The phytohormone auxin is implied in steering various developmental decisions during plant morphogenesis in a concentration-dependent manner. Auxin maxima have been shown to maintain meristematic activity, for example, of the root apical meristem, and position new sites of outgrowth, such as during lateral root initiation and phyllotaxis. More recently, it has been demonstrated that sites of auxin minima also provide positional information. In the developing Arabidopsis fruit, auxin minima are required for correct differentiation of the valve margin. It remains unclear, however, how this auxin minimum is generated and maintained. Here, we employ a systems biology approach to model auxin transport based on experimental observations. This allows us to determine the minimal requirements for its establishment. Our simulations reveal that two alternative processes—which we coin “flux-barrier” and “flux-passage”—are both able to generate an auxin minimum, but under different parameter settings. Both models are in principle able to yield similar auxin profiles but present qualitatively distinct patterns of auxin flux. The models were tested by tissue-specific inducible ablation, revealing that the auxin minimum in the fruit is most likely generated by a flux-passage process. Model predictions were further supported through 3D PIN localization imaging and implementing experimentally observed transporter localization. Through such an experimental–modeling cycle, we predict how the auxin minimum gradually matures during fruit development to ensure timely fruit opening and seed dispersal.

植物激素生长素暗示以浓度依赖的方式指导植物形态发生过程中的各种发育决定。已经证明最大的生长素保持例如根尖分生组织的分生组织活性，并定位新的生长产物位点，例如在侧根起始和叶序发育过程中。最近，已经证明最小生长素的位点也提供位置信息。在发展中的拟南芥中水果，需要最小的生长素才能正确区分瓣膜边缘。然而，尚不清楚如何产生和维持这种最低的生长素。在这里，我们根据实验观察结果采用系统生物学方法来模拟植物生长素的运输。这使我们能够确定其建立的最低要求。我们的模拟表明，两个替代过程（我们称之为“通量屏障”和“通量通道”）都能够产生最小的生长素，但是在不同的参数设置下。两种模型原则上都能够产生相似的生长素曲线，但在质量上呈现出不同的生长素通量模式。通过组织特异性诱导消融对模型进行了测试，结果表明水果中的生长素最低含量很可能是通过通量传递过程产生的。通过3D PIN定位成像并实施实验观察到的转运蛋白定位，进一步支持了模型预测。通过这样的实验建模周期，我们可以预测生长素最低限度在果实发育过程中如何逐渐成熟，以确保及时开放果实和分散种子。