Anthocyanin biosynthesis is regulated by a conserved transcriptional MBW complex composed of MYB, bHLH and WD40 subunits. However, molecular mechanisms underlying transcriptional regulation of these MBW subunits remain largely elusive. In this study, we isolated an Arabidopsis mutant that displays a constitutive red color in aboveground tissues with retarded growth phenotypes. In the presence of sucrose, the mutant accumulates more than 3-fold anthocyanins of the wild type (WT), but cannot produce anthocyanins as WT in the absence of sucrose. Map-based cloning results demonstrated that the mutation occurs in the locus At4G01000, which encodes a conserved nuclear-localized ubiquitin-like (UBL) superfamily protein, silencing defective 2 (SDE2), in eukaryotes. SDE2 is ubiquitously expressed in various tissues. In the sucrose-induced anthocyanin biosynthesis, SDE2 expression was not responded to sucrose treatment at the early stage but was enhanced at the late stage. SDE2 mutations result in up-regulation of anthocyanin biosynthetic and regulatory genes. Yeast-two hybrid analysis indicated that SDE2 has no direct interaction with the MYB transcription factor PAP1 and bHLH factor TT8, indicating that SDE2 is a indirect factor to affect anthocyanin accumulation. Taking together, our data suggest that SDE2 may play a role in finely coordinating anthocyanin biosynthesis with other biological processes.

花青素生物合成受保守的转录 MBW 复合体调节，该复合体由 MYB、bHLH 和 WD40 亚基组成。然而，这些 MBW 亚基转录调控的分子机制在很大程度上仍然难以捉摸。在这项研究中，我们分离出一种拟南芥突变体，该突变体在具有迟缓生长表型的地上组织中显示出本构红色。在蔗糖存在的情况下，突变体积累的花青素是野生型 (WT) 的 3 倍以上，但在没有蔗糖的情况下不能像 WT 那样产生花青素。基于图谱的克隆结果表明突变发生在 At4G01000 位点，该位点编码真核生物中保守的核定位泛素样 (UBL) 超家族蛋白，沉默缺陷 2 (SDE2)。SDE2在各种组织中普遍表达。在蔗糖诱导的花青素生物合成中，SDE2表达在早期对蔗糖处理没有反应，但在后期得到增强。SDE2突变导致花青素生物合成和调节基因的上调。酵母-二杂交分析表明SDE2与MYB转录因子PAP1和bHLH因子TT8没有直接相互作用，表明SDE2是影响花青素积累的间接因素。总之，我们的数据表明 SDE2 可能在花青素生物合成与其他生物过程的精细协调中发挥作用。