Ethylene receptor ETHYLENE RECEPTOR1 domain requirements for ethylene responses in Arabidopsis seedlings

Ethylene influences many processes in Arabidopsis (Arabidopsis thaliana) through the action of five receptor isoforms. We used high-resolution, time-lapse imaging of dark-grown Arabidopsis seedlings to better understand the roles of each isoform in the regulation of growth in air, ethylene-stimulated nutations, and growth recovery after ethylene removal. We found that ETHYLENE RECEPTOR1 (ETR1) is both necessary and sufficient for nutations. Transgene constructs in which the ETR1 promoter was used to drive expression of cDNAs for each of the five receptor isoforms were transferred into etr1-6;etr2-3;ein4-4 triple loss-of-function mutants that have constitutive growth inhibition in air, fail to nutate in ethylene, and take longer to recover a normal growth rate when ethylene is removed. The patterns of rescue show that ETR1, ETR2, and ETHYLENE INSENSITIVE4 (EIN4) have the prominent roles in rapid growth recovery after removal of ethylene whereas ETR1 was the sole isoform that rescued nutations. ETR1 histidine kinase activity and phosphotransfer through the receiver domain are not required to rescue nutations. However, REVERSION TO SENSITIVITY1 modulates ethylene-stimulated nutations but does not modulate the rate of growth recovery after ethylene removal. Several chimeric receptor transgene constructs where domains of EIN4 were swapped into ETR1 were also introduced into the triple mutant. The pattern of phenotype rescue by the chimeric receptors used in this study supports a model where a receptor with a receiver domain is required for normal growth recovery and that nutations specifically require the full-length ETR1 receptor.     

Linking individual diet variation and fecundity in an omnivorous marine consumer

Individual diet variation is a common feature of populations. This variation may be particularly common in near-shore marine benthic habitats where omnivory is prevalent and prey availability is spatially variable. Accurately predicting population responses to anthropogenic change that is occurring rapidly in these systems requires a quantitative link between individual diet variation and fecundity. Here I develop this quantitative link for the European green crab Carcinus maenas, specifically focusing on variation in the relative amounts of plant and animal material included in the diet. I demonstrate both short- and long-term diet variation between crabs as well as large individual variation in fecundity. I then quantitatively link variation in diet and fecundity using a laboratory feeding experiment. Fecundity increased by approximately 5,200 eggs when daily consumption of animal tissue increased by 1 % of body weight, but was not influenced by the most commonly consumed algal species. Results presented here have important implications for understanding population dynamics in general, and also provide information necessary for accurately predicting population growth of this widespread invader.     

Flight activity of USDA-ARS Russian honey bees (Hymenoptera: Apidae) during pollination of lowbush blueberries in Maine

Flight activity was compared in colonies of Russian honey bees, Apis mellifera L. (Hymenoptera: Apidae), and Italian bees during commercial pollination of lowbush blueberries (principally Vaccinium angustifolium Aiton) in Washington Co., ME, in late May and early June in 2003 and 2004. Colonies of the two stocks were managed equally in Louisiana during autumn through early spring preceding observations in late spring each year. Resulting average populations of adult bees and of brood were similar in colonies of the two bee stocks during pollination. Flight during pollination was monitored hourly on 6 d each year by counting bees exiting each colony per minute; counts were made manually with flight cones on 17 colonies per stock in 2003 and electronically with ApiSCAN-Plus counters on 20 colonies per stock in 2004. Analysis of variance showed that temperature, colony size (population of adult bees or brood), and the interaction of these effects were the strongest regulators of flight activity in both years. Russian and Italian bees had similar flight activity at any given colony size, temperature, or time of day. Flight increased linearly with rising temperatures and larger colony sizes. Larger colonies, however, were more responsive than smaller colonies across the range of temperatures measured. In 2003, flight responses to varying temperatures were less in the afternoon and evening (1500-1959 hours) than they were earlier in the day. Russian colonies had flight activity that was suitable for late spring pollination of lowbush blueberries.     

Tween 80 effect on glucosyltransferase synthesis by Streptococcus salivarius.

Streptococcus salivarius (ATCC 25975) produced very low or nondetectable amounts of the extracellular enzyme glucosyltransferase (GTase) when grown in a chemically defined medium. The addition of Tween 80 to this medium resulted in the production of markedly enhanced levels of the enzyme. Oleic acid, the methyl ester of oleic acid, and sucrose each could not substitute for Tween 80 in this regard. The surfactant had no direct activating effect on performed enzyme activity. Tween 80 also stimulated the production of GTase by concentrated cells suspended in defined medium during a time when no measurable growth occurred. Under these conditions, the stimulatory effect of Tween 80 was blocked by chloramphenicol. It was further found that the surfactant dramatically stimulated the differential rate of GTase synthesis. These and other data strongly suggest that Tween 80 stimulates the production of extracellular GTase by acting either directly or indirectly at the level of enzyme synthesis.     

Isolation and characterization of a T suppressor factor by using a monoclonal antibody

We have developed a monoclonal antibody to a T cell-derived suppressor factor (TsF) found in the serum of C57BL/6 mice hyperimmune to sheep red blood cells (SRBC). The antibody binds to the SRBC-specific TsF as well as to a TsF (TNP-TsF) from another system differing in both antigen specificity and MHC. It does not bind to unrelated proteins. The antibody inhibits the activity of the SRBC-specific TsF in vitro. By using the monoclonal anti-TsF, we can isolate sufficient quantities of TsF to demonstrate that it fulfills several properties that have been attributed to TsF, namely, MHC restriction, antigen specificity, and the requirement for a second chain. Also, the purified TsF gives a single 68,000 dalton band upon SDS-PAGE gel analysis under reducing conditions. We conclude, therefore, that we have a method of the isolation of pure TsF, as well as a probe for the genetic, biochemical, and biologic analysis of TsF.     

Heat killing of bacterial spores analyzed by differential scanning calorimetry.

Thermograms of the exosporium-lacking dormant spores of Bacillus megaterium ATCC 33729, obtained by differential scanning calorimetry, showed three major irreversible endothermic transitions with peaks at 56, 100, and 114 degrees C and a major irreversible exothermic transition with a peak at 119 degrees C. The 114 degrees C transition was identified with coat proteins, and the 56 degrees C transition was identified with heat inactivation. Thermograms of the germinated spores and vegetative cells were much alike, including an endothermic transition attributable to DNA. The ascending part of the main endothermic 100 degrees C transition in the dormant-spore thermograms corresponded to a first-order reaction and was correlated with spore death; i.e., greater than 99.9% of the spores were killed when the transition peak was reached. The maximum death rate of the dormant spores during calorimetry, calculated from separately measured D and z values, occurred at temperatures above the 73 degrees C onset of thermal denaturation and was equivalent to the maximum inactivation rate calculated for the critical target. Most of the spore killing occurred before the release of most of the dipicolinic acid and other intraprotoplast materials. The exothermic 119 degrees C transition was a consequence of the endothermic 100 degrees C transition and probably represented the aggregation of intraprotoplast spore components. Taken together with prior evidence, the results suggest that a crucial protein is the rate-limiting primary target in the heat killing of dormant bacterial spores.