This document summarizes research on engineering agricultural plants for improved salt tolerance through genetic engineering. It discusses genes from model organisms like Arabidopsis and yeast that improve salt tolerance when transferred to crop plants. Genes from halophytic plants, which are naturally salt tolerant, are also discussed. The document outlines past research and calls for future work, including combining multiple salt tolerance genes, comparative analysis of similar genes, and further research on halophytes and the biological costs of salt tolerance.
Identification and expression analysis of LEA gene family members in cucumber...asdasdas19
LEA (late embryogenesis abundant) proteins
are firstly discovered in seeds and then identified in vegetative tissues of different plant species. They are mainly
regulated under abiotic stress conditions. Although genome
wide studies of different gene family members have been
performed in cucumber, there is no such a study for LEA
genes. We have identified 79 LEA genes in the cucumber
genome. Based on phylogenetic analysis, CsLEA genes
could be classified into seven groups in which structural
motifs are relatively conserved. Tandem duplications play
an important role in cucumber genome for LEA gene
expansion. Orthologous and chromosomal relationships of
CsLEA genes were observed based on comparative mapping analysis with other species. The in silico micro-RNA
(miRNA) target analyses indicated that 37 CsLEA genes
were targeted by different miRNAs, especially mir854 and
mir414 are the most abundant identified ones. Public
available RNA-seq data were analyzed for expression
analysis of CsLEA genes in different tissues of cucumber
Anaerobic fungi particularly belonging to the phylum Neocallimastigomycota, are the most basal lineage of the kingdom Fungi. These fungi are principally known from the digestive tracts of the larger mammalian herbivores, where they play an inevitable role as primary colonisers of ingested forage. Recent researches indicate their appearance in herbivorous reptiles like the green iguana and termites also.
.
Identification and expression analysis of LEA gene family members in cucumber...asdasdas19
LEA (late embryogenesis abundant) proteins
are firstly discovered in seeds and then identified in vegetative tissues of different plant species. They are mainly
regulated under abiotic stress conditions. Although genome
wide studies of different gene family members have been
performed in cucumber, there is no such a study for LEA
genes. We have identified 79 LEA genes in the cucumber
genome. Based on phylogenetic analysis, CsLEA genes
could be classified into seven groups in which structural
motifs are relatively conserved. Tandem duplications play
an important role in cucumber genome for LEA gene
expansion. Orthologous and chromosomal relationships of
CsLEA genes were observed based on comparative mapping analysis with other species. The in silico micro-RNA
(miRNA) target analyses indicated that 37 CsLEA genes
were targeted by different miRNAs, especially mir854 and
mir414 are the most abundant identified ones. Public
available RNA-seq data were analyzed for expression
analysis of CsLEA genes in different tissues of cucumber
Anaerobic fungi particularly belonging to the phylum Neocallimastigomycota, are the most basal lineage of the kingdom Fungi. These fungi are principally known from the digestive tracts of the larger mammalian herbivores, where they play an inevitable role as primary colonisers of ingested forage. Recent researches indicate their appearance in herbivorous reptiles like the green iguana and termites also.
.
Root is the part where plant interact with microbes. Microbes really plays an important role in the overall wellbeing of the crop. Here is some basics regarding root colonization
The different types of external stresses that influence the plant growth and development.
These stresses are grouped based on their characters
Biotic
Abiotic
Almost all the stresses, either directly or indirectly, lead to the production of reactive oxygen species (ROS) that create oxidative stress in plants.
This damages the cellular constituents of plants which are associated with a reduction in plant yield.
Abstract— Storage roots are important for the growth and development in plants because they provide nutrients, water, and energy storage. Storage roots are also modulating growth direction, disease resistance, and root formation at the cellular and molecular level through interactions of genes and gene networks. However, molecular mechanisms regulating storage root formation in plants are not fully understood. In this review, we have overviewed transcriptional regulation of storage root formation, proteomic regulation of storage root formation, ethylene regulation of storage root formation, auxin regulation of storage root formation, gene expression regulation of storage root formation, and metabolism regulation of storage root formation. We have reviewed the basic regulatory principles of storage root formation from the network of genomics to proteomics and metabolism in plants that will be valuable to research work in storage root growth and development regulation at the molecular level.
