Organic acid carriers in tolerance to toxic aluminum in wheat/Transportadores de acidos organicos na tolerancia ao aluminio toxico em trigo

Aluminum (Al) toxicity in plants is seen in about 15% of the soils worldwide, restraining yields in arable land. In Brazil, acidic soils limit production of wheat (Triticum aestivum L.) and other cereals. Al is toxic for most winter cereals when its concentration increases and soilpH is below 5. One of the main concerns with acidic soil is the increase in the mobility of [Al.sup.3+]ions. Al binds to cell walls in roots, preventing meristematic elongation in sensitive species, causing damage to the root system and results in lower yields. [Al.sup.3+]forms highly stable complexes with phosphorus (P), limiting its availability to plants, as well as reducing cell division and elongation. To deal with Al toxicity, plants have developed strategies such as organic acid (OA) exudation by roots; this mechanism of detoxification has been well- characterized. OAs, in turn, chelate ions [Al.sup.3], forming non-toxic compounds that do not penetrate the root system. Some genes responsible for Al tolerance in wheat have been identified, particularly TaALMT1 and TaMATE1B that transport malate and citrate OAs, respectively. In this review, we discussed the mechanisms by which Al damages roots those by which plants are protected, primarily through two genes. We also described the interaction of the ALMT1 gene with P and iron (Fe). Key words: Triticum aestivum L. [Al.sup.3+], acid soils, ALMT1, MATE. A toxicidade do aluminio (Al) as plantas e observada em cerca de 15% dos solos no planeta, sendo um fator restritivo a produtividade em terras cultivaveis. No Brasil, os solos acidos sao limitantes a producao de trigo (Triticum aestivum L.) e outros cereais. O Al e toxico para a maioria dos cereais de inverno, quando a sua concentracao aumenta e o pH do solo atinge valores inferiores a 5. Uma das principais preocupacoes sobre o solo acido e o aumento da mobilidade dos ions [Al.sup.3+]. O Al pode se ligar as paredes celulares das raizes e, como consequencia, impedir o alongamento meristematico em especies sensiveis, provocando danos ao sistema radicular, que resulta em menor desempenho agronomico das plantas. O [Al.sup.3+] e tambem capaz de formar complexos altamente estaveis com fosforo (P), limitando sua disponibilidade para as plantas, e tambem reduzindo a divisao e o alongamento celular. Para lidar com a toxicidade ao Al, as plantas desenvolveram algumas estrategias como a exsudacao de acido organicos (AOs) pelas raizes, sendo este mecanismo de destoxificacao bem caracterizad