The role of aluminum sensing and signaling in plant aluminum resistance

As researchers have gained a better understanding in recent years into the physiological, molecular, and genetic basis of how plants deal with aluminum （AI） toxicity in acid soils prevalent in the tropics and sub-tropics, it has become clear that an important component of these responses is the triggering and regulation of cellular pathways and processes by AI. In this review of plant AI signaling, we begin by summarizing the understanding of physiological mechanisms of AI resistance, which first led researchers to realize that AI stress induces gene expression and modifies protein function during the activation of AI resistance responses. Subsequently, an overview of AI resistance genes and their function provides verification that AI induction of gene expression plays a major role in AI resistance in many plant species. More recent research into the mechanistic basis for Al-induced transcrip- tional activation of resistance genes has led to the identifica- tion of several transcription factors as well as cis-elements in the promoters of AI resistance genes that play a role in greater Al-induced gene expression as well as higher constitutive expression of resistance genes in some plant species. Finally, the post-transcriptional and translational regulation of AI resistance proteins is addressed, where recent research has shown that AI can both directly bind to and alter activity of certain organic acid transporters, and also influence AI resistance proteins indirectly, via protein phosphorylation.