Abundance,diversity and geographic distribution of cassava mosaic disease pandemic‐associated Bemisia tabaci in Tanzania

Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), one of the most economically important agricultural pests worldwide, is the vector of cassava mosaic geminiviruses that cause cassava mosaic disease (CMD). In East and Central Africa, a severe CMD pandemic that spread from Uganda in the late 1980s still continues to devastate cassava crops. To assess the association of distinct B. tabaci genetic groups with the CMD pandemic, mitochondrial cytochrome oxidase I gene sequences were analysed from whiteflies collected during surveys conducted from 2010 to 2013 in Tanzania. Four genetic groups – Sub‐Saharan Africa 1 (SSA1), Mediterranean, Indian Ocean and East Africa 1, and a group of unknown whitefly species were identified. SSA1 comprised four subgroups: SSA1‐SG1, SSA1‐SG2, SSA1‐SG1/2 and SSA1‐SG3. SSA1‐SG1 was confined to the pandemic‐affected north‐western parts of Tanzania whilst SSA1‐SG2 and SSA1‐SG3 were found in the central and eastern parts not yet affected by the pandemic. The CMD pandemic front was estimated to lie in Geita Region, north‐western Tanzania, and to be spreading south‐east at a rate of ca 26 km/year. The pandemic‐associated B. tabaci SSA1‐SG1 predominated up to 180 km ahead of the CMD front indicating that changes in whitefly population characteristics precede changes in disease characteristics.     

Diversity of symbiotic bacteria associated with Bemisia tabaci (Homoptera: Aleyrodidae) in cassava mosaic disease pandemic areas of Tanzania

All Bemisia tabaci individuals harbour an obligate bacterial symbiont (Portiera aleyrodidarum), and many also harbour non‐essential facultative symbionts. The association of symbiotic bacteria with the various genetic groups of B. tabaci remains unknown for East Africa. This study aimed to assess any association between the various whitefly genetic groups and the endosymbionts they harbour; to investigate if a unique endosymbiont is associated with super‐abundant whiteflies, and to provide baseline information on endosymbionts of whiteflies for a part of East Africa. Whiteflies collected during surveys in Tanzania were genotyped and screened for the presence of the obligate and six secondary symbionts (SS): Rickettsia (R), Hamiltonella (H), Arsenophonus (A), Wolbachia (W), Cardinium (C) and Fritschea (F). The results revealed the presence of Mediterranean (MED), East Africa 1 (EA1), Indian Ocean (IO) and Sub‐Saharan Africa 1 (SSA1) genetic groups of Bemisia tabaci, with SSA1 further clustered into four sub‐groups: SSA1‐SG1, SSA1‐SG2, SSA1‐SG1/2 and SSA1‐SG3. F was completely absent from all of the whiteflies tested while R was always found in double or multiple infections. In general, no particular symbiont appeared to be associated with the super‐abundant SSA1‐SG1 B. tabaci, although A or AC infections were common among infected individuals. The most striking feature of these super‐abundant whiteflies, dominating cassava mosaic disease pandemic areas, was the high prevalence of individuals uninfected by any of the six SS tested. This study of the endosymbionts of B. tabaci in East Africa showed contrasting patterns of infection in crop and weed hosts.     

Pleistocene camelids from the Syrian Desert: The diversity in El Kowm

The family Camelidae has been present in Eurasia since the latest Miocene, and several species are recognized, but their evolution is poorly known. The region of El Kowm, central Syria, includes several sites spanning the Early to Late Pleistocene and provides the only abundant fossil record of camelids in the Middle East. Our preliminary results show that several species are present over the sequence, revealing some surprising evolutionary trends.     

Two new taxa of Achnanthidium and Encyonema (Bacillariophyceae) from the Yom River,Thailand, with special reference to the areolae occlusions implying ontogenetic relationship

We discovered two new taxa of Achnanthidium and Encyonema occurring with high abundance in the upstream of the Yom River, which is one of four major rivers in Northern Thailand. Achnanthidium pseudoconspicuum var. yomensis var. nov. closely resembles Achnanthidium pseudoconspicuum var. pseudoconspicuum in scanning electron microscopy (SEM), but has clearly different valve morphometry under the light microscopy (LM). Achnanthidium pseudoconspicuum var. yomensis is also similar to A. japonicum in valve morphology under LM, but differs to this species based on SEM observation. Encyonema yuwadeeanum sp. nov. shows similarities to Encyonema leei and Encyonema subkukenanum, but differs in valve shape and/or polar fissure shape. We discuss the possible valve ontogenetic relationship between Achnanthidium and Cymbellales based on the detailed areolae structures of these two new taxa.     

抗癌镇痛肽AGAP肺靶向融合体在毕赤酵母中的表达

利用构建好的质粒pPIC9K-RGD-4C-His Tag-AGAP（analgesic-antitumor peptide,抗癌镇痛肽）进行单酶切线性化,然后电转化毕赤酵母GS115,电转之后的菌落通过菌落PCR进行筛选,最终得到阳性菌落。阳性菌落经增菌培养,甲醇诱导后的上清SDS-PAGE电泳后经western blot检测证明,抗癌镇痛肽肺靶向融合体已经成功得到表达。     

Tree dieback and regeneration in secondary Acacia zanzibarica woodlands on an abandoned cattle ranch in coastal Tanzania

