Involvement of Pyridoxine/Pyridoxamine 5′- Phosphate Oxidase (PDX3) in Ethylene-Induced Auxin Biosynthesis in the Arabidopsis Root

  • Kim, Gyuree ;
  • Jang, Sejeong ;
  • Yoon, Eun Kyung ;
  • Lee, Shin Ae ;
  • Dhar, Souvik ;
  • Kim, Jinkwon ;
  • Lee, Myeong Min ;
  • Lim, Jun
  • Received : 2018.08.29
  • Accepted : 2018.10.10
  • Published : 2018.12.31


As sessile organisms, plants have evolved to adjust their growth and development to environmental changes. It has been well documented that the crosstalk between different plant hormones plays important roles in the coordination of growth and development of the plant. Here, we describe a novel recessive mutant, mildly insensitive to ethylene (mine), which displayed insensitivity to the ethylene precursor, ACC (1-aminocyclopropane-1-carboxylic acid), in the root under the dark-grown conditions. By contrast, mine roots exhibited a normal growth response to exogenous IAA (indole-3-acetic acid). Thus, it appears that the growth responses of mine to ACC and IAA resemble those of weak ethylene insensitive (wei) mutants. To understand the molecular events underlying the crosstalk between ethylene and auxin in the root, we identified the MINE locus and found that the MINE gene encodes the pyridoxine 5′-phosphate (PNP)/pyridoxamine 5′-phosphate (PMP) oxidase, PDX3. Our results revealed that MINE/PDX3 likely plays a role in the conversion of the auxin precursor tryptophan to indole-3-pyruvic acid in the auxin biosynthesis pathway, in which TAA1 (TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1) and its related genes (TRYPTOPHAN AMINOTRANSFERASE RELATED 1 and 2; TAR1 and TAR2) are involved. Considering that TAA1 and TARs belong to a subgroup of PLP (pyridoxal-5′-phosphate)-dependent enzymes, we propose that PLP produced by MINE/PDX3 acts as a cofactor in TAA1/TAR-dependent auxin biosynthesis induced by ethylene, which in turn influences the crosstalk between ethylene and auxin in the Arabidopsis root.


Arabidopsis;auxin biosynthesis;ethylene;PDX3;PLP

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Fig. 1. The mine mutant shows root-specific insensitivity to ACC.

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Fig. 2. The mine mutant exhibits normal growth responses to IAA.

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Fig. 3. The mine mutant shows aberrant expression of auxin maxima monitored by DR5 under ACC treatment.

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Fig. 4. Genetic analysis of ethylene-induced auxin biosynthesis in mine roots.

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Fig. 5. The mine mutant exhibits retarded root growth under normal growth conditions.

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Fig. 6. The MINE gene encodes the PNP/PMP oxidase, PDX3.

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Fig. 7. Ethylene-insensitive responses of mine roots are restored by IAA, but not by Trp.

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Fig. 8. A schematic model for the involvement of MINE/PDX3 in ethylene-induced auxin biosynthesis.


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Supported by : National Research Foundation