Rice is one of the most important cereal crops of developing countries and
the staple food of about 65% of the world’s population. The rice crops have been
greatly disturbed by the heavy metals. The present study deals with the toxic effect of
sodium arsenate on morphological and molecular variation through SDS
-
PAGE in 10
rice (
Oryza sativa
L.) varieties. Ten varieties of rice were grown under different
concentration (25 ppm, 50 ppm and 100 ppm) of sodium arsenate against control.
Morphological parameters like shoot length, root length, leaf area and biomass
showed marked differences among ten rice varieties. The proteins were separated
through SDS
-
PAGE gel electrophoresis and calculated their molecular weight. The
morphological and molecular variations induced in rice varieties by arsenic stress
provide a new insight leading to a better understanding of the heavy metal response
in plants.
Rice is one of the most important cereal crops of developing countries and the staple food of about 65% of the world’s population. The rice crops have been greatly disturbed by the heavy metals. The present study deals with the toxic effect of sodium arsenate on morphological and molecular variation through SDS-PAGE in 10 rice (Oryza sativa L.) varieties. Ten varieties of rice were grown under different concentration (25 ppm, 50 ppm and 100 ppm) of sodium arsenate against control. Morphological parameters like shoot length, root length, leaf area and biomass showed marked differences among ten rice varieties. The proteins were separated through SDS-PAGE gel electrophoresis and calculated their molecular weight. The morphological and molecular variations induced in rice varieties by arsenic stress provide a new insight leading to a better understanding of the heavy metal response in plants.
Article Citation:
John De Britto R, Mary Sujin R, Steena Roshan Sebastian and Dharmar K.
Toxic effect of arsenic on ten rice varieties.
Journal of Research in Agriculture (2011) 1(1): 011-016.
Full Text:
http://www.jagri.info/documents/AG0003.pdf
Impact of Compost Prepared from Invasive Alien Species in Alleviating Water S...YogeshIJTSRD
Invasive alien plant species are major thread to biodiversity, climate change and environmental sustainability. Management of these invasive alien plant species become a typical task at global level. Composting can be an efficient and environment friendly solution for management of these invasive alien species. The aim of present study was to evaluate the effect of compost prepared from three invasive alien species Cuscutareflexa, Eupatorium adenophorum and Lantana camaraon the tomato plant vigour, antioxidant and nutrient content under water deficit and irrigated well watered conditions. The results revealed that Cuscutareflexa CR compost treatment gave highest shoot length 23.0 , 23.7 , root length 30.0 , 21.4 , shoot fresh weight 47.9 , 52.2 , shoot dry weight 71.0 , 49.4 and root dry weight 66.7 , 51.5 , under water stressand irrigated conditions, respectively. The application of compostCR under water stress has enhanced chlorophyll and prolinecontent over control. Similarly, antioxidant enzymes analysis showed the increased superoxide dismutase 1.33 2.17fold , peroxidase 1.38 1.82fold and catalase 1.06 1.73fold activity under water deficit condition. Nutrient content such as nitrogen, phosphorus, potassium and sodiumin tomato leaf were higher under both water stress and irrigated conditions compared to their respective control. It can be concluded from above outcomes that compost prepared from invasive alien species have potential to ameliorate the negative effects of water stress and enhance the tomato growth. Sandhya Bind | A. K. Sharma "Impact of Compost Prepared from Invasive Alien Species in Alleviating Water Stress in Tomato (Solanum Lycopersicum L.)" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-3 , April 2021, URL: https://www.ijtsrd.com/papers/ijtsrd39961.pdf Paper URL: https://www.ijtsrd.com/biological-science/botany/39961/impact-of-compost-prepared-from-invasive-alien-species-in-alleviating-water-stress-in-tomato-solanum-lycopersicum-l/sandhya-bind
Root is the part where plant interact with microbes. Microbes really plays an important role in the overall wellbeing of the crop. Here is some basics regarding root colonization
The different types of external stresses that influence the plant growth and development.
