Molecular basis of salt stress tolerance in crop plants (original) (raw)

New Molecular Approaches to Improving Salt Tolerance in Crop Plants

Annals of Botany, 1998

The last century has seen enormous gains in plant productivity and in resistance to a variety of pests and diseases through much innovative plant breeding and more recently molecular engineering to prevent plant damage by insects. In contrast, improvements to salt and drought tolerance in crop and ornamental plants has been elusive, partially because they are quantitative traits and part of the multigenic responses detectable under salt\drought stress conditions. However, the rapidly expanding base of information on molecular strategies in plant adaptation to stress is likely to improve experimental strategies to achieve improved tolerance. Recently studies of salinity tolerance in crop plants have ranged from genetic mapping to molecular characterization of salt\drought induced gene products. With our increasing understanding of biochemical pathways and mechanisms that participate in plant stress responses it has also become apparent that many of these responses are common protective mechanisms that can be activated by salt, drought and cold, albeit sometimes through different signalling pathways. This review focuses on recent progress in molecular engineering to improve salt tolerance in plants in context of our current knowledge of metabolic changes elicited by salt\drought stress and the known plant characteristics useful for salt tolerance. While it is instructive to draw parallels between molecular mechanisms responsive to salt-stress with accumulating evidence from studies of related abiotic stress-responses, more data are needed to delineate those mechanisms specific for salt tolerance. Also discussed is the alternative genetic strategy that combines single-step selection of salt tolerant cells in culture, followed by regeneration of salt tolerant plants and identification of genes important in the acquired salt tolerance. Currently, transgenic plants have been used to test the effect of overexpression of specific prokaryotic or plant genes, known to be up-regulated by salt\drought stress. The incremental success of these experiments indicates a potentially useful role for these stress-induced genes in achieving long term tolerance. In addition, it is possible that enhanced expression of gene products that function in physiological systems especially sensitive to disruption by salt, could incrementally improve salt tolerance. Current knowledge points towards a need to reconcile our findings that many genes are induced by stress with the practical limitations of overexpressing all of them in a plant in a tissue specific manner that would maintain developmental control as needed. New approaches are being developed towards being able to manipulate expression of functionally related classes of genes by characterization of signalling pathways in salt\drought stress and characterization and cloning of transcription factors that regulate the expression of many genes that could contribute to salt\drought tolerance. Transcription factors that regulate functionally related genes could be particularly attractive targets for such investigations, since they may also function in regulating quantitative traits. Transgenic manipulation of such transcription factors should help us understand more about multigene regulation and its relationship to tolerance.

Plant Molecular Responses to Salt Stress

2020

Plants are frequenly exposed to environmental changes. In fact, abiotic stresses are the most serious factors limiting the productivity of agricultural crops, with adverse effects on germination, plant vigor and crop quality and yield. In particular, salinity stress is a global problem widespread that affects over 800 million ha. In the Mediterranean area, seawater intrusion into freshwater aquifers highly contribute to soil salinisation, resulting in crops productivity decrease. Responses to abiotic stresses are complicated pathways involving the interaction of different signalling molecules to coordinate a specific metabolic pathways. The regulation of these responses involves transcriptional factors, which regulate gene expression by binding to specific DNA promoter sequences. Transcription factors involved in salt stress responses include DRE-related binding factors, leucine zipper DNA binding proteins, putative zinc finger proteins, myb proteins, bZIP/HD-ZIPs, and AP2/EREBP. Particularly, AP2/ERF domain proteins include the DREB or CBF proteins binding to dehydration response elements (DRE) or C-repeats. Transcription factors are powerful targets for genetic engineering in abiotic stress resistance in crops and many studies have been focused on this topic.

