Growth regulators from the seaweed Chondrus crispus L. (Lyn.)

The level of auxin-like compounds extracted from the seaweed Chondrus crispus L. (Lyn.) is reported. Their presence before and after alkaline hydrolysis is studied to confirm that the bound auxin-like substances are present in algae in greater concentration than the free form.     

The NF1 locus encodes a protein functionally related to mammalian GAP and yeast IRA proteins

The von Recklinghausen neurofibromatosis locus, NF1, encodes a protein with homology restricted to the catalytic region of the RAS GTPase-activating protein, GAP, and with extensive homology to the IRA1 and IRA2 gene products of the yeast S. cerevisiae. A segment of the NF1 cDNA gene, expressed in yeast, can complement loss of IRA function and can inhibit both wild-type and mutant activated human H-ras genes that are coexpressed in yeast. Yeast expressing the NF1 segment have increased H-ras GTPase-stimulating activity. These studies indicate that the NF1 gene product can interact with RAS proteins and demonstrate structural and functional similarities and differences among the GAP, IRA1, IRA2, and NF1 proteins.     

Oxidative mitigation of aquatic methane emissions in large Amazonian rivers

The flux of methane (CH₄) from inland waters to the atmosphere has a profound impact on global atmospheric greenhouse gas (GHG) levels, and yet, strikingly little is known about the dynamics controlling sources and sinks of CH₄ in the aquatic setting. Here, we examine the cycling and flux of CH₄ in six large rivers in the Amazon basin, including the Amazon River. Based on stable isotopic mass balances of CH₄, inputs and outputs to the water column were estimated. We determined that ecosystem methane oxidation (MOX) reduced the diffusive flux of CH₄ by approximately 28–96% and varied depending on hydrologic regime and general geochemical characteristics of tributaries of the Amazon River. For example, the relative amount of MOX was maximal during high water in black and white water rivers and minimal in clear water rivers during low water. The abundance of genetic markers for methane‐oxidizing bacteria (pmoA) was positively correlated with enhanced signals of oxidation, providing independent support for the detected MOX patterns. The results indicate that MOX in large Amazonian rivers can consume from 0.45 to 2.07 Tg CH₄ yr^?1, representing up to 7% of the estimated global soil sink. Nevertheless, climate change and changes in hydrology, for example, due to construction of dams, can alter this balance, influencing CH₄ emissions to atmosphere.     

Eleutherinone,a novel fungitoxic naphthoquinone from Eleutherine bulbosa (Iridaceae)

The dichloromethane extract prepared from the underground parts of Eleutherine bulbosa (Miller) Urban (Iridaceae) showed strong activity in the direct bioautography assay with the phytopathogenic fungus Cladosporium sphaerospermum. This assay was used to guide the fractionation of this extract and allowed the isolation of four compounds: the new naphthoquinone eleutherinone[8-methoxy-1-methyl-1,3-dihydro-naphtho(2,3-c)furan-4,9 -dione] and the known compounds, previously isolated from this species, eleutherin [9-methoxy-1(R),3(S)-dimethyl-3,4-dihydro-1H-benzo(g)isochromene-5,10-dione], isoeleutherin [9-methoxy-1(R),3(R)-dimethyl-3,4-dihydro-1H-benzo(g)isochromene-5,10-dione], and eleutherol [4-hydroxy-5-methoxy-3(R)-methyl-3H-naphtho(2,3-c)furan-1 -one]. All quinonoid compounds showed strong antifungal activity in the bioautography assay at 100 g/spot, while eleutherol was inactive.     

Cryopreservation of somatic embryos and embryonic axes of Camellia japonica L.

Summary Cryopreservation in liquid nitrogen was attempted with both somatic embryos and zygotic embryonic axes of the ornamental Camellia japonica L. Several protective measures were applied to somatic embryos (desiccation, chemical protectors, hardening by culture at low temperatures, encapsulation in alginate beads), but none allowed somatic embryos cultures to survive after 24 h in liquid nitrogen. Embryonic axes, however, were easily cryopreserved by means of the simplest technique: desiccation in a laminar flow hood and direct immersion in liquid nitrogen. Although the causes of the difference in cryopreservability between the two types of material are not known, one might be the difference between their degrees of differentiation and water content.Abbreviations ANOVA analysis of variance - BA N6-benzyladenine - DMSO dimethyl sulfoxide - IBA indole-3-butyric acid - LN liquid nitrogen - MS Murashige and Skoog mineral solution - fwt fresh weight - LSD Least Significant Difference     

Characterization of the Wsc1 protein, a putative receptor in the stress response of Saccharomyces cerevisiae.

