Sete Lagoas, Brazil
Sete Lagoas, Brazil

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Zhou G.,University of Tasmania | Zhou G.,CSIRO | Pereira J.F.,Embrapa Wheat | Delhaize E.,CSIRO | And 3 more authors.
Journal of Experimental Botany | Year: 2014

Malate and citrate efflux from root apices is a mechanism of Al 3+ tolerance in many plant species. Citrate efflux is facilitated by members of the MATE (multidrug and toxic compound exudation) family localized to the plasma membrane of root cells. Barley (Hordeum vulgare) is among the most Al3+-sensitive cereal species but the small genotypic variation in tolerance that is present is correlated with citrate efflux via a MATE transporter named HvAACT1. This study used a biotechnological approach to increase the Al3+ tolerance of barley by transforming it with two MATE genes that encode citrate transporters: SbMATE is the major Al 3+-tolerance gene from sorghum whereas FRD3 is involved with Fe nutrition in Arabidopsis. Independent transgenic and null T3 lines were generated for both transgenes. Lines expressing SbMATE showed Al 3+-activated citrate efflux from root apices and greater tolerance to Al3+ toxicity than nulls in hydroponic and short-term soil trials. Transgenic lines expressing FRD3 exhibited similar phenotypes except citrate release from roots occurred constitutively. The Al3+ tolerance of these lines was compared with previously generated transgenic barley lines overexpressing the endogenous HvAACT1 gene and the TaALMT1 gene from wheat. Barley lines expressing TaALMT1 showed significantly greater Al3+ tolerance than all lines expressing MATE genes. This study highlights the relative efficacy of different organic anion transport proteins for increasing the Al3+ tolerance of an important crop species. © 2014 The Author.

Gomide R.L.,Embrapa Maize and Sorghum | De Paula Boratto I.M.,PUC of Minas Gerais
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The determination of crop evapotranspiration (ETc) values is very useful information for planning irrigation, water supply estimation, regulation of water rights and river basins hydrologic studies. Values of ETc in the North region of Minas Gerais state, Brazil, were estimated in this research from the multispectral images of the Landsat 5 TM by means of the model Surface Energy Balance Algorithm for Land- SEBAL, based on the simplified energy balance equation of a surface covered by vegetation, using a few daily surface climatological parameters (wind speed, rainfall, air temperature and relative humidity, solar radiation). The aim of this study was to estimate the regional spatial distribution of the energy balance components and evapotranspiration in the study area, covering the irrigated perimeter of Gorutuba, involving the cities of Nova Porteirinha, Janaúba, Porteirinha, Verdelândia and Pai Pedro. Thematic maps of regional evapotranspiration and energy balance components were generated from spectral analyzes of the images obtained, associated with the used weather data. The ability of SEBAL to provide the spatial variability of energy balance components, including evapotranspiration, demonstrated its sensitivity to different occupation of the soil surface vegetation, and to high data temporal and spatial resolutions data, indicating that the SEBAL model can be used in scales and operational routine for north region of Minas Gerais. © 2014 SPIE.

Background: Aluminium (Al) toxicity is a major agricultural constraint for crop cultivation on acid soils, which comprise a large portion of the world's arable land. One of the most widely accepted mechanisms of Al tolerance in plants is based on Al-activated organic acid release into the rhizosphere, with organic acids forming stable, non-toxic complexes with Al. This mechanism has recently been validated by the isolation of bona-fide Al-tolerance genes in crop species, which encode membrane transporters that mediate Al-activated organic acid release leading to Al exclusion from root apices. In crop species such as sorghum and barley, members in the multidrug and toxic compound extrusion (MATE) family underlie Al tolerance by a mechanism based on Al-activated citrate release. Scope and Conclusions: The study of Al tolerance in plants as conferred by MATE family members is in its infancy. Therefore, much is yet to be discovered about the functional diversity and evolutionary dynamics that led MATE proteins to acquire transport properties conducive to Al tolerance in plants. In this paper we review the major characteristics of transporters in the MATE family and will relate this knowledge to Al tolerance in plants. The MATE family is clearly extremely flexible with respect to substrate specificity, which raises the possibility that Al tolerance as encoded by MATE proteins may not be restricted to Al-activated citrate release in plant species. There are also indications that regulatory loci may be of pivotal importance to fully explore the potential for Al-tolerance improvement based on MATE genes. © The Author 2010.

