Long J, Barton M K
Department of Genetics, Program in Cell and Molecular Biology, University of Wisconsin at Madison, 445 Henry Mall, Madison, Wisconsin 053706, USA.
Dev Biol. 2000 Feb 15;218(2):341-53. doi: 10.1006/dbio.1999.9572.
Shoot development is reiterative: shoot apical meristems (SAMs) give rise to branches made of repeating leaf and stem units with new SAMs in turn formed in the axils of the leaves. Thus, new axes of growth are established on preexisting axes. Here we describe the formation of axillary meristems and floral meristems in Arabidopsis by monitoring the expression of the SHOOT MERISTEMLESS and AINTEGUMENTA genes. Expression of these genes is associated with SAMs and organ primordia, respectively. Four stages of axillary meristem development and previously undefined substages of floral meristem development are described. We find parallels between the development of axillary meristems and the development of floral meristems. Although Arabidopsis flowers develop in the apparent absence of a subtending leaf, the expression patterns of AINTEGUMENTA and SHOOT MERISTEMLESS RNAs during flower development suggest the presence of a highly reduced, "cryptic" leaf subtending the flower in Arabidopsis. We hypothesize that the STM-negative region that develops on the flanks of the inflorescence meristem is a bract primordium and that the floral meristem proper develops in the "axil" of this bract primordium. The bract primordium, although initially specified, becomes repressed in its growth.
茎尖分生组织（SAMs）产生由重复的叶和茎单元组成的分支，新的SAMs又依次在叶腋处形成。因此，新的生长轴在已有的轴上建立。在这里，我们通过监测无茎分生组织（SHOOT MERISTEMLESS）和拟南芥中花分生组织基因（AINTEGUMENTA）的表达来描述腋生分生组织和花分生组织的形成。这些基因的表达分别与SAMs和器官原基相关。描述了腋生分生组织发育的四个阶段以及花分生组织发育中以前未定义的亚阶段。我们发现腋生分生组织的发育与花分生组织的发育之间存在相似之处。虽然拟南芥的花在明显没有苞片叶的情况下发育，但在花发育过程中AINTEGUMENTA和无茎分生组织RNA的表达模式表明拟南芥花的下方存在一片高度退化的“隐性”叶。我们假设在花序分生组织侧面发育的STM阴性区域是苞片原基，而花分生组织本身在这个苞片原基的“叶腋”中发育。苞片原基虽然最初已确定，但在其生长过程中受到抑制。
