Graduate School of Biostudies, Kyoto University, Kyoto, 606-8501 Japan.
Plant Cell Physiol. 2012 Feb;53(2):287-303. doi: 10.1093/pcp/pcs002. Epub 2012 Jan 13.
The proper timing of flowering is of crucial importance for reproductive success of plants. Regulation of flowering is orchestrated by inputs from both environmental and endogenous signals such as daylength, light quality, temperature and hormones, and key flowering regulators construct several parallel and interactive genetic pathways. This integrative regulatory network has been proposed to create robustness as well as plasticity of the regulation. Although knowledge of key genes and their regulation has been accumulated, there still remains much to learn about how they are organized into an integrative regulatory network. Here, we have analyzed the CRYPTIC PRECOCIOUS (CRP) gene for the Arabidopsis counterpart of the MED12 subunit of the Mediator. A novel dominant mutant, crp-1D, which causes up-regulation of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), FRUITFULL (FUL) and APETALA1 (AP1) expression in a FLOWERING LOCUS T (FT)-dependent manner, was identified in an enhancer screen of the early-flowering phenotype of 35S::FT. Genetic and molecular analysis of both crp-1D and crp loss-of-function alleles showed that MED12/CRP is required not only for proper regulation of SOC1, FUL and AP1, but also for up-regulation of FT, TWIN SISTER OF FT (TSF) and FD, and down-regulation of FLOWERING LOCUS C (FLC). These observations suggest that MED12/CRP is a novel flowering regulator with multiple regulatory target steps both upstream and downstream of the key flowering regulators including FT florigen. Our work, taken together with recent studies of other Mediator subunit genes, supports an emerging view that the Mediator plays multiple roles in the regulation of flowering.
开花时间的把握对植物的生殖成功至关重要。开花的调控是由环境和内源性信号（如日照长度、光质、温度和激素）输入共同协调的，关键的开花调控因子构建了几个平行且相互作用的遗传途径。这个综合调控网络被认为具有稳健性和可塑性。尽管已经积累了关于关键基因及其调控的知识，但对于它们如何组织成一个综合调控网络，还有很多需要了解。在这里，我们分析了拟南芥 MED12 亚基 CRYPTIC PRECOCIOUS（CRP）基因的同源物。在一个增强子筛选中，我们鉴定到了一个新型显性突变体 crp-1D，该突变体以 FT 依赖的方式导致 SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1（SOC1）、FRUITFULL（FUL）和 APETALA1（AP1）的表达上调。 crp-1D 和 crp 功能缺失等位基因的遗传和分子分析表明，MED12/CRP 不仅是 SOC1、FUL 和 AP1 正确调控所必需的，而且是 FT、TWIN SISTER OF FT（TSF）和 FD 的上调以及 FLOWERING LOCUS C（FLC）的下调所必需的。这些观察结果表明，MED12/CRP 是一种新的开花调控因子，具有多个调控目标步骤，位于包括 FT 成花素在内的关键开花调控因子的上游和下游。我们的工作，结合最近对其他 Mediator 亚基基因的研究，支持了一个新兴的观点，即 Mediator 在开花调控中发挥多种作用。
