Indole-3-acetic acid, that is, auxin, is a molecule found in a broad phylogenetic distribution of organisms, from bacteria to eukaryotes. In the ancestral land plant auxin was co-opted to be the paramount phytohormone mediating tropic responses and acting as a facilitator of developmental decisions throughout the life cycle. The evolutionary origins of land plant auxin biology genes can now be traced with reasonable clarity. Genes encoding the two enzymes of the land plant auxin biosynthetic pathway arose in the ancestral land plant by a combination of horizontal gene transfer from bacteria and possible neofunctionalization following gene duplication. Components of the auxin transcriptional signaling network have their origins in ancestral alga genes, with gene duplication and neofunctionalization of key domains allowing integration of a portion of the preexisting transcriptional network with auxin. Knowledge of the roles of orthologous genes in extant charophycean algae is lacking, but could illuminate the ancestral functions of both auxin and the co-opted transcriptional network.

中文翻译：

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论陆生植物生长素生物学的进化起源

Indole-3-acetic acid，即生长素，是一种在从细菌到真核生物的广泛系统发育分布的生物体中发现的分子。在祖先的陆地植物中，生长素被选为最重要的植物激素，可调节热带反应并在整个生命周期中充当发育决策的促进者。现在可以相当清晰地追溯陆生植物生长素生物学基因的进化起源。编码陆生植物生长素生物合成途径的两种酶的基因在祖先的陆生植物中出现，是通过细菌的水平基因转移和基因复制后可能的新功能化相结合而产生的。生长素转录信号网络的成分起源于祖先的藻类基因，具有基因复制和关键域的新功能化，允许将预先存在的转录网络的一部分与生长素整合。对现存轮藻纲中直系同源基因的作用的了解尚缺乏，但可以阐明生长素和增选转录网络的祖先功能。