The aluminum tolerance and detoxification mechanisms in plants; recent advances and prospects

Aluminum (Al) toxicity is the main limiting factor of crop growth in acid soil. Plants can resist Al toxicity by regulating a series of mechanisms. Many physiological functions have been developed to improve the Al tolerance in plants which can be briefly outlined as two mechanisms. One such well-documented mechanism is external exclusion, which mainly reduces Al entry into cells, and the other one is the internal detoxification, consisting of the antioxidant defense system, the redistribution of Al3+ such as vacuolar compartmentalization, and the response of auxin. In external exclusion mechanism, with special emphasis on the mechanism of Al-induced organic acid secretion from roots, the current understanding of genes regulating organic acid secretion has been reviewed. In terms of the internal detoxification mechanism, we generalized the deposition and redistribution of Al in the cytoplasm, particularly, summarized the genes encoding Al3+ absorption and transport, and also discussed other possible mechanisms for improving plant tolerance to Al. Therefore, this review describes the recent research progress of Al tolerance mechanisms in plants, and provide future perspectives regarding more practical approaches for Al toxicity alleviation, which can create important social benefits and huge economic value for screening Al-tolerant plants and developing crop breeding.