Donald Danforth Plant Science Center, St Louis, MO, 63132, USA.
Department of Plant Biology, Ecology and Evolution, Oklahoma State University, Stillwater, OK, 74078, USA.
New Phytol. 2020 Feb;225(4):1799-1815. doi: 10.1111/nph.16087. Epub 2019 Aug 28.
Abscission is a process in which plants shed their parts, and is mediated by a particular set of cells, the abscission zone (AZ). In grasses (Poaceae), the position of the AZ differs among species, raising the question of whether its anatomical structure and genetic control are conserved. The ancestral position of the AZ was reconstructed. A combination of light microscopy, transmission electron microscopy, RNA-Seq analyses and RNA in situ hybridisation were used to compare three species, two (weedy rice and Brachypodium distachyon) with the AZ in the ancestral position and one (Setaria viridis) with the AZ in a derived position below a cluster of flowers (spikelet). Rice and Brachypodium are more similar anatomically than Setaria. However, the cell wall properties and the transcriptome of rice and Brachypodium are no more similar to each other than either is to Setaria. The set of genes expressed in the studied tissues is generally conserved across species, but the precise developmental and positional patterns of expression and gene networks are almost entirely different. Transcriptional regulation of AZ development appears to be extensively rewired among the three species, leading to distinct anatomical and morphological outcomes.
离区是植物脱落部分的过程，由一个特定的细胞群，离区（AZ）介导。在禾本科植物中，AZ 的位置在不同物种之间存在差异，这就提出了一个问题，即其解剖结构和遗传控制是否保守。对 AZ 的祖先位置进行了重建。使用了组合的光学显微镜、透射电子显微镜、RNA-Seq 分析和 RNA 原位杂交来比较三个物种，两个（杂草稻和短柄草）的 AZ 在祖先位置，一个（柳枝稷）的 AZ 在一个簇花（小穗）下面的衍生位置。水稻和短柄草在解剖结构上比柳枝稷更相似。然而，细胞壁特性和水稻和短柄草的转录组彼此之间的相似性并不比它们与柳枝稷的相似性更大。在所研究的组织中表达的基因集在物种间通常是保守的，但表达和基因网络的精确发育和位置模式几乎完全不同。AZ 发育的转录调控在三个物种之间似乎广泛地重新布线，导致了不同的解剖和形态结果。
