Aboveground herbivory induced jasmonates disproportionately reduce plant reproductive potential by facilitating root nematode infestation

Different plant feeders, including insects and parasitic nematodes, can influence each other by triggering systemic changes in their shared host plants. In most cases, however, the underlying mechanisms are unclear, and the consequences for plant fitness are not well understood. We studied the interaction between leaf feeding Manduca sexta caterpillars and root parasitic nematodes in Nicotiana attenuata. Simulated M. sexta attack increased the abundance of root parasitic nematodes in the field and facilitated Meloidogyne incognita reproduction in the glasshouse. Intact jasmonate biosynthesis was found to be required for both effects. Flower counts revealed that the jasmonate‐dependent facilitation of nematode infestation following simulated leaf attack reduces the plant's reproductive potential to a greater degree than would be expected from the additive effects of the individual stresses. This work reveals that jasmonates mediate the interaction between a leaf herbivore and root parasitic nematodes and illustrates how plant‐mediated interactions can alter plant's reproductive potential. The selection pressure resulting from the demonstrated fitness effects is likely to influence the evolution of plant defense traits in nature.     

The evolution of pyrrolizidine alkaloid diversity among and within Jacobaea species

Plants produce many secondary metabolites showing considerable inter- and intraspecific diversity of concentration and composition as a strategy to cope with environmental stresses. The evolution of plant defenses against herbivores and pathogens can be unraveled by understanding the mechanisms underlying chemical diversity. Pyrrolizidine alkaloids are a class of secondary metabolites with high diversity. We performed a qualitative and quantitative analysis of 80 pyrrolizidine alkaloids with liquid chromatography-tandem mass spectrometry of leaves from 17 Jacobaea species including one to three populations per species with 4–10 individuals per population grown under controlled conditions in a climate chamber. We observed large inter- and intraspecific variation in pyrrolizidine alkaloid concentration and composition, which were both species-specific. Furthermore, we sequenced 11 plastid and three nuclear regions to reconstruct the phylogeny of the 17 Jacobaea species. Ancestral state reconstruction at the species level showed mainly random distributions of individual pyrrolizidine alkaloids. We found little evidence for phylogenetic signals, as nine out of 80 pyrrolizidine alkaloids showed a significant phylogenetic signal for Pagel's λ statistics only, whereas no significance was detected for Blomberg's K measure. We speculate that this high pyrrolizidine alkaloid diversity is the result of the upregulation and downregulation of specific pyrrolizidine alkaloids depending on ecological needs rather than gains and losses of particular pyrrolizidine alkaloid biosynthesis genes during evolution.     

绿色杜氏藻不同β-胡萝卜素羟化酶基因家族胁迫应答模式研究

β-胡萝卜素羟化酶(β-carotenoid hydroxylase, CHYB)是植物类胡萝卜素生物合成途径中的一个重要限速酶。本研究对绿色杜氏藻转录组测序数据进行分析,获得2条β-胡萝卜素羟化酶家族基因chyb1和chyb2。采用染色体步移法分别克隆并获得了绿色杜氏藻chyb1和chyb2基因的启动子序列,全长分别为1080 bp(GenBank登录号：KY012338)和1155 bp (GenBank登录号：KY012339)。利用Plantcare软件分析两个启动子的顺式作用元件,结果表明绿色杜氏藻chyb1基因启动子含有与甲基茉莉酸、花生四烯酸、水杨酸等非生物胁迫相关的顺式作用元件,而绿色杜氏藻chyb2基因启动子含有与光照相关的顺式作用元件。通过qRT-PCR分析了绿色杜氏藻CHYB基因家族在不同胁迫下的基因表达水平,结果表明该基因家族的基因表达水平与启动子调控相关,且不同的家族基因应答不同的胁迫。     

Oxylipins and plant abiotic stress resistance

Oxylipins are signaling molecules formed enzymatically or spontaneously from unsaturated fatty acids in all aerobic organisms. Oxylipins regulate growth, development, and responses to environmental stimuli of organisms. The oxylipin biosynthesis pathway in plants includes a few parallel branches named after first enzyme of the corresponding branch as allene oxide synthase, hydroperoxide lyase, divinyl ether synthase, peroxygenase, epoxy alcohol synthase, and others in which various biologically active metabolites are produced. Oxylipins can be formed non-enzymatically as a result of oxygenation of fatty acids by free radicals and reactive oxygen species. Spontaneously formed oxylipins are called phytoprostanes. The role of oxylipins in biotic stress responses has been described in many published works. The role of oxylipins in plant adaptation to abiotic stress conditions is less studied; there is also obvious lack of available data compilation and analysis in this area of research. In this work we analyze data on oxylipins functions in plant adaptation to abiotic stress conditions, such as wounding, suboptimal light and temperature, dehydration and osmotic stress, and effects of ozone and heavy metals. Modern research articles elucidating the molecular mechanisms of oxylipins action by the methods of biochemistry, molecular biology, and genetics are reviewed here. Data on the role of oxylipins in stress signal transduction, stress-inducible gene expression regulation, and interaction of these metabolites with other signal transduction pathways in cells are described. In this review the general oxylipin-mediated mechanisms that help plants to adjust to a broad spectrum of stress factors are considered, followed by analysis of more specific responses regulated by oxylipins only under certain stress conditions. New approaches to improvement of plant resistance to abiotic stresses based on the induction of oxylipin-mediated processes are discussed.     

