Evolution of temperature responses in the Cladophora vagabunda complex and the C. albida/sericea complex (Chlorophyta)

Differentiation in temperature responses (survival and growth) was investigated among isolates of two tropical to temperate green algal lineages: the Cladophora vagabunda complex and the C. albida/sericea complex. The results were analysed in relation to published data on 18S rRNA and ITS sequence divergence, which have shown that the overall degree of genetic divergence is similar in the two lineages but that very different patterns of radiation have occurred. In the C. vagabunda complex, the two main clades in the well-resolved phylogenetic tree differed mainly in their tolerance to low temperatures. Within-clade variation was no stronger in the Atlantic/Pacific than in the all-Pacific clade. In the C. albida/sericea complex, six distinctive ITS types indicated early radiation. Although distinctive differences were found between some of these types, the thermal responses of others were very similar, indicating physiological stasis. In both lineages there was evidence for some adaptation to local temperature regimes but phylogenetic constraints were generally more important. Isolates with the same ITS sequences showed similar temperature responses even though collected from different climate zones. Evidence was found for a physiological trade-off between growth at high and at low temperatures in the C. albida/sericea complex, whereas, in the C. vagabunda complex, one clade showed more eurythermal growth responses than the other. In the C. vagabunda complex, which is the ancestral lineage of the C. albida/sericea complex, major differentiation was found in cold tolerance but not in heat tolerance, whereas the reverse pattern was found in the derived C. albida/sericea complex. These findings suggest that an acquisition of cold tolerance preceded the loss of heat tolerance during adaptation to colder climates.     

Pepper osmotin-like protein 1 (CaOSM1) is an essential component for defense response, cell death, and oxidative burst in plants

Osmotin or osmotin-like protein, a PR-5 family member, is differentially induced in plants by abiotic and biotic stresses. Here, we demonstrate that the pepper (Capsicum annuum) osmotin-like protein 1 gene, CaOSM1, was required for the defense and hypersensitive cell death response and oxidative burst signaling during Xanthomonas campestris pv. vesicatoria (Xcv) infection. CaOSM1 protein was localized to the plasma membrane in leaf cells of Nicotiana benthamiana. Agrobacterium-mediated transient expression of CaOSM1 in pepper distinctly induced the hypersensitive cell death response and H₂O₂ accumulation. Knock-down of CaOSM1 in pepper by virus-induced gene silencing increased the susceptibility to Xcv infection, which was accompanied by attenuation of the cell death response and decreased accumulation of H₂O₂. CaOSM1 overexpression in transgenic Arabidopsis conferred reduced susceptibility and accelerated cell death response and H₂O₂ accumulation to infection by Pseudomonas syringe pv. tomato and Hyaloperonospora arabidopsidis. Together, these results suggest that CaOSM1 is involved in cell death and oxidative burst responses during plant defense against microbial pathogens.     

Cultivation of the two perennial brown algae Ecklonia cava and E. stolonifera for abalone feeds in Korea

Ecklonia cava and Ecklonia stolonifera are perennial brown algae that form sea forests off the coast of Korea. Both species are cultured to supply a summer feed for the abalone industry. Recent expansion of the abalone industry in Korea has been bringing an increase in demand for fresh algal supply. Zoospores of the two algae were seeded in October 2006 on seed frames coiled with 100 m of seed fibers. After 2 months of indoor culture and 2 months of intermediate culture, growth and production of the two algae were compared during their main cultivation period from March 2007 to June 2008, in the culture ground in Wando, Korea (34°26′18.68″ N, 127°05′43.88″ E), in situ. Growth rate of E. cava and E. stolonifera was 1.058 and 3.089 mm day^?1, respectively. The mean production of E. stolonifera obtained from the culture ropes was ca. 12 kg wet wt. m^?1 of culture rope while production of E. cava was ca. 3 kg wet wt. m^?1 of culture rope. The difference in production was attributed from the different growth strategies of the two algae, with only E. stolonifera being able to regenerate blades from the holdfast. The ability to regenerate blades from the holdfast therefore makes E. stolonifera the preferred species for biomass production for abalone feeds. In a 120-day feeding experiment, growth rate, weight gain, and survival rate of abalone showed that E. cava and E. stolonifera feeds could provide an alternative feed to Saccharina japonica during summer months.     

