The transcription factor CsART1 activates the aluminum transporter CsALS3s to promote the absorption and tolerance of aluminum in tea plants

Tea plants are typical aluminum hyperaccumulators, characterized by high aluminum accumulation in roots and old leaves. However, the systematic mechanisms underlying aluminum uptake and translocation in tea plants remain largely unclear. Here, we characterized the functions of the transporter CsALS3s and their transcription factor CsART1 in the process of aluminum tolerance in tea plants. Two ABC transporter genes, CsALS3.1 and CsALS3.2, were identified via bioinformatic and expression analyses. Transcriptomic and qRT-PCR assays showed that CsALS3.1 and CsALS3.2 were highly expressed in mature leaves and roots, respectively, and specifically induced by aluminum but not by other metal ions. Subcellular localization revealed that CsALS3.1 was targeted to the tonoplast, whereas CsALS3.2 was localized to the plasma membrane. Heterologous overexpression of CsALS3s significantly enhanced aluminum tolerance of Arabidopsis. Transient overexpression in tea leaves elevated aluminum concentration in the symplast but reduced it in the apoplast. When CsALS3s was stably overexpressed into the roots of tea seedlings, the content of aluminum in the transgenic roots was significantly increased, proved that CsALS3s mediate aluminum uptake and transport. Promoter analysis identified aluminum-responsive cis-elements in CsALS3s promoters, and Dual-luciferase and yeast one-hybrid assays confirmed that CsALS3s are transcriptionally activated by CsART1. Overexpression of CsART1 in Arabidopsis and tea plants improved aluminum tolerance and root aluminum accumulation, respectively. This study reveals that the transcription factor CsART1 activates CsALS3s to promote aluminum uptake and transport in tea plants, providing a basis for elucidating the molecular mechanisms of aluminum tolerance and hyperaccumulation in tea plants.