N-glucosyltransferase GbNGT1 from ginkgo complements the auxin metabolic pathway

Qinggang Yin; Jing Zhang; Shuhui Wang; Jintang Cheng; Han Gao; Cong Guo; Lianbao Ma; Limin Sun; Xiaoyan Han; Shilin Chen; An Liu

doi:10.1038/s41438-021-00658-0

N-glucosyltransferase GbNGT1 from ginkgo complements the auxin metabolic pathway

Hortic Res. 2021 Nov 1;8(1):229. doi: 10.1038/s41438-021-00658-0.

Authors

Qinggang Yin^{1

2}, Jing Zhang¹, Shuhui Wang¹, Jintang Cheng¹, Han Gao¹, Cong Guo¹, Lianbao Ma³, Limin Sun⁴, Xiaoyan Han⁵, Shilin Chen¹, An Liu⁶

Affiliations

¹ Key Laboratory of Beijing for Identification and Safety Evaluation of Chinese Medicine, Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, China.
² Artemisinin Research Center, China Academy of Chinese Medical Sciences, Beijing, 100700, China.
³ Institute of Ginkgo, Pizhou, Jiangsu, 221300, China.
⁴ State Forestry and Grassland Administration Key Laboratory of Silviculture in downstream areas of the Yellow River, College of Forestry, Shandong Agricultural University, Tai'an, 271000, Shandong, China.
⁵ Beijing Botanical Garden, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
⁶ Key Laboratory of Beijing for Identification and Safety Evaluation of Chinese Medicine, Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, China. aliu@icmm.ac.cn.

Abstract

As auxins are among the most important phytohormones, the regulation of auxin homeostasis is complex. Generally, auxin conjugates, especially IAA glucosides, are predominant at high auxin levels. Previous research on terminal glucosylation focused mainly on the O-position, while IAA-N-glucoside and IAA-Asp-N-glucoside have been neglected since their discovery in 2001. In our study, IAA-Asp-N-glucoside was found to be specifically abundant (as high as 4.13 mg/g) in the seeds of 58 ginkgo cultivars. Furthermore, a novel N-glucosyltransferase, termed GbNGT1, was identified via differential transcriptome analysis and in vitro enzymatic testing. It was found that GbNGT1 could catalyze IAA-Asp and IAA to form their corresponding N-glucosides. The enzyme was demonstrated to possess a specific catalytic capacity toward the N-position of the IAA-amino acid or IAA from 52 substrates. Docking and site-directed mutagenesis of this enzyme confirmed that the E15G mutant could almost completely abolish its N-glucosylation ability toward IAA-Asp and IAA in vitro and in vivo. The IAA modification of GbNGT1 and GbGH3.5 was verified by transient expression assay in Nicotiana benthamiana. The effect of GbNGT1 on IAA distribution promotes root growth in Arabidopsis thaliana.