Developing salt tolerant plants in a new century: A molecular biology approach

2003

Soil salinity is a major abiotic stress in plant agriculture strongly, influencing plant productivity world-wide. Classical breeding for salt tolerance in crop plants has been attempted to improve field performance without success. Therefore, an alternative strategy is to generate salt tolerant plants through genetic engineering. Several species and experimental approaches have been used in order to identify those genes that are important for salt tolerance. Due to high level of salt tolerance, halophytes are good candidates to identify salt tolerance genes. However, other species such as yeast and glycophytes have also been employed. Three approaches are commonly used to identify genes important for salt tolerance. The first approach is to identify genes involved in processes known to be critical for salt tolerance (osmolyte synthesis, ion homeostasis, etc.). The second approach is to identify genes whose expression is regulated by salt stress. This is relatively simply and applicable to any plant species. Genetic amenability of some species allows the third approach, which consists in the identification of salt tolerance determinants based on functionality. At the moment, there is a large number of reports in the literature claiming that plants with increased salt tolerance have been obtained. The main problem is that different plant species, stage of development, organs, promoters and salt conditions used it is difficult to compare the degree of salt tolerance conferred by different genes. In this review, we discuss progress made towards understanding the molecular elements involved in salt stress responses that have been used in transgenic approaches to improve salt tolerance.

Salt stress proteins in plants: An overview

Frontiers in Plant Science, 2022

Salinity stress is considered the most devastating abiotic stress for crop productivity. Accumulating different types of soluble proteins has evolved as a vital strategy that plays a central regulatory role in the growth and development of plants subjected to salt stress. In the last two decades, efforts have been undertaken to critically examine the genome structure and functions of the transcriptome in plants subjected to salinity stress. Although genomics and transcriptomics studies indicate physiological and biochemical alterations in plants, it do not reflect changes in the amount and type of proteins corresponding to gene expression at the transcriptome level. In addition, proteins are a more reliable determinant of salt tolerance than simple gene expression as they play major roles in shaping physiological traits in salt-tolerant phenotypes. However, little information is available on salt stress-responsive proteins and their possible modes of action in conferring salinity stress tolerance. In addition, a complete proteome profile under normal or stress conditions has not been established yet for any model plant species. Similarly, a complete set of low abundant and key stress regulatory proteins in plants has not been identified. Furthermore, insufficient information on posttranslational modifications in salt stress regulatory proteins is available. Therefore, in recent past, studies focused on exploring changes in protein expression under salt stress, which will complement genomic, transcriptomic, and physiological studies in understanding mechanism of salt tolerance in plants. This review focused on recent studies on proteome profiling in plants subjected to salinity stress, and provide synthesis of updated literature about Frontiers in Plant Science frontiersin.org 01

Molecular Mechanisms of Salt Tolerance in Plants Article ID: 41060

Salinity is a significant stressor that hinders the growth and productivity of plants in many parts of the world, resulting from the increasing use of low-quality irrigation water and soil salinization. To develop salt-tolerant plant varieties for these affected areas, it is essential to have a comprehensive understanding of how plants respond to salinity stress at various levels and to integrate molecular tools with physiological and biochemical techniques. Plant adaptation or tolerance to salinity stress involves a complex interplay of physiological traits, metabolic pathways, and gene networks. Recent research has identified various adaptive responses to salinity stress at the molecular, cellular, metabolic, and physiological levels. However, the mechanisms underlying salinity tolerance are still not fully understood.

Review Article Molecular mechanisms of plant salinity tolerance: a review

2015

Accompanied with increasing world's population, we need more food. In the other hands, most important crops and vegetables are susceptible to salinity. Unfortunately the salinization process in agricultural fields will decrease the suitable land for cultivation by 30% within the next 25 years, and up to 50% by the year 2050. Therefore, developments of salt tolerant crops can be the best and most practical way to produce enough food. In the course of evolution, plants have developed several protecting mechanisms (avoidance and tolerance) so as to adapt to salt stress. Understanding the cellular basis of salt stress tolerance mechanisms is necessary for breeding and genetic engineering of salt tolerance in crops. Tolerance mechanisms mainly are applicable to practical manipulations. Tolerance mechanisms in plant can be categorized as: a)-antioxidative defense, b)-ion homeostasis, c)-compatible solute and d)-transcription factors. In this review we tried to make a comprehensive review on these 4 tolerance mechanisms from the molecular aspects.

Factors Influencing the Salt Stress Tolerance in Plants – An Overview

Salinity stress is one of the adverse stresses among abiotic stress which mitigates ion toxicity, water unavailability and oxidative stress apart from the hampering growth and productivity of plants. Various anthropogenic activities also indulge in limiting the cultivatable land thus minimizing the food productivity. For sustainable food supply to world population which is increasing at its peril, it is important to develop stress tolerant crops. Salt adaptation involves various trait of gene which comes across in an integrated manner to lessen the adverse effect of salt. This salt signaling cascade activates various mechanisms after perceiving the signal at membrane level receptor which leads to activate the various genes and transcription factors involved in production of osmolytes and ion sequestration. In this review we tried to accentuate the impacts of salinity on plant, role of calcium ion, transcription factor, osmolytes and plant hormone in salt tolerance.