These stresses are grouped based on their characters
Biotic
Abiotic
Almost all the stresses, either directly or indirectly, lead to the production of reactive oxygen species (ROS) that create oxidative stress in plants.
This damages the cellular constituents of plants which are associated with a reduction in plant yield.
Abstract— Storage roots are important for the growth and development in plants because they provide nutrients, water, and energy storage. Storage roots are also modulating growth direction, disease resistance, and root formation at the cellular and molecular level through interactions of genes and gene networks. However, molecular mechanisms regulating storage root formation in plants are not fully understood. In this review, we have overviewed transcriptional regulation of storage root formation, proteomic regulation of storage root formation, ethylene regulation of storage root formation, auxin regulation of storage root formation, gene expression regulation of storage root formation, and metabolism regulation of storage root formation. We have reviewed the basic regulatory principles of storage root formation from the network of genomics to proteomics and metabolism in plants that will be valuable to research work in storage root growth and development regulation at the molecular level.
Rice is one of the most important cereal crops of developing countries and
the staple food of about 65% of the world’s population. The rice crops have been
greatly disturbed by the heavy metals. The present study deals with the toxic effect of
sodium arsenate on morphological and molecular variation through SDS
-
PAGE in 10
rice (
Oryza sativa
L.) varieties. Ten varieties of rice were grown under different
concentration (25 ppm, 50 ppm and 100 ppm) of sodium arsenate against control.
Morphological parameters like shoot length, root length, leaf area and biomass
showed marked differences among ten rice varieties. The proteins were separated
through SDS
-
PAGE gel electrophoresis and calculated their molecular weight. The
morphological and molecular variations induced in rice varieties by arsenic stress
provide a new insight leading to a better understanding of the heavy metal response
in plants.
Rice is one of the most important cereal crops of developing countries and the staple food of about 65% of the world’s population. The rice crops have been greatly disturbed by the heavy metals. The present study deals with the toxic effect of sodium arsenate on morphological and molecular variation through SDS-PAGE in 10 rice (Oryza sativa L.) varieties. Ten varieties of rice were grown under different concentration (25 ppm, 50 ppm and 100 ppm) of sodium arsenate against control. Morphological parameters like shoot length, root length, leaf area and biomass showed marked differences among ten rice varieties. The proteins were separated through SDS-PAGE gel electrophoresis and calculated their molecular weight. The morphological and molecular variations induced in rice varieties by arsenic stress provide a new insight leading to a better understanding of the heavy metal response in plants.
Article Citation:
John De Britto R, Mary Sujin R, Steena Roshan Sebastian and Dharmar K.
Toxic effect of arsenic on ten rice varieties.
Journal of Research in Agriculture (2011) 1(1): 011-016.
