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"Tolerant"
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Contrasting Responses of Photosynthesis to Salt Stress in the Glycophyte Arabidopsis and the Halophyte Thellungiella: Role of the Plastid Terminal Oxidase as an Alternative Electron Sink
The effects of short-term salt stress on gas exchange and the regulation of photosynthetic electron transport were examined in Arabidopsis (Arabidopsis thaliana) and its salt-tolerant close relative Thellungiella (Thellungiella halophila). Plants cultivated on soil were challenged for 2 weeks with NaCl. Arabidopsis showed a much higher sensitivity to salt than Thellungiella; while Arabidopsis plants were unable to survive exposure to greater than 150 mM salt, Thellugiella could tolerate concentrations as high as 500 mM with only minimal effects on gas exchange. Exposure of Arabidopsis to sublethal salt concentrations resulted in stomatal closure and inhibition of CO₂ fixation. This lead to an inhibition of electron transport though photosystem II (PSII), an increase in cyclic electron flow involving only PSI, and increased nonphotochemical quenching of chlorophyll fluorescence. In contrast, in Thellungiella, although gas exchange was marginally inhibited by high salt and PSI was unaffected, there was a large increase in electron flow involving PSII. This additional electron transport activity is oxygen dependent and sensitive to the alternative oxidase inhibitor n-propyl gallate. PSII electron transport in Thellungiella showed a reduced sensitivity to 2'-iodo-6-isopropyl-3-methyl-2',4,4'-trinitrodiphenylether, an inhibitor of the cytochrome b₆f complex. At the same time, we observed a substantial up-regulation of a protein reacting with antibodies raised against the plastid terminal oxidase. No such up-regulation was seen in Arabidopsis. We conclude that in salt-stressed Thellungiella, plastid terminal oxidase acts as an alternative electron sink, accounting for up to 30% of total PSII electron flow.
Journal Article
Overexpression of the trehalose-6-phosphate synthase gene OsTPS1 enhances abiotic stress tolerance in rice
Trehalose plays an important role in metabolic regulation and abiotic stress tolerance in a variety of organisms. In plants, its biosynthesis is catalyzed by two key enzymes: trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP). The genome of rice (Oryza sativa) contains 11 OsTPS genes, and only OsTPS1 shows TPS activity. To demonstrate the physiological function of OsTPS1, we introduced it into rice and found that OsTPS1 overexpression improved the tolerance of rice seedling to cold, high salinity and drought treatments without other significant phenotypic changes. In transgenic lines overexpressing OsTPS1, trehalose and proline concentrations were higher than in the wild type and some stress-related genes were up-regulated, including WSI18, RAB16C, HSP70, and ELIP. These results demonstrate that OsTPS1 may enhance the abiotic stress tolerance of plants by increasing the amount of trehalose and proline, and regulating the expression of stress-related genes. Furthermore, we found that overexpression of some Class II TPSs also enhanced plant tolerance of abiotic stress. This work will help to clarify the role of trehalose metabolism in abiotic stress response in higher plants.
Journal Article
The dry gardening handbook : plants and practices for a changing climate
Would you like a garden that can withstand summer drought and does not require watering? Illustrated with more than 400 original photos, this book shows how to turn the dream of a dry garden into a reality.
Book
Plant growth promoting rhizobacteria Dietzia natronolimnaea modulates the expression of stress responsive genes providing protection of wheat from salinity stress
Plant growth promoting rhizobacteria (PGPR) hold promising future for sustainable agriculture. Here, we demonstrate a carotenoid producing halotolerant PGPR
Dietzia natronolimnaea
STR1 protecting wheat plants from salt stress by modulating the transcriptional machinery responsible for salinity tolerance in plants. The expression studies confirmed the involvement of ABA-signalling cascade, as
TaABARE
and
TaOPR1
were upregulated in PGPR inoculated plants leading to induction of
TaMYB
and
TaWRKY
expression followed by stimulation of expression of a plethora of stress related genes. Enhanced expression of
TaST
, a salt stress-induced gene, associated with promoting salinity tolerance was observed in PGPR inoculated plants in comparison to uninoculated control plants. Expression of SOS pathway related genes (
SOS1
and
SOS4
) was modulated in PGPR-applied wheat shoots and root systems. Tissue-specific responses of ion transporters
TaNHX1
,
TaHAK
, and
TaHKT1
, were observed in PGPR-inoculated plants. The enhanced gene expression of various antioxidant enzymes such as
APX
,
MnSOD
,
CAT
,
POD
,
GPX
and
GR
and higher proline content in PGPR-inoculated wheat plants contributed to increased tolerance to salinity stress. Overall, these results indicate that halotolerant PGPR-mediated salinity tolerance is a complex phenomenon that involves modulation of ABA-signalling, SOS pathway, ion transporters and antioxidant machinery.
Journal Article
Water-smart gardening : save money, save water, and grow the garden you want
\"Garden within your environment using these design ideas, plantings, and water-conserving irrigation strategies.\"--Provided by publisher.
Book
Potential Use of Halophytes to Remediate Saline Soils
Salinity is one of the rising problems causing tremendous yield losses in many regions of the world especially in arid and semiarid regions. To maximize crop productivity, these areas should be brought under utilization where there are options for removing salinity or using the salt-tolerant crops. Use of salt-tolerant crops does not remove the salt and hence halophytes that have capacity to accumulate and exclude the salt can be an effective way. Methods for salt removal include agronomic practices or phytoremediation. The first is cost- and labor-intensive and needs some developmental strategies for implication; on the contrary, the phytoremediation by halophyte is more suitable as it can be executed very easily without those problems. Several halophyte species including grasses, shrubs, and trees can remove the salt from different kinds of salt-affected problematic soils through salt excluding, excreting, or accumulating by their morphological, anatomical, physiological adaptation in their organelle level and cellular level. Exploiting halophytes for reducing salinity can be good sources for meeting the basic needs of people in salt-affected areas as well. This review focuses on the special adaptive features of halophytic plants under saline condition and the possible ways to utilize these plants to remediate salinity.
Journal Article
Specialized Microbiome of a Halophyte and its Role in Helping Non-Host Plants to Withstand Salinity
Root microbiota is a crucial determinant of plant productivity and stress tolerance. Here, we hypothesize that the superior halo-tolerance of seepweed
Suaeda salsa
is tightly linked to a specialized belowground microbiome. To test this hypothesis, we performed a phylogenetic trait-based framework analysis based on bacterial 16S rRNA gene and fungal nuclear rRNA internal transcribed spacer profiling. Data showed that the dominant α-proteobacteria and γ-proteobacteria communities in bulk soil and root endosphere tend to be phylogenetically clustered and at the same time exhibit phylogenetic over-dispersion in rhizosphere. Likewise, the dominant fungal genera occurred at high phylogenetic redundancy. Interestingly, we found the genomes of rhizospheric and endophytic bacteria associated with
S. salsa
to be enriched in genes contributing to salt stress acclimatization, nutrient solubilization and competitive root colonization. A wide diversity of rhizobacteria with similarity to known halotolerant taxa further supported this interpretation. These findings suggest that an ecological patterned root-microbial interaction strategy has been adopted in
S. salsa
system to confront soil salinity. We also demonstrated that the potential core microbiome members improve non-host plants growth and salt tolerance. This work provides a platform to improve plant fitness with halophytes-microbial associates and novel insights into the functions of plant microbiome under salinity.
Journal Article