Abstract
Abscisic acid (ABA) is involved in plant development, and mediates responses to environmental stress. The Arabidopsis thaliana abi1-1 is a dominant mutant allele of ABI1, which encodes a type-2C protein phosphatase (PP2C) and functions as a negative regulator of ABA-signaling. We demonstrated that transient expression of abi1-1 also resulted in the repression of ABA-signaling in Physcomitrella patens, suggesting that PP2Cs are involved in ABA-signaling in the moss. The moss abi1-1 overexpressor (abi1-1 OE) lines were less sensitive to ABA and osmotic stress. The gametophores of abi1-1 OEs were bigger compared to wild type, and sporophyte development was abnormal in abi1-1 OEs. Furthermore, an ABI1 homolog from P. patens (PpABI1) strongly repressed ABA-signaling in P. patens. These results suggest that PP2C-regulated ABA-signaling is involved not only in stress tolerance but also in development in P. patens, and that PpABI1 functions as a negative regulator of ABA-signaling in P. patens.
