Interactive effects of low atmospheric CO2 and elevated temperature on growth, photosynthesis and respiration in Phaseolus vulgaris

For most of the past 250 000 years, atmospheric CO₂ has been 30–50% lower than the current level of 360 μmol CO₂ mol^–1 air. Although the effects of CO₂ on plant performance are well recognized, the effects of low CO₂ in combination with abiotic stress remain poorly understood. In this study, a growth chamber experiment using a two-by-two factorial design of CO₂ (380 μmol mol^–1, 200 μmol mol^–1) and temperature (25/20 °C day/night, 36/29 °C) was conducted to evaluate the interactive effects of CO₂ and temperature variation on growth, tissue chemistry and leaf gas exchange of Phaseolus vulgaris. Relative to plants grown at 380 μmol mol^–1 and 25/20 °C, whole plant biomass was 36% less at 380 μmol mol^–1× 36/29 °C, and 37% less at 200 μmol mol^–1× 25/20 °C. Most significantly, growth at 200 μmol mol^–1× 36/29 °C resulted in 77% less biomass relative to plants grown at 380 μmol mol^–1× 25/20 °C. The net CO₂ assimilation rate of leaves grown in 200 μmol mol^–1× 25/20 °C was 40% lower than in leaves from 380 μmol mol^–1× 25/20 °C, but similar to leaves in 200 μmol mol^–1× 36/29 °C. The leaves produced in low CO₂ and high temperature respired at a rate that was double that of leaves from the 380μmol mol^–1× 25/20 °C treatment. Despite this, there was little evidence that leaves at low CO₂ and high temperature were carbohydrate deficient, because soluble sugars, starch and total non-structural carbohydrates of leaves from the 200μmol mol^–1× 36/29 °C treatment were not significantly different in leaves from the 380μmol mol^–1× 25/20 °C treatment. Similarly, there was no significant difference in percentage root carbon, leaf chlorophyll and leaf/root nitrogen between the low CO₂× high temperature treatment and ambient CO₂ controls. Decreased plant growth was correlated with neither leaf gas exchange nor tissue chemistry. Rather, leaf and root growth were the most affected responses, declining in equivalent proportions as total biomass production. Because of this close association, the mechanisms controlling leaf and root growth appear to have the greatest control over the response to heat stress and CO₂ reduction in P. vulgaris.     

1-Thio-beta-D-galactofuranosides: synthesis and evaluation as beta-D- galactofuranosidase inhibitors

Beta-D-galactofuranosidase is a good chemotherapeutic target for the design of inhibitors, since beta-D-galactofuranose is a constituent of important parasite glycoconjugates but is not present in the host mammals. With this aim, we have synthesized for the first time alkyl, benzyl and aryl 1-thio-beta-D-galactofuranosides by condensation of penta-O-benzoyl-alpha,beta-D-galactofuranose with the corresponding thiols, in the presence of SnCl4as catalyst. The complete chemical and spectroscopical characterization of these compounds showed that the reaction was stereoselective. Debenzoylation with sodium methoxide afforded the beta-S-galactofuranosides in high yield. The thioglycosides were tested as inhibitors of the beta-D- galactofuranosidase of Penicillium fellutanum, using for the first time 4-nitrophenyl-beta-D-galactofuranoside as chromogenic substrate. The 4- aminophenyl-1-thio-beta-D-galactofuranoside, obtained by catalytic hydrogenation of the nitrophenyl derivative, was the best inhibitor being then an adequate ligand for the preparation of an affinity phase aimed at the isolation of beta-d-galactofuranosidases from different sources. Also the inhibitory activity of d-galactono-1, 4-lactone was shown.      

Gibberellin: inhibitor of an inhibitor of...?

Gibberellin is an endogenous plant growth regulator. Here, we describe our present understanding of how gibberellin regulates plant growth, using recent results gained from studies of gibberellin-signalling mutants of Arabidopsis. These results show that a signalling pathway represses plant growth and that gibberellin releases this repression. In consequence, the well-known growth-promoting properties of gibberellin are due to its activity as an "inhibitor of an inhibitor" [Brian Pw. Sym Soc. Exp Bio 1957; 11:166-182 (Ref. 1)] of plant growth.     

Regional differences in WT-1 and Tcf21 expression during ventricular development: implications for myocardial compaction

Background

Morphological and functional differences of the right and left ventricle are apparent in the adult human heart. A differential contribution of cardiac fibroblasts and smooth muscle cells (populations of epicardium-derived cells) to each ventricle may account for part of the morphological-functional disparity. Here we studied the relation between epicardial derivatives and the development of compact ventricular myocardium.

