Arabidopsis Homologs of the Petunia HAIRY MERISTEM Gene Are Required for Maintenance of Shoot and Root Indeterminacy
Arabidopsis Homologs of the Petunia HAIRY MERISTEM Gene Are Required for Maintenance of Shoot and Root Indeterminacy
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DOI：
10.1104/pp.110.168757
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发表时间：
2011-02-01
期刊：
影响因子：
7.4
通讯作者：
Bowman, John L.
中科院分区：
文献类型：
--
作者：
Engstrom, Eric M.;Andersen, Carl M.;Bowman, John L.
不确定性的维持是植物构型生成的基础，也是植物生命策略的核心组成部分。植物的不定性是茎和根分生组织的一个特征，它必须在维持不定性与器官发生之间取得平衡。矮牵牛HAIRY MERISTEM（HAM）基因是转录调控因子GRAS家族的一员，其通过未定义的非细胞自主信号传导机制促进芽的不确定性。在这里，我们报告了三个拟南芥HAM直系同源物（Atham 1、2、3突变体）中敲除等位基因的三倍纯合的拟南芥突变体，在茎和根中表现出不确定性的丧失。在芽中，Atham 1，2，3突变体的不确定性丧失表型的突变程度在芽系统中不同，初级营养芽分生组织的停滞很少或从不发生，次级芽分生组织通常在启动器官发生之前停滞，以及花序和花分生组织表现出从野生型（花）延伸到分生组织停滞的表型范围，（花和花序）。Atham 1，2，3突变体也表现出异常的芽叶序，侧器官异常，并改变分生组织形态的莲座丛和花序的功能分生组织。Atham 1，2，3突变体的根分生组织在纵向和径向轴上都明显小于野生型，这是分生组织细胞分裂速率降低的结果，最终导致根分生组织停滞。Atham1，2，3表型不太可能反映HAM功能的完全丧失，作为第四个，更远的相关拟南芥HAM同源物，AtHAM4，表现出与AtHAM1和AtHAM2在促进芽不确定性的重叠功能。
Maintenance of indeterminacy is fundamental to the generation of plant architecture and a central component of the plant life strategy. Indeterminacy in plants is a characteristic of shoot and root meristems, which must balance maintenance of indeterminacy with organogenesis. The Petunia hybrida HAIRY MERISTEM (HAM) gene, a member of the GRAS family of transcriptional regulators, promotes shoot indeterminacy by an undefined non-cell-autonomous signaling mechanism(s). Here, we report that Arabidopsis (Arabidopsis thaliana) mutants triply homozygous for knockout alleles in three Arabidopsis HAM orthologs (Atham1,2,3 mutants) exhibit loss of indeterminacy in both the shoot and root. In the shoot, the degree of penetrance of the loss-of-indeterminacy phenotype of Atham1,2,3 mutants varies among shoot systems, with arrest of the primary vegetative shoot meristem occurring rarely or never, secondary shoot meristems typically arresting prior to initiating organogenesis, and inflorescence and flower meristems exhibiting a phenotypic range extending from wild type (flowers) to meristem arrest preempting organogenesis (flowers and inflorescence). Atham1,2,3 mutants also exhibit aberrant shoot phyllotaxis, lateral organ abnormalities, and altered meristem morphology in functioning meristems of both rosette and inflorescence. Root meristems of Atham1,2,3 mutants are significantly smaller than in the wild type in both longitudinal and radial axes, a consequence of reduced rates of meristem cell division that culminate in root meristem arrest. Atham1,2,3 phenotypes are unlikely to reflect complete loss of HAM function, as a fourth, more distantly related Arabidopsis HAM homolog, AtHAM4, exhibits overlapping function with AtHAM1 and AtHAM2 in promoting shoot indeterminacy.