The OsNRAMP1 iron transporter is involved in Cd accumulation in rice

Cadmium (Cd) is a heavy metal toxic to humans and the accumulation of Cd in the rice grain is a major agricultural problem, particularly in Asia. The role of the iron transporter OsNRAMP1 in Cd uptake and transport in rice was investigated here. An OsNRAMP1:GFP fusion protein was localized to the plasma membrane in onion epidermal cells. The growth of yeast expressing OsNRAMP1 was impaired in the presence of Cd compared with yeast transformed with an empty vector. Moreover, the Cd content of OsNRAMP1-expressing yeast exceeded that of the vector control. The expression of OsNRAMP1 in the roots was higher in a high Cd-accumulating cultivar (Habataki) than a low Cd-accumulating cultivar (Sasanishiki) regardless of the presence of Cd, and the amino acid sequence of OsNRAMP1 showed 100% identity between Sasanishiki and Habataki. Over-expression of OsNRAMP1 in rice increased Cd accumulation in the leaves. These results suggest that OsNRAMP1 participates in cellular Cd uptake and Cd transport within plants, and the higher expression of OsNRAMP1 in the roots could lead to an increase in Cd accumulation in the shoots. Our results indicated that OsNRAMP1 is an important protein in high-level Cd accumulation in rice

A family of dual-activity glycosyltransferasesphosphorylases mediates mannogen turnover and virulence in Leishmania parasites

Parasitic protists belonging to the genus Leishmania synthesize the non-canonical carbohydrate reserve, mannogen, which is composed of β-1,2-mannan oligosaccharides. Here, we identify a class of dual-activity mannosyltransferase/phosphorylases (MTPs) that catalyze both the sugar nucleotide-dependent biosynthesis and phosphorolytic turnover of mannogen. Structural and phylogenic analysis shows that while the MTPs are structurally related to bacterial mannan phosphorylases, they constitute a distinct family of glycosyltransferases (GT108) that have likely been acquired by horizontal gene transfer from gram-positive bacteria. The seven MTPs catalyze the constitutive synthesis and turnover of mannogen. This metabolic rheostat protects obligate intracellular parasite stages from nutrient excess, and is essential for thermotolerance and parasite infectivity in the mammalian host. Our results suggest that the acquisition and expansion of the MTP family in Leishmania increased the metabolic flexibility of these protists and contributed to their capacity to colonize new host niches

Iron biofortification in rice: an update on quantitative trait loci and candidate genes

ReviewRice is the most versatile model for cereals and also an economically relevant food crop; as a result, it is the most suitable species for molecular characterization of Fe homeostasis and biofortification. Recently there have been significant efforts to dissect genes and quantitative trait loci (QTL) associated with Fe translocation into rice grains; such information is highly useful for Fe biofortification of cereals but very limited in other species, such as maize (Zea mays) and wheat (Triticum aestivum). Given rice’s centrality as a model for Poaceae species, we review the current knowledge on genes playing important roles in Fe transport, accumulation, and distribution in rice grains and QTLs that might explain the variability in Fe concentrations observed in different genotypes. More than 90 Fe QTLs have been identified over the 12 rice chromosomes. From these, 17 were recorded as stable, and 25 harbored Fe-related genes nearby or within the QTL. Among the candidate genes associated with Fe uptake, translocation, and loading into rice grains, we highlight the function of transporters from the YSL and ZIP families; transporters from metal-binding molecules, such as nicotianamine and deoxymugineic acid; vacuolar iron transporters; citrate efflux transporters; and others that were shown to play a role in steps leading to Fe delivery to seeds. Finally, we discuss the application of these QTLs and genes in genomics assisted breeding for fast-tracking Fe biofortification in rice and other cereals in the near futureinfo:eu-repo/semantics/publishedVersio

Influence of arsenic stress on synthesis and localization of low-molecular-weight thiols in Pteris vittata

