Analysis of the nuclear proteome of the resurrection plant Xerophyta viscosa (Baker) and its response to dehydration stress

Xerophyta viscosa Baker (family Velloziaceae) can survive extremes of dehydration (desiccation), down to 5% relative water content (RWC) and resumes full physiological activity within 80 h of rehydration. A thorough understanding of this phenomenon may provide further insight into possible mechanisms for improving drought tolerance in other plants. In this respect a comprehensive analysis of the nuclear proteome of this plant and its response to dehydration stress at 35% RWC was carried out. The RWC at 35% represents a distinct phase of the dehydration process where induction of late protection mechanisms is initiated and is a characteristic of desiccation tolerant species. We optimized nuclei isolation and nuclear protein extraction protocols and successfully employed these protocols to isolate highly purified nuclei and subsequently nuclear proteins from fully hydrated and dehydrated X. viscosa leaf samples. The integrity of the purified nuclei was confirmed with light and fluorescent microscopy. The nuclei were uniform spheres, approximately 5 μm in size. The purity and enrichment of the nuclear proteins were confirmed by chlorophyll assay and Western blot analysis. The nuclear proteins were investigated using two-dimensional (2D) and isobaric tags for relative and absolute quantitation (iTRAQ) technologies. Using the 2DE approach, a total of 438 proteins spots were reproducibly detected and analysed of which 18 protein spots were shown to be up-regulated in response to dehydration. These proteins contained both regulatory and functional proteins. The largest category comprised five novel protein factors and two proteins with unassigned functions. The second category comprised proteins involved in gene regulation and signal transduction. The third category comprised stress responsive proteins with chaperone type activities. Other categories include proteins involved in energy metabolism, protein degradation and translation. These results demonstrate that dehydration was controlled by multiple genes within the plant nucleus and X. viscosa may possess its own specific nuclear proteins that are involved in desiccation stress. In addition we comprehensively analyzed the nuclear proteome of X. viscosa using iTRAQ with two-dimensional liquid chromatography and tandem mass spectrometry to complement the data obtained from the 2DE approach. Using iTRAQ, we reproducibly University of Cape Town identified 128 proteins with confidence ¥ 95% (Ï < 0.05). Sixty six percent of the identified proteins showed consistent expression levels. The remaining 34% proteins showed significant changes in expressions. Of the latter, 23% were shown to be up regulated in response to dehydration stress. The remaining 11% were shown to be down regulated. The nuclear proteins of X. viscosa up-regulated in response to dehydration stress showed a coordinated response involving both regulatory and functional proteins and were implicated in diverse cellular functions. The characteristic feature of the X. viscosa nuclear proteins is the high level of stress molecules among the dehydration responsive proteins with evident functions in defense mechanisms compared to down regulated proteins and proteins showing consistent expression levels. These results demonstrate that enhanced defense capacity is crucial to desiccation tolerance and strongly support the notion that late dehydration responsive proteins are involved in protection of the cellular structures during dehydration. Proteins showing consistent expression levels during dehydration most likely maintain the minimum viability in cells under all conditions or may be indirectly associated with desiccation tolerance. Down-regulated proteins are likely important for plant survival under normal growth conditions. The proteins up-regulated in response to dehydration stress were assumed to be associated directly with the acquisition of desiccation tolerance. The up-regulated proteins were further categorized into nine functional groups to gain more insight into their roles in desiccation tolerance. The largest group was shown to be involved in gene regulation and signal transduction (36%), which reflects the role of the nucleus in gene expression and regulation. The second group included stress responsive molecules such as antioxidants, molecular chaperones and compatible solutes (33%). This reflects the importance of strong defense systems in preventing lipid peroxidation, protein aggregation, membrane leakage and maintaining the integrity of cellular structures during dehydration and in the dried state. The third group contained proteins involved in nucleocytoplasmic transport (10%). This might reflect the capacity of this plant to control the movement of molecules to and from the nucleus during dehydration and the importance of this process in adaptation to dehydration stress. The fourth group contained proteins involved in protein translation (7%). Proteins categorized to other functions, include proteins with miscellaneous and unknown functions. Proteins with unknown functions were considered to be X. viscosa nuclear-specific proteins. There was good correlation between the up-regulated proteins identified by 2-DE and iTRAQ approaches. In conclusion, this study revealed that X. viscosa nuclear proteome was responsive to dehydration stress and desiccation tolerance is University of Cape Town genetically encoded. Secondly, X. viscosa relies on readily inducible protection to combat desiccation and desiccation tolerance is controlled by multiple genes within the plant nucleus. Thirdly, the protective mechanisms of desiccation tolerance utilized by X. viscosa appear to involve signal perception genes and modulating gene expression of appropriate genes encoding protective molecules including antioxidants, molecular chaperones, compatible solutes, proteins of translation and degradation machinery, proteins with miscellaneous functions and novel protein factors. Lastly, proteins are crucial to desiccation tolerance allowing X. viscosa to possess a unique stress tolerance with versatile and coordinated actions to provide protection for its cellular structures during desiccation and in the dried state. To our best knowledge this is the first study to provide insight into the nuclear (organellar) proteome of a desiccation tolerant plant

