Consonni G, Geuna F, Gavazzi G, Tonelli C
Plant J. 1993 Feb;3(2):335-46. doi: 10.1111/j.1365-313x.1993.tb00185.x.
The R gene family determines the timing, distribution and amount of anthocyanin pigmentation in maize. This family comprises a set of regulatory genes, consisting of a cluster of several elements at the R locus, on chromosome 10, the Lc and Sn gene lying about two units R distal and B on chromosome 2. Each gene determines a tissue-specific pigmentation of different parts of the seed and plant. The proposed duplicated function of R, Sn, Lc and B loci is reflected in cDNA sequence similarity. In this paper an extensive analysis of the predicted proteins of the R, Sn, Lc and B genes together with a search for putative sites of post-translational modification is reported. A comparison with the prosite database discloses several N-glycosylation and phosphorylation sites, as well as the basic Helix-Loop-Helix (HLH) domain of transcriptional activators. Sn, Lc, and R-S show a high conservation of these sites, while B is more divergent. Analysis of the 5' leader of mRNA sequences discloses the presence of five ATG triplets with two upstream open reading frames (uORFs) of 38 and 15 amino acids and a loop structure indicating a possible mechanism of control at the translational level. It is conceivable that possible mechanisms acting at the translational and post-translational level could modulate the expression and the activation of these transcription factors. Northern analysis of various tissues of different R alleles highlights a strict correlation between pigment accumulation in different tissues and the expression of the regulatory and structural genes suggesting that the pattern of pigmentation relies on a mechanism of differential expression of the members of the R family. Analysis of the Sn promoter discloses the presence of several sequences resembling binding sites of known transcription factors (as GAGA and GT) that might be responsible for the spatial and light-induced expression of this gene. Two regions include a short sequence homologous to the consensus binding site of the B-HLH domain suggesting a self-regulatory control of the Sn gene.
R基因家族决定了玉米中花青素色素沉着的时间、分布和数量。该家族包含一组调控基因，由位于第10号染色体R位点的几个元件簇组成，Lc和Sn基因位于第2号染色体上距离R约两个单位且在B的远端。每个基因决定种子和植株不同部位的组织特异性色素沉着。R、Sn、Lc和B位点的推测重复功能体现在cDNA序列相似性上。本文报道了对R、Sn、Lc和B基因预测蛋白的广泛分析以及对翻译后修饰假定位点的搜索。与prosite数据库的比较揭示了几个N-糖基化和磷酸化位点，以及转录激活因子的基本螺旋-环-螺旋（HLH）结构域。Sn、Lc和R-S在这些位点上具有高度保守性，而B则差异更大。对mRNA序列5'前导区的分析揭示了五个ATG三联体的存在，带有两个分别为38和15个氨基酸的上游开放阅读框（uORF）以及一个环结构，这表明在翻译水平上可能存在一种控制机制。可以想象，在翻译和翻译后水平起作用的可能机制可以调节这些转录因子的表达和激活。对不同R等位基因的各种组织进行Northern分析，突出了不同组织中色素积累与调控基因和结构基因表达之间的严格相关性，这表明色素沉着模式依赖于R家族成员的差异表达机制。对Sn启动子的分析揭示了几个类似于已知转录因子（如GAGA和GT）结合位点的序列，这些序列可能负责该基因的空间和光诱导表达。两个区域包含一个与B-HLH结构域共有结合位点同源的短序列，这表明Sn基因存在自我调控。
