WRKY46 functions as a transcriptional repressor of ALMT1, regulating aluminum‐induced malate secretion in Arabidopsis

Summary Aluminum ( A l) toxicity is the major limiting factor for crop production on acid soils, but the transcriptional regulation of A l tolerance genes is largely unknown. Here, we found that the expression of a WRKY domain‐containing transcription factor WRKY 46 is inhibited by A l and expressed in root stele, whereas the expression of ALMT 1 , which encodes a malate efflux transporter, is induced by A l stress and spatially co‐localized with WRKY 46 in root stele, indicating the possible interaction between WRKY 46 and ALMT 1 in A rabidopsis. Mutation of WRKY4 6 by T–DNA insertion leads to better root growth under A l stress, and lower root A l content compared with the wild‐type Col–0. The wrky46 mutant shows increased root malate secretion, which is consistent with the higher ALMT 1 expression in the mutant. Transient expression analysis using truncated promoter of ALMT 1 showed that ALMT 1 expression can be inhibited by WRKY 46 in tobacco leaves. The yeast one‐hybrid assay and C h IP ‐q PCR analysis revealed that WRKY 46 directly binds to ALMT1 promoter through specific W –boxes. Taken together, we demonstrated that WRKY46 is a negative regulator of ALMT1 , mutation of WRKY 46 leads to increased malate secretion and reduced Al accumulation in root apices, and thus confers higher A l resistance.