Functional analysis of cotton orthologs of GA signal transduction factors GID1 and SLR1

Gibberellic acid (GA) is both necessary and sufficient to promote fiber elongation in cultured fertilized ovules of the upland cotton variety Coker 312. This is likely due to the temporal and spatial regulation of GA biosynthesis, perception, and subsequent signal transduction that leads to alterations in gene expression and morphology. Our results indicate that the initiation of fiber elongation by the application of GA to cultured ovules corresponds with increased expression of genes that encode xyloglucan endotransglycosylase/hydrolase (XTH) and expansin (EXP) that are involved in promoting cell elongation. To gain a better understanding of the GA signaling components in cotton, that lead to such changes in gene expression, two GA receptor genes (GhGID1a and GhGID1b) and two DELLA protein genes (GhSLR1a and GhSLR1b) that are orthologous to the rice GA receptor (GID1) and the rice DELLA gene (SLR1), respectively, were characterized. Similar to the GA biosynthetic genes, expression of GhGID1a and GhGID1b is under the negative regulation by GA while GA positively regulates GhSLR1a. Recombinant GST-GhGID1s showed GA-binding activity in vitro that was augmented in the presence of GhSLR1a, GhSLR1b, or rice SLR1, indicating complex formation between the receptors and repressor proteins. This was further supported by the GA-dependent interaction of these proteins in yeast cells. Ectopic expression of the GhGID1a in the rice gid1-3 mutant plants rescued the GA-insensitive dwarf phenotype, which demonstrates that it is a functional GA receptor. Furthermore, ectopic expression of GhSLR1b in wild type Arabidopsis led to reduced growth and upregulated expression of DELLA-responsive genes.     

The Effect of Criticism on Functional Brain Connectivity and Associations with Neuroticism

Neuroticism is a robust personality trait that constitutes a risk factor for psychopathology, especially anxiety disorders and depression. High neurotic individuals tend to be more self-critical and are overly sensitive to criticism by others. Hence, we used a novel resting-state paradigm to investigate the effect of criticism on functional brain connectivity and associations with neuroticism. Forty-eight participants completed the NEO Personality Inventory Revised (NEO-PI-R) to assess neuroticism. Next, we recorded resting state functional magnetic resonance imaging (rsfMRI) during two sessions. We manipulated the second session before scanning by presenting three standardized critical remarks through headphones, in which the subject was urged to please lie still in the scanner. A seed-based functional connectivity method and subsequent clustering were used to analyse the resting state data. Based on the reviewed literature related to criticism, we selected brain regions associated with self-reflective processing and stress-regulation as regions of interest. The findings showed enhanced functional connectivity between the clustered seed regions and brain areas involved in emotion processing and social cognition during the processing of criticism. Concurrently, functional connectivity was reduced between these clusters and brain structures related to the default mode network and higher-order cognitive control. Furthermore, individuals scoring higher on neuroticism showed altered functional connectivity between the clustered seed regions and brain areas involved in the appraisal, expression and regulation of negative emotions. These results may suggest that the criticized person is attempting to understand the beliefs, perceptions and feelings of the critic in order to facilitate flexible and adaptive social behavior. Furthermore, multiple aspects of emotion processing were found to be affected in individuals scoring higher on neuroticism during the processing of criticism, which may increase their sensitivity to negative social-evaluation.     

The p85alpha regulatory subunit of phosphoinositide 3-kinase potentiates c-Jun N-terminal kinase-mediated insulin resistance

Insulin resistance is a defining feature of type 2 diabetes and the metabolic syndrome. While the molecular mechanisms of insulin resistance are multiple, recent evidence suggests that attenuation of insulin signaling by c-Jun N-terminal kinase (JNK) may be a central part of the pathobiology of insulin resistance. Here we demonstrate that the p85alpha regulatory subunit of phosphoinositide 3-kinase (PI3K), a key mediator of insulin's metabolic actions, is also required for the activation of JNK in states of insulin resistance, including high-fat diet-induced obesity and JNK1 overexpression. The requirement of the p85alpha regulatory subunit for JNK occurs independently of its role as a component of the PI3K heterodimer and occurs only in response to specific stimuli, namely, insulin and tunicamycin, a chemical that induces endoplasmic reticulum stress. We further show that insulin and p85 activate JNK by via cdc42 and MKK4. The activation of this cdc42/JNK pathway requires both an intact N terminus and functional SH2 domains within the C terminus of the p85alpha regulatory subunit. Thus, p85alpha plays a dual role in regulating insulin sensitivity and may mediate cross talk between the PI3K and stress kinase pathways.     

