Research progress of aldehyde oxidases in plants

Abstract

Plant aldehyde oxidases (AOs) are multi-functional enzymes, and they could oxidize abscisic aldehyde into ABA (abscisic acid) or indole acetaldehyde into IAA (indoleacetic acid) as the last step, respectively. AOs can be divided into four groups based on their biochemical and physiological functions. In this review, we summarized the recent studies about AOs in plants including the motif information, biochemical, and physiological functions. Besides their role in phytohormones biosynthesis and stress response, AOs could also involve in reactive oxygen species homeostasis, aldehyde detoxification and stress tolerance.

Keywords: Abscisic acid; Aldehyde oxidases; Indoleacetic acid; Stress.

Figure 1. ABA and IAA biosynthesis.

(A) ABA precursor is synthesized from the methylerythritol phosphate (MEP) pathway. Enzymes are shown in red colour. BCH1/BCH2: β-carotene hydroxylases; ZEP: Zeaxanthin epoxidase; NSY: Neoxanthin synthase; NCED: 9-cis-epoxycarotenoid dioxygenase; XD: Xanthoxin dehydrogenase; ABAO: Abscisic aldehyde oxidase; CYP707A: ABA 8′-hydroxylase; ABH1: Phaseic acid reductase 1; ABAGT: ABA glucosyltransferase; βG: β-glucosidase; VDE: violaxanthin de-epoxidase, AOs: aldehyde oxidases were indicated with an asterisk (*). Adapted from Dejonghe, Okamoto & Cutler (2018); Song et al. (2020b); Finkelstein (2013). (B) ANT, anthranilate; IAA, indole-3-acetic acid; IAAld, indole-3-acetaldehyde; IAN, indole-3-acetonitrile; IGP, indole-3-glycerol phosphate; IND, indole; AAO, aldehydeoxidase; CYP79B2/3, cytochrome P450 monooxygenases2/3; IMI, amidase; INS, indole synthase; NIT, nitrilase; TAA, tryptophan aminotransferase; TRP3/TSA1, Trp synthase α-subunit; TRP2/TSB1, Trp synthase β-subunit; VAS1, pyridoxal phosphate-dependentaminotransferase1; YUC, YUCCA flavin-containing monooxygenase. Adapted from Kasahara (2016); Song et al. (2020a).