Differential regulation of salt tolerance mechanisms in Arabidopsis thaliana and Thellungiella halophila (salsuginea)

PhD ThesisHigh salt concentrations in soil are the leading cause of salt stress restraining crop production in different parts of the globe. It is anticipated that stresses from abiotic factors including salinity will result in over 50% decrease in average yield of major crops under current agricultural practices by 2050. Therefore, extensive work has been conducted during the last 20 years to understand the basic mechanisms for stresstolerance to develop plants that can survive under extreme environmental conditions including salinity. The key mechanisms for salt-tolerance are now well known and they involve osmoregulation via increased production of compatible solutes (e.g. proline, glycine betaine), sequestration of salts in the vacuole, exclusion of salts by the roots and extrusion of salts from the roots and/or leaves as well as alleviation of the negative effects of salt-stress. It is becoming clear that these mechanisms are expressed in most plants, with differential and spatiotemporal regulation of the expression of these mechanisms being the key to the salt-tolerance trait. It is, however, not clear as to what is behind the differential expression of these mechanisms and the research already conducted in this field lacks detail in terms of the responses to salt-stress. This project aimed at exploring in depth the differences in salt-responses shown by two close relatives, Arabidopsis thaliana (salt-sensitive) and Thellungiella halophila (salt-tolerant). It also aimed at understanding the regulatory processes behind the observed differential responses by exploring the regulation of genes playing key roles under salt-stress in the two plant species. Detailed analysis of the kinetics of responses to salt-stress were conducted in the two plant species including physiological responses (growth, photosynthesis), metabolic responses (production of osmoregulators, accumulation of sugars, uptake of salts), gene responses (P5CS1 and SOS1) and role of regulatory components in A. thaliana null mutants (signalling elements and transcription factors). T. halophila showed faster and stronger responses to salttreatment in the regulation of the accumulation of key compatible metabolites such as sucrose, fructose, inositol and proline compared to A. thaliana. The difference in proline accumulation between the two species was mirrored by P5CS1 transcript abundance. Along with P5CS1 gene the SUS3, UGP2, FBA1 and PPC1genes showed higher transcript levels under saline conditions in T. halophila. Analysis of the P5CS1 gene suggests the possibility of the presence of two isogenes in T. halophila as suggested by the promoter regions as well as the numbers of introns. Moreover differential splicing of the P5CS1 transcripts under salt-treatment occurred between T. halophila and A. iii thaliana. Finally targeted screening for potential key signalling elements (protein kinases: NPK15, CPK11 and ORG1) and transcription factors (Rp2.4f) using A. thaliana null-mutants for these genes suggested these components had an indirect role in the regulation of the responses to salt-treatment, probably via the regulation of the metabolic background of the plant. The results suggest that along with differential gene regulation between glycophytes and halophytes, salt tolerance also depends upon the level of metabolic plasticity of the plant to mount rapidly appropriate responses to salt stress and the capacity of the plant to modulate the response

Automated exploration of prebiotic chemical reaction space: progress and perspectives

Prebiotic chemistry often involves the study of complex systems of chemical reactions that form large networks with a large number of diverse species. Such complex systems may have given rise to emergent phenomena that ultimately led to the origin of life on Earth. The environmental conditions and processes involved in this emergence may not be fully recapitulable, making it difficult for experimentalists to study prebiotic systems in laboratory simulations. Computational chemistry offers efficient ways to study such chemical systems and identify the ones most likely to display complex properties associated with life. Here, we review tools and techniques for modelling prebiotic chemical reaction networks and outline possible ways to identify self-replicating features that are central to many origin-of-life models

Tuning phase-stability and short-range order through Al-doping in (CoCrFeMn)100-xAlx high entropy alloys

For (CoCrFeMn)$_{100-x}$Al$_{x}$ high-entropy alloys, we investigate the phase evolution with increasing Al-content (0 $\le$ x $\le$ 20 at.%). From first-principles theory, the Al-doping drives the alloy structurally from FCC to BCC separated by a narrow two-phase region (FCC+BCC), which is well supported by our experiments. We highlight the effect of Al-doping on the formation enthalpy and electronic structure of (CoCrFeMn)$_{100-x}$Al$_{x}$ alloys. As chemical short-range order (SRO) in multicomponent alloys indicates the nascent local order (and entropy changes), as well as expected low-temperature ordering behavior, we use thermodynamic linear-response within density-functional theory to predict SRO and ordering transformation and temperatures inherent in (CoCrFeMn)$_{100-x}$Al$_{x}$. The predictions agree with our present experimental findings, and other reported ones.Comment: 27 pages, 9 figures, 1 tabl

Effect of passive smoking as a risk factor for chronic obstructive pulmonary disease in normal healthy women

Background: Environmental tobacco smoke (ETS) is a risk factor for cardiovascular disease, asthma in children and lung cancer. There is a biological plausibility of ETS as a causal factor for COPD. Objectives of the study were to examine the effect of passive smoking on lung function in non-smoking healthy women and to co-relate the effects of passive smoke as a risk factor for COPD.Methods: 50 women between 20-40 years of age exposed to passive smoke at home and workplace were assessed by questionnaire. The pulmonary function tests were performed and the values of FEV1 and FVC were obtained by a spirometer.Results: Out of 50 women, 34 % at workplace, 54% at home and 12% at home and workplace were exposed. Mean age was 30.3 years. Mean±SD of FEV1 was 1.94±0.9, FVC was 2.54±1.06, FEV1/FVC was 73.5±10.06 predicted FEV1 % was 63.2±23.2. FEV1/FVC of women exposed at home and workplace was 70.84 indicating that they have higher chances of developing COPD later in life.Conclusions: Passive smoking represents a serious health hazard that can be prevented by health education campaigns