We investigated the effect of oxygen on the expressions of respiratory genes encoded in the nuclear and mitochondrial genomes of rice (Oryza sativa L.). Hypoxic treatment decreased the transcript levels of nuclear-encoded, but not mitochondrial-encoded respiratory genes. The effects of ruthenium red (an inhibitor of Ca2+ fluxes from organelles) and/or CaCl2 on plants under hypoxic conditions suggested that Ca2+ is a physiological transducer of a low-oxygen signaling pathway for expression of the alternative oxidase 1a gene (AOX1a), but not for expressions of genes involved in the cytochrome respiratory pathway, in rice.
