Occurrence and non-detectability of maytansinoids in individual plants of the genera Maytenus and Putterlickia

Individual plants belonging to different species of the family Celastraceae collected from their natural habitats in South Africa (Putterlickia verrucosa (E. Meyer ex Sonder) Szyszyl., Putterlickia pyracantha (L.) Szyszyl., Putterlickia retrospinosa van Wyk and Mostert) and Brazil (Maytenus ilicifolia Mart. ex Reiss., Maytenus evonymoides Reiss., Maytenus aquifolia Mart.) were investigated for the presence of maytansinoids and of maytansine, an ansamycin of high cytotoxic activity. Maytansinoids were not detectable in plants grown in Brazil. Analysis of plants growing in South Africa, however, showed clearly that maytansinoids were present in some individual plants but were not detectable in others. Molecular biological analysis of a Putterlickia verrucosa cell culture gave no evidence for the presence of the aminohydroxybenzoate synthase gene which is unique to the biosynthesis of aminohydroxybenzoate, a precursor of the ansamycins including maytansinoids. Moreover, this gene was not detectable in DNA extracted from the aerial parts of Putterlickia plants. In contrast, observations indicate that this gene may be present in microbes of the rhizosphere of Putterlickia plants. Our observations are discussed with respect to the possibility that the roots of Putterlickia plants may be associated with microorganisms which are responsible for the biosynthesis of maytansine or maytansinoids.     

Attraction of four entomopathogenic nematodes to four white grub species

To better understand the differences in the efficacy of entomopathogenic nematode species against white grub species, we are studying the various steps of the infection process of entomopathogenic nematodes into different white grub species using nematode species/strains with particular promise as white grub control agents. In this study we compared the attraction of the entomopathogenic nematodes Steinernema scarabaei (AMK001 strain), Steinernema glaseri (NC1 strain), Heterorhabditis zealandica (X1 strain), and Heterorhabditis bacteriophora (GPS11 strain) to third-instars of the scarabs Popillia japonica, Anomala orientalis, Cyclocephala borealis, and Rhizotrogus majalis, and late-instar greater wax moth, Galleria mellonella, larvae. Individual larvae were confined at the bottom of 5.5 cm vertical sand columns, nematodes added to the sand surface after 24 h, and nematodes extracted after another 24 h. Nematode attraction to hosts was strongly affected by nematode species but the effect of insect species varied with nematode species. S. glaseri had a high innate dispersal rate (i.e., in absence of insects) and was strongly attracted to insects without significant differences among insect species. S. scarabaei had a very low innate dispersal rate so that even a strong relative response to insects resulted in low absolute dispersal rates toward insects. S. scarabaei tended to be most attracted to G. mellonella and least attracted to C. borealis. H. zealandica had a high innate dispersal rate but only responded weakly to insects without significant differences among species. H. bacteriophora had limited innate dispersal and only weakly responded to insects with G. mellonella tending to be the most attractive and C. borealis the least attractive insect. It has to be noted that we cannot exclude that the use of different rearing hosts (A. orientalis and P. japonica larvae for S. scarabaei, G. mellonella larvae for the other nematodes) might have had an impact on the nematodes dispersal and relative attraction behavior. This study indicates that host attractiveness and nematode dispersal rates may contribute but do not play a major role in the variability in white grub susceptibility and/or nematode virulence.     

Molecular phylogeny of Phoma and allied anamorph genera: Towards a reclassification of the Phoma complex

The present generic concept of Phoma is broadly defined, with nine sections being recognised based on morphological characters. Teleomorph states of Phoma have been described in the genera Didymella, Leptosphaeria, Pleospora and Mycosphaerella, indicating that Phoma anamorphs represent a polyphyletic group. In an attempt to delineate generic boundaries, representative strains of the various Phoma sections and allied coelomycetous genera were included for study. Sequence data of the 18S nrDNA (SSU) and the 28S nrDNA (LSU) regions of 18 Phoma strains included were compared with those of representative strains of 39 allied anamorph genera, including Ascochyta, Coniothyrium, Deuterophoma, Microsphaeropsis, Pleurophoma, Pyrenochaeta, and 11 teleomorph genera. The type species of the Phoma sections Phoma, Phyllostictoides, Sclerophomella, Macrospora and Peyronellaea grouped in a subclade in the Pleosporales with the type species of Ascochyta and Microsphaeropsis. The new family Didymellaceae is proposed to accommodate these Phoma sections and related anamorph genera. The present study demonstrated that Phoma radicina, the type species of Phoma sect. Paraphoma and Phoma heteromorphospora, the type species of Phoma sect. Heterospora can be assigned to the Phaeosphaeriaceae and Leptosphaeriaceae respectively.     

