Aldoximes are precursors of auxins in Arabidopsis and maize

Authors: PEREZ, VERONICA - University Of Florida; DAI, RU - University Of Florida; BAI, BING - University Of Florida; TMOICZEK, BREANNA - University Of Florida; ASKEY, BRYCE - University Of Florida; ZHANG, YI - University Of Florida; RUBIN, GARRET - University Of Florida; DING, YOUSONG - University Of Florida; GRENNING, ALEXANDER - University Of Florida; Block, Anna; KIM, JEONGIM - University Of Florida

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2021
Publication Date: 6/10/2021
Citation: Perez, V.E.; Dai, R.; Bing Bai, B.; Tomiczek, B.; Askey, B.; Zhang, Y.; Ding, Y.; Grenning, A.; Block, A.K.; and Kim, J. 2021 Aldoxime-derived auxin biosynthesis occurs in both Arabidopsis and maize. New Phytologist. https://doi: 10.1111/nph.17447
DOI: https://doi.org/10.1111/nph.17447

Interpretive Summary: For plants to grow well and produce adequate yield in sub-optimal growth conditions, it is vital that agricultural commodities balance growth and defense responses to stressors such as pests or adverse environmental conditions. An ARS scientist at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL in collaboration with researchers at the University of Florida, have discovered a new mechanism by which plants regulate their growth while experiencing adverse conditions. This is accomplished by plants producing growth regulating hormones and defense chemicals from the same pathway. This new knowledge can potentially lead to molecular breeding approaches for the development of crops that are more hardy and pest resistant while mantaining yield.

Technical Abstract: Auxins are plant growth hormones that play crucial roles in various biological processes. Two major natural auxins, phenylacetic acid (PAA) and indole-3-acetic acid (IAA), are produced mainly via the well-characterized YUCCA pathway. An alternative route of IAA biosynthesis uses the glucosinolate intermediate indole-3-acetaldoxime (IAOx) as a precursor. The IAOx-IAA pathway is thought to occur only in glucosinolate-producing plants in Brassicales. Here, we show the existence of a phenylacetaldoxime (PAOx)-derived PAA biosynthesis pathway and that aldoxime-derived auxin biosynthesis occurs beyond Brassicales. Arabidopsis glucosinolate-deficient mutant sur1 still produces PAA from PAOx, so the conversion of PAOx to PAA does not require benzyl glucosinolate hydrolysis, which is reminiscent of the IAOx-IAA pathway. Stable isotope labeling assays demonstrate that maize produces PAA and IAA from PAOx and IAOx respectively, indicating that aldoxime-derived auxin biosynthesis also occurs in maize. Considering that aldoxime production occurs widely in the plant kingdom including gymnosperms and ferns, aldoxime-derived auxin biosynthesis may be much more widespread than originally believed. A genome-wide transcriptomics study using PAA-overproduction plants identified complex metabolic networks among IAA, PAA, phenylpropanoid, and tryptophan metabolism. It appears that aldoximes, known as defense-related molecules, are linked to plant growth through altering the production of auxins and phenylpropanoids.