Live imaging of nuage and polar granules: evidence against a precursor-product relationship and a novel role for Oskar in stabilization of polar granule components.
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Nuage, a germ line specific organelle, is remarkably conserved between species, suggesting that it has an important germline cell function. Very little is known about the specific role of this organelle, but in Drosophila three nuage components have been identified, the Vasa, Tudor and Aubergine proteins. Each of these components is also present in polar granules, structures that are assembled in the oocyte and specify the formation of embryonic germ cells. We used GFP-tagged versions of Vasa and Aubergine to characterize and track nuage particles and polar granules in live preparations of ovaries and embryos. We found that perinuclear nuage is a stable structure that maintains size, seldom detaches from the nuclear envelope and exchanges protein components with the cytoplasm. Cytoplasmic nuage particles move rapidly in nurse cell cytoplasm and passage into the oocyte where their movements parallel that of the bulk cytoplasm. These particles do not appear to be anchored at the posterior or incorporated into polar granules, which argues for a model where nuage particles do not serve as the precursors of polar granules. Instead, Oskar protein nucleates the formation of polar granules from cytoplasmic pools of the components shared with nuage. Surprisingly, Oskar also appears to stabilize at least one shared component, Aubergine, and this property probably contributes to the Oskar-dependent formation of polar granules. We also find that Bruno, a translational control protein, is associated with nuage, which is consistent with a model in which nuage facilitates post transcriptional regulation by promoting the formation or reorganization of RNA-protein complexes. (+info)
The SOL Genomics Network: a comparative resource for Solanaceae biology and beyond.
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The SOL Genomics Network (SGN; http://sgn.cornell.edu) is a rapidly evolving comparative resource for the plants of the Solanaceae family, which includes important crop and model plants such as potato (Solanum tuberosum), eggplant (Solanum melongena), pepper (Capsicum annuum), and tomato (Solanum lycopersicum). The aim of SGN is to relate these species to one another using a comparative genomics approach and to tie them to the other dicots through the fully sequenced genome of Arabidopsis (Arabidopsis thaliana). SGN currently houses map and marker data for Solanaceae species, a large expressed sequence tag collection with computationally derived unigene sets, an extensive database of phenotypic information for a mutagenized tomato population, and associated tools such as real-time quantitative trait loci. Recently, the International Solanaceae Project (SOL) was formed as an umbrella organization for Solanaceae research in over 30 countries to address important questions in plant biology. The first cornerstone of the SOL project is the sequencing of the entire euchromatic portion of the tomato genome. SGN is collaborating with other bioinformatics centers in building the bioinformatics infrastructure for the tomato sequencing project and implementing the bioinformatics strategy of the larger SOL project. The overarching goal of SGN is to make information available in an intuitive comparative format, thereby facilitating a systems approach to investigations into the basis of adaptation and phenotypic diversity in the Solanaceae family, other species in the Asterid clade such as coffee (Coffea arabica), Rubiaciae, and beyond. (+info)
Latex-vegetable syndrome due to custard apple and aubergine: new variations of the hevein symphony.
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An increasing number of vegetables with crossreactions to latex are being described in patients with latex-vegetable syndrome. We present two of these vegetables, custard apple linked in two previous cases with latex sensitisation, and aubergine, that had not been described up to now in patients with latex sensitisation. The diagnosis of both cases was based on the clinical history, positive skin prick test (SPT) and specific IgE to the offending vegetables, as well as to positive SPT and specific IgE levels to latex and the major fruits involved in the latex-fruit syndrome (avocado, banana, and chestnut). Further, crude extracts from latex, custard apple and aubergine, as well as the purified allergens Hev b 6.02 and Prs a 1 were used in in vitro and in vivo assays: IgE immunodetection, histamine release (HRT) and basophil activation (BAT) tests and skin prick tests. In case 1, both purified Hev b 6.02 and Prs a 1 induced positive responses in skin prick tests, high levels of basophil activation and histamine release. Specific IgE immunodetection uncovered a reactive band of 45 kd in the crude custard apple extract, which was also recognized by anti-chitinase monospecific antibodies. The serum from patient 1 also detected Prs a 1 in immunodetection. Hev b 6.02 produced positive skin responses and showed high biological activity in HRT and BAT in the case of patient 2. However, Prs a 1 was reactive neither in SPT nor in IgE immunodetection. In fact, no band was detected using the serum of patient 2 in avocado or aubergine extracts. By contrast, Prs a 1 reached high values of basophil activation and over 10% of histamine release in case 2. (+info)
Heterologous expression of the Mi-1.2 gene from tomato confers resistance against nematodes but not aphids in eggplant.
