title: Molecular and physiological strategies to increase aluminum resistance in plants.
abstract: Aluminum (Al) toxicity is a primary limitation to plant growth on acid soils. Root meristems are the first site for toxic Al accumulation, and therefore inhibition of root elongation is the most evident physiological manifestation of Al toxicity. Plants may resist Al toxicity by avoidance (Al exclusion) and/or tolerance mechanisms (detoxification of Al inside the cells). The Al exclusion involves the exudation of organic acid anions from the root apices, whereas tolerance mechanisms comprise internal Al detoxification by organic acid anions and enhanced scavenging of free oxygen radicals. One of the most important advances in understanding the molecular events associated with the Al exclusion mechanism was the identification of the ALMT1 gene (Al-activated malate transporter) in Triticum aestivum root cells, which codes for a plasma membrane anion channel that allows efflux of organic acid anions, such as malate, citrate or oxalate. On the other hand, the scavenging of free radicals is dependent on the expression of genes involved in antioxidant defenses, such as peroxidases (e.g. in Arabidopsis                         thaliana and Nicotiana tabacum), catalases (e.g. in Capsicum annuum), and the gene WMnSOD1 from T. aestivum. However, other recent findings show that reactive oxygen species (ROS) induced stress may be due to acidic (low pH) conditions rather than to Al stress. In this review, we summarize recent findings regarding molecular and physiological mechanisms of Al toxicity and resistance in higher plants. Advances have been made in understanding some of the underlying strategies that plants use to cope with Al toxicity. Furthermore, we discuss the physiological and molecular responses to Al toxicity, including genes involved in Al resistance that have been identified and characterized in several plant species. The better understanding of these strategies and mechanisms is essential for improving plant performance in acidic, Al-toxic soils.
authors.affiliation: Programa de Doctorado en Ciencias de Recursos Naturales, Departamento de Ciencias Químicas y Recursos Naturales, Universidad de La Frontera, Casilla 54-D, Temuco, Chile.
authors.forename: Claudio
authors.initials: C
authors.lastname: Inostroza-Blancheteau
authors.forename: Zed
authors.initials: Z
authors.lastname: Rengel
authors.forename: Miren
authors.initials: M
authors.lastname: Alberdi
authors.forename: María
authors.initials: M
authors.lastname: de la Luz Mora
authors.forename: Felipe
authors.initials: F
authors.lastname: Aquea
authors.forename: Patricio
authors.initials: P
authors.lastname: Arce-Johnson
authors.forename: Marjorie
authors.initials: M
authors.lastname: Reyes-Díaz
mesh_terms: D000535:Aluminum / Q000493:pharmacokinetics / Q000633:toxicity*; D029681:Arabidopsis Proteins / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D060467:Disease Resistance / Q000235:genetics / Q000276:immunology*; D016166:Free Radical Scavengers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000276:immunology*; D053858:Metabolic Networks and Pathways / Q000276:immunology*; D008954:Models, Biological; D027361:Organic Anion Transporters / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects; D010935:Plant Diseases / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology; D010944:Plants; D017382:Reactive Oxygen Species / Q000378:metabolism; D012987:Soil / Q000737:chemistry*
chemical_list: C512361:ALMT1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D016166:Free Radical Scavengers; D027361:Organic Anion Transporters; D017382:Reactive Oxygen Species; D012987:Soil; D000535:Aluminum