A multidrug and toxic compound extrusion (MATE) transporter modulates auxin levels in root to regulate root development and promotes aluminium tolerance

MATE (multidrug and toxic compound extrusion) transporters play multiple roles in plants including detoxification, secondary metabolite transport, aluminium (Al) tolerance, and disease resistance. Here we identify and characterize the role of the Arabidopsis MATE transporter DETOXIFICATION30. AtDTX30 regulates auxin homeostasis in Arabidopsis roots to modulate root development and Al-tolerance. DTX30 is primarily expressed in roots and localizes to the plasma membrane of root epidermal cells including root hairs. dtx30 mutants exhibit reduced elongation of the primary root, root hairs, and lateral roots. The mutant seedlings accumulate more auxin in their root tips indicating role of DTX30 in maintaining auxin homeostasis in the root. Al induces DTX30 expression and promotes its localization to the distal transition zone. dtx30 seedlings accumulate more Al in their roots but are hyposensitive to Al-mediated rhizotoxicity perhaps due to saturation in root growth inhibition. Increase in expression of ethylene and auxin biosynthesis genes in presence of Al is absent in dtx30. The mutants exude less citrate under Al conditions, which might be due to misregulation of AtSTOP1 and the citrate transporter AtMATE. In conclusion, DTX30 modulates auxin levels in root to regulate root development and in the presence of Al indirectly modulates citrate exudation to promote Al tolerance.