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 growth- and tissue-specific manner. In seedlings, the CatA, CatB and CatC genes were h ighly 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, diurn al oscillations of CatC expression were detected in the leaf blade when pla nts were grown in the dark. The beta-glucuronidase (GUS) gene driven by the 5'-flanking region of CatA was expressed with diurnal fluctuations, the pa ttern 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 sugg est that the circadian rhythmic expression of CatA is due to a transcriptio nal 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. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved .