Table_8_Sub-epidermal Expression of ENHANCER OF TRIPTYCHON AND CAPRICE1 and Its Role in Root Hair Formation Upon Pi Starvation.docx

Root hair patterning is best studied in Arabidopsis thaliana. A pattern of root hair and non-root hair files is governed by a gene-regulatory network of activators and inhibitors. Under phosphate starvation conditions, extra root hairs are formed in non-root hair positions. This raises the question, whether and how this environmental stimulus is mediated by the known root hair gene network. In this study, we provide genetic and molecular data on the role of ETC1 in the phosphate starvation induced ectopic root hair formation. We show that the expression in the epidermis is irregular and reduced and that a new expression domain is induced in the sub-epidermis. By expressing ETC1 in the sub-epidermis, we show that this is sufficient to induce extra root hair formation in N-files. This suggests that the phosphate induced expressional switch from epidermal to epidermal plus sub-epidermal expression of ETC1 is one environmental input to the underlying patterning network.

根毛模式建成（root hair patterning）的研究以拟南芥（Arabidopsis thaliana）为最优模型。根毛与非根毛细胞列的模式由激活因子与抑制因子构成的基因调控网络（gene-regulatory network）所调控。在磷酸盐饥饿（phosphate starvation）条件下，非根毛位置会形成额外的根毛。这一现象引出了核心问题：该环境刺激是否以及如何通过已知的根毛基因调控网络进行介导。本研究中，我们提供了关于ETC1在磷酸盐饥饿诱导的异位根毛形成（ectopic root hair formation）中作用的遗传学与分子生物学数据。我们发现，表皮（epidermis）中的基因表达呈现不规则且下调的状态，同时亚表皮（sub-epidermis）中被诱导出了新的表达区域。通过在亚表皮中表达ETC1，我们证实该操作足以在非根毛细胞列中诱导额外根毛的形成。这表明，磷酸盐诱导的ETC1表达模式从仅表皮表达转向表皮与亚表皮共同表达的转变，是作用于下游模式建成网络的一类环境输入信号。