Quattrocchio F, Wing J F, van der Woude K, Mol J N, Koes R
Department of Genetics, Vrije Universiteit, BioCentrum Amsterdam, The Netherlands.
Plant J. 1998 Feb;13(4):475-88. doi: 10.1046/j.1365-313x.1998.00046.x.
The regulatory anthocyanin loci, an1, an2, an4 and an11 of Petunia hybrida, and r and c1 from Zea mays, control transcription of different sets of target genes. Both an2 and c1 encode a MYB-type protein. This study reports the isolation of a P. hybrida gene, jaf13, encoding a basic helix-loop-helix protein that, on the basis of sequence homology and intron/exon structure, represents the P. hybrida orthologue of the Z. mays r genes. Ectopic expression of an2 and jaf13 is sufficient for activation of the dihydroflavonol 4-reductase-A (dfrA) promoter and enhanced pigment accumulation in P. hybrida. This indicates that an2 and jaf13 play a key role in determining the tissue-specific expression pattern of structural genes. However, because chalcone synthase (chs) and flavanone-3-hydroxylase (f3h) are not activated, the pattern of pigmentation is not fundamentally altered. Expression of an2 in Z. mays complements a mutation in pl, a c1 paralogue, indicating that an2 activates a wider set of target genes in this host. Transient expression assays in Z. mays and P. hybrida tissues showed that C1 and R or AN2 and JAF13 can activate the promoter of the c2 gene, encoding Z. mays CHS, but not the chsA promoter from P. hybrida. These results indicate that regulatory anthocyanin genes are conserved between species and that divergent evolution of the target gene promoters is responsible for the species-specific differences in regulatory networks.
矮牵牛的调控花青素基因座an1、an2、an4和an11，以及玉米的r和c1，控制着不同组靶基因的转录。an2和c1都编码一种MYB型蛋白。本研究报道了一个矮牵牛基因jaf13的分离，该基因编码一种碱性螺旋-环-螺旋蛋白，基于序列同源性和内含子/外显子结构，它代表了玉米r基因在矮牵牛中的直系同源基因。an2和jaf13的异位表达足以激活二氢黄酮醇4-还原酶-A（dfrA）启动子，并增强矮牵牛中的色素积累。这表明an2和jaf13在决定结构基因的组织特异性表达模式中起关键作用。然而，由于查尔酮合酶（chs）和黄烷酮-3-羟化酶（f3h）未被激活，色素沉着模式没有发生根本性改变。an2在玉米中的表达弥补了pl（c1的一个旁系同源基因）的突变，这表明an2在该宿主中激活了更广泛的一组靶基因。在玉米和矮牵牛组织中的瞬时表达分析表明，C1和R或AN2和JAF13可以激活编码玉米CHS的c2基因的启动子，但不能激活矮牵牛的chsA启动子。这些结果表明，调控花青素基因在物种间是保守的，并且靶基因启动子的趋异进化是调控网络中物种特异性差异的原因。
