Transcription Profi les of Genes Encoding Catalase and Ascorbate Peroxidase in the Rice Leaf Tissues under Salinity

We analyzed the response of transcripts corresponding to ascorbate peroxidase (APX) and catalase (CAT) under salinity in the basal region of the rice leaf, which is tolerant to salinity compared with the apical region. In the NaCl treated plants, the transcript levels of CATB, CATC, APX1, APX4, APX6 and APX7 increased. The transcript level of APX2 was comparable to that of the control, but the transcript level of APX8 was slightly decreased by salinity. The activity of dehydroascorbate reductase decreased by salinity. These results suggest that the increase in CAT activity observed in our previous study is due to the enhancement of transcript levels of CATB and CATC, and the increase in the transcript level of APX1, APX4, APX6 and APX7 may contribute to maintain APX activity under salinity. The enhancement of the enzyme activities involved in regeneration of ascorbate under salinity is needed to increase APX activity and salinity tolerance in rice plants.