AUX1 regulates root gravitropism in Arabidopsis by facilitating auxin uptake within root apical tissues

Plants employ a specialized transport system composed of separate influx and efflux carriers to mobilize the plant hormone auxin between its site(s) of synthesis and action. Mutations within the permease-like AUX1 protein significantly reduce the rate of carrier-mediated auxin uptake within Arabidopsis roots, conferring an agravitropic phenotype. We are able to bypass the defect within auxin uptake and restore the gravitropic root phenotype of aux1 by growing mutant seedlings in the presence of the membrane-permeable synthetic auxin, 1-naphthaleneacetic acid. We illustrate that AUX1 expression overlaps that previously described for the auxin efflux carrier, AtPIN2, using transgenic lines expressing an AUX1 promoter::uidA (GUS) gene. Finally, we demonstrate that AUX1 regulates gravitropic curvature by acting in unison with the auxin efflux carrier to co-ordinate the localized redistribution of auxin within the Arabidopsis root apex. Our results provide the first example of a developmental role for the auxin influx carrier within higher plants and supply new insight into the molecular basis of gravitropic signalling.     

Behavioural evidence of colour vision in free flying stingless bees

Colour vision was first demonstrated with behavioural experiments in honeybees 100 years ago. Since that time a wealth of quality physiological data has shown a highly conserved set of trichromatic colour receptors in most bee species. Despite the subsequent wealth of behavioural research on honeybees and bumblebees, there currently is a relative dearth of data on stingless bees, which are the largest tribe of the eusocial bees comprising of more than 600 species. In our first experiment we tested Trigona cf. fuscipennis, a stingless bee species from Costa Rica in a field setting using the von Frisch method and show functional colour vision. In a second experiment with these bees, we use a simultaneous colour discrimination test designed for honeybees to enable a comparative analysis of relative colour discrimination. In a third experiment, we test in laboratory conditions Tetragonula carbonaria, an Australian stingless bee species using a similar simultaneous colour discrimination test. Both stingless bee species show relatively poorer colour discrimination compared to honeybees and bumblebees; and we discuss the value of being able to use these behavioural methods to efficiently extend our current knowledge of colour vision and discrimination in different bee species.     

Design and synthesis of a peptide derived from positions 195–244 of human cdc25C phosphatase

We have designed, synthesized and purified a 51 amino acid peptide derived from an essential domain of human cdc25C phosphatase. In vivo, differential phosphorylation of this domain regulates either the induction of mitotic processes, or the checkpoint arrest of eukaryotic cells in response to DNA damage. Peptide synthesis was achieved using the stepwise Fmoc strategy and resulted in an important yield of highly pure peptide. The final peptide was identified by amino acid analysis, electrospray mass spectrometry and nuclear magnetic resonance, which revealed that one of the two methionines within the peptide was oxidized into its sulphoxide derivative We investigated whether this 51 amino acid peptide folded into secondary structures in solution by circular dichroism and observed the formation of alpha helices in TFE. Finally, we verified that this peptide could bind to its biologically relevant 14‐3‐3 partner in vitro by fluorescence spectroscopy. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.     

Energy minimization in low-frequency normal modes to efficiently allow for global flexibility during systematic protein-protein docking

Protein-protein association can frequently involve significant backbone conformational changes of the protein partners. A computationally rapid method has been developed that allows to approximately account for global conformational changes during systematic protein-protein docking starting from many thousands of start configurations. The approach employs precalculated collective degrees of freedom as additional variables during protein-protein docking minimization. The global collective degrees of freedom are obtained from normal mode analysis using a Gaussian network model for the protein. Systematic docking searches were performed on 10 test systems that differed in the degree of conformational change associated with complex formation and in the degree of overlap between observed conformational changes and precalculated flexible degrees of freedom. The results indicate that in case of docking searches that minimize the influence of local side chain conformational changes inclusion of global flexibility can significantly improve the agreement of the near-native docking solutions with the corresponding experimental structures. For docking of unbound protein partners in several cases an improved ranking of near native docking solutions was observed. This was achieved at a very modest ( approximately 2-fold) increase of computational demands compared to rigid docking. For several test cases the number of docking solutions close to experiment was also significantly enhanced upon inclusion of soft collective degrees of freedom. This result indicates that inclusion of global flexibility can facilitate in silico protein-protein association such that a greater number of different start configurations results in favorable complex formation.     