Wsc1p, Wsc2p, Wsc3p, and Wsc4p, members of a novel protein family in the yeast Saccharomyces cerevisiae, are putative sensors or receptors in the stress response. Genetic characterization suggests that the WSC family are upstream regulators of the stress-activated PKC1-MAP kinase cascade and are required for the heat shock response and for maintenance of cell wall integrity. The Wsc proteins share sequence characteristics: at their N terminus they have a cysteine motif and a serine/threonine-rich domain predicted to be extracellular, a hydrophobic domain suggested to be transmembranous, and a variable, highly charged C terminus that may be involved in intracellular signaling. Although a role for the WSC genes in maintenance of cell wall integrity has been firmly established, little is known about the properties of the proteins. As reported here, to study its properties in vivo, we epitope tagged the Wsc1 protein. Wsc1p was found to fractionate with the membrane pellet after high-speed centrifugation. Extraction experiments show that Wsc1p is an integral membrane protein present in two forms: one solubilized by detergent, the other Triton X-100 insoluble. Our results also show that Wsc1p is glycosylated and phosphorylated. To characterize the contribution of different domains to the function of Wsc1p, we generated various deletion constructs. Analysis of the properties and function of the mutant proteins shows that the predicted extracellular serine/threonine-rich domain is required for Wsc1p functionality, as well as its glycosylation. A mutant Wsc1 protein lacking the putative transmembrane domain is not functional and partitions to the soluble fraction. Overexpression of full-length Wsc1p inhibits cell growth, with the N terminus alone being sufficient for this inhibition. This suggests that Wsc1p may function in a complex with at least one other protein important for normal cell growth.     

Isolation and characterization of a high molecular weight antibiotic produced by a marine bacterium

Many marine bacteria demonstrate antibiotic activity against organisms of terrestrial origin. Low molecular weight antibiotics have been extracted and, in some cases, purified, but few attempts have been made to isolate high molecular weight antibiotics produced by marine bacteria. In the study reported here, a high molecular weight antibiotic was extracted from whole cells ofAlteromonas strain P18 (NCMB 1890) grown on 2216E medium. Purification included ammonium sulfate precipitation, ultracentrifugation, chromatography on DEAE cellulose, and gel filtration on Ultrogel. A rapid method for measuring specific activity of the antibiotic was developed.     

Exaggerated Mg2+ inhibition of Kir2.1 as a consequence of reduced PIP2 sensitivity in Andersen syndrome

Andersen syndrome is an autosomal dominant disorder characterized by cardiac arrhythmias, periodic paralysis and dysmorphic features. Many Andersen syndrome cases have been associated with loss-of-function mutations in the inward rectifier K(+) channel Kir2.1 encoded by KCNJ2. Using engineered concatenated tetrameric channels we determined the mechanism for dominant loss-of-function associated with a trafficking-competent missense mutation, Kir2.1-T74A. This mutation alters a conserved threonine residue in an N-terminal domain analogous to the slide helix identified in the structure of a bacterial inward rectifier. Incorporation of a single mutant subunit in channel tetramers was sufficient to cause a selective impairment of whole-cell outward current, but no difference in the level of inward current compared with wild-type (WT) tetramers. The presence of two mutant subunits resulted in greatly reduced outward and impaired inward currents. Experiments using excised inside-out membrane patches revealed that tetramers with one mutant subunit exhibited increased Mg(2+) inhibition. Additional experiments demonstrated that concatenated tetramers containing one T74A subunit had reduced PIP(2) sensitivity, and that outward current carried by mutant tetramers could be restored by addition of PIP(2) in the absence of Mg(2+). Our results are consistent with the involvement of the Kir2.1 N-terminus in PIP(2) modulation of channel activity and support the existence of an inverse relationship between PIP(2) sensitivity and Mg(2+) inhibition of Kir2.1 channels. Our data also indicate that a single mutant subunit is sufficient to explain dominant-negative behavior of Kir2.1-T74A in Andersen syndrome.