Full Text:
http://www.jagri.info/documents/AG0003.pdf
Impact of Compost Prepared from Invasive Alien Species in Alleviating Water S...YogeshIJTSRD
Invasive alien plant species are major thread to biodiversity, climate change and environmental sustainability. Management of these invasive alien plant species become a typical task at global level. Composting can be an efficient and environment friendly solution for management of these invasive alien species. The aim of present study was to evaluate the effect of compost prepared from three invasive alien species Cuscutareflexa, Eupatorium adenophorum and Lantana camaraon the tomato plant vigour, antioxidant and nutrient content under water deficit and irrigated well watered conditions. The results revealed that Cuscutareflexa CR compost treatment gave highest shoot length 23.0 , 23.7 , root length 30.0 , 21.4 , shoot fresh weight 47.9 , 52.2 , shoot dry weight 71.0 , 49.4 and root dry weight 66.7 , 51.5 , under water stressand irrigated conditions, respectively. The application of compostCR under water stress has enhanced chlorophyll and prolinecontent over control. Similarly, antioxidant enzymes analysis showed the increased superoxide dismutase 1.33 2.17fold , peroxidase 1.38 1.82fold and catalase 1.06 1.73fold activity under water deficit condition. Nutrient content such as nitrogen, phosphorus, potassium and sodiumin tomato leaf were higher under both water stress and irrigated conditions compared to their respective control. It can be concluded from above outcomes that compost prepared from invasive alien species have potential to ameliorate the negative effects of water stress and enhance the tomato growth. Sandhya Bind | A. K. Sharma "Impact of Compost Prepared from Invasive Alien Species in Alleviating Water Stress in Tomato (Solanum Lycopersicum L.)" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-3 , April 2021, URL: https://www.ijtsrd.com/papers/ijtsrd39961.pdf Paper URL: https://www.ijtsrd.com/biological-science/botany/39961/impact-of-compost-prepared-from-invasive-alien-species-in-alleviating-water-stress-in-tomato-solanum-lycopersicum-l/sandhya-bind
Effect of soil acidity on some soybean varietiesInnspub Net
This study aims to determine the mechanism of adaptation and morphophysiology character of soybean genotypes to soil acidity levels. Research using randomized block design with four replications, the first factor consists of soybean varieties: Tanggamus varieties, Detam 2, Anjasmoro and Detam 1, while the second factor is the media's treatment consisted of medium acid soils and limed soil. The results showed that the low level acidity of planting medium will affect the growth and development of plants. There are different mechanisms of adaptation to acidity on soybean varieties. Avoidance mechanism is indicated by an increase in pH around the roots on Tanggamus varieties, Detam2, Anjasmoro and Detam1. Tolerant mechanism is indicated by the maturation age and high production on Tanggamus varieties
Morphological and physiological attributes associated to drought tolerance of...Innspub Net
The experiment was conducted to assess the differential morpho-physiological response to stimulated water deficit and to determine the relationship between some of these morphological and physiological traits and yield components of eighteen durum wheat genotypes grown in pots under lathhouse condition. Water deficit significantly affected gas exchange and chlorophyll fluorescence parameters. It reduced the net photosynthesis rate (Pn), transpiration rate (E) and stomatal conductance (gs) measured both at anthesis and grain-filling stages. Similarly, the value of initial fluorescence (Fo) was increased while variable fluorescence (Fv), maximum fluorescence (Fm) and optimum quantum yield fluorescence (Fv/Fm) were decreased under water deficit. RWC of the leaves was decreased by 36.7% while SLA increased by 12.6% due to moisture stress relative to the well-watered control. No significant correlations were found between chlorophyll fluorescence parameters and grain yield under water deficit condition. Similarly, no significant correlations were found between leaf gas exchange parameters and grain yield. On the other hand, peduncle length and excursion were positively correlated with grain yield while negatively correlated with drought susceptibility index under water deficit condition. Leaf posture and rolling had also a profound effect on grain yield and other attributes. Erect-leaved genotypes had more grain yield, HI, kernel numbers per spikelet and grain-filling rate but had lower kernel weight than droopy leaved. Similarly, genotypes exhibited strong leaf rolling under water deficit condition had more grain yield, kernel numbers per spike and water use efficiency. The genetic variability found for leaf posture, leaf rolling, peduncle length and excursion among the Ethiopian durum wheat genotypes suggests the opportunity for selection superior and adapted genotype in water-limited environments. These can be achieved by integrating these morphological traits as indirect selection in conjunction with other yield components. Get the full articles at: http://www.innspub.net/volume-1-number-2-april-2011-2/
In this presentation, I would like to provide the Resistance Mechanism and Molecular Responses to the Salinity.
There are two types of plants Halophytes and Glycophytes (categories on the basis of their responses to the salinity) examples are Thellungiella halophila and Arabidopsis thaliana, respectively.
