Aluminum-induced citric acid secretion is not the sole mechanism of Al-resistance in maize

• Published in: Acta physiologiae plantarum 2016-12, Vol.38 (12), p.1-9, Article 279
• Main Authors: Cardoso, Flávio Barcellos, Cambraia, José, de Oliveira, Juraci Alves, Ribeiro, Cleberson, de Souza, Leandro Torres, Braun, Heder, DaMatta, Fábio Murilo
• Format: Article
• Language: English
• Subjects: Agriculture; Aluminum; Biomedical and Life Sciences; Citric acid; Corn; Electrolyte leakage; Elongation; Genotype & phenotype; Genotypes; H+-transporting ATPase; Hydrogen; Inhibition; Leakage; Life Sciences; Membrane permeability; Original Article; Permeability; Plant Anatomy/Development; Plant Biochemistry; Plant Genetics and Genomics; Plant growth; Plant Pathology; Plant Physiology; Secretion; Sterol composition; Sterols; Tips
• ISSN: 0137-5881; 1861-1664
• DOI: 10.1007/s11738-016-2286-4

Aluminum-induced citric acid (CA) root secretion is a widely accepted mechanism to explain Al-resistance in maize. Nonetheless, several aspects of this mechanism remain controversial. In this study, we used paclobutrazol (PBZ), a plant growth retardant, to gain new insights into the relationship between Δ 5 -sterol composition, membrane permeability, (PM) H + -ATPase activity and CA secretion in an Al-sensitive (UFVM-100) and Al-resistant (UFVM-200) maize genotypes challenged with Al. The Al-sensitive genotype displayed greater concentrations of Al in the root tips and greater inhibition of root elongation (RE), which was accompanied by greater electrolyte leakage and greater reduction in the Δ 5 -sterols content after Al treatment. CA secretion by roots increased in both genotypes after Al treatment but to a greater extent in the Al-resistant genotype. The (PM) H + -ATPase activity was down-regulated in the sensitive cultivar and up-regulated in its resistant counterpart upon Al treatment. A significant correlation between (PM) H + -ATPase activity and CA secretion was observed, but only in the Al-resistant genotype. Upon adding PBZ to the Al-treated plants, differences in the RE and Δ 5 -sterol composition between the maize genotypes were fully abolished, whereas genotypic differences in CA secretion and (PM) H + -ATPase activity were reduced but not completely eliminated. Taken together, this information suggests the existence of other processes or mechanisms operating in the Al resistance in these two maize genotypes.