Abstract
In Arabidopsis, stromal and thylakoid membrane-bound ascorbate peroxidase isoenzymes (sAPX and tAPX, respectively) are encoded by two different loci. The aim of this study is to clarify the regulatory mechanism of each chloroplastic APX gene in Arabidopsis. Arabidopsis suspension cells were grown under low light intensity (50 μmol/m2/s), then transferred to mild light intensity (ML; 420 μmol/m2/s), which is the condition to show the maximum O2 evolution. Both the activity and protein levels of tAPX significantly increased in about 24 h of ML illumination, but those of sAPX remained unchanged. Northern hybridization revealed a constant level of two chlroplastic APX transcripts during the experiment period. These results suggest that the light induction of tAPX is post-transcriptionally regulated. Expression pattern of these two chloroplastic APX genes in Arabidopsis plant is now being examined.
