Phytochrome-mediated regulation of β-amylase mRNA level in mustard (Sinapis alba L.) cotyledons |
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Authors: | R Sharma P Schopfer |
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Institution: | (1) Biologisches Institut II der Universität, Schänzlestrasse 1, D-7800 Freiburg, Germany;(2) School of Life Sciences, University of Hyderabad, 500 134 Hyderabad, India |
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Abstract: | Phytochrome, activated by continuous red light, increases the amount of total polyadenylated RNA during photomorphogenesis of mustard (Sinapis alba L.) cotyledons. In-vitro translation of total polyadenylated RNA in a reticulocyte translation system has shown that the activity of translatable -amylase mRNA is increased by phytochrome about threefold in the 3-d-old cotyledons, based on equal amounts of polyadenylated RNA, and about eightfold on a per-cotyledon basis. Cordycepin prevents the accumulation of translatable -amylase mRNA. It is concluded that the phytochrome-mediated control of -amylase synthesis is exerted on the level of mRNA synthesis. During seedling development in continuous red light, a phytochrome-dependent increase of -amylase mRNA can be observed at least 6 h before the onset of -amylase synthesis. If, after a period of enzyme synthesis, phytochrome action is interrupted by long-wavelength far-red light followed by darkness, -amylase mRNA as well as -amylase synthesis remain at a high level for 8–10 h and then decline sharply. It is concluded that -amylase mRNA, having an apparent lifetime of the order of 8–10 h, can be formed under the influence of phytochrome during early seedling development but it activates -amylase synthesis only after a lag-phase of about 8 h, when the cotyledons acquire competence to synthesize the enzyme. The consequences of these findings for the signal-transduction chain of phytochrome are discussed.Abbreviations EDTA
Na2-ethylenediaminotetraacetic acid
- PAGE
polyacrylamide gel electrophoresis
- poly(A)+RNA
polyadenylated mRNA
- Pr, Pfr
red- and far-red-absorbing forms of phytochrome
- SDS
sodium dodecyl sulfate
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol |
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Keywords: | Amylase synthesis mRNA (amylase) Photomorphogenesis (amylase induction) Phytochrome (enzyme synthesis) Polyadenylated RNA (amylase) Sinapis (amylase synthesis) |
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