Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.     

First genetic characterization of the brown dog tick <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> sensu lato in Peninsular Malaysia

The brown dog tick Rhipicephalus sanguineus sensu lato (s.l.) is a species complex comprising three main mitochondrial lineages, namely tropical, temperate and southeast European lineages. Despite its medical and veterinary importance, little attention has been paid to the genetic lineage of this species in Southeast Asia. Rhipicephalus sanguineus s.l. from Malaysia was investigated genetically, for the first time, using the mitochondria-encoded cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S) genes. Specifically, a pair of primers was developed to amplify the COI sequences in the present study. Both genes unambiguously assigned Malaysian material into the tropical lineage of R. sanguineus s.l. The 16S sequences were highly conserved; no variation site was observed. The COI sequences revealed slightly higher variation by recovering four haplotypes, one of which is restricted to the northernmost of Peninsular Malaysia. This finding will be a stepping stone in promoting more biological studies of this species complex in this region.     

Physiological and quantitative proteomic analyses unraveling potassium deficiency stress response in alligator weed (<Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis> L.) root

Key message

KEG is involved in mediating the proteasome-dependent degradation of FDH, a stress-responsive enzyme. The UPS may function to suppress FDH mediated stress responses under favorable growth conditions.

Abstract

Formate dehydrogenase (FDH) has been studied in bacteria and yeasts for the purpose of industrial application of NADH co-factor regeneration. In plants, FDH is regarded as a universal stress protein involved in responses to various abiotic and biotic stresses. Here we show that FDH abundance is regulated by the ubiquitin proteasome system (UPS). FDH is ubiquitinated in planta and degraded by the 26S proteasome. Interaction assays identified FDH as a potential substrate for the RING-type ubiquitin ligase Keep on Going (KEG). KEG is capable of attaching ubiquitin to FDH in in vitro assays and the turnover of FDH was increased when co-expressed with a functional KEG in planta, suggesting that KEG contributes to FDH degradation. Consistent with a role in regulating FDH abundance, transgenic plants overexpressing KEG were more sensitive to the inhibitory effects of formate. In addition, FDH is a phosphoprotein and dephosphorylation was found to increase the stability of FDH in degradation assays. Based on results from this and previous studies, we propose a model where KEG mediates the ubiquitination and subsequent degradation of phosphorylated FDH and, in response to unfavourable growth conditions, reduction in FDH phosphorylation levels may prohibit turnover allowing the stabilized FDH to facilitate stress responses.

     

Development of Species-Specific InDel Markers in Citrus

Citrus taxonomy is complex owing to the existence of a wide range of species: Poncirus is used mainly for rootstock; Fortunella produces small fruit and edible pericarp; and Citrus comprises the most widespread fruit crop species worldwide. Rapidly increasing genome resources from different citrus species facilitate the development of convenient and genome-wide molecular markers that can be applied to both inter- and intra-species analyses. In this study, by comparing the genome sequences of four citrus species, a set of 1958 InDels were identified and 453 candidate InDels were converted into PCR-based markers. Among these candidate InDels, 268 (65%) exhibited length polymorphisms from 30 bp to 200 bp when applied to seven species from the genera Poncirus, Fortunella and Citrus. Seven InDel markers exhibited high intraspecific polymorphisms in a natural pummelo population. The results showed that the InDel markers are effective for both inter- and intra-specific variation and identification analyses. These InDel markers are expected to be applied to germplasm identification, phylogenetic analysis, genetic diversity evaluation and marker-assisted breeding in citrus.     

Phylogenetic relationships of artiodactyls and cetaceans as deduced from the comparison of cytochrome b and 12S rRNA mitochondrial sequences

A data set of complete mitochondrial cytochrome b and 12S rDNA sequences is presented here for 17 representatives of Artiodactyla and Cetacea, together with potential outgroups (two Perissodactyla, two Carnivora, two Tethytheria, four Rodentia, and two Marsupialia). We include seven sequences not previously published from Hippopotamidae (Ancodonta) and Camelidae (Tylopoda), yielding a total of nearly 2.1 kb for both genes combined. Distance and parsimony analyses of each gene indicate that 11 clades are well supported, including the artiodactyl taxa Pecora, Ruminantia (with low 12S rRNA support), Tylopoda, Suina, and Ancodonta, as well as Cetacea, Perissodactyla, Carnivora, Tethytheria, Muridae, and Caviomorpha. Neither the cytochrome b nor the 12S rDNA genes resolve the relationships between these major clades. The combined analysis of the two genes suggests a monophyletic Cetacea +Artiodactyla clade (defined as "Cetartiodactyla"), whereas Perissodactyla, Carnivora, and Tethytheria fall outside this clade. Perissodactyla could represent the sister taxon of Cetartiodactyla, as deduced from resampling studies among outgroup lineages. Cetartiodactyla includes five major lineages: Ruminantia, Tylopoda, Suina, Ancodonta, and Cetacea, among which the phylogenetic relationships are not resolved. Thus, Suiformes do not appear to be monophyletic, justifying their split into the Suina and Ancodonta infraorders. An association between Cetacea and Hippopotamidae is supported by the cytochrome b gene but not by the 12S rRNA gene. Calculation of divergence dates suggests that the Cetartiodactyla could have diverged from other Ferungulata about 60 MYA.      