Differences in penetration routes and establishment rates of four entomopathogenic nematode species into four white grub species

We compared the penetration of the entomopathogenic nematodes Steinernema scarabaei (AMK001 strain), S. glaseri (NC1 strain), Heterorhabditis zealandica (X1 strain), and H. bacteriophora (GPS11 strain) into third-instars of the scarabs Popillia japonica, Anomala orientalis, Cyclocephala borealis, and Rhizotrogus majalis. When larvae were exposed to nematodes for 6-72 h larval mortality and nematode establishment rate and occasionally speed of kill often showed the same pattern within nematode-white grub combinations. But no two nematodes or white grub species had the same pattern for these observations for all white grub or nematode species, respectively. Mortality, establishment, and speed of kill followed a similar pattern for H. zealandica, S. glaseri, and S. scarabaei, but there was no clear relationship for H. bacteriophora. Significant nematode establishment was only observed after at least 48 h exposure in most nematode-white grub combinations. Faster establishment was observed only for H. zealandica in A. orientalis and R. majalis (after 24 h) and for S. scarabaei in P. japonica and R. majalis (after 12 h). Nematode establishment after 72 h in the different scarab species was generally low for S. glaseri (<1.5%) and H. bacteriophora (<3%), higher for H. zealandica (2-5%), and the highest for S. scarabaei (1-14%). However, in another experiment establishment was generally higher after 96h exposure. Nematode penetration sites were determined by comparing nematode establishment in larvae with mouth, anus, mouth+anus, or none sealed with glue. The trends for each nematode species were very similar in the different white grub species. H. zealandica and H. bacteriophora showed excellent cuticular penetration ability but may also penetrate through mouth and/or anus. S. glaseri also penetrated through the cuticle but lower establishment in larvae with mouth or mouth+anus sealed suggested that the mouth is an important penetration site. S. scarabaei showed a preference for the mouth as a penetration site, but it showed some cuticular penetration ability and may also use the anus as a penetration site. The methodology used cannot exclude that cuticular penetration also included penetration through the spiracles. To fully understand the effect of nematode and white grub species on nematode virulence, future studies will have to compare host immune response to the penetrating IJs and the role of the symbiotic bacteria in these interactions.     

New Afrotropical species belonging to genera never recorded before for the Afrotropical fauna (Diptera: Tachinidae)

Five remarkable new Afrotropical species belonging to four Old World genera never recorded before for the Afrotropical region (Neophryxe, Calliethilla, Metadrinomyia, Pseudalsomyia) are described and compared with congeners. Existing keys to tropical African tachinid genera are implemented. A brief discussion on the apomorphic support to each genus is provided.     

Flavonoids in the species of Cyrtomium (Dryopteridaceae) and related genera

Flavonoids in 19 Cyrtomium, three Cyrtogonellum and two Phanerophlebia taxa were surveyed. Major flavonoids were flavonol O-glycosides based on kaempferol, quercetin, and sometimes myricetin, and C-glycosylflavones, such as isovitexin, vitexin, isoorientin, orientin and their O-glycosides. The C-methylflavanones, farrerol and cyrtominetin, and their 7-O-glucosides were isolated from Cyrtomium devexiscapulae and Cyrtomium laetevirens. Flavanones have been reported from Cyrtomium falcatum sensu lato. Though C. falcatum sensu lato is divided into four taxa, i.e. C. falcatum subsp. falcatum, C. falcatum subsp. australe, C. falcatum subsp. littorale, and C. devexiscapulae, the occurrence of the flavanones was restricted to C. devexiscapulae, and they did not occur in C. falcatum sensu stricto.     

Phylogeny of the Celastreae (Celastraceae) and the relationships of Catha edulis (qat) inferred from morphological characters and nuclear and plastid genes

The phylogeny of Celastraceae tribe Celastreae, which includes about 350 species of trees and shrubs in 15 genera, was inferred in a simultaneous analysis of morphological characters together with nuclear (ITS and 26S rDNA) and plastid (matK, trnL-F) genes. A strong correlation was found between the geography of the species sampled and their inferred relationships. Species of Maytenus and Gymnosporia from different regions were resolved as polyphyletic groups. Maytenus was resolved in three lineages (New World, African, and Austral-Pacific), while Gymnosporia was resolved in two lineages (New World and Old World). Putterlickia was resolved as nested within the Old World Gymnosporia. Catha edulis (qat, khat) was resolved as sister to the clade of Allocassine, Cassine, Lauridia, and Maurocenia. Gymnosporia cassinoides, which is reportedly chewed as a stimulant in the Canary Islands, was resolved as a derived member of Gymnosporia and is more closely related to Lydenburgia and Putterlickia than it is to Catha. Therefore, all eight of these genera are candidates for containing cathinone- and/or cathine-related alkaloids.     