Jasmonate-related mutants of Arabidopsis as tools for studying stress signaling

Jasmonates are naturally occurring signal compounds that regulate plant growth and development, and are involved in plant responses to several environmental stress factors. The mode of action of jasmonates has been investigated traditionally by analysis of the effects of exogenous application of these compounds, including identification of jasmonate-responsive genes and determination of their expression and responsive promoter elements. In addition, jasmonate biosynthesis has been studied by identification of biosynthetic enzymes, use of inhibitors and determination of endogenous jasmonate levels. Recently, several mutants defective in jasmonate biosynthesis and signaling have been isolated and their phenotypes shed new light on the role of jasmonates and jasmonate signaling in plant responses to pathogens, insects and ozone.     

Enzymes involved in jasmonic acid biosynthesis

(+)-7-epi-Jasmonic acid has attracted much attention as an inducible plant signal that stimulates the expression of an array of wound-inducible and defence-related genes as well as playing a role in various developmental responses. This review focuses on the enzymology of jasmonate biosynthesis and addresses open questions with respect to the regulation and subcellular localisation of the jasmonic acid pathway. The apparent analogy of jasmonate biosynthesis from a -linolenic acid in plants with that of the arachidonate-derived signalling molecules of the leukotriene- and prostaglandin-type in animals make the jasmonic acid cascade one of general biological interest.     

Meta‐analysis of the effects of small mammal disturbances on species diversity,richness and plant biomass

The disturbance activities of many small mammals, including building burrows, mounds, trails and tunnels, and herbivory, can have significant impacts on their ecosystems, both through trophic and non‐trophic interactions. Some species have large enough impacts through their disturbances to be classed as ecosystem engineers and/or keystone species. Others have negative or null effects. However, at present it is difficult to predict whether the disturbances created by a given species will have significant effects on common measures of ecosystem response such as species richness, diversity and biomass. We ask whether variables characterizing disturbance type, responding species, disturbance‐making species and the environment can predict changes in magnitude and direction of effects on biomass, richness and diversity. We test these predictions with a meta‐analysis of 106 data entries in a database derived from 63 papers, representing 40 small mammal species. We find that small mammal disturbances in general increase biomass, and both increase and decrease richness and diversity. We also identify individual environmental, disturbance‐related, and species‐related variables associated with these changes in magnitude and direction. We discuss the likely interactions between these variables, and how current proxy measures of disturbance impact could be replaced by more accurate direct measures. We recommend that future studies focus on conditions characterized by combinations of variables we identify as significant, in order to understand how these variable interactions (which cannot be analysed through meta‐analysis) affect disturbance outcomes. Based on the gaps in our database and results, we also recommend that future studies directly measure disturbance impact, measure disturbance effects on animal and well as plant taxa, and take measurements on multiple scales.     

药用植物长春花WRKY转录因子的鉴定及表达谱分析

WRKY是调控植物生长发育和逆境胁迫反应等生命活动的一个转录因子大家族.然而,有关药用植物长春花CrWRKY转录因子的种类和功能却知之甚少.从26 009个长春花蛋白中鉴定出47个CrWRKY转录因子.依据WRKY结构域和系统进化,将CrWRKY分为G1、G2和G3三大类群.表达谱数据分析表明,长春花CrWRKY基因的表达具有器官特异性.47个CrWRKY基因的表达谱可分为3种表达模式:第1类型主要在花、甲基茉莉酸甲酯(MeJA)或酵母提取物(YE)处理的原生质体中高表达;第2类型主要在茎和毛状根中高表达;第3类型在根、茎、叶、幼苗和MeJA处理的毛状根中高表达.进一步用实时定量PCR检测了16个代表性CrWRKY基因在不同器官、MeJA处理原生质体和毛状根中的表达模式,检测结果与上述数字基因表达谱数据基本一致.约1/3以上CrWRKY基因的表达受MeJA和YE的调控,暗示它们可能参与萜类吲哚生物碱的合成和逆境胁迫反应.为进一步解析长春花WRKY转录因子的功能和萜类吲哚生物碱合成调控的网络奠定了基础.