The roles of low-molecular-weight thiols (LMWTs), such as glutathione and phytochelatins, in arsenic (As) tolerance and hyperaccumulation in Pteris vittata an As-hyperaccumulator fern remain to be better understood. This study aimed to thoroughly characterize LMWT synthesis in P. vittata to understand the roles played by LMWTs in As tolerance and hyperaccumulation. LMWT synthesis in P. vittata was induced directly by As, and not by As-mediated oxidative stress. Expression of PvECS2. one of the putative genes of γ-glutamylcysteine synthetase (γECS), increases in P. vittata shoots at 48 h after the onset of As exposure, almost corresponding to the increase in the concentrations of γ-glutamylcysteine and glutathione. Furthermore, localization of As showed similar trends to those of LMWTs in fronds at both whole-frond and cellular levels. This study thus indicates the specific contribution of LMWTs to As tolerance in P. vittata. γECS may be responsible for the As-induced enhancement of LMWT synthesis

Role of Thiol Compounds in Arsenic Tolerance in Pteris vittata

It has been suggested that thiol compounds such as glutathione (GSH) and phytochelatin (PC) contribute to arsenic (As) tolerance mechanisms in higher plant. In contrast, the role of thiol compounds in As tolerance and hyperaccumulation in Pteris vittata, an As hyperaccumulator fern, has not been well demonstrated so far. The purpose of this study was to elucidate that role. Gel-filtration chromatography showed that fronds of P. vittata contained high-molecular-weight As compounds containing thiol compounds. Localization of As showed similar trends to that of thiol compounds, increasing with getting higher in position of pinna. Besides, the molar ratio of thiol to As was nearly equal to the ideal molar ratio of As-thiol complexes. These results suggest that As makes complex with thiol compounds in fronds of P. vittata. When comparing P. vittata with Nephrolepis exaltata, an As nonaccumulator fern, As-induced enhancement of thiol synthesis was observed only in P. vittata. The enhancement of thiol synthesis was induced directly by As, not indirectly by As-mediated oxidative stress. γ-glutamylcysteine (γEC) synthetase is a key enzyme for the synthesis of GSH and PC. Two putative genes of γEC synthetase, PvECS1 and PvECS2, were found in P. vittata. Expression of PvECS2 in shoots increased at 48 h after the onset of As exposure, almost corresponding to the increase in concentrations of γEC and GSH. Moreover, As accumulation in shoots began just before these increases. Thus, this study strongly suggests the contribution of thiol compounds to As tolerance in P. vittata

Role of Thiol Compounds in Arsenic Tolerance in Pteris vittata

It has been suggested that thiol compounds such as glutathione (GSH) and phytochelatin (PC) contribute to arsenic (As) tolerance mechanisms in higher plant. In contrast, the role of thiol compounds in As tolerance and hyperaccumulation in Pteris vittata, an As hyperaccumulator fern, has not been well demonstrated so far. The purpose of this study was to elucidate that role. Gel-filtration chromatography showed that fronds of P. vittata contained high-molecular-weight As compounds containing thiol compounds. Localization of As showed similar trends to that of thiol compounds, increasing with getting higher in position of pinna. Besides, the molar ratio of thiol to As was nearly equal to the ideal molar ratio of As-thiol complexes. These results suggest that As makes complex with thiol compounds in fronds of P. vittata. When comparing P. vittata with Nephrolepis exaltata, an As nonaccumulator fern, As-induced enhancement of thiol synthesis was observed only in P. vittata. The enhancement of thiol synthesis was induced directly by As, not indirectly by As-mediated oxidative stress. γ-glutamylcysteine (γEC) synthetase is a key enzyme for the synthesis of GSH and PC. Two putative genes of γEC synthetase, PvECS1 and PvECS2, were found in P. vittata. Expression of PvECS2 in shoots increased at 48 h after the onset of As exposure, almost corresponding to the increase in concentrations of γEC and GSH. Moreover, As accumulation in shoots began just before these increases. Thus, this study strongly suggests the contribution of thiol compounds to As tolerance in P. vittata

Characterization of OsNramp1, a metal transporter from rice

Cadmium (Cd) is one of the most toxic heavy metals for both plants and humans, and Cd accumulation in rice grains has become a major agricultural problem in Japan. In this study, we investigated the role of OsNramp1 in Cd uptake and transport in rice. An OsNramp1::GFP fusion protein localized to the plasma membrane in onion epidermal cells, and yeast expressing OsNramp1 showed increased sensitivity to Cd. Furthermore, OsNramp1-overexpressing rice accumulated more Cd in the leaf blades than non-transformed rice when cultured in Cd-contaminated soil. These results suggest that OsNramp1 increases the cellular uptake and accumulation of Cd in plants