Auxin Metabolism in Plants

Dynamics of Auxin and Cytokinin Metabolism during Early Root and Hypocotyl Growth in Theobroma cacao

“…At 10 DAI, oxIAA levels were overall increased in all root segments and hypocotyls, with the highest concentration found in the Dz ( Figure 2 D). Worth highlighting is that oxIAA was a minor IAA catabolite compared to the conjugates IAAsp and IAGlu across our developmental segments and time points ( Figure 2 E), contrary to what has been traditionally observed in many other plant species [ 27 , 40 , 45 , 47 , 48 ]. This suggests that IAA conjugation to Asp and Glu is a major catabolic pathway regulating endogenous IAA levels in roots and hypocotyl during early cacao seedling development.…”

“…IAA conjugates with specific amino acids and glucose are well-known reversible storage forms [ 25 ]. The oxidized form of IAA, 2-oxindole-3-acetic acid (oxIAA), and the IAA conjugates to aspartate (IAAsp) and glutamate (IAGlu) are irreversible catabolites that regulate auxin levels after accumulation [ 26 , 27 , 28 , 29 ] or during regulated auxin minima formation [ 13 , 20 ]. IAA, oxIAA, IAAsp and IAGlu are thus key indicators of the auxin metabolic status in plant tissues.…”

Redefining the roles of UDP-glycosyltransferases in auxin metabolism and homeostasis during plant development

“…Oxidation and conjugation have been shown to play important roles in the regulation of auxin levels for the control of plant growth and development (Casanova-Sáez et al, 2021).…”

“…Indole-3-acetic acid (IAA), the major natural auxin in plants, coordinates developmental programs throughout the plant's life cycle by integrating external and internal signals into regulated plant responses (Zažímalová et al, 2014;Casanova-Sáez et al, 2021). This is achieved by the formation of concentration gradients that establish auxin maxima and minima within plant tissues.…”

“…This is achieved by the formation of concentration gradients that establish auxin maxima and minima within plant tissues. In combination with inter-and intracellular transport, IAA metabolism modulates auxin gradients and is therefore critical for plant growth (Casanova-Sáez et al, 2021). In addition to the many layers of regulation of IAA biosynthesis, redundant mechanisms exist to keep about 75% of the pool of IAA molecules as either transient storage forms or catabolites, thus providing a robust and rapid-response system to fine-tune IAA levels (Ludwig-Muller, 2011).…”