Earlier Arabidopsis was considered as Model organism incase of plants but it can't tolerate high saline condition that's the reason for the limited study of plant towards salinity responses. But in the year 2004 the discovery of new plant Thellungiella halophila generates new knowledge about the tolerance mechanism of plants towards salinity responses because it's a halophytes which can tolerate extreme saline condition.
And also it has very similarity with the Arabidopsis so it's considered as the Model organism for the study of Salt stress physiology.
There are major two pathways involved in response to Salt stress (described in presentation).
Alleviation of Salinity Effects by Poultry Manure and Gibberellin Application...IJEAB
Capsicum is one of the most widely consumed vegetables and is also used as a spice for its pungency. Many species of Capsicum are being cultivated worldwide. Capsicum is considered as a commercial crop for their economic value. However, the yield of the crop suffers severely due to salt stress, Soil salinity reduces water availability of plant roots via negative (low) osmosis potential, as well as decrease of germination dynamics of plant seeds by ionic toxicity of Na and Cl , Significant differences in fruit-set, yield, photo synthetic rates, stomata conductance, total chlorophyll content, proline, In general, salinity affects almost every aspect of the physiology and biochemistry of plants. The aim of this study was to determine the salt tolerance of pepper (Capsicum annuum L) under salinity stress by saline irrigation water, Poultry and gibberellins applications were used to alleviated the negative effects on growth parameters and yield of Pepper under salinity stress. The water salinity levels led to a significant elevation in the values of electrical conductivity of the soil with the peroxidase activity, and Sodium and proline contents in leaves, while resulting in decrease in growth parameters and leave contents of ( NPK),The poultry and gibberellins applications increased the growth parameters ( Dry weight of shoot and root &fruit weight) and (NPK) contents in leaves with slight dropping of peroxidase activity in leaves while a clear dropping of sodium and proline contents in leave. That possible to mitigation the negative affect of salt stress by some application like exogenous hormones and Decomposed organic matter to solve the disruption of endohormons and lack of available nutrients under salt stress, and elevation of osmotic stress in soil solution in roots area. The GA & poultry application improved the growth and it has increased the Pepper tolerance to the abiotic stress which was exerted by saline irrigation water.
DocumThe effect of Amaranthus hybridus on fluoride removal by iron (III) salt...Hezron Mwakabona
The use of iron (Fe) (III) salts as fluoride coagulants in water is challenged by the requirement of high
pH for maximum efficiency. At their natural pH, these salts have low fluoride removal efficiency. This
study examines the effect of amaranth plants on enhancement of the defluoridation efficiency of Fe (III)
salts as coagulants. Amaranthus hybridus plants were suspended in fluoride water treated with varying
concentrations of Fe (III) with its roots immersed completely in fluoride water for varying time from 720
to 1440 min. The study shows that fluoride coagulation by Fe (III) in the absence of plants is limited to
10%, whereas when plants were introduced, it increased from 10 to 40%. These results suggest that
amaranth plants enhance the defluoridation efficiency of Fe (III). This enhanced removal may be
attributed to increased coagulation effected by exudates released by plant root which contain organic
compounds and CO2 or charged root surfaces by the formation of Fe (III) oxide film. The exact factor
that has a major contribution to enhanced removal observed remains to be subject of further studies.
Effect of mineral acids on rooting response of aging mung bean (phaseolus aur...
Kern, John - Transgenic Salt Tolerance Review
1. Review: Engineering agricultural plant species for improved salt tolerance
John Kern
Plant Development & Biotechnology w/ Marina Tourlakis
16/10/2015
Introduction
The vast majority of the water on earth is found in the ocean, which is 3.5% salt (599 mM). Not only is
the largest reserve of water high is salt, the available reserves of freshwater relative to human demands
are steadily decreasing. It has been estimated that barring drought and other abiotic factors, salinity
hampers the efficiency of 20% to 50% of land that is presently used for agriculture (1). This effect
includes semi-arid areas that have been used in long term agriculture. The very process itself causes
buildup of mineral salts in soil when drainage or rainfall are limited. As such, a means to deal with
salinity is a factor even in landlocked areas.
