Exner Vivien, Taranto Patti, Schönrock Nicole, Gruissem Wilhelm, Hennig Lars
Institute of Plant Sciences and Basel-Zurich Plant Science Center, ETH Zurich, 8092 Zurich, Switzerland.
Development. 2006 Nov;133(21):4163-72. doi: 10.1242/dev.02599. Epub 2006 Oct 4.
Chromatin assembly factor CAF-1 facilitates the formation of nucleosomes on newly replicated DNA in vitro. However, the role of CAF-1 in development is poorly understood because mutants are not available in most multicellular model organisms. Biochemical evidence suggests that FASCIATA1, FASCIATA2 and MSI1 form CAF-1 in Arabidopsis thaliana. Because fasciata mutants are viable, CAF-1 is not essential for cell division in plants. Arabidopsis CAF-1 mutants have defects in shoot apical meristems; in addition, CAF-1 is required to establish seedling architecture, leaf size and trichome differentiation. CAF-1 is needed to restrict branching of trichomes on rosette leaves. Increased trichome branching in CAF-1 mutants is not strictly correlated with increased nuclear DNA content. In addition, fas2 glabra3 double mutants show an additive genetic interaction, demonstrating that CAF-1 acts genetically parallel to the GLABRA3-containing, endoreduplication-coupled trichome branching pathway. However, CAF-1 is often needed to restrict endoreduplication, because seedlings of most CAF-1 mutants have increased ploidy. Notably, in the Landsberg erecta background, loss of CAF-1 does not affect ploidy, demonstrating that loss of CAF-1 can be compensated in some Arabidopsis accessions. These results reveal that the functions of FAS1, FAS2 and MSI1 are not restricted to meristems, but are also needed to control genome replication at multiple steps of development.
染色质组装因子CAF-1在体外促进新复制的DNA上核小体的形成。然而，由于大多数多细胞模式生物中没有CAF-1的突变体，其在发育过程中的作用尚不清楚。生化证据表明，拟南芥中的FASCIATA1、FASCIATA2和MSI1组成CAF-1。由于fasciata突变体是可存活的，因此CAF-1对植物细胞分裂不是必需的。拟南芥CAF-1突变体在茎尖分生组织中存在缺陷；此外，建立幼苗结构、叶片大小和毛状体分化需要CAF-1。限制莲座叶上毛状体的分支需要CAF-1。CAF-1突变体中毛状体分支增加与核DNA含量增加并不严格相关。此外，fas2 glabra3双突变体表现出累加遗传相互作用，表明CAF-1在遗传上与含GLABRA3的、内复制偶联的毛状体分支途径平行发挥作用。然而，CAF-1通常需要限制内复制，因为大多数CAF-1突变体的幼苗多倍体增加。值得注意的是，在Landsberg erecta背景下，CAF-1的缺失不影响多倍体，表明在某些拟南芥种质中，CAF-1的缺失可以得到补偿。这些结果表明，FAS1、FAS2和MSI1的功能不仅限于分生组织，在发育的多个步骤中控制基因组复制也需要它们。