Liu J.,Cornell University | Luo X.,Cornell University | Luo X.,Southwest University | Shaff J.,Cornell University | And 7 more authors.
Plant Journal | Year: 2012

The primary mechanism of Arabidopsis aluminum (Al) resistance is based on root Al exclusion, resulting from Al-activated root exudation of the Al 3+-chelating organic acids, malate and citrate. Root malate exudation is the major contributor to Arabidopsis Al resistance, and is conferred by expression of AtALMT1, which encodes the root malate transporter. Root citrate exudation plays a smaller but still significant role in Arabidopsis Al resistance, and is conferred by expression of AtMATE, which encodes the root citrate transporter. In this study, we demonstrate that levels of Al-activated root organic acid exudation are closely correlated with expression of the organic acid transporter genes AtALMT1 and AtMATE. We also found that the AtALMT1 promoter confers a significantly higher level of gene expression than the AtMATE promoter. Analysis of AtALMT1 and AtMATE tissue- and cell-specific expression based on stable expression of promoter-reporter gene constructs showed that the two genes are expressed in complementary root regions: AtALMT1 is expressed in the root apices, while AtMATE is expressed in the mature portions of the roots. As citrate is a much more effective chelator of Al 3+ than malate, we used a promoter-swap strategy to test whether root tip-localized expression of the AtMATE coding region driven by the stronger AtALMT1 promoter (AtALMT1P::AtMATE) resulted in increased Arabidopsis Al resistance. Our results indicate that expression of AtALMT1 P::AtMATE not only significantly increased Al resistance of the transgenic plants, but also enhanced carbon-use efficiency for Al resistance. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

Caniato F.F.,Embrapa Maize and Sorghum | Hamblin M.T.,Cornell University | Guimaraes C.T.,Embrapa Maize and Sorghum | Zhang Z.,Cornell University | And 3 more authors.
PLoS ONE | Year: 2014

Root damage caused by aluminum (Al) toxicity is a major cause of grain yield reduction on acid soils, which are prevalent in tropical and subtropical regions of the world where food security is most tenuous. In sorghum, Al tolerance is conferred by SbMATE, an Al-activated root citrate efflux transporter that underlies the major Al tolerance locus, AltSB, on sorghum chromosome 3. We used association mapping to gain insights into the origin and evolution of Al tolerance in sorghum and to detect functional variants amenable to allele mining applications. Linkage disequilibrium across the AltSB locus decreased much faster than in previous reports in sorghum, and reached basal levels at approximately 1000 bp. Accordingly, intralocus recombination events were found to be extensive. SNPs and indels highly associated with Al tolerance showed a narrow frequency range, between 0.06 and 0.1, suggesting a rather recent origin of Al tolerance mutations within AltSB. A haplotype network analysis suggested a single geographic and racial origin of causative mutations in primordial guinea domesticates in West Africa. Al tolerance assessment in accessions harboring recombinant haplotypes suggests that causative polymorphisms are localized to a ∼6 kb region including intronic polymorphisms and a transposon (MITE) insertion, whose size variation has been shown to be positively correlated with Al tolerance. The SNP with the strongest association signal, located in the second SbMATE intron, recovers 9 of the 14 highly Al tolerant accessions and 80% of all the Al tolerant and intermediately tolerant accessions in the association panel. Our results also demonstrate the pivotal importance of knowledge on the origin and evolution of Al tolerance mutations in molecular breeding applications. Allele mining strategies based on associated loci are expected to lead to the efficient identification, in diverse sorghum germplasm, of Al tolerant accessions able maintain grain yields under Al toxicity. © 2014 Caniato et al.

Kochian L.V.,Cornell University | Pineros M.A.,Cornell University | Liu J.,Cornell University | Magalhaes J.V.,Embrapa Maize and Sorghum
Annual Review of Plant Biology | Year: 2015

Aluminum (Al) toxicity in acid soils is a significant limitation to crop production worldwide, as approximately 50 of the world's potentially arable soil is acidic. Because acid soils are such an important constraint to agriculture, understanding the mechanisms and genes conferring resistance to Al toxicity has been a focus of intense research interest in the decade since the last article on crop acid soil tolerance was published in this journal. An impressive amount of progress has been made during that time that has greatly increased our understanding of the diversity of Al resistance genes and mechanisms, how resistance gene expression is regulated and triggered by Al and Al-induced signals, and how the proteins encoded by these genes function and are regulated. This review examines the state of our understanding of the physiological, genetic, and molecular bases for crop Al tolerance, looking at the novel Al resistance genes and mechanisms that have been identified over the past ten years. Additionally, it examines how the integration of molecular and genetic analyses of crop Al resistance is starting to be exploited for the improvement of crop plants grown on acid soils via both molecular-assisted breeding and biotechnology approaches. ©2015 by Annual Reviews. All rights reserved.

Martins B.A.B.,Embrapa Maize and Sorghum | Christoffoleti P.J.,University of Sao Paulo
Scientia Agricola | Year: 2015

Knowledge of the effects of seed burial depth and the presence of straw on the soil surface on weed seedling emergence provides useful information for the development of weed management tactics. Buttonweed (Borreria densiflora DC.) is a troublesome weed that occurs in large infestations in soybean and sugarcane crops from north-central Brazil. This study investigated buttonweed emergence at different seed burial depths and straw amounts present on the soil surface. The experiment was conducted in greenhouse conditions, under a factorial design between four seed burial depths and four amounts of surface straw. Percent seedling emergence and fresh biomass (g) were evaluated at twenty-five days after installation (DAI). Greater buttonweed emergence occurred in seeds that were placed on the soil surface either without surface straw or with up to 1,000 kg ha−1 of straw on the soil surface. With 4,000 kg ha−1 of surface straw, buttonweed emergence was prevented when seeds were placed at a depth of 0.5 cm or deeper in the soil. These data indicated emergence of this weed species was greater at depths near the soil surface and in soils with the least amounts of surface straw. Information generated in this study provides a starting point for the development of knowledge for understanding the biology of buttonweed emergence and its population dynamics. Such information may be directly transmitted to growers and lays the groundwork for an integrated management approach for this weed species. © 2015, Scientia Agricola , All rights reserved.

