Spillane C, MacDougall C, Stock C, Köhler C, Vielle-Calzada J P, Nunes S M, Grossniklaus U, Goodrich J
Institute of Plant Biology, University of Zürich, CH-8008,., Zürich, Switzerland.
Curr Biol. 2000 Nov 30;10(23):1535-8. doi: 10.1016/s0960-9822(00)00839-3.
Genes of the FERTILISATION INDEPENDENT SEED (FIS) class regulate cell proliferation during reproductive development in Arabidopsis [1-5]. The FIS genes FERTILISATION INDEPENDENT ENDOSPERM (FIE) and MEDEA (MEA) encode homologs of animal Polycomb group (Pc-G) proteins, transcriptional regulators that modify chromatin structure and are thought to form multimeric complexes [3-11]. To test whether similarities in fis mutant phenotypes reflect interactions between their protein products, we characterised FIE RNA and protein localisation in vivo, and FIE protein interactions in yeast and in vitro. Expression of FIE mRNA overlaps with that of MEA during embryo sac and seed development and is unaffected in mea mutants. Results from the yeast two-hybrid system and an in vitro pull-down assay indicate that MEA and FIE proteins interact. The relevance of this interaction in vivo is supported by the finding that FIE and MEA co-localise in the nucleus in transfected plant cells. Interaction of MEA and FIE is mediated by the amino-terminal region of MEA. Despite sequence divergence in this domain, MEA can interact with its corresponding animal partner Extrasexcombs (ESC) in the yeast two-hybrid system. We conclude that FIE and MEA act together as part of a multimeric complex and that this accounts for the similarities in mutant phenotypes. We propose that an ancient mechanism for chromatin modification has been independently recruited to different developmental processes in the two kingdoms.
拟南芥中，独立受精种子（FIS）类基因在生殖发育过程中调控细胞增殖[1 - 5]。FIS基因中的独立受精胚乳（FIE）和MEA基因编码动物多梳蛋白家族（Pc - G）蛋白的同源物，这些转录调节因子可修饰染色质结构，被认为能形成多聚体复合物[3 - 11]。为了测试fis突变体表型的相似性是否反映其蛋白质产物之间的相互作用，我们对FIE在体内的RNA和蛋白质定位以及在酵母和体外的FIE蛋白质相互作用进行了表征。在胚囊和种子发育过程中，FIE mRNA的表达与MEA的表达重叠，且在MEA突变体中不受影响。酵母双杂交系统和体外下拉实验的结果表明MEA和FIE蛋白相互作用。FIE和MEA在转染植物细胞的细胞核中共定位这一发现支持了这种相互作用在体内的相关性。MEA和FIE的相互作用是由MEA的氨基末端区域介导的。尽管该结构域存在序列差异，但在酵母双杂交系统中MEA仍能与其相应的动物伙伴Extra - sexcombs（ESC）相互作用。我们得出结论，FIE和MEA作为多聚体复合物的一部分共同发挥作用，这解释了突变体表型的相似性。我们提出，一种古老的染色质修饰机制已在两个王国中被独立招募到不同的发育过程中。
