The cyanobacterial PilT protein responsible for cell motility and transformation hydrolyzes ATP

The unicellular cyanobacterium, Synechocystis sp. PCC 6803 is motile. A homologue of the PilT protein family, required for twitching motility in Pseudomonas aeruginosa and social gliding motility in Myxococcus xanthus, was found to be necessarily associated with cyanobacterial motility. The pilT1 (slr0161) mutant shows a pleotropic phenotype, defects in individual cell motility, and an increased number of long surface pili. Furthermore, the mutant loses its ability of natural competency. These findings demonstrate that PilT1 is essential for both cell motility and competency. Since the pilT gene contains a consensus ATP-binding motif (Walker boxes), the PilT protein is suggested for supplying energy for cell motility. The product of pilT1, overproduced in Escherichia coli and purified by Ni-affinity chromatography, hydrolyzes ATP in vitro.     

Nuatigenin-type steroidal saponins from Veronica fuhsii and V. muldtfida

A new nuatigenin-type steroidal saponin, multifidoside (2), was isolated from the aerial parts of Veronica fuhsii and V multifida and its structure was identified as 3-O-([alpha-L-rhamnopyranosyl-(1-->2glu)]-[beta-D-glucopyranosyl-(1-->4rha)-alpha-L-rhamnopyranosyl (1-->4glu)]-beta-D-glucopyranosyl]nuatigenin 26-O-beta-D-glucopyranoside. Additionally, a known steroidal saponoside, aculeatiside A (1), from V. fuhsii, a phenylethanoid glycoside, verpectoside A (3), and a flavon glycoside, isoscutellarein 7-O-(2"-O-6"-O-acetyl-beta-D-allopyranosyl-beta-D-glucopyranoside) (4) from V. multifida were isolated.     

Interaction of plexin-B1 with PDZ domain-containing Rho guanine nucleotide exchange factors

The Rho family GTPase has been implicated in plexin-B1, a receptor for Semaphorin 4D (Sema4D), mediating signal transduction. Rho may also play a function in this signaling pathway as well as Rac, but the mechanisms for Rho regulation are poorly understood. In this study, we have identified two kinds of PDZ domain-containing Rho-specific guanine nucleotide exchange factors (RhoGEFs) as proteins interacting with plexin-B1 cytoplasmic domain. These PDZ domain-containing RhoGEFs showed significant homology to human KIAA0380 (PDZ-RhoGEF) and LARG (KIAA0382), respectively. Both KIAA0380 and LARG could bind plexin-B1 and a deletion mutant analysis of plexin-B1, KIAA0380 and LARG revealed that KIAA0380 and LARG bound plexin-B1 cytoplasmic tail through their PDZ domains. The tissue distribution analysis indicated that plexin-B1 was co-localized with KIAA0380 and LARG in various tissues. Immunocytochemical analysis showed that LARG was recruited to plasma membrane by plexin-B1. These results suggest that PDZ domain-containing RhoGEFs play a role in Sema4D-plexin-B1 mediating signal transduction.     

Prediction of biologically significant components from microarray data: Independently Consistent Expression Discriminator (ICED)

MOTIVATION: Class distinction is a supervised learning approach that has been successfully employed in the analysis of high-throughput gene expression data. Identification of a set of genes that predicts differential biological states allows for the development of basic and clinical scientific approaches to the diagnosis of disease. The Independent Consistent Expression Discriminator (ICED) was designed to provide a more biologically relevant search criterion during predictor selection by embracing the inherent variability of gene expression in any biological state. The four components of ICED include (i) normalization of raw data; (ii) assignment of weights to genes from both classes; (iii) counting of votes to determine optimal number of predictor genes for class distinction; (iv) calculation of prediction strengths for classification results. The search criteria employed by ICED is designed to identify not only genes that are consistently expressed at one level in one class and at a consistently different level in another class but identify genes that are variable in one class and consistent in another. The result is a novel approach to accurately select biologically relevant predictors of differential disease states from a small number of microarray samples. RESULTS: The data described herein utilized ICED to analyze the large AML/ALL training and test data set (Golub et al., 1999, Science, 286, 531-537) in addition to a smaller data set consisting of an animal model of the childhood neurodegenerative disorder, Batten disease, generated for this study. Both of the analyses presented herein have correctly predicted biologically relevant perturbations that can be used for disease classification, irrespective of sample size. Furthermore, the results have provided candidate proteins for future study in understanding the disease process and the identification of potential targets for therapeutic intervention.     

(+)-Strigol,a witchweed seed germination stimulant,from Menispermum dauricum root culture

(+)-Strigol was isolated from Menispermum dauricum root culture filtrate. Its identity was confirmed by HPLC, 1H NMR, UV and MS, and on the basis of its CD spectrum. This is the first report on isolation of strigolactone from aseptic plant culture.     

Possible involvement of leaf gibberellins in the clock-controlled expression of XSP30, a gene encoding a xylem sap lectin, in cucumber roots

Root-produced organic compounds in xylem sap, such as hormones and amino acids, are known to be important in plant development. Recently, biochemical approaches have revealed the identities of several xylem sap proteins, but the biological functions and the regulation of the production of these proteins are not fully understood. XYLEM SAP PROTEIN 30 kD (XSP30), which is specifically expressed in the roots of cucumber (Cucumis sativus), encodes a lectin and is hypothesized as affecting the development of above-ground organs. In this report, we demonstrate that XSP30 gene expression and the level of XSP30 protein fluctuate in a diurnal rhythm in cucumber roots. The rhythmic gene expression continues for at least two or three cycles, even under continuous light or dark conditions, demonstrating that the expression of this gene is controlled by a circadian clock. Removal of mature leaves or treatment of shoots with uniconazole-P, an inhibitor of gibberellic acid (GA) biosynthesis, dampens the amplitude of the rhythmic expression; the application of GA negates these effects. These results suggest that light signals perceived by above-ground organs, as well as GA that is produced, possibly, in mature leaves, are important for the rhythmic expression of XSP30 in roots. This is the first demonstration of the regulation of the expression of a clock-controlled gene by GA.     

A kinesin,invA, plays an essential role in volvox morphogenesis

In Volvox carteri adults, reproductive cells called gonidia are enclosed within a spherical monolayer of biflagellate somatic cells. Embryos must "invert" (turn inside out) to achieve this configuration, however, because at the end of cleavage the gonidia are on the outside and the flagellar ends of all somatic cells point inward. Generation of a bend region adequate to turn the embryo inside out involves a dramatic change in cell shape, plus cell movements. Here, we cloned a gene called invA that is essential for inversion and found that it codes for a kinesin localized in the cytoplasmic bridges that link all cells to their neighbors. In invA null mutants, cells change shape normally, but are unable to move relative to the cytoplasmic bridges. A normal bend region cannot be formed and inversion stops. We conclude that the InvA kinesin provides the motile force that normally drives inversion to completion.