Aside from land that is already used for agriculture, there is a glut of arid land that had been deemed
feasible to use should irrigation using sea water become an option. Studies have estimated that as much as
20% of coastal arid land could potentially be irrigated in this manner (1). Should this become an option,
the ability to greatly increase both food production and carbon fixation would be greatly increased. If salt
water agriculture becomes viable, benefits should be felt in both short and long term scales.
With the advent of genetic engineering, the ability to mix the beneficial traits between salt tolerant
(halophytic) and agriculturally useful plant species is close to within reach. There are however several
approaches that scientists can take. Methods are greatly varied but by no means incompatible. Some
experiments work to isolate genes in well-known species (like Arabidopsis and Yeast) that will improve
salinity response when overexpressed. Other studies work to compare freshwater plants’ and halophytes’
salt tolerance in order to identify genomic differences that convey the resistance. Other researchers
examine plants that grow in salt that have simply never been examined in detail as to whether they could
be cultivated and/or upgraded for utilitarian purposes.
Between 2001 and 2005, four science reviews discussing transgenic saline tolerance improvement have
been published. In 2001, work on Arabidopsis and yeast was acknowledged and more work on halophytes
was called for (2). In 2002, it was predicted that future plants would be engineered to sequester sodium in
leaves, away from fruit (3), a hypothesis which I will argue has since been disproven. In 2005, reviews
called for attempts at combining several slat tolerance improving genes in the same plant (4), and for
more precise work to be done to quantify the productive effects of transgenic approaches (5). In this
2. review, the possible approaches to improving salt tolerance using transgenes will be outlined, and future
directions for improving on the work will be contrasted.
Stress Response Genes in Model Organisms
A popular approach by groups that study salt tolerance is to compare gene expression in individuals of the
same species before and after stress exposure. One such study was able to isolate the BADH gene
complex from spinach, which express it under stress. When the gene complex transferred to and
overexpressed in carrots and potatoes, the resulting specimens had higher tolerance to stresses including
both drought and saline exposure (6, 7).
The HAL1 gene complex is another stress tolerance candidate. I can be moved from yeast to plants like
tomatoes and watermelons to improve their salt tolerances (8, 9). Teams that have produced transgenic
plants with this gene have observed that under non-stressed circumstances, the plants behave
indistinguishably from wild types. In this gene’s case, there remains further work to be completed, as the
exact mechanism by which it improves stress tolerance remains unverified. However, there has been some
work suggesting that it plays a role in a larger gene complex that helps keep cells from losing K+ ions
while subjected to salt stress (10). The exact mechanism used to accomplish this is as of yet unidentified
though.
The GmDREB2 gene, isolated from soybean and moved to Arabidopsis and Tobacco has been found to
play a role in abiotic stress response (11). Salinity was one such abiotic stress, however, the gene played a
role in protecting from other stresses, like droughts. Further research in genes like this show potential in
producing hardier crops, as opposed to ones that are tailored to specific environments. Similar works have
included study of the SNAC1 gene complex, which codes for several transcription factors, has been found
to play a role in abiotic stress response in rice, producing hardier (to salt and drought) plants when
overexpressed (12).
Beyond these genes, several studies have experimented with the roles of other genes in salt tolerance, and
are working to understand the mechanisms by which they assist. Genes that help with salinity tolerance
generally fall into three categories; vacuolar antiporters, membrane antiporters, and stress response genes.
Of these, the first two categories generally play roles in the mechanics behind sodium evacuation, while
the latter play roles in plants’ response to stress after being otherwise unprepared. Each method
contributes the plant’s resilience by a unique mechanism.
3. Genes Promoting Intrinsic Salt Tolerance in Model Organisms
The other genes that have been researched each play roles in increasing plants’ normal levels of salt
expulsion. As opposed to genes that are primarily activated in response to abiotic stress, these constantly
maintain levels of proteins that contribute to their evacuative function. One such gene which is in the
early phases of research is the OsNHX1 gene, which is naturally present in rice and codes for a vacuolar
Na+/H+ antiporter (13). Researcher have found a positive correlation between the gene’s expression and
Oryza Sativa’s tolerance to saline water.
