Light regulation of Fed-1 mRNA requires an element in the 5' untranslated region and correlates with differential polyribosome association.
Light regulation of Fed-1 mRNA abundance in the leaves of green plants is primarily a post-transcriptional process. Previously, we have shown that the Fed-1 mRNA light response requires an open reading frame, indicating that the light regulation of the mRNA depends on its concurrent translation. We now show that light-induced increases in Fed-1 mRNA abundance are associated with increases in polyribosome association that require both a functional AUG and a normal Fed-1 translational start context. We also present evidence that light regulation of Fed-1 mRNA levels requires more than efficient translation per se. Substitution of the efficiently translated tobacco mosaic virus Omega 5' untranslated region resulted in a loss of Fed-1 light regulation. In addition, we identified a CAT T repeat element located near the 5' terminus of the Fed-1 5' untranslated region that is essential for light regulation. We introduced two different mutations in the CAT T repeat element, but only one of these substitutions blocked the normal light effect on polyribosome association, whereas both altered dark-induced Fed-1 mRNA disappearance. The element may thus be important for Fed-1 mRNA stability rather than polyribosome loading. We propose a model in which Fed-1 mRNA is relatively stable when it is associated with polyribosomes in illuminated plants but in darkness is not polyribosome associated and is thus rapidly degraded by a process involving the CAT T repeat element.
Dickey
L F
LF
Department of Botany, North Carolina State University, Raleigh, North Carolina 27695-7612, USA. lfd@unity.ncsu.edu
Petracek
M E
ME
Nguyen
T T
TT
Hansen
E R
ER
Thompson
W F
WF
D003062:Codon; D004742:Enhancer Elements, Genetic; D005288:Ferredoxins / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D008027:Light; D016297:Mutagenesis, Site-Directed; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011132:Polyribosomes / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D014026:Nicotiana / Q000235:genetics*
D003062:Codon; D005288:Ferredoxins; D012333:RNA, Messenger