Differential diurnal expression of rice catalase genes: the 5%-flanking region of CatA is not sufficient for circadian control

Three rice catalase genes (CatA, CatB, CatC) are expressed in a growthand tissue-specific manner. In seedlings, the CatA, CatB and CatC genes were highly expressed in the leaf sheath, root and leaf blade, respectively. The expression of the CatA gene in the leaf sheath was modulated by a circadian rhythm with the maximum late in the light period. On the other hand, diurnal oscillations of CatC expression were detected in the leaf blade when plants were grown in the dark. The b-glucuronidase (GUS) gene driven by the 5%-flanking region of CatA was expressed with diurnal fluctuations, the pattern of which is different from that of the endogenous CatA mRNA, both at the pre-mRNA and at the mRNA level in transgenic plants. These results suggest that the circadian rhythmic expression of CatA is due to a transcriptional or post-transcriptional event such as modulation of pre-mRNA stability and requires some other region(s), in addition to the promoter region, exon-1 and intron-1. © 2000 Elsevier Science Ireland Ltd. All rights reserved.