LcERF2 modulates cell wall metabolism by directly targeting a UDP‐glucose‐4‐epimerase gene to regulate pedicel development and fruit abscission of litchi

• Published in: The Plant journal : for cell and molecular biology 2021-05, Vol.106 (3), p.801-816
• Main Authors: Yi, Jun‐Wen, Wang, Yi, Ma, Xiao‐Sha, Zhang, Jie‐Qiong, Zhao, Ming‐Lei, Huang, Xu‐Ming, Li, Jian‐Guo, Hu, Gui‐Bing, Wang, Hui‐Cong
• Format: Article
• Language: English
• Subjects: Abscission; APETALA2/ethylene‐response factor; Arabidopsis thaliana; cell wall metabolism; Cell walls; Electrophoretic mobility; Epimerase; fruit abscission; Fruit crops; Fruit set; Fruits; Galactose; Gene expression; Glucose; Hexoses; Homology; Litchi chinensis; Metabolism; Pectin; pedicel development; Plant growth; Transcriptomes; UDP‐glucose‐4‐epimerase gene; Yeasts
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.15201

SUMMARY Elucidating the biochemical and molecular basis of premature abscission in fruit crops should help develop strategies to enhance fruit set and yield. Here, we report that LcERF2 contributes to differential abscission rates and responses to ethylene in Litchi chinensis (litchi). Reduced LcERF2 expression in litchi was observed to reduce fruit abscission, concurrent with enhanced pedicel growth and increased levels of hexoses, particularly galactose, as well as pectin abundance in the cell wall. Ecoptic expression of LcERF2 in Arabidopsis thaliana caused enhanced petal abscission, together with retarded plant growth and reduced pedicel galactose and pectin contents. Transcriptome analysis indicated that LcERF2 modulates the expression of genes involved in cell wall modification. Yeast one‐hybrid, dual‐luciferase reporter and electrophoretic mobility shift assays all demonstrated that a UDP‐glucose‐4‐epimerase gene (LcUGE) was the direct downstream target of LcERF2. This result was further supported by a significant reduction in the expression of the A. thaliana homolog AtUGE2‐4 in response to LcERF2 overexpression. Significantly reduced pedicel diameter and enhanced litchi fruit abscission were observed in response to LcUGE silencing. We conclude that LcERF2 mediates fruit abscission by orchestrating cell wall metabolism, and thus pedicel growth, in part by repressing the expression of LcUGE. Significance Statement This study shed light upon the critical role of LcERF2 in regulating organ abscission by repressing the expression of LcUGE and thus inhibiting cell wall biosynthesis and organ growth. In addition, our work revealed the role of LcUGE in pedicel development and fruit abscission in litchi, and demonstrated that LcERF2 repressed the expression of LcUGE by binding to a region 800–850 bp upstream.