Zinc finger transcription factor STOP1 essential for proton and Al tolerance in Arabidopsis

Abstract

Acid soils are one of the major factors to limit crop production. We have isolated a single recessive mutant showing H⁺-hypersensitivity (designated as stop1; Sensitive TO Proton rhizotoxicity) from Arabidopsis thaliana EMS/M₂ population. The root growth of stop1 mutant was suppressed under low pH conditions. Positional mapping analysis and transgenic complementation test revealed that stop1 has a missense mutation at the zinc-finger domain of predicted Cys2/His2 type zinc-finger protein, designated as STOP1. Moreover, stop1 mutant shows hypersensitivity to Al³⁺ treatment. The stop1 mutant lacks the induction of AtALMT1 gene encoding a malate transporter, and malate exudation by Al³⁺ treatment does not take place in stop1. The AtALMT1 knockout mutant shows hypersensitive to Al³⁺, whereas the stop1 mutant shows hypersensitive to both Al³⁺ and low pH. These results suggest that STOP1 is a key gene that affects Al³⁺ tolerance and low pH tolerance.