春小麦水分利用效率日变化及其生理生态基础的研究

采用光合速率和蒸腾速率之比 (Pn/Tr)表示植物水分利用效率 (WUE) ,发现在两种不同水分处理下春小麦拔节期 .WUE日变化中都有上午高于下午值 ,且 8∶0 0～ 1 0∶0 0为明显峰值的特征 ,这种特征与Pn、Tr日变化存在的上、下午值不对称性和反向性 (Pn为上午高于下午 ,Tr相反 )紧密相关 ,水分胁迫处理中 ,Pn、Tr值均有降低 ,但不同品种的WUE反应不一 .研究表明 ,叶水势 ( ψw)、气孔阻力 (Rs)等生理因素和空气相对湿度 (RH)、光照 (Q)及冠层温度 (Tc)等生态因子 ,通过对Tr和Pn的不同影响而同WUE显著相关 ,40 %RH是WUE变化的一个重要阈值 .     

小麦类脱水素的表达、纯化及多克隆抗体的制备

脱水素在胚胎发育后期累积,外源脱落酸(ABA)、低温、干旱和其他一些环境条件下能诱导脱水素的产生,尽管植物在脱水条件下脱水素广泛存在于细胞中,但其生化功能仍不清楚.为研究小麦在不同时期脱水素基因的表达情况和生物学功能及抗体制备,以小麦幼芽为材料,经干旱胁迫处理后,提取总RNA,通过RT-PCR得到小麦类脱水素基因片段(WZY1-1),再连接至克隆载体PUCM-T,并成功构建重组表达质粒PET-32a( )-wzy1-1,将阳性重组质粒转化于受体菌BL21(DE3)感受态细胞中,经IPTG诱导表达,进行表达产物的聚丙烯酰胺凝胶电泳(SDS-PAGE)检测.结果表明,表达蛋白位于37ku处,小麦类脱水素基因获得高效表达.表达蛋白经Ni2 琼脂糖凝胶亲和层析和透析袋电洗脱法纯化后,对兔子进行免疫,制备的抗血清通过ELISA检测到较高的多克隆抗体效价.蛋白质印迹结果显示,利用纯化的蛋白质制备的兔抗血清可以很好地和所表达的蛋白质带特异性结合,且郑引1号小麦幼苗进行干旱处理,提取粗蛋白,SDS-PAGE,蛋白质印迹检测显示,在分子质量28ku处出现特异的蛋白质条带,这说明所制备的抗血清可以与小麦叶片所表达的dehydrin蛋白特异性结合,证明其具有良好的免疫原性.     

SYSTEMATICS OF THE CALCIFIED GENERA OF THE GALAXAURACEAE (NEMALIALES,RHODOPHYTA) WITH AN EMPHASIS ON TAIWAN SPECIES1

The current separation of the calcified genera Actinotrichia Decaisne, Galaxaura Lamouroux, and Tricleocarpa Huisman et Borowitzka in the Galaxauraceae is largely based on type of life history (whether the gametophytes and tetrasporophytes are isomorphic or heteromorphic with respect to gross morphology or cortical‐cell features) and on features of postfertilization development (such as the composition of the pericarp). We reexamined the phylogenetic relationships of these genera based on comparative rbcL sequence analysis, types of life cycle, and cystocarp development. Four distinct assemblages have been identified: an Actinotrichia clade, a Tricleocarpa clade, a Galaxaura clade (containing the type species), and a Dichotomaria clade made of a number of formerly Galaxaura species (D. obtusata [Ellis et Solander] Lamarck, D. marginata [Ellis et Solander] Lamarck, and D. diesingiana [Zanardini] Huisman, Harper and Saunders). Key differences between Dichotomaria and Galaxaura include the habit of the gametophytic and tetrasporophytic generations (isomorphic in Dichotomaria and dimorphic in Galaxaura) as well as the presence or absence of a persistent pericarp in the cystocarp (present in Dichotomaria and absent in Galaxaura). Molecular data do not support monophyly for the putatively pantropical species Galaxaura rugosa, Dichotomaria obtusata, and D. marginata, all of which we conclude are in need of taxonomic revision.