Evolution of gene expression after gene amplification.
We took a rather unique approach to investigate the conservation of gene expression of prolamin storage protein genes across two different subfamilies of the Poaceae. We took advantage of oat plants carrying single maize chromosomes in different cultivars, called oat-maize addition (OMA) lines, which permitted us to determine whether regulation of gene expression was conserved between the two species. We found that γ-zeins are expressed in OMA7.06, which carries maize chromosome 7 even in the absence of the trans-acting maize prolamin-box-binding factor (PBF), which regulates their expression. This is likely because oat PBF can substitute for the function of maize PBF as shown in our transient expression data, using a γ-zein promoter fused to green fluorescent protein (GFP). Despite this conservation, the younger, recently amplified prolamin genes in maize, absent in oat, are not expressed in the corresponding OMAs. However, maize can express the oldest prolamin gene, the wheat high-molecular weight glutenin Dx5 gene, even when maize Pbf is knocked down (through PbfRNAi), and/or another maize transcription factor, Opaque-2 (O2) is knocked out (in maize o2 mutant). Therefore, older genes are conserved in their regulation, whereas younger ones diverged during evolution and eventually acquired a new repertoire of suitable transcriptional activators.
Waksman Institute of Microbiology, Rutgers University.
Nelson
N
Garcia
Waksman Institute of Microbiology, Rutgers University.
Wei
W
Zhang
Waksman Institute of Microbiology, Rutgers University Present address: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
Yongrui
Y
Wu
Waksman Institute of Microbiology, Rutgers University messing@waksman.rutgers.edu.
Joachim
J
Messing
D018554:Avena / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005784:Gene Amplification; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D005983:Glutens / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D003313:Zea mays / Q000235:genetics*; D015028:Zein / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; C115836:PBF protein, plant; D010940:Plant Proteins; D014157:Transcription Factors; C067402:opaque-2 protein, Zea mays; D005983:Glutens; D015028:Zein; C037302:glutenin
Opaque2; high-molecular weight glutenin Dx5; oat–maize addition (OMA) lines; prolamin-box-binding factor; zeins