Expulsion of live pathogenic yeast by macrophages

Phagocytic cells, such as neutrophils and macrophages, perform a critical role in protecting organisms from infection by engulfing and destroying invading microbes . Although some bacteria and fungi have evolved strategies to survive within a phagocyte after uptake, most of these pathogens must eventually kill the host cell if they are to escape and infect other tissues . However, we now demonstrate that the human fungal pathogen Cryptococcus neoformans is able to escape from within macrophages without killing the host cell by a novel expulsive mechanism. This process occurs in both murine J774 cells and primary human macrophages. It is extremely rapid and yet can occur many hours after phagocytosis of the pathogen. Expulsion occurs independently of the initial route of phagocytic uptake and does not require phagosome maturation . After the expulsive event, both the host macrophage and the expelled C. neoformans appear morphologically normal and continue to proliferate, suggesting that this process may represent an important mechanism by which pathogens are able to escape from phagocytic cells without triggering host cell death and thus inflammation .     

Energy and emission benefits of alternative transportation liquid fuels derived from switchgrass: a fuel life cycle assessment

We conducted a mobility chains, or well-to-wheels (WTW), analysis to assess the energy and emission benefits of cellulosic biomass for the U.S. transportation sector in the years 2015-2030. We estimated the life-cycle energy consumption and emissions associated with biofuel production and use in light-duty vehicle (LDV) technologies by using the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model. Analysis of biofuel production was based on ASPEN Plus model simulation of an advanced fermentation process to produce fuel ethanol/protein, a thermochemical process to produce Fischer-Tropsch diesel (FTD) and dimethyl ether (DME), and a combined heat and power plant to co-produce steam and electricity. Our study revealed that cellulosic biofuels as E85 (mixture of 85% ethanol and 15% gasoline by volume), FTD, and DME offer substantial savings in petroleum (66-93%) and fossil energy (65-88%) consumption on a per-mile basis. Decreased fossil fuel use translates to 82-87% reductions in greenhouse gas emissions across all unblended cellulosic biofuels. In urban areas, our study shows net reductions for almost all criteria pollutants, with the exception of carbon monoxide (unchanged), for each of the biofuel production option examined. Conventional and hybrid electric vehicles, when fueled with E85, could reduce total sulfur oxide (SO(x)) emissions to 39-43% of those generated by vehicles fueled with gasoline. By using bio-FTD and bio-DME in place of diesel, SO(x) emissions are reduced to 46-58% of those generated by diesel-fueled vehicles. Six different fuel production options were compared. This study strongly suggests that integrated heat and power co-generation by means of gas turbine combined cycle is a crucial factor in the energy savings and emission reductions.     

Reconstitution of catecholamine-stimulated adenylate cyclase activity using three purified proteins

beta-Adrenergic receptors, the GTP-binding regulatory protein that stimulates adenylate cyclase (Gs), and adenylate cyclase were each purified and reconstituted into unilamellar vesicles composed of phosphatidylethanolamine and phosphatidylserine (3:2, w/w). The molar ratio of receptor:Gs:adenylate cyclase was estimated to be about 1:10:1. Adenylate cyclase activity in the vesicles was stimulated up to 2.6-fold by beta-adrenergic agonists. Stimulation was dependent on the presence of guanine nucleotide, displayed appropriate beta-adrenergic selectivity and stereoselectivity for agonists, and was blocked appropriately by beta-adrenergic antagonists. Therefore, while additional proteins may modulate adenylate cyclase activity in native membranes, these results show that these three proteins are sufficient for the expression of hormone-stimulated adenylate cyclase.     

Relationships Between Tolerance and Resistance to Meloidogyne incognita in Cotton

The southern root-knot nematode, Meloidogyne incognita, is the most damaging pathogen of cotton in the United States, and both resistance and tolerance to M. incognita could be valuable management approaches. Our objectives were to evaluate advanced cotton breeding lines for resistance and tolerance to M. incognita and to determine if a relationship between resistance and tolerance exists. Reproduction of M. incognita was evaluated on 17 breeding lines, a susceptible control (Delta and Pine Land DP5415), and a resistant control (M-120) in two greenhouse trials with six replications in a randomized complete block design. Two-week-old seedlings were inoculated with 8,000 M. incognita eggs and assessed for egg production 8 weeks later. Reproduction on the resistant control was only 10% of that on the susceptible control. Eight breeding lines supported 45% to 57% less (P <= 0.05) nematode reproduction than the susceptible control, and none of them were as resistant as M-120. Yield was determined in 2001 and 2002 in fumigated (1,3-dichloropropene at 56 liters/ha) and nonfumigated plots in a strip-plot design with three replications in a field naturally infested with M. incognita. Yield suppression caused by nematode infection differed among genotypes (P ≤ 0.05 for genotype × fumigation interaction). Six genotypes in 2001 and nine in 2002 were tolerant to M. incognita based on no difference in yield between the fumigated and nonfumigated plots (P ≥ 0.10). However, only three genotypes had no significant yield suppression in both years, of which two also were resistant to M. incognita. Regression analysis indicated that yield suppression decreased linearly as nematode resistance increased.