干旱胁迫对黄土高原4种蒿属植物叶形态解剖学特征的影响

以黄土高原演替初期阶段的猪毛蒿(Artemisia scoparia Waldst.et Kit.)、茭蒿(Artemisia giraldii Pamp.)、铁杆蒿(Artemisia gmelinii Web.ex Stechm.)3种优势种和1种常见种黄花蒿(Artemisia annua Linn.)为供试材料,采用盆栽试验与称重控水法,将土壤含水量分别控制在田间最大持水量的75%(适宜水分对照)、55%(中度干旱)和35%(重度干旱),研究干旱胁迫对菊科蒿属植物叶片形态解剖学的影响,揭示植物叶片生态适应机制,为生态恢复过程中植被演替的规律提供理论依据。于植物营养生长末期选取代表性的叶片,分别采用电子扫描显微镜、电子透射显微镜和光学显微镜对叶表皮特征、亚细胞显微特征和组织结构进行观察。结果表明:干旱胁迫下,这4种植物表现为不同程度的叶片增厚、栅栏组织厚度、叶片紧实度和角质层厚度增加;3种旱生型植物猪毛蒿、茭蒿和铁杆蒿的叶片下表皮具有浓密的表皮毛,有利于防止水分过度蒸腾,而中生型黄花蒿叶片无此功能;铁杆蒿和黄花蒿上表皮毛稀少,不利于保水和防止强光照,干旱胁迫下依靠降低上表皮气孔密度和叶细胞叶绿体数目来适应环境;茭蒿和猪毛蒿叶绿体形态相似,具有较厚的基粒和浓密的基粒片层,强光下容易引起氧化损伤,猪毛蒿通过浓密的上表皮毛而茭蒿通过较强的抗氧化机制防止光能过剩,两者在重度干旱下均产生大量脂质体。4种蒿属植物中黄花蒿的叶片解剖学特征受到干旱的影响变化最大,铁杆蒿和猪毛蒿次之,茭蒿最弱,3种优势种的干旱适应性显著强于黄花蒿,干旱下叶片解剖学的结论与干旱耐受性指标结果一致。     

Unification of the genera Nonlabens, Persicivirga, Sandarakinotalea and Stenothermobacter into a single emended genus, Nonlabens, and description of Nonlabens agnitus sp. nov

Phylogenetic analyses based on 16S rRNA gene sequences showed that a bacterial isolate, designated JC2678(T), represents a distinct phyletic line within the suprageneric monophyletic clade containing the genera Nonlabens, Persicivirga, Stenothermobacter and Sandarakinotalea. The polyphasic data presented in this study demonstrated that the members belonging to the Nonlabens-like clade overall constitute a single genus. Therefore, it is proposed to transfer the members of genera Persicivirga O'Sullivan et al. 2006, Stenothermobacter Lau et al. 2006 and Sandarakinotalea Khan et al. 2006 to the genus Nonlabens Lau et al. 2005. Thus, P. dokdonensis (Yoon et al. 2006) Nedashkovskaya et al. 2009, P. ulvanivorans Barbeyron et al. 2010, P. xylanidelens O'Sullivan et al. 2006, Sandarakinotalea sediminis Khan et al. 2006 and Stenothermobacter spongiae Lau et al. 2006 should be transferred to Nonlabens dokdonensis comb. nov., Nonlabens ulvanivorans comb. nov., Nonlabens xylanidelens comb. nov., Nonlabens sediminis comb. nov. and Nonlabens spongiae comb. nov., respectively. In addition, strain JC2678(T) (=KACC 14155(T)=JCM 17109(T)) is proposed to constitute a novel species belonging to the genus Nonlabens with the name of Nonlabens agnitus sp. nov.     

