GH3 Auxin-Amido Synthetases Alter the Ratio of Indole-3-Acetic Acid and Phenylacetic Acid in Arabidopsis

Abstract

Auxin is the first discovered plant hormone and is essential for many aspects of plant growth and development. Indole-3-acetic acid (IAA) is the main auxin and plays pivotal roles in intercellular communication through polar auxin transport. Phenylacetic acid (PAA) is another natural auxin that does not show polar movement. Although a wide range of species have been shown to produce PAA, its biosynthesis, inactivation and physiological significance in plants are largely unknown. In this study, we demonstrate that overexpression of the CYP79A2 gene, which is involved in benzylglucosinolate synthesis, remarkably increased the levels of PAA and enhanced lateral root formation in Arabidopsis. This coincided with a significant reduction in the levels of IAA. The results from auxin metabolite quantification suggest that the PAA-dependent induction of GRETCHEN HAGEN 3 (GH3) genes, which encode auxin-amido synthetases, promote the inactivation of IAA. Similarly, an increase in IAA synthesis, via the indole-3-acetaldoxime pathway, significantly reduced the levels of PAA. The same adjustment of IAA and PAA levels was also observed by applying each auxin to wild-type plants. These results show that GH3 auxin-amido synthetases can alter the ratio of IAA and PAA in plant growth and development.

Quantitative proteomics reveals extensive lysine ubiquitination in the Arabidopsis root proteome and uncovers novel transcription factor stability states

“…Notable proteins which are ubiquitinated in response to auxin treatment include the IAA amido synthases GRETCHEN HAGAN 3.2 (GH3.2), GH3.3 (also called YDK1/BRU6/AUR3), GH3.5 (also called WES1), and GH3.6 (also called DFL1). Expression of GH3 paralogs are classically associated with auxin response and GH3 activity directly impacts auxin homeostasis (4,21,45). The observed increase in GH3 protein abundance is in line with conventional wisdom that auxin induces transcription of GH3 genes.…”

“…Thus, we examined how protein abundance and diGly modified sites are impacted following 3 hours of auxin treatment (1 µM IAA). We found that 70 proteins (Supplemental Table 4) and 59 diGly modified sites (Supplemental (4,21,45). The observed increase in GH3 protein abundance is in line with conventional wisdom that auxin induces transcription of GH3 genes.…”

From Spaceflight to Mars g-Levels: Adaptive Response of A. Thaliana Seedlings in a Reduced Gravity Environment Is Enhanced by Red-Light Photostimulation

“…According to KEGG Pathway analysis, the auxin pathway was activated at different steps in microgravity conditions (GRETCHEN HAGEN 3 (GH3) step in µgd and small auxin upregulated RNA (SAUR) in µgrl and repressed in Marsrl condition (GH3 step), suggesting cell enlargement and plant growth are promoted in microgravity but not at Mars g- level. GH3 genes, downregulated in µgd ( DFL1 ) and upregulated in Marsrl ( GH3.3 and AT1G48660 ) encode auxin-amido synthetases and promote the inactivation of indole acetic acid (IAA) [ 51 ]. Eleven SAUR genes which regulate auxin-mediated growth are upregulated in µgrl sample.…”

Organ-Specific Transcriptome Analysis Identifies Candidate Genes Involved in the Stem Specialization of Bermudagrass (Cynodon dactylon L.)

“…Secondly, expression profiling and RT-qPCR both indicated that GH3 and JAR1 were preferentially expressed in rhizome and shoot, respectively ( Figure 7 ). GH3 encodes an auxin-amido synthetase protein to promote the inactivation of auxin, thereby inhibiting the auxin signaling transduction ( Aoi et al, 2020 ). On the other hand, JAR1 encodes a JA-conjugating enzyme to catalyze the transformation of JA to active JA-isolecucine ( Chen et al, 2018 ).…”