of each leaf side and their analogous rhythmicity through the day.     

Natural hybridisation between <Emphasis Type="Italic">Populus nigra</Emphasis> L. and <Emphasis Type="Italic">P</Emphasis>. <Emphasis Type="Italic">x canadensis</Emphasis> Moench. Hybrid offspring competes for niches along the Rhine river in the Netherlands

Black poplar (Populus nigra L.) is a major species for European riparian forests but its abundance has decreased over the decades due to human influences. For restoration of floodplain woodlands, the remaining black poplar stands may act as source population. A potential problem is that P. nigra and Populus deltoides have contributed to many interspecific hybrids, which have been planted in large numbers. As these Populus x canadensis clones have the possibility to intercross with wild P. nigra trees, their offspring could establish themselves along European rivers. In this study, we have sampled 44 poplar seedlings and young trees that occurred spontaneously along the Rhine river and its tributaries in the Netherlands. Along these rivers, only a few native P. nigra L. populations exist in combination with many planted cultivated P. x canadensis trees. By comparison to reference material from P. nigra, P. deltoides and P. x canadensis, species-specific AFLP bands and microsatellite alleles indicated that nearly half of the sampled trees were not pure P. nigra but progeny of natural hybridisation that had colonised the Rhine river banks. The posterior probability method as implemented in NewHybrids using microsatellite data was the superior method in establishing the most likely parentage. The results of this study indicate that offspring of hybrid cultivated poplars compete for the same ecological niche as native black poplars. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Divergence of 3′ ends as a driver of short interspersed nuclear element (SINE) evolution in the Salicaceae

Short interspersed nuclear elements (SINEs) are small, non‐autonomous and heterogeneous retrotransposons that are widespread in plants. To explore the amplification dynamics and evolutionary history of SINE populations in representative deciduous tree species, we analyzed the genomes of the six following Salicaceae species: Populus deltoides, Populus euphratica, Populus tremula, Populus tremuloides, Populus trichocarpa, and Salix purpurea. We identified 11 Salicaceae SINE families (SaliS‐I to SaliS‐XI), comprising 27 077 full‐length copies. Most of these families harbor segmental similarities, providing evidence for SINE emergence by reshuffling or heterodimerization. We observed two SINE groups, differing in phylogenetic distribution pattern, similarity and 3′ end structure. These groups probably emerged during the ‘salicoid duplication’ (~65 million years ago) in the Salix–Populus progenitor and during the separation of the genus Salix (45–65 million years ago), respectively. In contrast to conserved 5′ start motifs across species and SINE families, the 3′ ends are highly variable in sequence and length. This extraordinary 3′‐end variability results from mutations in the poly(A) tail, which were fixed by subsequent amplificational bursts. We show that the dissemination of newly evolved 3′ ends is accomplished by a displacement of older motifs, leading to various 3′‐end subpopulations within the SaliS families.