title: Origin of plant auxin biosynthesis.
abstract: The recent finding of the tryptophan aminotransferase (TAA)/flavin monooxygenase (YUC) pathway as the principal route of auxin production in plants provides an opportunity to revisit the origin of plant auxin biosynthesis. Phylogenetic analyses of the TAA and YUC gene families provide very little evidence for the production of indole-3-acetic acid (IAA) in algae. Instead, horizontal gene transfer of YUCs from bacteria to the ancestral land plant suggests that the TAA/YUC pathway is a land plant innovation. In this Opinion article we postulate that the origin of tryptophan-dependent IAA biosynthesis in land plants might have evolved in response to interactions with microbes, particularly bacteria, allowing plants to counteract bacterial activities and control their own auxin signaling.
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China; Department of Biology, East Carolina University, Greenville, NC 27858, USA.
authors.forename: Jipei
authors.initials: J
authors.lastname: Yue
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Hu
authors.affiliation: Department of Biology, East Carolina University, Greenville, NC 27858, USA. Electronic address: huangj@ecu.edu.
authors.forename: Jinling
authors.initials: J
authors.lastname: Huang
mesh_terms: D005075:Biological Evolution; D022761:Gene Transfer, Horizontal / Q000235:genetics; D007210:Indoleacetic Acids / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids
keywords: IAA biosynthesis; gene transfer; microbe–plant interaction; plant evolution