Auxin Biosynthesis

Abstract

Indole-3-acetic acid (IAA), the most important natural auxin in plants, is mainly synthesized from the amino acid tryptophan (Trp). Recent genetic and biochemical studies in Arabidopsis have unambiguously established the first complete Trp-dependent auxin biosynthesis pathway. The first chemical step of auxin biosynthesis is the removal of the amino group from Trp by the TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) family of transaminases to generate indole-3-pyruvate (IPA). IPA then undergoes oxidative decarboxylation catalyzed by the YUCCA (YUC) family of flavin monooxygenases to produce IAA. This two-step auxin biosynthesis pathway is highly conserved throughout the plant kingdom and is essential for almost all of the major developmental processes. The successful elucidation of a complete auxin biosynthesis pathway provides the necessary tools for effectively modulating auxin concentrations in plants with temporal and spatial precision. The progress in auxin biosynthesis also lays a foundation for understanding polar auxin transport and for dissecting auxin signaling mechanisms during plant development.

Linking PHYTOCHROME-INTERACTING FACTOR to Histone Modification in Plant Shade Avoidance

“…In line with this idea, for all three examined genes, PIF7 was found enriched at the chromatin region around the G-box within the promoter and MRG2 was found at the 59-end of the gene body, two regions that are located closely in the case of IAA19 but much more distantly in the case of YUCCA8 and PRE1. YUCCA8 and IAA19 are important regulators involved in auxin biosynthesis and response (Zhao, 2014;Leyser, 2017), and PRE1 is implicated in BR signaling (Clouse, 2011)-two major types of hormones combined to act in SAS (Keuskamp et al, 2011). Thus, the PIF7-MRG2 module constitutes a crucial step linking shade response to output of hormonal regulation of cell growth.…”

The Yin-Yang of Hormones: Cytokinin and Auxin Interactions in Plant Development

“…Recent studies suggest that the most abundant auxin, indole-3-acetic acid (IAA), is primarily synthesized in a two-step process from the amino acid tryptophan (Zhao, 2014) (Figure 1). In the first step, tryptophan is converted to indole-3-pyruvate by the TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) family of transaminases (Stepanova et al, 2008;Tao et al, 2008).…”

“…Here, we review these recent studies together with some earlier work, focusing on the regulatory interactions that control growth and development. The literature on these two hormones is so extensive that an encompassing review is impossible, and we refer readers to excellent reviews on topics absent or only briefly touched on here (Argueso et al, 2009;Bishopp et al, 2011a;Domagalska and Leyser, 2011;Su et al, 2011;Hwang et al, 2012;Naseem and Dandekar, 2012;Del Bianco et al, 2013;El-Showk et al, 2013;O'Brien and Benková, 2013;Kieber and Schaller, 2014;Schaller et al, 2014;Zhao, 2014). We begin with an overview of cytokinin and auxin metabolism and signaling and then consider their interactions in controlling the development and growth of roots and shoots.…”

Translatome analyses capture of opposing tissue-specific brassinosteroid signals orchestrating root meristem differentiation

“…Only a few significantly enriched categories were defined in the inner tissues, whereas the outer tissues, LR/C and epidermis, contained more categories. Up-regulated genes responding to hormones prevailed in the epidermis, among them ethylene-and auxin-related genes and kinases enhancing the efflux activity of PIN2 in the epidermis (22)(23)(24)(25)(26) (Fig. 6A).…”