Melo J.O.,Embrapa Maize and Sorghum | Melo J.O.,Federal University of Minas Gerais | Lana U.G.P.,Embrapa Maize and Sorghum | Lana U.G.P.,Federal University of Minas Gerais | And 12 more authors.
Plant Journal | Year: 2013

Impaired root development caused by aluminum (Al) toxicity is a major cause of grain yield reduction in crops cultivated on acid soils, which are widespread worldwide. In sorghum, the major Al-tolerance locus, Alt SB, is due to the function of SbMATE, which is an Al-activated root citrate transporter. Here we performed a molecular and physiological characterization of various AltSB donors and near-isogenic lines harboring various AltSB alleles. We observed a partial transfer of Al tolerance from the parents to the nearisogenic lines that was consistent across donor alleles, emphasizing the occurrence of strong genetic background effects related to AltSB. This reduction in tolerance was variable, with a 20% reduction being observed when highly Al-tolerant lines were the Alt SB donors, and a reduction as great as 70% when other Alt SB alleles were introgressed. This reduction in Al tolerance was closely correlated with a reduction in SbMATE expression in near-isogenic lines, suggesting incomplete transfer of loci acting in trans on SbMATE. Nevertheless, AltSB alleles from the highly Al-tolerant sources SC283 and SC566 were found to retain high SbMATE expression, presumably via elements present within or near the AltSB locus, resulting in significant transfer of the Al-tolerance phenotype to the derived near-isogenic lines. Allelic effects could not be explained by coding region polymorphisms, although occasional mutations may affect Al tolerance. Finally, we report on the extensive occurrence of alternative splicing for SbMATE, which may be an important component regulating SbMATE expression in sorghum by means of the nonsense-mediated RNA decay pathway. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

Vargas-Solorzano J.W.,Federal Rural University of Rio de Janeiro | Carvalho C.W.P.,Embrapa Food Technology | Takeiti C.Y.,Embrapa Food Technology | Ascheri J.L.R.,Embrapa Food Technology | Queiroz V.A.V.,Embrapa Maize and Sorghum
Food Research International | Year: 2014

The diversity of sorghum grains is related to their intrinsic properties, which include starch type, non-starch components and phenolic compounds. The latter are genotype dependent and affect the pericarp characteristics such as color and presence of a pigmented testa. This diversity can be valuable for developing new food products by thermoplastic extrusion intended for human consumption. Flours from sorghum grains from the genotypes of varied pericarp color: white (CMSXS180; 9010032), red (BRS 310; BRS 308) and light brown (BRS 305; 9929034) were processed in a co-rotating twin-screw extruder. Changes promoted by extrusion cooking were evaluated via specific mechanical energy (SME), die pressure, apparent density, sectional expansion index (SEI), water absorption index (WAI) and water solubility index (WSI). Pericarp color affected die pressure, apparent density and WSI values of extrudates. Light brown genotypes, rich in tannin and fiber content, generated the lowest die pressure and SEI values. Red genotypes presented the lowest SME and the highest WAI values. White genotypes presented intermediate SME and the highest die pressure values. These results reflect differences in starch conversion induced by the pericarp type. These results further suggest the potential use of pigmented sorghum extrudates for human consumption. © 2013 Elsevier Ltd.

PubMed | University of Florida, Embrapa Maize and Sorghum, National Center for Research in Energy and Materials and University of Campinas
Type: Journal Article | Journal: Biochemical and biophysical research communications | Year: 2016

Plant aldo-keto reductases of the AKR4C subfamily play key roles during stress and are attractive targets for developing stress-tolerant crops. However, these AKR4Cs show little to no activity with previously-envisioned sugar substrates. We hypothesized a structural basis for the distinctive cofactor binding and substrate specificity of these plant enzymes. To test this, we solved the crystal structure of a novel AKR4C subfamily member, the AKR4C7 from maize, in the apo form and in complex with NADP(+). The binary complex revealed an intermediate state of cofactor binding that preceded closure of Loop B, and also indicated that conformational changes upon substrate binding are required to induce a catalytically-favorable conformation of the active-site pocket. Comparative structural analyses of homologues (AKR1B1, AKR4C8 and AKR4C9) showed that evolutionary redesign of plant AKR4Cs weakened interactions that stabilize the closed conformation of Loop B. This in turn decreased cofactor affinity and altered configuration of the substrate-binding site. We propose that these structural modifications contribute to impairment of sugar reductase activity in favor of other substrates in the plant AKR4C subgroup, and that catalysis involves a three-step process relevant to other AKRs.

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