Advances towards understanding the responses of root cells to acidic stress

Acid soil syndrome is a worldwide phenomenon characterized by low pH (pH < 5.5), scarce nutrient avail-ability (K+, Ca2+, Mg2+, P), and mineral toxicity such as those caused by soluble aluminium (Al) forms. Regardless of the mineral toxicity, the low pH by itself is detrimental to crop development causing striking sensitivity responses such as root growth arrest. However, low pH-induced responses are still poorly understood and underrated. Here, we review and discuss the core evidence about the action of low pH upon specific root zones, distinct cell types, and possible cellular targets (cell wall, plasma membrane, and alternative oxidase). The role of different players in signaling processes leading to low pH-induced responses, such as the STOP tran-scription factors, the reactive oxygen species (ROS), auxin, ethylene, and components of the antioxidant system, is also addressed. Information at the molecular level is still lacking to link the low pH targets and the subsequent actors that trigger the observed sensitivity responses. Future studies will have to combine genetic tools to identify the signaling processes triggered by low pH, unraveling not only the mechanisms by which low pH affects root cells but also finding new ways to engineer the tolerance of domesticated plants to acidic stress.

Automated summary

Acid soil syndrome is a global phenomenon characterized by low pH, nutrient scarcity, and mineral toxicity. The detrimental effects of low pH on crop development, particularly root growth, are still poorly understood and underrated. Future studies combining genetic tools are needed to uncover the signaling processes triggered by low pH and find new ways to enhance the tolerance of domesticated plants to acidic stress.