Could vesicular transport of Na+ and Cl– be a feature of salt tolerance in halophytes?

Flowers, T. J.; Glenn, Edward P.; Volkov, Vadim

doi:10.1093/aob/mcy164

Cited by 58 publications

(41 citation statements)

References 229 publications

(256 reference statements)

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“…The vacuole appears as a flexible bubble, widening and narrowing the space between the tonoplast and plasma membrane (L€ ofke et al, 2015). This provides the opportunity for direct contact of the two membranes and the possibility of a direct 'shunt' for ions to enter the vacuole either without crossing through the cytosol or crossing via a cytosolic micro domain with different conditions (Flowers et al, 2018).…”

Section: Membrane Dynamics Avoid Transmembrane Crossingsmentioning

confidence: 99%

Energy costs of salt tolerance in crop plants

et al. 2019

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Agricultureisexpandingintoregionsthatareaffectedbysalinity.Thisreviewconsiderstheenergetic costs of salinity tolerance in crop plants and provides a framework for a quantitative assessment of costs. Different sources of energy, and modifications of root system architecture that would maximize water vs ion uptake are addressed. Energy requirements for transport of salt (NaCl) to leaf vacuoles for osmotic adjustment could be small if there are no substantial leaks back across plasma membrane and tonoplast in root and leaf. The coupling ratio of the H +-ATPase also is a critical component. One proposed leak, that of Na + influx across the plasma membrane through certain aquaporin channels, might be coupled to water flow, thus conserving energy. For the tonoplast, control of two types of cation channels is required for energy efficiency. Transporters controlling the Na + and Cl À concentrations in mitochondria and chloroplasts are largely unknown and could be a major energy cost. The complexity of the system will require a sophisticated modelling approach to identify critical transporters, apoplastic barriers and root structures. This modelling approach will informexperimentationandallowaquantitativeassessmentoftheenergycostsofNaCltoleranceto guide breeding and engineering of molecular components.

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Section: Membrane Dynamics Avoid Transmembrane Crossingsmentioning

confidence: 99%

Energy costs of salt tolerance in crop plants

et al. 2019

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“…Energy consumption would increase if the Na + is transported by the cell-to-cell route and crosses multiple membranes. Alternatively Na + could be moved inside small vesicular compartments between cells in the symplasm and via plasmodesmata, or via extracellular vesicles transported in the vasculature (Rutter & Innes, 2017;Flowers et al, 2018) thereby minimising membrane crossing steps.…”

Section: Costs Of Ion Transport Across Rootsmentioning

confidence: 99%

Osmotic adjustment and energy limitations to plant growth in saline soil

et al. 2019

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Summary Plant roots must exclude almost all of the Na+ and Cl– in saline soil while taking up water, otherwise these ions would build up to high concentrations in leaves. Plants evaporate c. 50 times more water than they retain, so 98% exclusion would result in shoot NaCl concentrations equal to that of the external medium. Taking up just 2% of the NaCl allows a plant to osmotically adjust the Na+ and Cl– in vacuoles, while organic solutes provide the balancing osmotic pressure in the cytoplasm. We quantify the costs of this exclusion by roots, the regulation of Na+ and Cl– transport through the plant, and the costs of osmotic adjustment with organic solutes in roots.

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“…When L. bicolor leaves were treated with brefeldin A, a vesicle secretion inhibitor, the secretion rate of the salt glands was severely inhibited (Feng et al, 2015). Similarly, Flowers et al (2019) reported results that supported the hypothesis that vesicle transport plays a key role in salt gland secretion, although they also indicated that transporters may be simultaneously involved. Vesicle transport consumes less energy than transport proteins, and ions can accumulate to a high concentration in the vesicles (Lu et al, 2020).…”

Section: Resultsmentioning

confidence: 81%

Exogenous melatonin enhances salt secretion from salt glands by upregulating the expression of ion transporter and vesicle transport genes in Limonium bicolor

Yuan

Liu

et al. 2020

Preprint

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Background Salt, a common environmental stress factor, inhibits plant growth and reduces yields. Melatonin is a pleiotropic molecule that regulates plant growth and can alleviate environmental stress in plants. All previous research on this topic has focused on the use of melatonin to improve the relatively low salt tolerance of glycophytes by promoting growth and enhancing antioxidant ability. It is unclear whether exogenous melatonin can increase the salt tolerance of halophytes, particularly recretohalophytes, by enhancing salt secretion from the salt glands. Results To examine the mechanisms of melatonin-mediated salt tolerance, we explored the effects of exogenous applications of melatonin on the secretion of salt from the salt glands of Limonium bicolor (a kind of recretohalophyte) seedlings and on the expression of associated genes. A pretreatment with 5 µM melatonin significantly improved the growth of L. bicolor seedlings under 300 mM NaCl. Furthermore, exogenous melatonin significantly increased the dry weight and endogenous melatonin content of L. bicolor. In addition, this treatment reduced the content of Na+ and Cl− in leaves, but increased the K+ content. Both the salt secretion rate of the salt glands and the expression level of genes encoding ion transporters (LbHTK1, LbSOS1, LbPMA, and LbNHX1) and vesicular transport proteins (LbVAMP721, LbVAP27, and LbVAMP12) were significantly increased by exogenous melatonin treatment. These results indicate that melatonin improves the salt tolerance of the recretohalophyte L. bicolor via the upregulation of salt secretion by the salt glands. Conclusions Our results showed that melatonin can upregulate the expression of genes encoding ion transporters and vesicle transport proteins to enhance salt secretion from the salt glands. Combining the results of the current study with previous research, we formulated a novel mechanism by which melatonin increases salt secretion in L. bicolor. Melatonin binds to an unknown receptor located at the PM, which activates the downstream signaling pathway, and then a NO or ROS signaling pathway. This in turn upregulates the expression of genes encoding ion transporters and vesicle transport proteins. The ion transporters transport ions (mainly Na+) into the salt glands, which are subsequently secreted through the participation of various ion transporters and transport vesicles to maintain ionic homeostasis in the cells and alleviate NaCl-induced growth inhibition.

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Could vesicular transport of Na+ and Cl– be a feature of salt tolerance in halophytes?

Cited by 58 publications

References 229 publications

Energy costs of salt tolerance in crop plants

Energy costs of salt tolerance in crop plants

Osmotic adjustment and energy limitations to plant growth in saline soil

Exogenous melatonin enhances salt secretion from salt glands by upregulating the expression of ion transporter and vesicle transport genes in Limonium bicolor

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