Arabidopsis MBF1s control leaf cell cycle and its expansion.
Arabidopsis MBF1s control leaf cell cycle and its expansion.
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DOI：
10.1093/pcp/pcn187
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发表时间：
2009-02
影响因子：
4.9
通讯作者：
T. Tojo;K. Tsuda;T. Yoshizumi;A. Ikeda;J. Yamaguchi;M. Matsui;K. Yamazaki
中科院分区：
文献类型：
--
作者：
T. Tojo;K. Tsuda;T. Yoshizumi;A. Ikeda;J. Yamaguchi;M. Matsui;K. Yamazaki
多蛋白桥联因子1(MBF1)是一种转录共激活因子，通过在转录因子和TATA盒结合蛋白之间桥接真核生物中的TATA盒结合蛋白来增强靶基因的转录。拟南芥有三个MBF1基因：AtMBF1a-AtMBF1c。然而，AtMBF1的功能细节仍不清楚。在本研究中，构建了高表达AtMBF1的转基因拟南芥，并将其与一个活性转录抑制结构域(SRDX)融合。该嵌合蛋白在转基因植物中可能作为转录共抑制因子和内源AtMBF1功能的抑制因子发挥作用。高表达AtMBF1-SRDX的转基因拟南芥(AtMBF1-SRDX(OE))在连续白光条件下表现出极小的叶片表型。它的叶细胞--尤其是内源AtMBF1强表达的维管组织周围的细胞--比野生型(WT)的叶细胞小得多。此外，在AtMBF1-SRDX(OE)植株的叶片中观察到较少的细胞数量。细胞大小的时间进程分析表明，AtMBF1-SRDX(OE)植株叶片的细胞扩张在叶片发育后期(细胞膨大期)受到显著抑制，此时内源AtMBF1b在WT中强烈表达。结果表明，AtMBF1-SRDX(OE)植株的叶片倍性水平显著低于WT植株，且AtMBF1-SRDX(OE)植株中几种负调控因子的表达水平高于WT植株。这些观察结果表明，AtMBF1-SRDX与内复制调控因子相互作用。因此，AtMBF1被认为不仅影响叶片细胞的扩张，而且还影响叶片展开期间叶片细胞倍性水平的调节。
Multiprotein bridging factor 1 (MBF1) is known as a transcriptional co-activator that enhances transcription of its target genes by bridging between transcription factors and TATA-box-binding protein in eukaryotes. Arabidopsis thaliana has three MBF1 genes: AtMBF1a-AtMBF1c. However, details of the functions of AtMBF1 remain unclear. For this study, transgenic Arabidopsis overexpressing AtMBF1 fused to an active transcriptional repression domain (SRDX) was constructed. The chimeric protein putatively functions as a transcriptional co-repressor and as a suppressor of functions of endogenous AtMBF1 in transgenic plants. Transgenic Arabidopsis overexpressing AtMBF1-SRDX (AtMBF1-SRDX(OE)) showed an extremely small leaf phenotype under a continuous white light condition. Its leaf cells-especially those around vascular tissues, where strong expression of endogenous AtMBF1s is observed-were much smaller than those from the wild type (WT). In addition, a lower cell number was observed in leaves from AtMBF1-SRDX(OE) plants. Time course analysis of cell size revealed that cell expansion of leaves of AtMBF1-SRDX(OE) plants was dramatically suppressed during the late leaf developmental stage (cell expansion stage), when endogenous AtMBF1b is strongly expressed in the WT. The results show that ploidy levels of leaves from AtMBF1-SRDX(OE) plants were dramatically lower than those from the WT; moreover, expression levels of several negative regulators of endoreduplication were more elevated in AtMBF1s-SRDX(OE) plants than those in the WT. These observations suggest that AtMBF1-SRDX interacts with regulators of endoreduplication. Therefore, AtMBF1s are considered to affect not only leaf cell expansion but also regulation of the ploidy level in leaf cells during the leaf expansion stage.