CNRS-Université Pierre et Marie Curie, UMR 7139 Marine Plants and Biomolecules, and Platform of Cytology, CNRS FR2424, Station Biologique de Roscoff, 29682 Roscoff Cedex, France.
Plant Physiol. 2010 May;153(1):128-44. doi: 10.1104/pp.109.149708. Epub 2010 Mar 3.
Ectocarpus siliculosus is a small brown alga that has recently been developed as a genetic model. Its thallus is filamentous, initially organized as a main primary filament composed of elongated cells and round cells, from which branches differentiate. Modeling of its early development suggests the involvement of very local positional information mediated by cell-cell recognition. However, this model also indicates that an additional mechanism is required to ensure proper organization of the branching pattern. In this paper, we show that auxin indole-3-acetic acid (IAA) is detectable in mature E. siliculosus organisms and that it is present mainly at the apices of the filaments in the early stages of development. An in silico survey of auxin biosynthesis, conjugation, response, and transport genes showed that mainly IAA biosynthesis genes from land plants have homologs in the E. siliculosus genome. In addition, application of exogenous auxins and 2,3,5-triiodobenzoic acid had different effects depending on the developmental stage of the organism, and we propose a model in which auxin is involved in the negative control of progression in the developmental program. Furthermore, we identified an auxin-inducible gene called EsGRP1 from a small-scale microarray experiment and showed that its expression in a series of morphogenetic mutants was positively correlated with both their elongated-to-round cell ratio and their progression in the developmental program. Altogether, these data suggest that IAA is used by the brown alga Ectocarpus to relay cell-cell positional information and induces a signaling pathway different from that known in land plants.
泡叶藻是一种小型的褐色海藻，最近被开发为一种遗传模式生物。它的藻体呈丝状，最初组织为一个由长形细胞和圆形细胞组成的主初级丝状体，从该丝状体分化出侧枝。其早期发育的模型表明，细胞间识别介导的非常局部的位置信息参与其中。然而，该模型也表明，需要额外的机制来确保侧枝模式的正确组织。在本文中，我们表明，生长素吲哚-3-乙酸（IAA）可在成熟的泡叶藻生物体内检测到，并且在发育的早期阶段主要存在于丝状体的顶端。生长素生物合成、共轭、反应和运输基因的计算机预测表明，主要来自陆地植物的 IAA 生物合成基因在泡叶藻基因组中有同源物。此外，外源性生长素和 2,3,5-三碘苯甲酸的应用根据生物体的发育阶段而有不同的效果，我们提出了一个模型，其中生长素参与发育程序中进展的负调控。此外，我们从小规模微阵列实验中鉴定了一个称为 EsGRP1 的生长素诱导基因，并表明其在一系列形态发生突变体中的表达与它们的长形细胞与圆形细胞的比例及其在发育程序中的进展呈正相关。总之，这些数据表明，IAA 被褐藻泡叶藻用来传递细胞间的位置信息，并诱导一种不同于陆地植物的信号通路。