砷诱导蚕豆气孔保卫细胞死亡的毒性效应

采用蚕豆(Vicia faba L.)叶面气孔保卫细胞,研究砷对细胞的毒性效应。结果表明,0.3—10 mg/L的NaAsO_2能降低保卫细胞活性,使部分细胞死亡,死亡率随砷浓度升高而增高。死细胞中呈现核固缩、核崩解等典型程序性死亡特征,且泛caspase抑制剂Z-Asp-CH_2-DCB能阻止NaAsO_2诱发的细胞死亡。过氧化氢清除剂过氧化氢酶与NaAsO_2共同作用时,细胞死亡率显著低于砷单独处理组,保卫细胞内Ca~(2+)水平降低,具程序性死亡特征的细胞数减少;Ca~(2+)特异性螯合剂EGTA亦能降低NaAsO_2诱发的细胞死亡。研究结果表明,NaAsO_2能诱发蚕豆保卫细胞程序性死亡,该过程由胁迫引发的ROS升高引起,ROS可能通过激活质膜Ca~(2+)通道,使胞外Ca~(2+)内流,造成胞内Ca~(2+)浓度升高,进而诱导细胞程序性死亡。     

A comparative study of latex-producing tissues in genera of Liabeae (Asteraceae)

Laticifers are highly specialized living plant cells which produce and contain latex. Occurrence of latex was used to establish morphological affinities (i) between Liabeae and other Asteracean tribes, (ii) among the Liabean genera, and (iii) in order to obtain phylogenies within Liabeae. However, structures and types of latex-producing tissues in this tribe have not yet been studied anatomically. In the present paper latex-producing structures of aerial parts in species of Microliabum, Munnozia, and Paranephelius (Liabeae), from open areas in mid-elevation Andean forests and in Andean high-elevation habitats, were studied. In all the analyzed species, latex secretion was easily observed in stem and leaf blade hand sections. Laticifers accompanied vascular tissues in all the cases, throughout stems and leaves, and they were of the articulated anastomosed type, at least in fully developed stages. Laticifers were found facing both, the xylem and the phloem, except for Paranephelius stems, in which they occur merely next to the phloem. Leaf laticifers form a reticulum accompanying the vein system. The type of latex-producing tissue shared by Microliabum and Munnozia could be a character shared by common ancestry whereas the laticifer system of Paranephelius stems could represent an evolutionary novelty for this genus. The laticifer type described in this study in aerial parts of Liabeae may allow establishing morphological affinities with tribes Cichorieae and Arctoteae.     

Glucans of lichenized fungi: significance for taxonomy of the genera Parmotrema and Rimelia

The glucans of lichenized fungi are an important class of polysaccharides with structural and chemotaxonomic roles. The water-insoluble glucans of the genus Parmotrema (P. austrosinense, P. delicatulum, P. mantiqueirense, P. schindleri, and P. tinctorum) and those of Rimelia (R. cetrata and R. reticulata), were investigated in order to evaluate the significance in chemotyping, with nigeran [(1-->3),(1-->4)-alpha-glucan] and lichenan [(1-->3),(1-->4)-beta-glucan] characterized using (1)H and (13)C NMR, methylation analysis, and controlled Smith degradations. Results from all species were similar, suggesting that glucan chemistry does not support separation of Rimelia from Parmotrema.     

A critical role of teashirt for patterning the ventral epidermis is masked by ectopic expression of tiptop, a paralog of teashirt in Drosophila

The teashirt gene encodes a protein with three widely spaced zinc finger motifs that is crucial for specifying trunk identity in Drosophila embryos. Here, we describe a gene called tiptop, which encodes a protein highly similar to Teashirt. We have analyzed the expression patterns and functions of these two genes in the trunk of the embryo. Initially, teashirt and tiptop expressions are detected in distinct domains; teashirt in the trunk and tiptop in parts of the head and tail. In different mutant situations, we show that, in the trunk and head, they repress each other's expression. Unlike teashirt, we found that deletion of tiptop is homozygous viable and fertile. However, embryos lacking both gene activities display a more severe trunk phenotype than teashirt mutant embryos alone. Ectopic expression of either gene produces an almost identical phenotype, indicating that Teashirt and Tiptop have, on the whole, common activities. We conclude that Teashirt and Tiptop repress each other's expression and that Teashirt has a crucial role for trunk patterning that is in part masked by ectopic expression of Tiptop.     

Differences in the response sensitivity of stomatal index to atmospheric CO2 among four genera of Cupressaceae conifers

Background and Aims

The inverse relationship between stomatal density (SD: number of stomata per mm² leaf area) and atmospheric concentration of CO₂ ([CO₂]) permits the use of plants as proxies of palaeo-atmospheric CO₂. Many stomatal reconstructions of palaeo-[CO₂] are based upon multiple fossil species. However, it is unclear how plants respond to [CO₂] across genus, family or ecotype in terms of SD or stomatal index (SI: ratio of stomata to epidermal cells). This study analysed the stomatal numbers of conifers from the ancient family Cupressaceae, in order to examine the nature of the SI–[CO₂] relationship, and potential implications for stomatal reconstructions of palaeo-[CO₂].