Asymmetric response of forest and grassy biomes to climate variability across the African Humid Period: influenced by anthropogenic disturbance?

A comprehensive understanding of the relationship between land cover, climate change and disturbance dynamics is needed to inform scenarios of vegetation change on the African continent. Although significant advances have been made, large uncertainties exist in projections of future biodiversity and ecosystem change for the world's largest tropical landmass. To better illustrate the effects of climate–disturbance–ecosystem interactions on continental-scale vegetation change, we apply a novel statistical multivariate envelope approach to subfossil pollen data and climate model outputs (TraCE-21ka). We target paleoenvironmental records across continental Africa, from the African Humid Period (AHP: ca 14 700–5500 yr BP) – an interval of spatially and temporally variable hydroclimatic conditions – until recent times, to improve our understanding of overarching vegetation trends and to compare changes between forest and grassy biomes (savanna and grassland). Our results suggest that although climate variability was the dominant driver of change, forest and grassy biomes responded asymmetrically: 1) the climatic envelope of grassy biomes expanded, or persisted in increasingly diverse climatic conditions, during the second half of the AHP whilst that of forest did not; 2) forest retreat occurred much more slowly during the mid to late Holocene compared to the early AHP forest expansion; and 3) as forest and grassy biomes diverged during the second half of the AHP, their ecological relationship (envelope overlap) fundamentally changed. Based on these asymmetries and associated changes in human land use, we propose and discuss three hypotheses about the influence of anthropogenic disturbance on continental-scale vegetation change.     

Deletion of flavoredoxin gene in Desulfovibrio gigas reveals its participation in thiosulfate reduction

The gene encoding Desulfovibrio gigas flavoredoxin was deleted to elucidate its physiological role in the sulfate metabolism. Disruption of flr gene strongly inhibited the reduction of thiosulfate and exhibited a reduced growth in the presence of sulfite with lactate as electron donor. The growth with sulfate was not however affected by the lack of this protein. Additionally, flr mutant cells revealed a decrease of about 50% in the H2 consumption rate using thiosulfate as electron acceptor. Altogether, our results show in vivo that during sulfite respiration, trithionate and thiosulfate are produced and that flavoredoxin is specific for thiosulfate reduction.     

Positional-scanning combinatorial libraries of fluorescence resonance energy transfer peptides for defining substrate specificity of the angiotensin I-converting enzyme and development of selective C-domain substrates

Positional-scanning combinatorial libraries of fluorescence resonance energy transfer peptides were used for the analyses of the S(3) to S(1)' subsites of the somatic angiotensin I-converting enzyme (ACE). Substrate specificity of ACE catalytic domains (C- and N-domains) was assessed in an effort to design selective substrates for the C-domain. Initially, we defined the S(1) specificity by preparing a library with the general structure Abz-GXXZXK(Dnp)-OH [Abz = o-aminobenzoic acid, K(Dnp) = N(epsilon)-2,4-dinitrophenyllysine, and X is a random residue], where Z was successively occupied with one of the 19 natural amino acids with the exception of Cys. The peptides containing Arg and Leu in the P(1) position had higher C-domain selectivity. In the sublibraries Abz-GXXRZK(Dnp)-OH, Abz-GXZRXK(Dnp)-OH, and Abz-GZXRXK(Dnp)-OH, Arg was fixed at P(1) so we could define the C-domain selectivity of the S(1)', S(2), and S(3) subsites. On the basis of the results from these libraries, we synthesized peptides Abz-GVIRFK(Dnp)-OH and Abz-GVILFK(Dnp)-OH which contain the most favorable residues for C-domain selectivity. Systematic reduction of the length of these two peptides resulted in Abz-LFK(Dnp)-OH, which demonstrated the highest selectivity for the recombinant ACE C-domain (k(cat)/K(m) = 36.7 microM(-1) s(-1)) versus the N-domain (k(cat)/K(m) = 0.51 microM(-1) s(-1)). The substrate binding of Abz-LFK(Dnp)-OH with testis ACE using a combination of conformational analysis and molecular docking was examined, and the results shed new light on the binding characteristics of the enzyme.