opaque2 modifiers act post-transcriptionally and in a polar manner on gamma-zein gene expression in maize endosperm.
AUTOR(ES)
Or, E
RESUMO
The opaque2 (o2) modifier genes convert the soft endosperm of an o2 mutant to a hard, vitreous phenotype. The primary biochemical change associated with the expression of these genes is a two- to threefold increase in synthesis of the 27-kD gamma-zein storage protein. To investigate the mechanism of modifier gene activity, we examined the level of gamma-zein mRNA and protein synthesis during the early stages of endosperm development in normal, o2, and modified o2 geno-types. Although the o2 mutation was found to reduce expression of the 27-kD gamma-zein genes, the activity of o2 modifier genes dramatically increased the level of both gamma-zein protein and mRNAs as early as 16 days after pollination. At this stage, transcription of gamma-zein genes is reduced by approximately 50% in both o2 and modified o2 genotypes compared to wild type. Thus, it appears that the modifiers regulate gamma-zein synthesis through a post-transcriptional mechanism. Analysis of transcripts from the two nearly identical genes (A and B) encoding the 27-kD gamma-zein protein showed differences in the mRNA ratios in different genotypes. In modified o2 mutants, accumulation of A over B transcript was greatly enhanced during endosperm development. Somatic recombination at this locus was found to reduce the number of B genes in the endosperm, but this could not account for the preferential accumulation of the A transcript. Our results suggest that a product of the o2 modifier genes increases the translation or stability of the A gene mRNA, leading to enhanced synthesis of 27-kD gamma-zein protein.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=160389Documentos Relacionados
- opaque-2 modifiers increase gamma-zein synthesis and alter its spatial distribution in maize endosperm.
- The maize gamma-zein sequesters alpha-zein and stabilizes its accumulation in protein bodies of transgenic tobacco endosperm.
- Dominant Negative Mutants of Opaque2 Suppress Transactivation of a 22-kD Zein Promoter by Opaque2 in Maize Endosperm Cells.
- The role of opaque2 in the control of lysine-degrading activities in developing maize endosperm.
- The Chlamydomonas reinhardtii Organellar Genomes Respond Transcriptionally and Post-Transcriptionally to Abiotic StimuliW⃞