McConnell J R, Barton M K
Cellular and Molecular Biology Program and Department of Genetics, University of Wisconsin-Madison, Madison, WI, USA.
Development. 1998 Aug;125(15):2935-42. doi: 10.1242/dev.125.15.2935.
Shoot apical meristems (SAMs) of seed plants are small groups of pluripotent cells responsible for making leaves, stems and flowers. While the primary SAM forms during embryogenesis, new SAMs, called axillary SAMs, develop later on the body of the plant and give rise to branches. In Arabidopsis plants, axillary SAMs develop in close association with the adaxial leaf base at the junction of the leaf and stem (the leaf axil). We describe the phenotype caused by the Arabidopsis phabulosa-1d (phb-1d) mutation. phb-1d is a dominant mutation that causes altered leaf polarity such that adaxial characters develop in place of abaxial leaf characters. The adaxialized leaves fail to develop leaf blades. This supports a recently proposed model in which the juxtaposition of ad- and abaxial cell fates is required for blade outgrowth. In addition to the alteration in leaf polarity, phb-1d mutants develop ectopic SAMs on the undersides of their leaves. Also, the phb-1d mutation weakly suppresses the shoot meristemless (stm) mutant phenotype. These observations indicate an important role for adaxial cell fate in promoting the development of axiallary SAMs and suggest a cyclical model for shoot development: SAMs make leaves which in turn are responsible for generating new SAMs.
种子植物的茎尖分生组织（SAMs）是一小群多能细胞，负责形成叶子、茎和花。虽然初生SAM在胚胎发生过程中形成，但新的SAM，即腋生SAM，随后在植物体内发育并产生分支。在拟南芥植物中，腋生SAM在叶和茎的交界处（叶腋）与近轴叶基部紧密相连处发育。我们描述了拟南芥phabulosa-1d（phb-1d）突变引起的表型。phb-1d是一种显性突变，会导致叶极性改变，使得近轴特征取代远轴叶特征发育。近轴化的叶子无法发育出叶片。这支持了最近提出的一个模型，即近轴和远轴细胞命运的并置是叶片生长所必需的。除了叶极性改变外，phb-1d突变体在其叶片下侧发育出异位SAM。此外，phb-1d突变对无茎分生组织（stm）突变体表型有弱抑制作用。这些观察结果表明近轴细胞命运在促进腋生SAM发育中起重要作用，并提出了一个茎发育的循环模型：SAM形成叶子，而叶子反过来负责产生新的SAM。