Adaptor Protein Complex 2–Mediated Endocytosis Is Crucial for Male Reproductive Organ Development in Arabidopsis

Fertilization in flowering plants requires the temporal and spatial coordination of many developmental processes, including pollen production, anther dehiscence, ovule production, and pollen tube elongation. However, it remains elusive as to how this coordination occurs during reproduction. Here, we present evidence that endocytosis, involving heterotetrameric adaptor protein complex 2 (AP-2), plays a crucial role in fertilization. An Arabidopsis thaliana mutant ap2m displays multiple defects in pollen production and viability, as well as elongation of staminal filaments and pollen tubes, all of which are pivotal processes needed for fertilization. Of these abnormalities, the defects in elongation of staminal filaments and pollen tubes were partially rescued by exogenous auxin. Moreover, DR5rev:GFP (for green fluorescent protein) expression was greatly reduced in filaments and anthers in ap2m mutant plants. At the cellular level, ap2m mutants displayed defects in both endocytosis of N-(3-triethylammonium-propyl)-4-(4-diethylaminophenylhexatrienyl) pyridinium dibromide, a lypophilic dye used as an endocytosis marker, and polar localization of auxin-efflux carrier PIN FORMED2 (PIN2) in the stamen filaments. Moreover, these defects were phenocopied by treatment with Tyrphostin A23, an inhibitor of endocytosis. Based on these results, we propose that AP-2–dependent endocytosis plays a crucial role in coordinating the multiple developmental aspects of male reproductive organs by modulating cellular auxin level through the regulation of the amount and polarity of PINs.     

An ultrathin carbon nanoribbon study as a component of nanoelectromechanical devices

We investigated a carbon nanoribbon (CNR) using atomistic simulations based on Tersoff–Brenner potential function. The CNR was obtained from a compressed (5,5) carbon nanotube (CNT). The obtained CNR had a cross-sectional view as a binocular telescope structure composed of both sp² and sp³ bonds. One carbon atom per ten carbon atoms had sp³ bond. For the optimized structures, the residual forces on the CNR were 3-order higher than that on the CNR and the lattice constant of the CNR was higher 0.0624?Å than that of the CNT along the tube axis. The Young's modulus of the CNR was the same as that of the CNT whereas the critical strain of the CNR was significantly lower than that of the CNT because the residual stresses on the CNR was very higher than those on the CNT. The tensile force curve vs. the strain of the CNT was slightly higher than that of the CNR.     

Molecular dynamics simulations of carbon nanotube oscillators deformed by encapsulated copper nanowires

Pure carbon nanotube (CNT) oscillators are compared to the corresponding CNT oscillators encapsulating copper nanowires (Cu@CNTs) by molecular dynamics simulations. The classical oscillation theory provides a fairly good estimate of the mass dependence of the operating frequency when the CNT surface is not deformed by the Cu nanowire. The structural deformations of the CNT induced by the encapsulated copper nanowire have a greater effect on the oscillation frequency than the mass of the copper nanowire. The excess forces of the Cu@CNT oscillator are slightly higher than those of the CNT oscillator and the excess van der Waals forces induced by the inter-wall interactions are 17 times higher than the excess forces induced by the Cu nanowire–CNT interactions.     

Intracellular Distribution and Some Properties of β-Glucosidases of a Cellulolytic Pseudomonad

Two distinct forms of β-glucosidase, A and B, were found to occur in the cells of Pseudomonas fluorescens var. cellulosa : A was membrane-bound, while B cytosolic. They differed also from each other in some properties, such as molecular size, kinetic parameters, and susceptibility to various compounds. β-Glucosidase B was partially purified and studied especially of its substrate specificity. The results indicated that it may be an atypical β-glucosidase which possesses a certain character of exo-cellulase.