Strategies in a metallophyte species to cope with manganese excess.

The effect of exposure to high Mn concentration was studied in a metallophyte species, Erica andevalensis, using hydroponic cultures with a range of Mn concentrations (0.06, 100, 300, 500, and 700 mg L). At harvest, biomass production, element uptake, and biochemical indicators of metal stress (leaf pigments, organic acids, amino acids, phenols, and activities of catalase, peroxidase, superoxide dismutase) were determined in leaves and roots.

Assessing the Nutritional Value of Root and Tuber Crops from Bolivia and Peru.

All over the world, there are species which may be considered as neglected or underutilized despite their nutritious properties. At present, such crops contribute to food security in isolated areas by providing energy and nutrients in a diversified diet. Such genetic heritage-improved by ancient cultures-is under threat of losing biodiversity as well as the traditional knowledge associated with their cultivation and usage.

A Critical Role of Sodium Flux via the Plasma Membrane Na/H Exchanger SOS1 in the Salt Tolerance of Rice.

Rice () stands among the world's most important crop species. Rice is salt sensitive, and the undue accumulation of sodium ions (Na) in shoots has the strongest negative correlation with rice productivity under long-term salinity. The plasma membrane Na/H exchanger protein Salt Overly Sensitive 1 (SOS1) is the sole Na efflux transporter that has been genetically characterized to date.

Regulation of K Nutrition in Plants.

Modern agriculture relies on mineral fertilization. Unlike other major macronutrients, potassium (K) is not incorporated into organic matter but remains as soluble ion in the cell sap contributing up to 10% of the dry organic matter. Consequently, K constitutes a chief osmoticum to drive cellular expansion and organ movements, such as stomata aperture.

Active proton efflux, nutrient retention and boron-bridging of pectin are related to greater tolerance of proton toxicity in the roots of two Erica species.

Background And Aims: Tolerance to soil acidity was studied in two species of Ericaceae that grow in mine-contaminated soils (S Portugal, SW Spain) to find out if there are interspecific variations in H tolerance which might be related to their particular location.

Methods: Tolerance to H toxicity was tested in nutrient solutions using seeds collected in SW Spain. Plant growth and nutrient contents in leaves, stems and roots were determined.

Pleiotropic effects of enhancing vacuolar K/H exchange in tomato.

Cation antiporters of the NHX family are widely regarded as determinants of salt tolerance due to their capacity to drive sodium (Na) and sequester it into vacuoles. Recent work shows, however, that NHX transporters are primarily involved in vacuolar potassium (K) storage. Over-expression of the K/H antiporter AtNHX1 in tomato increases K accumulation into vacuoles and plant sensitivity to K deprivation.

Control of vacuolar dynamics and regulation of stomatal aperture by tonoplast potassium uptake.

Stomatal movements rely on alterations in guard cell turgor. This requires massive K(+) bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K(+) into the vacuole remain to be identified.

A constitutively active form of a durum wheat Na⁺/H⁺ antiporter SOS1 confers high salt tolerance to transgenic Arabidopsis.

The SOS signaling pathway has emerged as a key mechanism in preserving the homeostasis of Na⁺ and K⁺ under saline conditions. We have recently identified and functionally characterized, by complementation studies in yeast, the gene encoding the durum wheat plasma membrane Na⁺/H⁺ antiporter (TdSOS1). To extend these functional studies to the whole plant level, we complemented Arabidopsis sos1-1 mutant with wild-type TdSOS1 or with the hyperactive form TdSOS1∆972 and compared them to the Arabidopsis AtSOS1 protein.

Ion exchangers NHX1 and NHX2 mediate active potassium uptake into vacuoles to regulate cell turgor and stomatal function in Arabidopsis.

Intracellular NHX proteins are Na(+),K(+)/H(+) antiporters involved in K(+) homeostasis, endosomal pH regulation, and salt tolerance. Proteins NHX1 and NHX2 are the two major tonoplast-localized NHX isoforms. Here, we show that NHX1 and NHX2 have similar expression patterns and identical biochemical activity, and together they account for a significant amount of the Na(+),K(+)/H(+) antiport activity in tonoplast vesicles.

Expression of wheat Na(+)/H(+) antiporter TNHXS1 and H(+)- pyrophosphatase TVP1 genes in tobacco from a bicistronic transcriptional unit improves salt tolerance.