Questions: Bush encroachment is a major problem when African savanna ecosystems are used for cattle ranching. How do secondary woodlands develop after ranching is abandoned? What are the patterns and rates of tree mortality and regeneration? Location: Mkwaja Ranch (now part of Saadani National Park) in coastal Tanzania. Methods: Ninety‐seven circular plots (4‐m radius) were set in secondary Acacia zanzibarica woodland along a gradient of tree density. Variables relating to tree and grass layers and soil characteristics of plots were recorded. Seedlings were counted twice in the wet seasons, and resprouts once. Tree flowering and pod production were assessed during the fruiting season, while survival of trees initially present was recorded after 12 and 32 months. Interrelationships among variables were investigated using multiple linear regression, binary logistic regression and mixed effects models. Results: After 32 months, over one‐third of trees in plots had died. Most died after fire, especially on heavy soils, and mortality was significantly related to the tree live biomass ratio and soil conditions. Seed production was very low, especially in denser stands. Numbers of seedlings correlated with soil and grass variables but not with seed rain. Half of trees killed above‐ground produced coppice shoots from the base; in contrast, root suckering was independent of topkill. By the end of the study, no seedlings survived and no resprouts emerged above the grass layer. Conclusions: A. zanzibarica woodlands at Mkwaja Ranch were able to develop because of ranching, and can only persist under intensive grazing. The woodlands do not represent a successional stage towards forest and will probably revert to predominantly grassland vegetation within 10–20 years unless grazing pressure from wild ungulates increases considerably and/or fire regimes change.     

Tyrosine 656 in topoisomerase IIβ is important for the catalytic activity of the enzyme: Identification based on artifactual +80-Da modification at this site

Topoisomerase (topo) II catalyzes topological changes in DNA. Although both human isozymes, topo IIα and β are phosphorylated, site‐specific phosphorylation of topo IIβ is poorly characterized. Using LC‐MS/MS analysis of topo IIβ, cleaved with trypsin, Arg C or cyanogen bromide (CNBr) plus trypsin, we detected four +80‐Da modified sites: tyr656, ser1395, thr1426 and ser1545. Phosphorylation at ser1395, thr1426 and ser1545 was established based on neutral loss of H₃PO₄ (?98 Da) in the CID spectra and on differences in 2‐D‐phosphopeptide maps of ³²P‐labeled wild‐type (WT) and S1395A or T1426A/S1545A mutant topo IIβ. However, phosphorylation at tyr656 could not be verified by 2‐D‐phosphopeptide mapping of ³²P‐labeled WT and Y656F mutant protein or by Western blotting with phosphotyrosine‐specific antibodies. Since the +80‐Da modification on tyr656 was observed exclusively during cleavage with CNBr and trypsin, this modification likely represented bromination, which occurred during CNBr cleavage. Re‐evaluation of the CID spectra identified +78/+80‐Da fragment ions in CID spectra of two peptides containing tyr656 and tyr711, confirming bromination. Interestingly, mutation of only tyr656, but not ser1395, thr1326 or ser1545, decreased topo IIβ activity, suggesting a functional role for tyr656. These results, while identifying an important tyrosine in topo IIβ, underscore the importance of careful interpretation of modifications having the same nominal mass.     

Cranial deformation in a subadult sample from Değirmentepe (Chalcolithic,Turkey)

Human skeletal remains from the Chalcolithic period of De?irmentepe, Turkey, near the Euphrates River, display artificial cranial deformation of the circular type. Human skeletal remains belonging to 31 individual have been dated to the Chalcolithic period (second half of the fifth millennium BC, uncalibrated). The remains include foetuses, infants, children and juveniles; but no adult skeletons. Either the adults were buried elsewhere or flooding of the Euphrates dragged the adult remains away. Artificial cranial deformation was observed in 13 of the 31 subadults ranging in age from 1 month to 13–14 years. De?irmentepe villagers might have used one or two circular constricting bands with the intent of producing artificial head deformation. As far as Anatolia and the Near Eastern region is concerned, the widespread use of circular head deformation may be an indication of longer‐distance trade and more need for ethnic markers. Am J Phys Anthropol 115:238–244, 2001. © 2001 Wiley‐Liss, Inc.     

Biogeographical patterns of marine larval trematode parasites in two intermediate snail hosts in Europe

Aim We used published inventories of trematodes in Littorina littorea (L.) and Hydrobia ulvae (Pennant) in European seas to search for two basic biogeographical patterns in the spatial occurrence of various trematode species: (1) do parasite distribution and richness patterns in the two host snails overlap with known ecoregions of free‐living organisms; and (2) does trematode species richness in the snails follow latitudinal or longitudinal gradients? Location North East Atlantic. Methods We used multidimensional scaling (MDS), analysis of similarity (ANOSIM) and analysis of variance (ANOVA) to test whether there were overlaps of parasite distribution and richness with known ecoregions of free‐living organisms. In addition, we used linear regression analyses to test whether trematode richness in snails (corrected for sampling effort) was correlated with the latitude or longitude of the sampling sites. Results When corrected for sampling effort, mean trematode species richness per site did not differ among the different ecoregions in L. littorea. In contrast, in H. ulvae, mean species richness was much lower for sites from the Celtic Sea compared with sites from the Baltic Sea and the North Sea. Based on the results of MDS analyses, trematode species composition was distinct among ecoregions; in particular, communities from the Baltic Sea differed markedly from communities in the Celtic Sea, for both snail species. Latitude and longitude were not significantly correlated with parasite species richness in either snail species. Most trematode species had restricted distributions, and only three species in L. littorea and five species in H. ulvae occurred at more than 50% of the sites. Main conclusions There is more structure in the large‐scale distribution of trematodes in gastropods than one would expect from the large‐scale dispersal capabilities of their bird and fish final hosts. We propose mechanisms based both on limited dispersal via fish and bird final hosts and on gradients in environmental factors to explain the observed patterns.