Another such gene is AtHKT1 plays a role in salt response and is also in the early phase of research.
While naturally found in Arabidopsis, the gene has been found to play a role in moving sodium ions from
tissue into the phloem, so that it can be moved back down to the roots (14). A separate study has found
that the gene also plays a role in limiting Na+ ion entry at the roots (15). This gene may indeed play roles
in both evacuating and limiting the entry of sodium ions, in which case it would be a major component of
further transgenic work. It is worth noting that this mechanism actually evacuates sodium from the entire
plant, leaving it in groundwater.
Another such gene is the AtNHX1 complex, which is also naturally present in yeast, and has been studied
extensively. By examination of both the protein structure, and ion contents in plants with and without the
gene, researchers have identified the role of the protein it codes for. The AtNHX1 gene codes for a protein
that moves Na+ and H+ ions out of vacuoles, and into the cytosol. As such, it plays a role in moving the
ions out of the cells. By moving this gene to other species, researchers have found that when
overexpressed, it can increase salt tolerance in wheat, tomatoes, and maize (16, 17, and 18).
4. Sodium Transport in Stem Tissue
Figure 1: Cross Section of Plant stem tissue, arrows indicate net transport of Na+ ions as a result of
increased expression of associated genes. Arrow A: Vacuole to cytosol transport that genes such as
OsNHX1 & AtNHX1 contribute to. Arrow B: Cytosol to intercellular space by genes such as SOS1 and
subsidiaries of the HAL1 complex. Arrow C: Transport of NA+ to the phloem promoted by genes such as
SOS1 & AtHKT1. Arrow D: Transport of Na+ to the xylem promoted by the SOS1 gene that was
specifically derived from the halophyte Salicornia brachiate.
Study of Halophytes
Despite that extensive genomic research has been performed on the species that are popular to work on,
relatively little has been done to investigate the plants that are naturally tolerant of high salt levels. Plants
referred to as halophytes are a category of species that are able to thrive in highly saline environments.
Several have been investigated, but little extensive or genomic research has been done on most. However,
the field of halophyte study is in development.
Some of the earliest lines of research performed on halophytes has been to delve into their potential to be
used as crops unaltered. Studies have indeed found that Salicornia herbacea L. and Panicum Turgidum
could both be used as saline irrigated cattle feed crops (19, 20). They are however, inedible to people.
Recently, halophytes have been studied at the genome level significantly more extensively.
An investigation where halophyte gene expressions were compared to Arabidopsis under salt stressed
conditions has identified a number of candidate genes for further investigation. These included Fe-SOD,
Central Vacuole Parenchyma cell PhloemXylem
5. P5CS, PDF1.2, AtNCED and SOS1 (21). The SOS1 gene is the only that has been transgenically
investigated further. It has been found to code for a transmembrane Na+/H+ antiporter (22). It was found
to be expressed to a greater degree under normal conditions in halophytic plants than in regular plants
(23). It is worth noting that the SOS1 gene is present in several species, including both halophytes and
Arabidopsis, and are slightly varied in structure, though similar in function between them (24).
In other experiments, the SOS1 gene has successfully been moved from Salicornia brachiate (a succulent
halophyte) to tobacco in order to confer increased salt tolerance. This tolerance was achieved by loading
the xylem loading with sodium ions, an effect unique to that gene (25). This is one of the earliest attempts
at using halophyte genes using transgenes. Further work with similar plants has yet to be expanded upon.
