Mechanisms and regulation of aluminum-induced secretion of organic acid anions from plant roots / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Aluminum (Al) is the most abundant metal element in the earth’s crust. On acid soils, at pH 5.5 or lower, part of insoluble Al-containing minerals become solubilized into soil solution, with resultant highly toxic effects on plant growth and development. Nevertheless, some plants have developed Al-tolerance mechanisms that enable them to counteract this Al toxicity. One such well-documented mechanism is the Al-induced secretion of organic acid anions, including citrate, malate, and oxalate, from plant roots. Once secreted, these anions chelate external Al ions, thus protecting the secreting plant from Al toxicity. Genes encoding the citrate and malate transporters responsible for secretion have been identified and characterized, and accumulating evidence indicates that regulation of the expression of these transporter genes is critical for plant Al tolerance. In this review, we outline the recent history of research into plant Al-tolerance mechanisms, with special emphasis on the physiology of Al-induced secretion of organic acid anions from plant roots. In particular, we summarize the identification of genes encoding organic acid transporters and review current understanding of genes regulating organic acid secretion. We also discuss the possible signaling pathways regulating the expression of organic acid transporter genes.

Mechanisms and regulation of aluminum-induced secretion of organic acid anions from plant roots / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Aluminum (Al) is the most abundant metal element in the earth's crust. On acid soils, at pH 5.5 or lower, part of insoluble Al-containing minerals become solubilized into soil solution, with resultant highly toxic effects on plant growth and development. Nevertheless, some plants have developed Al-tolerance mechanisms that enable them to counteract this Al toxicity. One such well-documented mechanism is the Al-induced secretion of organic acid anions, including citrate, malate, and oxalate, from plant roots. Once secreted, these anions chelate external Al ions, thus protecting the secreting plant from Al toxicity. Genes encoding the citrate and malate transporters responsible for secretion have been identified and characterized, and accumulating evidence indicates that regulation of the expression of these transporter genes is critical for plant Al tolerance. In this review, we outline the recent history of research into plant Al-tolerance mechanisms, with special emphasis on the physiology of Al-induced secretion of organic acid anions from plant roots. In particular, we summarize the identification of genes encoding organic acid transporters and review current understanding of genes regulating organic acid secretion. We also discuss the possible signaling pathways regulating the expression of organic acid transporter genes.

Aluminum accumulation in two Pfaffia glomerata genotypes and its growth effects / Acumulação de alumínio em dois genótipos de Pfaffia glomerata e seus efeitos no crescimento

Aluminum (Al) toxicity is a limiting factor for crop production in acid soils, which cover approximately 60% of the Brazilian territory. This study aimed to evaluate the effects of Al on growth and tissue Al concentration of two Pfaffia glomerata accessions (BRA and JB/UFSM). Plantlets were grown in a hydroponic system with five Al concentrations (0, 50, 100, 150 and 200mg L-1) for 7 days. Most of the evaluated parameters presented significant interaction between both P. glomerata accessions and Al levels in nutrient solution and, in general, Al treatments negatively affected plant growth, especially roots. Moreover, BRA accession showed higher Al accumulation in its tissues than JB/UFSM and, consequently in BRA accession the growth was impaired substantially. Furthermore, the results suggest that, between P. glomerata accessions studied, BRA is less appropriated for medicinal uses when grown in soils with high Al levels, due to the higher accumulation of tissue Al content. .

A toxidez do alumínio (Al) é um fator limitante da produção agrícola em solos ácidos, os quais cobrem cerca de 60% do território Brasileiro. O objetivo deste estudo foi avaliar os efeitos do Al no crescimento e na concentração de Al nos tecidos de dois acessos de Pfaffia glomerata (BRA e JB/UFSM). As plantas foram cultivadas em sistema hidropônico, contendo cinco concentrações de Al (0, 50, 100, 150 e 200mg L-1) por 7 dias. Para a maioria dos parâmetros avaliados, houve interação significativa entre os dois acessos de P. glomerata e as concentrações de Al, sendo que, de modo geral, os tratamentos com Al afetaram negativamente o crescimento das plantas, especialmente as raízes. Além disso, o acesso BRA acumulou mais Al nos tecidos que o acesso JB/UFSM e, consequentemente, os parâmetros de crescimento foram afetados mais significativamente naquele acesso. Portanto, nossos resultados sugerem que, entre os acessos de P. glomerata estudados, BRA é menos indicado para usos medicinais quando cultivado em solos com altos níveis de Al, por acumular mais Al em seus tecidos.