PLANT PHYSIOLOGY , Vol 106, Issue 4 1373-1380, Copyright © 1994 by American Society of Plant Biologists
|
MOLECULAR BIOLOGY AND GENE REGULATION |
The Maize (Zea mays L.) Cat1 Catalase Promoter Displays Differential Binding of Nuclear Proteins Isolated from Germinated and Developing Embryos and from Embryos Grown in the Presence and Absence of Abscisic Acid
J. D. Williamson and J. G. Scandalios
Department of Genetics, Box 7614, North Carolina State University, Raleigh, North Carolina 27695-7614
We previously demonstrated that amounts of Cat1 RNA in developing immature
maize (Zea mays L.) embryos change in parallel with endogenous abscisic
acid (ABA) content. In excised immature embryos, addition of ABA leads to a
large increase in Cat1 RNA accumulation. The Cat1 transcript, however, also
accumulates to high amounts in scutella of germinating embryos, where ABA
content is low and decreasing. Here we show that application of ABA to
germinated embryos no longer results in the up-regulation of the Cat1
transcript accumulation that is seen during embryogenesis. This suggests
that factors other than ABA control Cat1 expression at this developmental
stage. Using band-shift and southwestern analyses, we show that the change
in sensitivity to ABA is paralleled by changes in nuclear proteins binding
to a 28-bp region of the Cat1 promoter in vitro. One protein (CAT1BP-20)
shows increased accumulation in the absence of ABA, suggesting that a
repressor-mediated mechanism accounts for at least a portion of the ABA
regulation of Cat1.