Discussion
Further study could include a wider variety of cultivar plants
Other reviews have suggested further expansion beyond yeast and Arabidopsis. There are some (tobacco,
carrots, tomatoes, maize, wheat) studies that have been performed since those calls. However, this work is
still in beginning phases, as the general pattern is to take a gene that has already been shown to work on
yeast &/or Arabidopsis, and then move it to the cultivar species. One such category of plants that could
see huge demand in the near to long term future are legumes. Regions that are so arid that saline irrigation
even becomes a factor also generally have extreme shortages of fixed nitrogen. As such, before highly
productive agriculture even comes into play, it may be necessary for future focus to be geared towards
soil structure and nutrient improvement. As such, plants with nitrogen fixing root bacteria may be the first
thing to invest in researching.
Combining transgenes in the same specimens: antiporters for vacuoles and cells
One avenue for future research would be to add several theoretically compatible genes to the same
recipient plants. As it stands, most of the experiments to date have involved one gene at a time. Many of
the genes that have been studied separately work by separate mechanisms. For example, the AtNHX1,
SOS1, and AtHKT1 genes could likely all be combined to provide a compounded intrinsic tolerance
beyond even the 400mM capacity achieved in BADH treated carrots. From that landmark, increasing
productive tolerance a further 50% would allow irrigation with untreated sea water. Several such
pathways that are theoretically possible could provide highly productive species with successful future
experiments.
Comparative analysis of genes that work by similar mechanisms
6. Ongoing studies of genes responsible for salinity tolerance have found both a variety of mechanisms,
along with several of genes that produce the same mechanisms. At present, there are no side by side
essays of similar transgenic species with slightly different genes that code for similar antiporters. For
example, the SOS1 complexes sourced from yeast and a halophytic plant could be compared. Such
analysis for every gene identified in the capability may play a crucial role in engineering crops to be as
efficiently halophytic as possible. Logically, those genes will be found in plants that undergo selective
pressure on tolerance, but only comparative experimentation can confirm the hypothesis.
Further study on plants that are already salt tolerant
Currently, some experimentation has worked on halophytic plants, this has lots of room to be furthered.
At the moment, the majority of genetic study on halophytes has been concentrated on genome comparison
against Arabidopsis or agricultural species. Should researchers wish to continue via the method of
database wide gene analysis, the next step could be to compare taxonomically diverse halophytes in
search of their similarities. Researchers could then cross reference those similarities with common
differences from large numbers of glycophytes. In essence, this would mean using gene databases to ask,
what halophytes have in common that is distinct from freshwater plants. The genes they find could then
be isolated and used in further transgenic study. Such an approach would be a major divergence from an
analysis of solely the genes glycophytes express under stressful conditions.
With reference of study into the potential naturally halophytic plants have as agricultural crops, another
future avenue of research would be to begin investigations into improving their nutrition and energy
content. In such a case, an entirely separate line of genomic analysis would be necessary, as the stress
tolerance, but not the nutrition, is already available in those species.
Research into the biological energy costs of salt tolerance
With the idea of using salt water crops for productive means, an avenue for research that is as of yet
untouched is an analysis of the energy toll of salinity tolerance. As of yet, researchers have not observed
any major productivity reduction in the transgenic species that have been produced. However, the
processes that provide saline resistance require the construction of new machinery within tissues. As such,
there is reason to suspect that it would be costly.
Considering the raw productive capacity of oceanic algae, there is reason to believe that salinity is not a
major limitation to well adapted autotrophs. However, a detailed study would be required to verify
whether the ability is costly or simply lost in freshwater plants through genetic drift when no longer
7. selected for. Understanding this difference could help in decisions as to whether desalination by organic
or mechanical means or saline agriculture are more energy efficient options for future primary production.
Conclusion
By examining the work that has been completed thus far, several avenues for future work emerge, ranging
from more aggressive approaches to genomic alteration, to broader database wide comparative analysis.
The current state of studies indicates fairly strongly that saline agriculture is possible, and on the horizon.
However, the strategies taken in future research will likely influence the time frame, and effectiveness
with which it can be implemented in the relatively near future. With hopes of improving global food
supplies, development of halophytic agriculture could potentially neutralize water supply limitations. This
area of research hold vast promise, barring legal and social barriers, evidence suggests that with adequate
investment, saline agriculture can be developed in the near future.
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