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The Mi-1.2 gene in tomato (Solanum lycopersicum) is a member of the nucleotide-binding leucine-rich repeat (NBLRR) class of plant resistance genes, and confers resistance against root-knot nematodes (Meloidogyne spp.), the potato aphid (Macrosiphum euphorbiae), and the sweet potato whitefly (Bemisia tabaci). Mi-1.2 mediates a rapid local defensive response at the site of infection, although the signaling and defensive pathways required for resistance are largely unknown. In this study, eggplant (S. melongena) was transformed with Mi-1.2 to determine whether this gene can function in a genetic background other than tomato. Eggplants that carried Mi-1.2 displayed resistance to the root-knot nematode Meloidogyne javanica but were fully susceptible to the potato aphid, whereas a susceptible tomato line transformed with the same transgene was resistant to nematodes and aphids. This study shows that Mi-1.2 can confer nematode resistance in another Solanaceous species. It also indicates that the requirements for Mi-mediated aphid and nematode resistance differ. Potentially, aphid resistance requires additional genes that are not conserved between tomato and eggplant. (+info)
Mutations in the lrpE gene of Ralstonia solanacearum affects Hrp pili production and virulence.
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The Ralstonia solanacearum hrpB-regulated gene lrpE (hpx5/brg24) encodes a PopC-like leucine-rich repeat (LRR) protein that carries 11 tandem LRR in the central region. Defects in the lrpE gene slightly reduced the virulence of R. solanacearum on host plants and changed the bacterial morphology leading to the formation of large aggregates in a minimal medium. The aggregation in the deltalrpE background required the presence of a functional Hrp type III secretion system. In wild-type R. solanacearum, Hrp pili disappeared from the bacterial surface at the end of the exponential growth phase, when the pili form into long bundles. However, even in the late growth phase, bundled Hrp pili were still observed on the cell surface of the deltalrpE mutant. Such bundles were entangled and anchored the mutant cells in the aggregates. In contrast to PopC, LrpE accumulated in bacterial cells and did not translocate into plant cells as an effector protein. The expression levels of hrp genes increased three- to fivefold in the deltalrpE background compared with those in the wild type. We propose that LrpE may negatively regulate the production of Hrp pili on the cell surface of R. solanacearum to disperse bacterial cells from aggregates. In turn, dispersal may contribute to the movement of the pathogen in the plant vascular system and, as a consequence, the pathogenicity of R. solanacearum. (+info)
Metabolism of conjugated sterols in eggplant. Part 2. Phospholipid : steryl glucoside acyltransferase.
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A membrane-bound phospholipid : steryl glucoside acyltransferase from Solanum melongena leaves was partially purified and its specificity and molecular as well as kinetic properties were defined. Among the steryl glycosides tested (e.g. typical plant steryl glucosides, steryl galactosides and cholesteryl xyloside) the highest activity was found with cholesteryl glucoside, but some structurally related compounds such as sito- and stigmasteryl glucoside or galactoside as well as cholesteryl galactoside were also acylated, albeit at lower rates. The investigated enzyme was able to use all classes of phosphoglycerolipids (phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol) as an acyl source for biosynthesis of acylated steryl glucoside. Among them 1,2-dimirystoylphosphatidylic acid appeared to be the best acyl donor. Apart from phosphoglycerolipids, 1,2-diacylglycerols were also used as acyl donor for steryl glucoside acylation, although at a distinctly lower rate. The acyl moiety was transferred from the C-1 position of phospholipid molecule. The investigated acyltransferase activity was stimulated by 2-mercaptoethanol, Triton X-100, 1-monoacylglycerols and inhibited in the presence of divalent cations such as Ca(2+), Mn(2+), Zn(2+) or Co(2+), some lipids (MDGD, ceramide), detergents (Tween 20, 40, 60 and 80, Tyloxapol, sodium deoxycholate) and high ionic strength. (+info)
Metabolism of conjugated sterols in eggplant. Part 1. UDP-glucose : sterol glucosyltransferase.
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A membrane-bound UDP-glucose : sterol glucosyltransferase from Solanum melongena (eggplant) leaves was partially purified and its specificity as well as molecular and kinetic properties were defined. Among a wide spectrum of 3-OH steroids (i.e. typical plant sterols, androstane, pregnane and cholestane derivatives, steroidal alkaloids and sapogenins) and triterpenic alcohols, the highest activity was found with 22-oxycholesterol. UDP-glucose appeared to be the best sugar donor. The enzyme preparation was also able to utilize UDP-galactose, TDP-glucose and CDP-glucose as a sugar source for sterol glucosylation, however, at distinctly lower rates. The investigated glucosyltrasferase was stimulated by 2-mercaptoethanol, Triton X-100 and negatively charged phospholipids, and inhibited in the presence of UDP, mono-, di- and triacylglycerols, divalent cations such as Zn(2+), Co(2+), high ionic strength, cholesteryl glucoside, galactoside and xyloside and some amino acid-modifying reagents (SITS, DIDS, PLP, DEPC, pCMBS, NEM, WRK and HNB). Our results suggest that unmodified residues of lysine, tryptophan, cysteine, histidine and dicarboxylic amino acids are essential for full enzymatic activity and indicate that a glutamic (or aspartic) acid residue is necessary for the binding of sugar donor, i.e. UDP-glucose in the active site of the GT-ase while histidine and cysteine residues are both important for the binding of the nucleotide-sugar as well as of the steroidal aglycone. (+info)
ISSR and isozyme characterization of androgenetic dihaploids reveals tetrasomic inheritance in tetraploid somatic hybrids between Solanum melongena and Solanum aethiopicum group Gilo.
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