Abiotic stresses, such as drought, salinity, extreme temperatures, chemical toxicity and oxidative stress are serious threats to agriculture and the natural status of the environment. Increased salinization of arable land is expected to have devastating global effects, resulting in 30% land loss within the next 25 years, and up to 50% by the year 2050. Therefore, breeding for drought and salinity stress tolerance in crop plants (for food supply) and in forest trees (a central component of the global ecosystem) should be given high research priority in plant biotechnology programs. Molecular control mechanisms for abiotic stress tolerance are based on the activation and regulation of specific stress-related genes. These genes are involved in the whole sequence of stress responses, such as signaling, transcriptional control, protection of membranes and proteins, and free-radical and toxic-compound scavenging. Recently, research into the molecular mechanisms of stress responses has started to bear fruit and, in parallel, genetic modification of stress tolerance has also shown promising results that may ultimately apply to agriculturally and ecologically important plants. The present review summarizes the recent advances in elucidating stress-response mechanisms and their biotechnological applications. Emphasis is placed on transgenic plants that have been engineered based on different stress-response mechanisms. The review examines the following aspects: regulatory controls, metabolite engineering, ion transport, antioxidants and detoxification, late embryogenesis abundant (LEA) and heat-shock proteins.

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Plant responses to drought, salinity and extreme temperatures: towards genetic engineering for stress tolerance

Na+ Tolerance and Na+ Transport in Higher Plants

Low temperature, drought, and high salinity are common stress conditions that adversely affect plant growth and crop production. The cellular and molecular responses of plants to environmental stress have been studied intensively ([Thomashow, 1999][1]; [Hasegawa et al., 2000][2]). Understanding the

/pdf/cell-signaling-during-cold-drought-and-salt-stress-2v6yqzaitr.pdf

Cell Signaling during Cold, Drought, and Salt Stress

Full-length cDNAs are essential for functional analysis of plant genes in the post-sequencing era of the Arabidopsis genome. Recently, cDNA microarray analysis has been developed for quantitative analysis of global and simultaneous analysis of expression profiles. We have prepared a full-length cDNA microarray containing approximately 7000 independent, full-length cDNA groups to analyse the expression profiles of genes under drought, cold (low temperature) and high-salinity stress conditions over time. The transcripts of 53, 277 and 194 genes increased after cold, drought and high-salinity treatments, respectively, more than fivefold compared with the control genes. We also identified many highly drought-, cold- or high-salinity- stress-inducible genes. However, we observed strong relationships in the expression of these stress-responsive genes based on Venn diagram analysis, and found 22 stress-inducible genes that responded to all three stresses. Several gene groups showing different expression profiles were identified by analysis of their expression patterns during stress-responsive gene induction. The cold-inducible genes were classified into at least two gene groups from their expression profiles. DREB1A was included in a group whose expression peaked at 2 h after cold treatment. Among the drought, cold or high-salinity stress-inducible genes identified, we found 40 transcription factor genes (corresponding to approximately 11% of all stress-inducible genes identified), suggesting that various transcriptional regulatory mechanisms function in the drought, cold or high-salinity stress signal transduction pathways.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-313X.2002.01359.x

Monitoring the expression profiles of 7000 Arabidopsis genes under drought, cold and high-salinity stresses using a full-length cDNA microarray.

Regulatory network of gene expression in the drought and cold stress responses.

http://faculty.ucr.edu/~jkzhu/articles/2001/bohnertPPB.pdf

A genomics approach towards salt stress tolerance

A piezoelectric tube actuator is employed as a sample positioning device in Nanocut, a cutting instrument conceived to study the mechanics of nanometric cutting. Extension of functionality of the instrument as a nanometric machine tool motivates the search for an accurate model of the actuator for implementing feedback control. A simple nonlinear model describing longitudinal expansion of the piezoelectric tube actuator is presented in this paper. The model derivation is based on a non-formal analogy with nonlinear viscoelastic materials under uniaxial extension, for which the responses to a step input are similar to the piezoelectric tube. Suitability of the model structure for arbitrary inputs is tested by cross-verification between time and frequency domains. Two parameter estimation procedures are examined and the results of the experimental work for characterization, estimation and validation are presented.

/pdf/modeling-nonlinear-behavior-in-a-piezoelectric-actuator-20oar27h3f.pdf

Modeling Nonlinear Behavior in a Piezoelectric Actuator

Discrete Variable Structure Control for Linear Multivariable Systems

This paper discusses the application of a class of discrete-time sliding mode controllers (DSMC) which was previously shown to be robustly stable. Further insight into design and performance of DSMC is obtained considering the case of linear plants. A simple numerical example is used to illustrate the properties of this technique.

Discrete-Time Sliding Mode Control: The Linear Case

This paper presents a technique for control system design that provides robust stability in the presence of bounded modeling errors The proposed method is a discrete-time version ofa well known sliding mode control technique with saturation functions that generates the boundary layer without requiring either matched uncertainties or smooth functions It is shown that the boundary layer can be made attractive and that the boundary layer thickness is bounded under mild conditions It is also shown that asymptotic stability can be guaranteed if the available model is assumed to be perfect An example is used to illustrate the proposed design technique

Eduardo A. Misawa

Papers

A genomics approach towards salt stress tolerance

Modeling Nonlinear Behavior in a Piezoelectric Actuator

Discrete Variable Structure Control for Linear Multivariable Systems

Discrete-Time Sliding Mode Control: The Linear Case

Discrete-Time Sliding Mode Control for Nonlinear Systems With Unmatched Uncertainties and Uncertain Control Vector