Evapotranspiration computed by Darcy?s Law: Sudan case study

International audienceThe present study applies Darcy's Law to compute evapotranspiration in the arid to semi-arid central Sudan. The average decline in groundwater level (s) along a distance (L) of the aquifer's cross section was calculated. Such decline is a function of discharge Q at any point across the unit width of the aquifer and effective porosity. Groundwater in the study area generally flows from NW to the SE along basin axial trough and is characterized by variable hydraulic gradient. As the aquifer discharge is directly proportional to the gradient, different values of groundwater level decline were calculated along the flow direction. The hydrogeological map constructed during this study indicates that the system is hydrologicaly closed and groundwater doesn't discharge in the neighboring White Nile River. Geological, hydrological and climatological settings of the discharge area demonstrate that evapotranspiration is the main mechanism of groundwater discharge and reveals that the area is suited for the application of Darcy's Law to compute evapotranspiration. Evapotranspiration was estimated from Darcy's law to be 1.2 mm/a and is sufficient to balance the present system. Greater similarity in geology, hydrology, climate and vegetation encourages the application of Darcy's Law in the Sahara and sub-Sahara to compute for evapotranspiration. Such cost effective method can be applied in arid to semi-arid areas if conditions are favorable

Integrable models: from dynamical solutions to string theory

We review the status of integrable models from the point of view of their dynamics and integrability conditions. Some integrable models are discussed in detail. We comment on the use it is made of them in string theory. We also discuss the Bethe Ansatz solution of the SO(6) symmetric Hamiltonian with SO(6) boundary. This work is especially prepared for the seventieth anniversaries of Andr\'{e} Swieca (in memoriam) and Roland K\"{o}berle.Comment: 24 pages, to appear in Brazilian Journal of Physic

Current Algebra of Super WZNW Models

We derive the current algebra of supersymmetric principal chiral models with a Wess-Zumino term. At the critical point one obtains two commuting super Kac-Moody algebra as expected, but in general there are intertwining fields connecting both right and left sectors, analogously to the bosonic case. Moreover, in the present supersymmetric extension we have a quadratic algebra, rather than an affine Lie algebra, due to the mixing between bosonic and fermionic fields since the purely fermionic sector displays a Lie algebra as well.Comment: 13 page

Mechanical Properties of Eco-friendly Concrete Made with Sugarcane Bagasse Ash

Modern concretes lay emphasis on high strength in order to reduce structural member sizes to reduce materials used; high early strength to promote fast construction; high durability to reduce maintenance costs; and the incorporation of industrial and agricultural wastes to reduce environmental degradation. The incorporation of industrial and agricultural wastes into concrete as cement replacement materials reduces the amount of cement used in the production of concrete and the CO2emissions arising from cement production. Sugarcane bagasse is a waste product from the extraction of juice from sugar cane. It is estimated that 1.7 million tons of bagasse are produced worldwide every year. Much of the bagasse is used as boiler fuel and to produce electricity, and the ash is dumped in earth fills, resulting in critical environmental pollution that requires immediate attention. Available literature shows that when burned under controlled conditions, a pozzolanic ash of high silica content can be obtained, which can be used in concrete production with several advantages. This study investigates the mechanical properties of concrete designed for high strength and incorporating processed sugarcane bagasse ash in amounts of 10–40% by weight of cement in a binary combination with silica fume. Concrete workability in the fresh state and compressive, flexural, and tensile strengths in the hardened state are investigated. Water absorption of hardened concrete is also investigated as an indicator of potential durability. The results show that the mix containing 10% SCBA has the highest mechanical strength, and increasing the SCBA percentage reduces water absorption. However, the workability of concrete in the fresh state reduces substantially with an increase in ash content. Doi: 10.28991/CEJ-2022-08-06-010 Full Text: PD

ANNz2: Photometric Redshift and Probability Distribution Function Estimation using Machine Learning

We present ANNz2, a new implementation of the public software for photometric redshift (photo-z) estimation of Collister & Lahav, which now includes generation of full probability distribution functions (PDFs). ANNz2 utilizes multiple machine learning methods, such as artificial neural networks and boosted decision/regression trees. The objective of the algorithm is to optimize the performance of the photo-z estimation, to properly derive the associated uncertainties, and to produce both single-value solutions and PDFs. In addition, estimators are made available, which mitigate possible problems of non-representative or incomplete spectroscopic training samples. ANNz2 has already been used as part of the first weak lensing analysis of the Dark Energy Survey, and is included in the experiment's first public data release. Here we illustrate the functionality of the code using data from the tenth data release of the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey. The code is available for download at http://github.com/IftachSadeh/ANNZ