Advanced study of functional proteins involved in salt stress regulatory pathways in plants

Salt stress is a major abiotic stress influencing plant growth, development, and crop yield. Inhibition of pho tosynthesis, decreased cell growth, cell division, decreased biomass, and stomatal closure are all symptoms of salt stress in plants. Salt stresses induce ionic, osmotic, and oxidative stresses, which trigger various cellu lar, molecular, metabolic, and physiological responses. This review presents the proteins involved in crop plants’ response to salt stress. This review also discusses the role of phytohormones in response to salt stress. The most recent explicit protein contributions to the salt stress response in agricultural plants are discussed in this review, along with crop models that will be used in upcoming environmental stress evaluations for crop development.

Molecular cloning and characterization of salt responsive genes in rice (Oryza sativa)

Journal of Plant Physiology, 2001

Salt Overly Sensitive (SOS) pathway comprising SOS1, SOS2 and SOS3 genes has been recognized as the key mechanism controlling ion homeostasis under salinity stress. SOS2 component of this pathway encodes a serine/threonine protein kinase that together with SOS3 activates downstream Na ? /H ? antiporter SOS1, reestablishing cellular ion homeostasis under salinity stress. In the present study, we have found that the transcript levels of BjSOS2 are induced in response to various abiotic stresses. We have isolated a 713 bp promoter region of SOS2 gene from Brassica juncea to study the regulation of BjSOS2 under various abiotic stress conditions and further, to examine utility of the cloned upstream region in genetic engineering experiments. For this purpose, 713 bp BjSOS2 promoter:b-glucuronidase (GUS) fusion construct, along with its two subsequent 5 0 deletion derivatives, D1 (443 bp) and D2 (209 bp), were stably transformed into B. juncea. Functional analysis of transgenic lines revealed significant increase in promoter activity under salinity, desiccation as well as abscisic acid (ABA) treatment which was consistent with increased transcript levels of GUS gene. BjSOS2 promoter possesses strong multi-stress inducible nature, suggesting its involvement in various aspects of stress signaling. Considering the fact that the simultaneous presence of multiple abiotic stress conditions under field conditions is a challenging threat to crop productivity, future studies may utilize the BjSOS2 promoter to drive stress-inducible expression of genes involved in imparting tolerance to multiple stresses. Keywords Brassica juncea Á BjSOS2 promoter Á Cis-acting elements Á Salinity Á Multi-stress response Á GUS activity Electronic supplementary material The online version of this article (

Salt Induced Change of Gene Expression in Salt Sensitive and Tolerant Rice Species

Journal of Agricultural Science, 2013

The aim of this study was to quantify the expression of the SalT, LTP-Plant, CDPK and PP1 genes, described as responsive to salinity in rice genotypes, describe the promoter region of these genes and identify possible cis-elements that may be involved in the induction of gene expression under salinity. The cultivars BRS Bojuru (tolerant) and BRS Agrisul (sensitive) were subjected to 0, 12, 24, 36 and 48 h of exposure to salt. For the analysis of qRT-PCR, two detoxification/defense genes and two cell signal transduction genes were selected. In the identification of cis-elements, a region spanning 1.000 bp in the promoter region of genes was analyzed. The Os01g0348900-SalT gene presented an increase in quantification of the relative expression (QR) of 2.081 times in the sensitive and 63.7 times in the tolerant cultivar. The Os03g0251000-LTP gene showed a contrasting increase of the expression between the cultivars BRS Agrisul (QR = 11.0) and BRS Bojuru (QR = 1.54). The genes Os03g0688300-CDPK and Os02g0820000-PP1 apparently do not show response to salinity, since in most treatments, the QR values were lower than the control. Thirty-eight cis-elements distributed in the four analyzed genes were identified. Of these, six were found only in the Os01g0348900-SalT gene promoter, suggesting a possible involvement of these cis-elements in the induction of expression of this gene under salinity. Based on these results, it can be concluded that these genes do not maintain a direct relation with salinity tolerance, but with mechanisms that allow acclimation to this condition.