Nemhauser J L, Feldman L J, Zambryski P C
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA.
Development. 2000 Sep;127(18):3877-88. doi: 10.1242/dev.127.18.3877.
The phytohormone auxin has wide-ranging effects on growth and development. Genetic and physiological approaches implicate auxin flux in determination of floral organ number and patterning. This study uses a novel technique of transiently applying a polar auxin transport inhibitor, N-1-naphthylphthalamic acid (NPA), to developing Arabidopsis flowers to further characterize the role of auxin in organogenesis. NPA has marked effects on floral organ number as well as on regional specification in wild-type gynoecia, as defined by morphological and histological landmarks for regional boundaries, as well as tissue-specific reporter lines. NPA's effects on gynoecium patterning mimic the phenotype of mutations in ETTIN, a member of the auxin response factor family of transcription factors. In addition, application of different concentrations of NPA reveal an increased sensitivity of weak ettin alleles to disruptions in polar auxin transport. In contrast, the defects found in spatula gynoecia are partially rescued by treatment with NPA. A model is proposed suggesting an apical-basal gradient of auxin during gynoecium development. This model provides a mechanism linking ETTIN's putative transcriptional regulation of auxin-responsive genes to the establishment or elaboration of tissue patterning during gynoecial development.
植物激素生长素对生长和发育具有广泛影响。遗传学和生理学方法表明生长素流在花器官数量和模式的决定中起作用。本研究采用一种新技术，即向发育中的拟南芥花瞬时施加极性生长素运输抑制剂N-1-萘基邻苯二甲酸（NPA），以进一步阐明生长素在器官发生中的作用。NPA对花器官数量以及野生型雌蕊中的区域特化有显著影响，区域特化由区域边界的形态学和组织学标志以及组织特异性报告系来定义。NPA对雌蕊模式的影响类似于生长素反应因子家族转录因子成员ETTIN突变的表型。此外，施加不同浓度的NPA揭示了弱ettin等位基因对极性生长素运输破坏的敏感性增加。相反，用NPA处理可部分挽救匙形雌蕊中发现的缺陷。提出了一个模型，表明在雌蕊发育过程中生长素存在顶基梯度。该模型提供了一种机制，将ETTIN对生长素反应基因的假定转录调控与雌蕊发育过程中组织模式的建立或细化联系起来。
