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Unformatted text preview: Copyright 1998 by the Genetics Society of America Circadian Expression of the Maize Catalase Cat3 Gene Is Highly Conserved Among Diverse Maize Genotypes With Structurally Different Promoters Alexios N. Polidoros and John G. Scandalios Department of Genetics, North Carolina State University, Raleigh, North Carolina 27695-7614 Manuscript received September 19, 1997 Accepted for publication February 4, 1998 ABSTRACT The Cat3 gene of maize exhibits a transcriptionally regulated circadian rhythm. In the present study we examined the following: (1) the extent of the circadian Cat3 expression between maize genotypes of diverse origin; (2) the functional significance of a Tourist transposable element located in the Cat3 promoter of the inbred line W64A, which harbors putative regulatory elements (GATA repeat, CCAAT boxes) shown to be involved in the light induction and circadian regulation of the Arabidopsis CAB2 , as well as other plant genes; and (3) aspects of the physiological role of CAT-3 in maize metabolism. Results confirm that the circadian Cat3 expression is a general phenomenon in maize. Regulation of Cat3 gene expression is not dependent on the presence of the Tourist element in the promoter of the gene nor on the presence of motifs similar to those found significant in the circadian expression of the Arabidopsis CAB2 gene. Structural diversity was revealed in the Cat3 promoters of maize genotypes of diverse origins. However, highly conserved regions with putative regulatory motifs were identified. Relevance of the conserved regions to the circadian regulation of the gene is discussed. Possible physiological roles of CAT-3 are suggested. T HE three maize catalase genes respond differen- when inserted in or near genes. The most common tially to light in developing maize leaves. Cat1 ex- effect is a null mutation when an element interrupts pression is light-independent ( Redinbaugh et al. 1990), the coding region of a gene ( McLaughlin and Walbot Cat2 is positively regulated by light ( Skadsen and Scan- 1987; McCarty et al. 1989; Abler and Scandalios dalios 1987; Acevedo et al. 1991), and Cat3 is regulated 1991). Insertion of an element in an intron may result by a circadian rhythm ( Redinbaugh et al. 1990; Ace- in novel RNA-processing events, as in the maize Adh1-S vedo et al. 1991). Studies on several aspects of the Cat3 gene ( Luehrsen and Walbot 1990). The presence of circadian expression as well as indications of putative an element in the promoter region can cause a spectrum physiological role(s) of CAT-3 have been recently re- of altered expression responses, as has been evident viewed ( Scandalios et al. 1997). Because studies with from paradigms in maize as well as in many other organ- other plant genes have fortified the assumption that isms. Low amounts of the Bz gene product ( Schiefel- light and circadian responsive elements are located in bein et al. 1988), reduced levels of Wx enzymatic activity the 5 9 flanking regions of structural genes (...
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This note was uploaded on 09/13/2010 for the course DGPB 024e taught by Professor Alexiospolidoros during the Spring '10 term at Aristotle University of Thessaloniki.
- Spring '10