A new protein phosphatase 2C (FsPP2C1) induced by abscisic acid is specifically expressed in dormant beechnut seeds

An abscisic acid (ABA)-induced cDNA fragment encoding a putative protein ph osphatase 2C (PP2C) was obtained by means of differential reverse transcrip tase-polymerase chain reaction approach. The full-length clone was isolated from a cDNA library constructed using mRNA from ABA-treated beechnut (Fagu s sylvatica) seeds. This clone presents all the features of plant type PP2C and exhibits homology to members of this family such as AthPP2CA (61%), AB I1 (48%), or ABI2 (47%), therefore it was named FsPP2C1. The expression of FsPP2C1 is detected in dormant seeds and increases after ABA treatment, whe n seeds are maintained dormant, but it decreases and tends to disappear whe n dormancy is being released by stratification or under gibberellic acid tr eatment. Moreover, drought stress seems to have no effect on FsPP2C1 transc ript accumulation. The FsPP2C1 transcript expression is tissue specific and was found to accumulate in ABA-treated seeds rather than in other ABA-trea ted vegetative tissues examined. These results suggest that the correspondi ng protein could be related to ABA-induced seed dormancy. By expressing FsP P2C1 in Escherichia coli as a histidine tag fusion protein, we have obtaine d direct biochemical evidence supporting Mg2+-dependent phosphatase activit y of this protein.