SlSEC1- and SlSPY-mediated O-glycosylation stabilizes the transcription factor SlNOR to promote tomato fruit ripening

  • Plant Cell. 2026 Jun 2;38(6):koag144. doi: 10.1093/plcell/koag144.
Yu-Di Wu  1 ,  Ruo-Han Ou  1 ,  Can Yang  1 ,  Tong-Hao Cui  1 ,  Qian-Yu Wang  1 ,  Yu-Yang Mei  1 ,  Jia-Fei Qian  1 ,  Yi-Long Liu  1 ,  Yuan-Jiang Pan  2 ,  Zhi-Ping Deng  3 ,  Qing-Qiu Gong  4 ,  Jing Li  5 ,  Zhen-Yu Qi  6 ,  Yan-Na Shi  1 ,  Donald Grierson  1  7 ,  Bo Zhang  1 ,  Kun-Song Chen  1 ,  Xian Li  1 ,  Xiao-Yong Zhao  1
Affiliations
  • 1. Zhejiang Key Laboratory of Horticultural Crop Quality Improvement, Zhejiang University, Hangzhou 310058, P.R. China.
  • 2. Department of Chemistry, Zhejiang University, Hangzhou 310058, P.R. China.
  • 3. Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, P.R. China.
  • 4. School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, P.R. China.
  • 5. College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310058, P.R. China.
  • 6. Agricultural Experiment Station of Zhejiang University, Zhejiang University, Hangzhou 310058, P.R. China.
  • 7. Plant and Crop Sciences Division, School of Biosciences, University of Nottingham, Loughborough LE12 5RD United Kingdom.
PMID: 42135064 DOI: 10.1093/plcell/koag144
Abstract

O-glycosylation is a critical post-translational modification (PTM) that regulates protein function, yet its role in regulating plant transcription factors (TFs) remains poorly understood. Here, we report that O-glycosylation regulates NON-RIPENING (SlNOR), the master NAC TF controlling tomato (Solanum lycopersicum) fruit ripening. Using proteomic and interaction assays, we identified SlNOR as a substrate of 2 conserved nucleocytoplasmic O-glycosyltransferases: the O-GlcNAc transferase SlSEC1 and the O-fucosyltransferase SlSPY. We mapped 3 O-glycosylation sites (Thr93, Thr134, and Ser165) within the NAC domain of SlNOR. Biochemical assays suggested that O-glycosylation protects SlNOR from protein degradation. Accordingly, simultaneous mutagenesis of the 3 O-glycosylation sites reduced SlNOR protein stability and nuclear accumulation. Functionally, O-glycosylated SlNOR exhibited enhanced transcriptional activation of the ethylene biosynthesis genes (SlACS2 and SlACO1), which was corroborated by its increased DNA-binding affinity in electrophoretic mobility shift assays. Genetic evidence from CRISPR/Cas9-generated mutants revealed that loss of SlSEC1 or SlSPY reduces ethylene production and delays ripening, while the Slsec1-1 Slspy double mutant displayed a cooperative ripening delay and severe growth defects. Collectively, our findings uncover a key PTM-based regulatory mechanism in which SlSEC1/SlSPY-mediated O-glycosylation enhances SlNOR stability and transcriptional activity, thereby coupling a master transcriptional regulator to ethylene biosynthesis for the control of fruit ripening.

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