Methods

Stomatal frequency measurements were taken from historical herbarium specimens of Athrotaxis cupressoides, Tetraclinis articulata and four Callitris species, and live A. cupressoides grown under CO₂-enrichment (370, 470, 570 and 670 p.p.m. CO₂).

Key Results

T. articulata, C. columnaris and C. rhomboidea displayed significant reductions in SI with rising [CO₂]; by contrast, A. cupressoides, C. preissii and C. oblonga show no response in SI. However, A. cupressoides does reduce SI to increases in [CO₂] above current ambient (approx. 380 p.p.m. CO₂). This dataset suggests that a shared consistent SI–[CO₂] relationship is not apparent across the genus Callitris.

Conclusions

The present findings suggest that it is not possible to generalize how conifer species respond to fluctuations in [CO₂] based upon taxonomic relatedness or habitat. This apparent lack of a consistent response, in conjunction with high variability in SI, indicates that reconstructions of absolute palaeo-[CO₂] based at the genus level, or upon multiple species for discrete intervals of time are not as reliable as those based on a single or multiple temporally overlapping species.     

Phylogenetic and morphological diversity of novel soil cercomonad species with a description of two new genera (Nucleocercomonas and Metabolomonas)

Cercomonads are important components of microbial food webs in soils and aquatic sediments. Here, we investigated the general morphology, behaviour, life cycle and 18S rDNA phylogeny of cercomonad cultures from a German grassland soil habitat. We describe ten new species including two new genera from 23 strains. Three Cercomonas, two Eocercomonas and three Paracercomonas species are described. Based on large phylogenetic distance and distinct morphology, we erect two novel clade B genera near the root of the cercomonad tree. Nucleocercomonas nov. gen. bears a number of characters unusual for cercomonads: Its anterior flagellum is extremely long, it mostly does not glide, and in its most frequent life stage the cell body does not attach to the substratum, but produces unattached pseudopodia. Furthermore, it has a unique nucleus with a peripheral nucleolus that attaches to the nuclear envelope opposite the basal body connection. Metabolomonas nov. gen. is extremely metabolic. It is characterized by a very high beating frequency of the anterior flagellum, fast gliding, rapid changes in shape and strong cytoplasmic streams. A new genus Brevimastigomonas is erected for the previously described species Paracercomonas anaerobica. The general morphology of cercomonad species often does not correspond with their phylogenetic position: closely related species may have a very different morphology.     

Comparative phytochemical analysis of four Mexican Nymphaea species

Four Mexican Nymphaea species, N. ampla, N. pulchella, N. gracilis and N. elegans belonging to subgenera Brachyceras were analyzed. In this work two 5-glycosyl isoflavones, 7,3',4'-trihydroxy-5-O-beta-D-(2'-acetyl)-xylopyranosylisoflavone (1) and 7,3',4'-trihydroxy-5-O-alpha-L-rhamnopyranosylisoflavone (2), were isolated from N. ampla and N. pulchella, respectively, together with other known 3-glycosyl flavones and triterpene saponins from the same four species. The structures were elucidated by 1D and 2D NMR, FABMS, and other spectroscopic analyses. These results confirmed that the four species were different from each other and established that N. pulchella represents a different taxa than N. ampla. In addition, the 5-glycosyl isoflavones could be considered as a taxonomic character of this group of plants.     

Polyphenoloxidase activity in coffee leaves and its role in resistance against the coffee leaf miner and coffee leaf rust

In plants, PPO has been related to defense mechanism against pathogens and insects and this role was investigated in coffee trees regarding resistance against a leaf miner and coffee leaf rust disease. PPO activity was evaluated in different genotypes and in relation to methyl-jasmonate (Meja) treatment and mechanical damage. Evaluations were also performed using compatible and incompatible interactions of coffee with the fungus Hemileia vastatrix (causal agent of the leaf orange rust disease) and the insect Leucoptera coffeella (coffee leaf miner). The constitutive level of PPO activity observed for the 15 genotypes ranged from 3.8 to 88 units of activity/mg protein. However, no direct relationship was found with resistance of coffee to the fungus or insect. Chlorogenic acid (5-caffeoylquinic acid), the best substrate for coffee leaf PPO, was not related to resistance, suggesting that oxidation of other phenolics by PPO might play a role, as indicated by HPLC profiles. Mechanical damage, Meja treatment, H. vastatrix fungus inoculation and L. coffeella infestation caused different responses in PPO activity. These results suggest that coffee resistance may be related to the oxidative potential of the tissue regarding the phenolic composition rather than simply to a higher PPO activity.