Leiomodin is an actin filament nucleator in muscle cells

Initiation of actin polymerization in cells requires nucleation factors. Here we describe an actin-binding protein, leiomodin, that acted as a strong filament nucleator in muscle cells. Leiomodin shared two actin-binding sites with the filament pointed end-capping protein tropomodulin: a flexible N-terminal region and a leucine-rich repeat domain. Leiomodin also contained a C-terminal extension of 150 residues. The smallest fragment with strong nucleation activity included the leucine-rich repeat and C-terminal extension. The N-terminal region enhanced the nucleation activity threefold and recruited tropomyosin, which weakly stimulated nucleation and mediated localization of leiomodin to the middle of muscle sarcomeres. Knocking down leiomodin severely compromised sarcomere assembly in cultured muscle cells, which suggests a role for leiomodin in the nucleation of tropomyosin-decorated filaments in muscles.     

Oceanographic observations of the 1982 warming of the tropical eastern pacific

Moored current meter, sea level, hydrographic, and surface drifter measurements show the large changes that took place in the eastern tropical Pacific during the onset of the warm episode of 1982. In August the near-surface flow at 0 degrees , 110 degrees W reversed direction to eastward. By October the sea surface temperature in the equatorial zone increased by 5 degrees Celsius above the long-term monthly mean value, sea level rose by 22 centimeters at the Galápagos Islands, and the thermocline was displaced downward by 50 to 70 meters along the equator and the South American coast.     

Initial results from the Mini-TES experiment in Gusev Crater from the Spirit Rover

The Miniature Thermal Emission Spectrometer (Mini-TES) on Spirit has studied the mineralogy and thermophysical properties at Gusev crater. Undisturbed soil spectra show evidence for minor carbonates and bound water. Rocks are olivinerich basalts with varying degrees of dust and other coatings. Dark-toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy (+/-5 to 10%) of 45% pyroxene (20% Ca-rich pyroxene and 25% pigeonite), 40% sodic to intermediate plagioclase, and 15% olivine (forsterite 45% +/-5 to 10). Two spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. Diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0.5 to 3 mm in soils.     

A comparison of the biochemical and physiological effects of the systemic fungicide cyprofuram with those of the related compounds metalaxyl and metolachlor

Strains of Phytophthora megasperma insensitive to the fungicide metalaxyl showed limited cross-resistance to the structurally related fungicide cyprofuram and to metolachlor, a herbicide with antifungal properties. The three compounds each inhibited nucleic acid synthesis, but the wide variation in resistance factors and in the degree of nucleic acid inhibition at the concentrations inhibiting mycelial growth by 50% indicated that cyprofuram and metolachlor possess alternative mechanisms of toxicity. Studies with protoplasts suggested that cyprofuram has a direct effect on the plasma membrane which may be important against those resistant strains where nucleic acid synthesis is least affected. Metolachlor also was extremely effective in causing protoplast lysis. Sporangia production by P. palmivora was stimulated by low concentrations of cyprofuram, and germination was delayed. As with other ‘acylalanine-type’ fungicides, inhibition of nucleic acid synthesis is considered to be the main mode of action. Some degree of cross-resistance between cyprofuram and other acylalanines is likely to occur in the field but the dual mode of action of cyprofuram might delay its onset. The effect of increased sporogenesis on the development of resistance is more difficult to assess.     

Co-current introgression of economically important traits in a potato-breeding program

Wild potato species contain many traits of economic importance. Late blight (LB) resistance and cold chipping are traits desired in potato cultivars. These traits could be co-currently introgressed if they occurred together in wild potato species. Our research objectives were (1) to determine if variation for cold chipping exists between potato species, accessions within species, and plants within accessions all having foliar LB resistance, and (2) to identify wild potato genotypes combining LB resistance and cold chipping. Materials include 665 genotypes from 43 LB-resistant accessions of 12 potato species having Endosperm Balance Numbers (EBN) of 1, 2, and 4, and 59 LB-resistant genotypes retained from these accessions for breeding. Potato chips were made from greenhouse-grown tubers following storage at 4 C for 6 months. Chip color was scored 1–10, ≤ 4 is acceptable by industry standards. Most of the variation for chip color was due to differences between species. Species ranged in the percentage of acceptably chipping genotypes (0% – 67%) with nine of 12 species having cold-chipping genotypes. Appreciable variation was present within accessions as well. The best chipping accessions wereS. verrucosum plant introduction (PI) 161173 – 4.33 / 0.67 (mean / proportion acceptable genotypes),S. stoloniferum PI 250510 -4.36 / 0.64,S. pinnatisectum PI 347766 -4.65 / 0.35 and 275233 -4.73 / 0.44, andS. megistacrolobum PI 195210 -5.14 / 0.29. Eleven 1EBN genotypes fromS. pinnatisectum andS. trifidum and five 2EBN genotypes fromS. verrucosum, S. fendleri,S. stoloniferum, andS. microdontum were identified that combined LB resistance and cold chipping. Co-current introgression would require fewer breeding cycles than other breeding methods to identify hybrid genotypes possessing both traits.     

Compositional relationships between organic matter in a grassland soil and its drainage waters

We present a novel study of the compositional relationships between soil organic components extractable in aqueous extractants and those in sub-soil drainage and surface runoff waters from the soil. The surface soil (0–20 cm) of a stagnogley in long-term grassland was sequentially and exhaustively extracted in aqueous media at pH values of 7, 10.6 and 12.6. Extracts from the soils and their runoff and drainage waters were processed by the procedures of the International Humic Substances Society (IHSS), and fractionated into humic, fulvic, and XAD-4 acids. Elemental, δ¹³C, δ¹⁵N, sugar, amino acids, and solid state CPMAS ¹³C NMR analyses were used to identify similarities and differences between the fractions from the different extracts. There were few differences between the compositions of drainage water samples taken 1 year apart, and these had compositional features similar to those from the more highly oxidized fractions isolated from the soil at pH 7. There were significant differences between the humic components from the drainage waters and isolated from the soil at pH 7 and those of the humic fractions isolated at the higher pH values whose compositions are more clearly related to origins in plants. The compositions of the surface runoff waters indicate origins in transformed plant and animal manures on the soil surface, whereas those of the deep drainage waters originate in more extensively transformed materials, including products of microbial metabolism. The resin technique used in the fractionation allowed the isolation of novel humic acid fractions from the soil extracts, in particular at pH 7 and 12.6. These fractions clearly originated in microbial sources, were rich in saccharides and amino acids (peptides), and low in lignin-derived components.     

Phytophthora genome sequences uncover evolutionary origins and mechanisms of pathogenesis

Draft genome sequences have been determined for the soybean pathogen Phytophthora sojae and the sudden oak death pathogen Phytophthora ramorum. O?mycetes such as these Phytophthora species share the kingdom Stramenopila with photosynthetic algae such as diatoms, and the presence of many Phytophthora genes of probable phototroph origin supports a photosynthetic ancestry for the stramenopiles. Comparison of the two species' genomes reveals a rapid expansion and diversification of many protein families associated with plant infection such as hydrolases, ABC transporters, protein toxins, proteinase inhibitors, and, in particular, a superfamily of 700 proteins with similarity to known o?mycete avirulence genes.