A cDNA encoding a phosphoinositide-specific phospholipase C (PI-PLC) from the higher plant Arabidopsis thaliana was cloned and characterized. The gene corresponding to this cDNA is designated AtPLC2. The overall structure of the predicted AtPLC2 protein is similar to those of plant PI-PLCs and mammalian delta-type PI-PLCs. Northern blot analysis revealed that AtPLC2 is expressed constitutively whereas AtPLC1S, another gene for PI-PLC of Arabidopsis, is induced by environmental stresses such as dehydration and salinity, indicating that the function of AtPLC2 is distinct from that of AtPLC1S. The AtPLC2 mRNA was detected in vegetative and floral tissues. We determined the positions of these two PI-PLCs genes on Arabidopsis chromosomes by RFLP mapping using P1 genomic clones.