Abstract
BackgroundIn Arabidopsis, the aluminum (Al) exclusion mechanism is mainly facilitated by ALMT1-mediated malate exudation and MATE-mediated citrate releases from the root. Recently, we have demonstrated that coordinated functioning between an ALMT1-mediated Al exclusion mechanism, via exudation of malate from the root tip, and a NIP1;2-facilitated internal detoxification mechanism, via removal of Al from the root cell wall and subsequent root-to-shoot Al translocation, plays critical roles in achieving overall Al resistance. However, the genetic relationship between ALMT1 and NIP1;2 in these processes remained unclear.ResultsThrough genetic and physiological analyses, we demonstrate that unlike ALMT1 and MATE, which function independently and additively, ALMT1 and NIP1;2 show an epistatic relationship in Al resistance. These results indicate that ALMT1 and NIP1;2 function in the same biochemical pathway, whereas ALMT1 and MATE in different ones.ConclusionThe establishment of the epistatic relationship and the coordinated functioning between the ALMT1 and NIP1;2-mediated exclusion and internal detoxification mechanisms are pivotal for achieving overall Al resistance in the non-accumulating Arabidopsis plant. We discuss and emphasize the indispensable roles of the root cell wall for the implementation of the Al exclusion mechanism and for the establishment of an epistatic relationship between the ALMT1-mediated exclusion mechanism and the NIP1;2-facilitated internal detoxification mechanism.
Highlights
In Arabidopsis, the aluminum (Al) exclusion mechanism is mainly facilitated by ALMT1-mediated malate exudation and Multidrug and toxic compound extrusion (MATE)-mediated citrate releases from the root
We provide further genetic evidence for the existence of an epistatic relationship between ALMT1 and nodulin 26-like intrinsic protein 1;2 (NIP1);2. We demonstrate that such an epistatic relationship is required for orchestrating the functions of different Al resistance mechanisms in Arabidopsis
Real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analyses indicated that in the wild type (WT, Col-0), the expression of ALMT1 and NIP1;2 in the root was both induced by Al treatment the levels of ALMT1 transcripts were about 4-fold higher than those of NIP1;2 (Fig. 1)
Summary
In Arabidopsis, the aluminum (Al) exclusion mechanism is mainly facilitated by ALMT1-mediated malate exudation and MATE-mediated citrate releases from the root. At low pH (< 5.0), aluminum ions (Al3+) are dissolved and released from the soil clays into the soil solutions, which could interact with multiple sites of the plant root cell, including the cell wall, cell membrane and cytosol with toxic effects, resulting severe root. Wang et al BMC Plant Biology (2020) 20:122 the root cell wall in the root apical region is one of the major targets for Al toxicity [12, 13]
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