Involvement of Pyridoxine/Pyridoxamine 5′- Phosphate Oxidase (PDX3) in Ethylene-Induced Auxin Biosynthesis in the Arabidopsis Root
Gyuree Kim1,5, Sejeong Jang1,5, Eun Kyung Yoon1,3, Shin Ae Lee1,4, Souvik Dhar1, Jinkwon Kim1, Myeong Min Lee2, and Jun Lim1,*
1Department of Systems Biotechnology, Konkuk University, Seoul, Korea, 2Department of Systems Biology, Yonsei University,Seoul, Korea, 3Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, Singapore, 4Department of Agricultural Biology, National Institute of Agricultural Sciences, Wanju, Korea
*Correspondence: jlim@konkuk.ac.kr
Received August 29, 2018; Revised October 10, 2018; Accepted November 14, 2018.; Published online November 14, 2018.
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ABSTRACT
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.
Keywords:
Arabidopsis, auxin biosynthesis, ethylene, PDX3, PLP


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30 November 2018 Volume 41,
Number 11, pp. 933~992

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