Results

Wildtype and Wt1^CreERT2/+ reporter mice were used to study WT-1 expressing cells, and Tcf21^lacZ/+ reporter mice and PDGFRα^-/-;Tcf21^LacZ/+ mice to study the formation of the cardiac fibroblast population. After covering the heart, intramyocardial WT-1+ cells were first observed at the inner curvature, the right ventricular postero-lateral wall and left ventricular apical wall. Later, WT-1+ cells were present in the walls of both ventricles, but significantly more pronounced in the left ventricle. Tcf21-^LacZ + cells followed the same distribution pattern as WT-1+ cells but at later stages, indicating a timing difference between these cell populations. Within the right ventricle, WT-1+ and Tcf21-lacZ+ cell distribution was more pronounced in the posterior inlet part. A gradual increase in myocardial wall thickness was observed early in the left ventricle and at later stages in the right ventricle. PDGFRα^-/-;Tcf21^LacZ/+ mice showed deficient epicardium, diminished number of Tcf21-^LacZ + cells and reduced ventricular compaction.

Conclusions

During normal heart development, spatio-temporal differences in contribution of WT-1 and Tcf21-^LacZ + cells to right versus left ventricular myocardium occur parallel to myocardial thickening. These findings may relate to lateralized differences in ventricular (patho)morphology in humans.     

Analysis of yield and oil from a series of canola breeding trials. Part II. Exploring variety by environment interaction using factor analysis

Exploring and exploiting variety by environment (V × E) interaction is one of the major challenges facing plant breeders. In paper I of this series, we presented an approach to modelling V × E interaction in the analysis of complex multi-environment trials using factor analytic models. In this paper, we develop a range of statistical tools which explore V × E interaction in this context. These tools include graphical displays such as heat-maps of genetic correlation matrices as well as so-called E-scaled uniplots that are a more informative alternative to the classical biplot for large plant breeding multi-environment trials. We also present a new approach to prediction for multi-environment trials that include pedigree information. This approach allows meaningful selection indices to be formed either for potential new varieties or potential parents.     

Discovery and initial optimization of 5,5′-disubstituted aminohydantoins as potent β-secretase (BACE1) inhibitors

8,8-Diphenyl-2,3,4,8-tetrahydroimidazo[1,5-a]pyrimidin-6-amine (1) was identified through HTS, as a weak (micromolar) inhibitor of BACE1. X-Ray crystallographic studies indicate the 2-aminoimidazole ring forms key H-bonding interactions with Asp32 and Asp228 in the catalytic site of BACE1. Lead optimization using structure-based focused libraries led to the identification of low nanomolar BACE1 inhibitors such as 20b with substituents which extend from the S₁ to the S₃ pocket.     

<Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> inhibits <Emphasis Type="Italic">in-vitro Candida</Emphasis> biofilm development

Background  

Elucidation of the communal behavior of microbes in mixed species biofilms may have a major impact on understanding infectious diseases and for the therapeutics. Although, the structure and the properties of monospecies biofilms and their role in disease have been extensively studied during the last decade, the interactions within mixed biofilms consisting of bacteria and fungi such as Candida spp. have not been illustrated in depth. Hence, the aim of this study was to evaluate the interspecies interactions of Pseudomonas aeruginosa and six different species of Candida comprising C. albicans, C. glabrata, C. krusei, C. tropicalis, C. parapsilosis, and C. dubliniensis in dual species biofilm development.     

The peninsula effect on bird species in native eucalypt forests in a wood production landscape in Australia

The peninsula effect – a decrease in species richness from the base to the tip of a peninsula – has been tested for a diverse range of taxa at continental and regional scales. We investigated the peninsula effect at a local scale by examining bird species occurrence in riparian strips (peninsulas) of native eucalypt forest within a radiata pine plantation in the Tumut region, south-eastern Australia. Peninsulas were elongated but 'blind' extensions of a core area of native eucalypt forest. Birds were surveyed by the area search method, within 1.0-ha quadrats established along peninsulas ( n =14), in October and November 2002. Data were analysed using generalized linear mixed models. A significant decrease in bird species richness from the base towards the tip of the peninsulas was observed. The proportion of large bird species recorded per quadrat showed a significant decrease from the base towards the tip of the peninsulas. This pattern was not observed for small birds. Several species were more abundant at the base of the peninsulas than away from the core area of eucalypt forest. The peninsula effect can occur locally in landscape mosaics. Factors leading to the observed patterns of species occurrence may be distinct from those proposed in investigations of the peninsula effect with a biogeographical (macroscale) context. In our microscale study, foraging incursions of individual birds from the core area of native forest through peninsulas were a major factor giving rise to higher bird species richness in the more basal portions of peninsulas.     

Thiophene substituted acylguanidines as BACE1 inhibitors

A series of thiophene-substituted acylguanidines were designed from a pyrrole substituted acylguanidine HTS lead. This template allowed a greater flexibility, through differential Suzuki couplings, to explore the binding site of BACE1 and to enhance the inhibitory potencies. This exploration provided a 25-fold enhancement in potency to yield compound 10a, which was 150 nM in a BACE1 FRET assay.