Auxin is an important signaling molecule synthesized in organisms from multiple kingdoms of life, including land plants, green algae, and bacteria. In this review, we highlight the similarities and differences in auxin biosynthesis among these organisms. Tryptophan-dependent routes to IAA are found in land plants, green algae and bacteria. Recent sequencing efforts show that the indole-3-pyruvic acid pathway, one of the primary biosynthetic pathways in land plants, is also found in the green algae. These similarities raise questions about the origin of auxin biosynthesis. Future studies comparing auxin biosynthesis across kingdoms will shed light on its origin and role outside of the plant lineage.

中文翻译：

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旧城之路：跨王国生长素生物合成的路线。

生长素是一种重要的信号分子，在多种生物的生物中合成，包括陆地植物，绿藻和细菌。在这篇综述中，我们着重介绍了这些生物之间生长素生物合成的异同。在陆地植物，绿藻和细菌中发现了依赖色氨酸的IAA途径。最近的测序工作表明，在绿藻中也发现了吲哚-3-丙酮酸途径，这是陆生植物中主要的生物合成途径之一。这些相似之处引起了关于植物生长素生物合成起源的疑问。未来比较王国间植物生长素生物合成的研究将阐明其起源和在植物谱系之外的作用。