title: Light control of nuclear gene mRNA abundance and translation in tobacco.
abstract: Photosynthetic signals modulate expression of nuclear genes at the levels of mRNA transcription, mRNA stability, and translation. In transgenic tobacco (Nicotiana tabacum), the pea (Pisum sativum) Ferredoxin 1 (Fed-1) mRNA dissociates from polyribosomes and becomes destabilized when photosynthesis is inhibited by photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. We used polymerase chain reaction suppressive-subtractive hybridization to identify similarly regulated endogenous tobacco genes. This screen identified 14 nuclear-encoded tobacco mRNAs whose light-induced increase in abundance is suppressed in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Sequence analysis of the cognate cDNAs revealed that nine of the mRNAs encode putative chloroplast-targeted proteins. We asked whether the abundance of these mRNAs was regulated transcriptionally or posttranscriptionally. Of the five mRNAs with sufficient abundance to detect using nuclear run-on assays, we observed transcriptional regulation of alpha-tubulin, thiazole biosynthetic enzyme, and pSKA10 (an unknown gene). Photosystem A subunit L and, to a lesser extent, alpha-tubulin and pSKA10 mRNAs, may also be stabilized in the light. In contrast, Rubisco small subunit mRNA abundance appears to be transcriptionally up-regulated but posttranscriptionally down-regulated in the light. To determine whether, like Fed-1 mRNA, the mRNAs identified in this screen were translationally responsive to light, we characterized the polyribosome association of these mRNAs in the light and after a 15-min dark treatment. A subset of the mRNAs showed dramatic dark-induced polyribosome dissociation, similar to Fed-1 mRNA, and all of the mRNAs showed at least slight polyribosome dissociation. Thus, both posttranscriptional and translational regulation appear to be important mechanisms regulating the expression of many nuclear-encoded mRNAs encoding proteins involved in photosynthesis.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tang
authors.forename: Sumana
authors.initials: S
authors.lastname: Bhat
authors.forename: Marie E
authors.initials: ME
authors.lastname: Petracek
mesh_terms: D002467:Cell Nucleus / Q000235:genetics* / Q000528:radiation effects; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D008027:Light; D010940:Plant Proteins / Q000235:genetics; D011132:Polyribosomes / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics* / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics* / Q000528:radiation effects; D014026:Nicotiana / Q000235:genetics* / Q000528:radiation effects
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger