A novel rice acidic pathogenesis-related (PR) class 1 cDNA (OsPR1a) was isolated from jasmonic acid (JA)-treated rice seedling leaf. The OsPR1a cDNA is 830 bp long and contains an open reading frame of 507 nucleotides encoding 168 amino acid residues with a predicted molecular mass of 17,560 and pI of 4.4. The deduced amino acid sequence of OsPR1a has a high level of identity with acidic and basic PR1 proteins from plants. Southern analysis revealed that OsPR1a is a member of a multigene family. The OsPR1a gene was found to be cut-inducible, whereas the phytohormones JA, salicylic acid (SA), 3-indoleacetic acid, gibberellin, and ethylene (using ethylene generator ethephon, ET) enhanced accumulation of OsPR1a transcript, as well as the protein phosphatase inhibitors cantharidin (CN) and endothall (EN). Induced expression of OsPR1a gene by JA, CN or EN, and ET was light/dark- and dose-dependent and was almost completely inhibited by cycloheximide. Dark downregulated CN-, EN-, and ET-induced OsPR1a gene expression, whereas it was further enhanced with JA, SA and abscisic acid blocked JA-induced OsPR1a transcript. Simultaneous application of staurosporine (ST) enhances CH- or EN-induced OsPR1a transcript, but not with JA. This is the first report on cloning of a rice acidic PR1 gene (OsPR1a), which is regulated by phytohormones, phosphorylation/dephosphorylation event(s), and light.