Leaf senescence, the final developmental stage of plant leaves, involves chlorophyll breakdown and nutrient redistribution, directly affecting the postharvest quality of leafy vegetables. In crops like pakchoi (Brassica rapa subsp. chinensis), premature yellowing during storage greatly reduces market value. Brassinosteroids are essential hormones that regulate plant growth, but their dual role in promoting and delaying senescence remains controversial. Understanding how brassinosteroids interact with senescence-related genes can help maintain leaf vitality and prolong storage life. Due to these challenges, it is essential to investigate how transcription factors mediate brassinosteroid-regulated postharvest senescence in pakchoi.
A research team from the Jiangsu Academy of Agricultural Sciences and Nanjing Agricultural University has revealed how the transcription factor BrWRKY8 mediates 2, 4-EBR-induced delay of postharvest senescence in pakchoi. The study, published (DOI: 10.1093/hr/uhaf004) on January 6, 2025, in Horticulture Research, demonstrates that EBR maintains chlorophyll levels and inhibits senescence-associated genes through suppression of BrWRKY8. The discovery provides new molecular insights into brassinosteroid-regulated leaf aging and offers practical implications for improving the freshness and storage resistance of leafy vegetables.
Using transcriptome sequencing, the team examined pakchoi leaves treated with 1.5 μM EBR and identified over 9,800 differentially expressed genes, many related to chlorophyll metabolism and brassinosteroid pathways. Among them, BrWRKY8 showed strong induction during natural senescence but was markedly inhibited by EBR treatment. Functional assays confirmed that BrWRKY8 acts as a transcriptional activator localized in the nucleus and binds directly to W-box motifs in the promoters of BrSGR2 and BrCHI2, two genes involved in chlorophyll and brassinosteroid degradation, respectively. Overexpression of BrWRKY8 in Arabidopsis thaliana accelerated leaf yellowing and reduced chlorophyll and hormone levels, while its silencing in pakchoi delayed senescence and maintained higher chlorophyll and brassinosteroid contents. Exogenous EBR treatment further reversed the premature senescence phenotype caused by BrWRKY8 overexpression, confirming that EBR acts upstream of BrWRKY8 to regulate leaf longevity. Together, these results establish the BrWRKY8–BrSGR2/BrCHI2 module as a key component in EBR-mediated anti-senescence signaling.
“Our findings uncover BrWRKY8 as a pivotal transcription factor that integrates hormone signaling and gene expression to regulate postharvest leaf senescence,” said Pengxia Li, corresponding author of the study. “By understanding how 2,4-EBR suppresses BrWRKY8, we can provide a molecular basis for maintaining freshness in leafy vegetables. This regulatory model not only advances the fundamental knowledge of brassinosteroid function but also guides the development of genetic and hormonal strategies to prolong vegetable shelf life.”
The discovery of the BrWRKY8-mediated pathway provides a promising target for improving the postharvest storage quality of pakchoi and other leafy vegetables. Through genetic manipulation or optimized EBR treatment, producers can potentially extend the shelf life and reduce waste caused by premature yellowing. Moreover, this study establishes a theoretical foundation for breeding brassinosteroid-responsive, anti-senescence vegetable varieties. By integrating molecular regulation and practical preservation strategies, the findings could significantly contribute to sustainable vegetable production, cold-chain logistics, and consumer satisfaction in the fresh produce industry.
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Funding information
The work was supported by the National Natural Science Foundation of China (grant number 32001451), the Jiangsu Province Agricultural Independent Innovation Fund (grant number CX(22)1014), and the Key and General Programs of Modern Agriculture in Jiangsu Province (grant number BE2022368).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2024. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
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