The present invention relates to a gene encoding a protein named as ARIA (armadillo repeat protein interacting with ABF2), which contains armadillo repeats and a BTB/POZ domain. The protein is a novel ABA signaling component, which affects ABA-regulated gene expression, seedling growth, ABA sensitivity, and stress tolerance of plants. Furthermore, the present invention provides a method of producing salt-tolerant plants comprising the introduction of an expression cassette containing the ARIA gene linked to a plant promoter to plants.