Biology Department, Muhlenberg College, Allentown, PA, USA.
Molecular Biology, Cell Biology, and Biochemistry Department, Brown University, Providence, RI, USA.
Planta. 2018 Sep;248(3):613-628. doi: 10.1007/s00425-018-2923-9. Epub 2018 May 30.
The histone acetyltransferase GCN5 and associated transcriptional coactivator ADA2b are required to couple endoreduplication and trichome branching. Mutation of ADA2b also disrupts the relationship between ploidy and leaf cell size. Dynamic chromatin structure has been established as a general mechanism by which gene function is temporally and spatially regulated, but specific chromatin modifier function is less well understood. To address this question, we have investigated the role of the histone acetyltransferase GCN5 and the associated coactivator ADA2b in developmental events in Arabidopsis thaliana. Arabidopsis plants with T-DNA insertions in GCN5 (also known as HAG1) or ADA2b (also known as PROPORZ1) display pleiotropic phenotypes including dwarfism and floral defects affecting fertility. We undertook a detailed characterization of gcn5 and ada2b phenotypic effects in rosette leaves and trichomes to establish a role for epigenetic control in these developmental processes. ADA2b and GCN5 play specific roles in leaf tissue, affecting cell growth and division in rosette leaves often in complex and even opposite directions. Leaves of gcn5 plants display overall reduced ploidy levels, while ada2b-1 leaves show increased ploidy. Endoreduplication leading to increased ploidy is also known to contribute to normal trichome morphogenesis. We demonstrate that gcn5 and ada2b mutants display alterations in the number and patterning of trichome branches, with ada2b-1 and gcn5-1 trichomes being significantly less branched, while gcn5-6 trichomes show increased branching. Elongation of the trichome stalk and branches also vary in different mutant backgrounds, with stalk length having an inverse relationship with branch number. Taken together, our data indicate that, in Arabidopsis, leaves and trichomes ADA2b and GCN5 are required to couple nuclear content with cell growth and morphogenesis.
组蛋白乙酰转移酶 GCN5 和相关转录共激活因子 ADA2b 是将内复制和毛状体分支偶联所必需的。ADA2b 的突变也破坏了倍性与叶细胞大小之间的关系。动态染色质结构已被确立为一种普遍的机制，通过该机制，基因功能在时间和空间上受到调节，但特定的染色质修饰因子的功能了解较少。为了解决这个问题，我们研究了组蛋白乙酰转移酶 GCN5 和相关共激活因子 ADA2b 在拟南芥发育事件中的作用。在 GCN5（也称为 HAG1）或 ADA2b（也称为 PROPORZ1）中具有 T-DNA 插入的拟南芥植物表现出多种表型，包括矮化和影响生殖力的花朵缺陷。我们对 gcn5 和 ada2b 表型效应在罗勒叶和毛状体中的详细特征进行了研究，以确定表观遗传控制在这些发育过程中的作用。ADA2b 和 GCN5 在叶片组织中发挥特定作用，影响罗勒叶中的细胞生长和分裂，通常以复杂甚至相反的方向影响。gcn5 植物的叶片显示整体降低的倍性水平，而 ada2b-1 叶片显示增加的倍性。导致增加倍性的内复制也已知有助于正常毛状体形态发生。我们证明 gcn5 和 ada2b 突变体显示出毛状体分支数量和模式的改变，ada2b-1 和 gcn5-1 毛状体分支明显减少，而 gcn5-6 毛状体显示出增加的分支。不同突变体背景下毛状体茎和分支的伸长也有所不同，茎长与分支数呈反比关系。总之，我们的数据表明，在拟南芥中，ADA2b 和 GCN5 是将核内容与细胞生长和形态发生偶联所必需的。
