Functional characterization of an aluminum (Al)-inducible transcription factor, ART2, revealed a different pathway for Al tolerance in rice

High aluminum (Al) tolerance in rice (Oryza sativa) is controlled by a Cys2His2-type zinc finger transcription factor ART1 (Al resistance transcription factor1). There are five close homologs of ART1 in the rice genome, but the role of these homologs is unknown. We functionally characterized one of the ART1 homologs, ART2, in terms of tissue and spatial expression, subcellular localization, transcriptional activation activity, and phenotypic analysis of the knockout lines. ART2 was localized to the nucleus and showed a transcriptional activation potential in yeast. ART2 was mainly expressed in the roots, but the expression level was much lower than that of ART1. The ART2 expression was rapidly induced by Al in the roots of the wild-type rice, but not in art1 mutant. Knockout of ART2 resulted in increased sensitivity to Al toxicity, but did not alter sensitivity to different pH values. Expression profile analysis by RNA-sequencing showed that ART2 was not involved in activation of genes regulated by ART1; however, four genes seems to be regulated by ART2, which are implicated in Al tolerance. These results indicate that ART1 and ART2 regulate different pathways leading to Al tolerance, and ATR2 plays a supplementary role in Al tolerance in rice.