Abstract
Abscisic acid (ABA) is a phytohormone that is necessary for stress adaptation. Recent studies have reported that attenuated levels of ABA improved grain yield and seedling growth under low temperature in cereals. To improve plant growth under low temperature, we attempted to generate ABA-insensitive transgenic rice by expressing a clade A type 2C protein phosphatase (OsPP2C), OsABIL2, with or without the mutation equivalent to the Arabidopsis abi1-1 mutation. A yeast two-hybrid assay revealed that the interaction between OsABIL2 and a putative rice ABA receptor, OsPYL1, was ABA-dependent, and the interaction was lost with amino acid substitution from glycine to aspartic acid at the 183rd amino acid of the OsABIL2 protein, corresponding to abi1-1 mutation. The constitutive expression of OsABIL2 or OsABIL2(G183D) in Arabidopsis or rice decreased ABA sensitivity to differing degrees. Moreover, the transgenic rice expressing OsABIL2(G183D) exhibited improved seedling growth under low temperature, although the transgenic lines showed unfavorable traits, such as viviparous germination and elongated internodes. These results indicated that the introduction of abi1-1 type dominant mutation was also effective in OsABIL2 at decreasing ABA sensitivity in plants, and the attenuation of ABA sensitivity could be an alternative parameter to improve rice performance under low temperatures.