Abiotic stress tolerance of plants is a very complex trait and involves multiple physiological and biochemical processes. Thus, the improvement of plant stress tolerance should involve pyramiding of multiple genes. In the present study, we report the construction and application of a bicistronic system, involving the internal ribosome entry site (IRES) sequence from the 5'UTR of the heat-shock protein of tobacco gene NtHSF-1, to the improvement of salt tolerance in transgenic tobacco plants.

Selective uptake of major and trace elements in Erica andevalensis, an endemic species to extreme habitats in the Iberian Pyrite Belt.

To assess the ecophysiological traits and the phytoremediation potential of the endemic heather Erica andevalensis, we determined the concentrations of major and trace elements in different plant parts and in rizosphere soils from Riotinto mining district (Huelva, Spain). The results showed that E. andevalensis may grow on substrates with very high As, Cu, Fe and Pb concentrations (up to 4114, 1050, 71900 and 15614 microg/g dry weight, respectively), very low availability of macro- and micronutrients and with pH values ranging from 3.

Effects of silicon on copper toxicity in Erica andevalensis Cabezudo and Rivera: a potential species to remediate contaminated soils.

The influence of silicon on responses to copper excess was studied in plants of Erica andevalensis. Plantlets were grown in nutrient solutions containing two Cu (1 and 500 µM) and three Si concentrations (0, 0.5 and 1 mM).

How do vacuolar NHX exchangers function in plant salt tolerance?

Potassium (K(+)) is a major osmoticum of plant cells, and the vacuolar accumulation of this element is a especially crucial feature for plants under high-salt conditions. Emerging evidence indicates that cation/proton transporters of the NHX family are instrumental in the H(+)-linked K(+) transport that mediate active K(+) uptake at the tonoplast for the unequal partitioning of K(+) between vacuole and cytosol. However, and in spite of tenuous supporting evidence, NHX proteins are widely regarded as key players in the sequestration of sodium (Na(+)) into vacuoles to avert ion toxicity in the cytosol of plants under salinity stress.

The AtNHX1 exchanger mediates potassium compartmentation in vacuoles of transgenic tomato.

NHX-type antiporters in the tonoplast have been reported to increase the salt tolerance of various plants species, and are thought to mediate the compartmentation of Na(+) in vacuoles. However, all isoforms characterized so far catalyze both Na(+)/H(+) and K(+)/H(+) exchange. Here, we show that AtNHX1 has a critical involvement in the subcellular partitioning of K(+), which in turn affects plant K(+) nutrition and Na(+) tolerance.

Loss of halophytism by interference with SOS1 expression.

The contribution of SOS1 (for Salt Overly Sensitive 1), encoding a sodium/proton antiporter, to plant salinity tolerance was analyzed in wild-type and RNA interference (RNAi) lines of the halophytic Arabidopsis (Arabidopsis thaliana)-relative Thellungiella salsuginea. Under all conditions, SOS1 mRNA abundance was higher in Thellungiella than in Arabidopsis. Ectopic expression of the Thellungiella homolog ThSOS1 suppressed the salt-sensitive phenotype of a Saccharomyces cerevisiae strain lacking sodium ion (Na(+)) efflux transporters and increased salt tolerance of wild-type Arabidopsis.

Alkali cation exchangers: roles in cellular homeostasis and stress tolerance.

Uptake and translocation of cations play essential roles in plant nutrition, signal transduction, growth, and development. Among them, potassium (K+) and sodium (Na+) have been the focus of numerous physiological studies because K+ is an essential macronutrient and the most abundant inorganic cation in plant cells, whereas Na+ toxicity is a principal component of the deleterious effects associated with salinity stress. Although the homeostasis of these two ions was long surmised to be fine tuned and under complex regulation, the myriad of candidate membrane transporters mediating their uptake, intracellular distribution, and long-distance transport is nevertheless perplexing.

Phenotypic and genotypic characterization of rhizobia from diverse geographical origin that nodulate Pachyrhizus species.

Legumes from the genus Pachyrhizus, commonly known as yam bean, are cultivated in several countries from the American continent and constitute an alternative source for sustainable starch, oil and protein production. The endosymbionts of these legumes have been poorly studied although it is known that this legume is nodulated by fast and slow growing rhizobia. In this study we have analyzed a collection of strains isolated in several countries using different phenotypic and molecular methods.