Functional characterization of allantoinase genes from Arabidopsis and a nonureide-type legume black locust.
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The availability of nitrogen is a limiting factor for plant growth in most soils. Allantoin and its degradation derivatives are a group of soil heterocyclic nitrogen compounds that play an essential role in the assimilation, metabolism, transport, and storage of nitrogen in plants. Allantoinase is a key enzyme for biogenesis and degradation of these ureide compounds. Here, we describe the isolation of two functional allantoinase genes, AtALN (Arabidopsis allantoinase) and RpALN (Robinia pseudoacacia allantoinase), from Arabidopsis and black locust (Robinia pseudoacacia). The proteins encoded by those genes were predicted to have a signal peptide for the secretory pathway, which is consistent with earlier biochemical work that localized allantoinase activity to microbodies and endoplasmic reticulum (Hanks et al., 1981). Their functions were confirmed by genetic complementation of a yeast mutant (dal1) deficient in allantoin hydrolysis. The absence of nitrogen in the medium increased the expression of the genes. In Arabidopsis, the addition of allantoin to the medium as a sole source of nitrogen resulted in the up-regulation of the AtALN gene. The black locust gene (RpALN) was differentially regulated in cotyledons, axis, and hypocotyls during seed germination and seedling growth, but was not expressed in root tissues. In the trunk wood of a mature black locust tree, the RpALN gene was highly expressed in the bark/cambial region, but had no detectable expression in the sapwood or sapwood-heartwood transition zone. In addition, the gene expression in the bark/cambial region was up-regulated in spring and fall when compared with summer, suggesting its involvement in nitrogen mobilization. (+info)
A novel family of lectins evolutionarily related to class V chitinases: an example of neofunctionalization in legumes.
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A lectin has been identified in black locust (Robinia pseudoacacia) bark that shares approximately 50% sequence identity with plant class V chitinases but is essentially devoid of chitinase activity. Specificity studies indicated that the black locust chitinase-related agglutinin (RobpsCRA) preferentially binds to high-mannose N-glycans comprising the proximal pentasaccharide core structure. Closely related orthologs of RobpsCRA could be identified in the legumes Glycine max, Medicago truncatula, and Lotus japonicus but in no other plant species, suggesting that this novel lectin family most probably evolved in an ancient legume species or possibly an earlier ancestor. This identification of RobpsCRA not only illustrates neofunctionalization in plants, but also provides firm evidence that plants are capable of developing a sugar-binding domain from an existing structural scaffold with a different activity and accordingly sheds new light on the molecular evolution of plant lectins. (+info)
High-resolution three-dimensional extracellular recording of neuronal activity with microfabricated electrode arrays.
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Bellojisia, a new sordariaceous genus for Jobellisia rhynchostoma and a description of Jobellisiaceae fam. nov.
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The phylogenetic analyses of partial nucLSU rDNA sequence data of three Jobellisia species indicate that J. rhynchostoma is distinct from the core species of Jobellisia. Jobellisia luteola, the type species of the genus, and J. fraterna reside as a strongly supported monophyletic clade in a basal position in a grouping containing the Diaporthales, the Calosphaeriales and the Togniniaceae, while all phylogenies confirm the placement of J. rhynchostoma within the Sordariales. The new family Jobellisiaceae (incertae sedis) is described for Jobellisia. A new perithecial ascomycete genus, Bellojisia (Lasiosphaeriaceae, Sordariales), is introduced for J. rhynchostoma. The fungus produces nonstromatic, long-necked perithecia with a superficial to semi-immersed pyriform venter and carbonaceous three-layered perithecial wall, 1-septate, hyaline, later brown, reniform to navicular ascospores with a polar germ pore formed in unitunicate asci. The fungus was not observed to produce a conidial anamorph in vitro. Both morphological and molecular data suggest Corylomyces selenosporus of the Sordariales is the closest relative of J. rhynchostoma. The other relatives of Bellojisia (viz. Cercophora, Lasiosphaeria and Podospora) recruit from the Lasiosphaeriaceae (Sordariales). Cercophora and Podospora are shown as polyphyletic within the Sordariales, which is in agreement with previous molecular studies. (+info)
Mesorhizobium robiniae sp. nov., isolated from root nodules of Robinia pseudoacacia.
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