The Role of Low-Molecular-Weight Organic Acids in Metal Homeostasis in Plants.

Low-molecular-weight organic acids (LMWOAs) are essential O-containing metal-binding ligands involved in maintaining metal homeostasis, various metabolic processes, and plant responses to biotic and abiotic stress. Malate, citrate, and oxalate play a crucial role in metal detoxification and transport throughout the plant. This review provides a comparative analysis of the accumulation of LMWOAs in excluders, which store metals mainly in roots, and hyperaccumulators, which accumulate metals mainly in shoots.

Nicotianamine: A Key Player in Metal Homeostasis and Hyperaccumulation in Plants.

Nicotianamine (NA) is a low-molecular-weight N-containing metal-binding ligand, whose accumulation in plant organs changes under metal deficiency or excess. Although NA biosynthesis can be induced in vivo by various metals, this non-proteinogenic amino acid is mainly involved in the detoxification and transport of iron, zinc, nickel, copper and manganese. This review summarizes the current knowledge on NA biosynthesis and its regulation, considers the mechanisms of NA secretion by plant roots, as well as the mechanisms of intracellular transport of NA and its complexes with metals, and its role in radial and long-distance metal transport.

Zinc- and nickel-induced changes in fatty acid profiles in the zinc hyperaccumulator Arabidopsis halleri and non-accumulator Arabidopsis lyrata.

This pilot study aimed at comparing zinc (Zn) and nickel (Ni) effects on the fatty acid (FA) profiles, oxidative stress and desaturase activity in the Zn hyperaccumulator Arabidopsis halleri and the excluder Arabidopsis lyrata to allow a better picture of the physiological mechanisms which may contribute to metal tolerance or acclimation. The most significant changes in the FA composition were observed in the shoots of the hyperaccumulator and in the roots of the excluder, and were not only metal-dependent, but also species-specific, since the most significant changes in the shoots of A. halleri were observed under Ni treatment, though Ni, in contrast to Zn, was accumulated mainly in its roots.

Phytochelatins: Sulfur-Containing Metal(loid)-Chelating Ligands in Plants.

Phytochelatins (PCs) are small cysteine-rich peptides capable of binding metal(loid)s via SH-groups. Although the biosynthesis of PCs can be induced in vivo by various metal(loid)s, PCs are mainly involved in the detoxification of cadmium and arsenic (III), as well as mercury, zinc, lead, and copper ions, which have high affinities for S-containing ligands. The present review provides a comprehensive account of the recent data on PC biosynthesis, structure, and role in metal(loid) transport and sequestration in the vacuoles of plant cells.

Polyunsaturated and Very-Long-Chain Fatty Acids Are Involved in the Adaptation of Maloideae (Rosaceae) to Combined Stress in the Mountains.

One of the mechanisms of plant adaptation to combined stress under conditions of altitudinal zonation is changing the lipid fatty acid (FA) composition. The main changes in the FA composition occurred in the outer cell layers of the pericarp, but not in the parenchyma. Adaptation was found to be species-specific.

Transcriptional effects of cadmium on iron homeostasis differ in calamine accessions of Noccaea caerulescens.

Calamine accessions of the zinc/cadmium/nickel hyperaccumulator, Noccaea caerulescens, exhibit striking variation in foliar cadmium accumulation in nature. The Ganges accession (GA) from Southern France displays foliar cadmium hyperaccumulation (>1000 μg g DW), whereas the accession La Calamine (LC) from Belgium, with similar local soil metal composition, does not (<100 μg g DW). All calamine accessions are cadmium hypertolerant.

Histidine promotes the loading of nickel and zinc, but not of cadmium, into the xylem in Noccaea caerulescens.

Histidine is known to be involved in Ni hyperaccumulation. Recently, histidine-dependent xylem loading of Ni and Zn has been demonstrated in the Zn/Ni/Cd hyperaccumulator, Noccaea caerulescens. Here we tested the hypothesis whether Cd xylem loading is histidine-dependent, too.

Histidine-mediated xylem loading of zinc is a species-wide character in Noccaea caerulescens.

Histidine plays a crucial role in nickel (Ni) translocation in Ni-hyperaccumulating plants. Here, we investigated its role in zinc (Zn) translocation in four accessions of the Zn hyperaccumulator, Noccaea caerulescens, using the related non-hyperaccumulator, Thlaspi arvense, as a reference. We compared the effects of exogenous histidine supply on Zn xylem loading, and of Zn-histidine complex formation on Zn uptake in energized tonoplast vesicles.

New nitrogen uptake strategy: specialized snow roots.

The evolution of plants has yielded a wealth of adaptations for the acquisition of key mineral nutrients. These include the structure, physiology and positioning of root systems. We report the discovery of specialized snow roots as a plant strategy to cope with the very short season for nutrient uptake and growth in alpine snow-beds, i.

Chelation by histidine inhibits the vacuolar sequestration of nickel in roots of the hyperaccumulator Thlaspi caerulescens.

* The mechanisms of enhanced root to shoot metal transport in heavy metal hyperaccumulators are incompletely understood. Here, we compared the distribution of nickel (Ni) over root segments and tissues in the hyperaccumulator Thlaspi caerulescens and the nonhyperaccumulator Thlaspi arvense, and investigated the role of free histidine in Ni xylem loading and Ni transport across the tonoplast. * Nickel accumulation in mature cortical root cells was apparent in T.