Abstract
Effect of abscisic acid (ABA) on chloroplast relocation in gemmae cells of the liverwort Marchantia polymorpha was examined. Cold incubation of gemmae of wild-type plants in a liquid medium under dim light caused relocation of chloroplasts from the periclinal to anticlinal position, but presence of 1 μM or greater concentrations of ABA inhibited this movement as observed by light and fluorescent microscopy. Gemma cells of the transgenic MT-2 line overexpressing MpABI1A encoding a group A protein phosphatase 2C known as a negative regulator of ABA signaling were also used for chloroplast observation. It was found that the cold-induced chloroplast relocation was observed at any ABA concentration tested in MT-2, indicating that the cells exhibited ABA insensitivity. These results indicated that ABA specifically acts on inhibition of the chloroplast movement.
