Characterization of Four Bifunctional Plant IAM/PAM-Amidohydrolases Capable of Contributing to Auxin Biosynthesis

Abstract

Amidases [EC 3.5.1.4] capable of converting indole-3-acetamide (IAM) into the major plant growth hormone indole-3-acetic acid (IAA) are assumed to be involved in auxin de novo biosynthesis. With the emerging amount of genomics data, it was possible to identify over forty proteins with substantial homology to the already characterized amidases from Arabidopsis and tobacco. The observed high conservation of amidase-like proteins throughout the plant kingdom may suggest an important role of theses enzymes in plant development. Here, we report cloning and functional analysis of four, thus far, uncharacterized plant amidases from Oryza sativa, Sorghum bicolor, Medicago truncatula, and Populus trichocarpa. Intriguingly, we were able to demonstrate that the examined amidases are also capable of converting phenyl-2-acetamide (PAM) into phenyl-2-acetic acid (PAA), an auxin endogenous to several plant species including Arabidopsis. Furthermore, we compared the subcellular localization of the enzymes to that of Arabidopsis AMI1, providing further evidence for similar enzymatic functions. Our results point to the presence of a presumably conserved pathway of auxin biosynthesis via IAM, as amidases, both of monocot, and dicot origins, were analyzed.

Benzyl Cyanide Leads to Auxin-Like Effects Through the Action of Nitrilases in Arabidopsis thaliana

“…PAA inhibited root elongation at 25 μM ( Figures 5A , 6A ), which is consistent with earlier reports on Arabidopsis (Sánchez-Parra et al, 2014; Sugawara et al, 2015). Bz-CN also led to reduced primary root length but the response was less severe than for PAA at equal concentrations ( Figures 1 , 5 ).…”

“…In addition, PAA is one of the few naturally occurring auxins and has been detected in several plant species, including Arabidopsis (Wightman and Lighty, 1982; Sauer et al, 2013; Sánchez-Parra et al, 2014; Sugawara et al, 2015). It was recently shown that PAA can be produced in vitro from phenyl pyruvate (PPA) by the activity of plant YUCCA (YUC) proteins and that the overexpression of YUC s led to increased PAA levels in Arabidopsis (Dai et al, 2013; Sugawara et al, 2015).…”

Dissecting the role of Arabidopsis thaliana AMIDASE 1 in auxin biosynthesis

“…4--Cl--IAA (Slovin et al 1999), and phenyl--2--acetic acid (PAA) . Moreover, a variety of IAA precursors such as indole--3--acetamide (IAM), indole--3--acetonitrile (IAN), indole--3--pyruvic acid (IPA), and indole--3--butyric acid (IBA) exhibit auxin--like effects, most likely due to their conversion to IAA (Sánchez--Parra et al 2014). However, these "other auxins" have commonly less pronounced effects than IAA (Abeles and Rubinstein 1964).…”

“…In any case, a rising number of recent publications seem to valorise the importance of PAA in plants Sánchez--Parra et al 2014;Sugawara et al 2015;Westfall et al 2016). …”

In-depth analysis of jasmonate-mediated indole-3-acetic acid (IAA) biosynthesis and its implication in plant development

“…is also a naturally occurring auxin species that can be found widespread in plants (Sánchez-Parra et al 2014). Likewise, 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthaleneacetic acid (NAA), are two synthetic auxin derivatives with important economic value as herbicide or fruit growth enhancer, respectively (Bonner & Bandurski 1952;Ortolá et al 1991;Teale et al 2006).…”