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Scientia Silvae Sinicae ›› 2025, Vol. 61 ›› Issue (6): 130-138.doi: 10.11707/j.1001-7488.LYKX20240340

• Research papers • Previous Articles     Next Articles

Reasons for the Difficulty of Differentiation of Embryogenic Callus in Long-Term Subculture of Catalpa bungei

Shan Zhao1,Jing Dong1,Shuai Zheng1,Faju Chen1,2,Wen Liu1,2,Hongwei Liang1,2,*()   

  1. 1. College of Biology and Pharmacy, Three Gorges University Yichang 443002
    2. Key Laboratory of Plant Genetics and Germplasm Innovation in the Three Gorges Region Three Gorges University Yichang 443002
  • Received:2024-06-07 Online:2025-06-10 Published:2025-06-26
  • Contact: Hongwei Liang E-mail:lianghwcn@ctgu.edu.cn

Abstract:

Objective: This study aims to explore the mechanism of difficulty in differentiation and regeneration of embryogenic callus of Catalpa bungei under long-term subculture, so as to provide a theoretical basis for the differentiation and regeneration of somatic embryogenesis system and genetic stability of C. bungei. Method: The newly induced non-embryogenic callus, primary embryogenic callus and 7-year subcultured embryogenic callus were used as materials to analyze the cell ploidy, differentially expressed genes and endogenous hormone levels. Result: 1) Through chromosome counting, it was found that the chromosome number of the primary embryogenic callus maintained diploid status (2n = 40), while the chromosome number of the embryogenic callus continuously cultured for 7 years was doubled, and the chromosome number ranged from 80 to 162. The result of flow cytometry measurement showed that the DNA content of embryogenic callus that was cultured continuously for 7 years was 3 times higher than that of C. bungei seedlings, and the cell ploidy was hexaploid. 2) Through GO and KEGG enrichment analysis of transcriptome data, it was found that differentially expressed genes were significantly enriched in plant hormone activation signaling pathway, transcriptional regulation, MAPK signaling pathway, development process regulation and other pathways. Among them, SAUR, ARF, AUX/IAA and GH3 which respond to auxin signaling, abscisic acid receptor PYR/PYL, extracellular protein AGP, transcription factor ABI3 and other genes that promote somatic embryo differentiation were all down-regulated, while the expression of ethylene synthesis inhibitor ETO1 was up-regulated. 3) Endogenous hormone level analysis showed that the content of IAA and ABA in embryogenic callus that was cultured continuously for 7 years was significantly lower than that in newly induced embryogenic callus, which corresponded to the down-regulated expression of genes involved in plant hormone signal transduction. It is suggested that high levels of IAA and ABA may be the key to regulating somatic embryogenesis. Conclusion: In summary, it is speculated that chromosome doubling, abnormal expression of genes related to somatic embryogenesis and significant decrease of endogenous hormone levels in the embryogenic callus of C. bungei during long-term subculture may be the fundamental cause of its difficulty in differentiation and regeneration.

Key words: Catalpa bungei, embryogenic callus, chromosome doubling, transcriptome sequencing, endogenous hormones

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