Opaque2 modifiers alter transcription of the 27-kDa gamma-zein genes in maize

Citation
Rj. Burnett et Ba. Larkins, Opaque2 modifiers alter transcription of the 27-kDa gamma-zein genes in maize, MOL G GENET, 261(6), 1999, pp. 908-916
Citations number
35
Categorie Soggetti
Molecular Biology & Genetics
Journal title
MOLECULAR AND GENERAL GENETICS
ISSN journal
00268925 → ACNP
Volume
261
Issue
6
Year of publication
1999
Pages
908 - 916
Database
ISI
SICI code
0026-8925(199907)261:6<908:OMATOT>2.0.ZU;2-D
Abstract
Opaque2 modifier genes cause a two- to threefold increase in the amount of gamma-zein RNA and protein in maize kernels, and can convert the soft, star chy endosperm of an opaque2 mutant to a hard, vitreous phenotype. We analyz ed several aspects of transcriptional and post-transcriptional regulation o f gamma-zein gene expression in wild-type, opaque2 and modified opaque2 gen otypes to investigate the molecular mechanisms by which opaque2 modifiers i nfluence the expression of gamma-zein genes. We Found that the poly(A) tail s of the gamma-zein RNAs A and B were of similar length in normal, opaque2 and modified opaque2 genotypes. Multiple poly(A) addition sites were detect ed for the gamma-zein A and B RNAs, but no evidence was obtained that o2 mo difiers influence the selection of these sites. Nucleotide sequence analysi s of gamma-zein A and B cDNAs derived from 18-DAP endosperm from normal, op aque2, and modified opaque2 kernels confirmed the use of eight different po ly(A) addition sites for gamma-zein A transcripts and six different sites f or the gamma-zein B transcripts. It also revealed that the A/B gamma-zein R NA ratio in modified opaque2 was at least 40:1, compared to I:lin wild type and 3:1 in opaque2. Nuclear run-on transcription assays showed a dramatic shift in the transcription rate of the gamma-zein A gene relative to the B gene in the modified opaque2 genotype. These results are consistent with a model in which the two opaque2 modifier loci influence gamma-zein gene expr ession through different mechanisms: one affects transcription of the gamma -zein locus and the other influences the steady state level of gamma-zein R NA.