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Scientia Silvae Sinicae ›› 2026, Vol. 62 ›› Issue (6): 166-177.doi: 10.11707/j.1001-7488.LYKX20250570

• Research papers • Previous Articles    

Construction of Tetraploid Olive (Olea europaea) and Identification and Expression Analysis of Key Genes in the EXP Family for the Cell Enlargement Phenotype

Yufei Li1,Gang Yi1,Shuyuan Li1,Qizhen Cui1,Yutong Fan1,Guodong Rao1,2,*()   

  1. 1. State Key Laboratory of Tree Genetics and Breeding Research Institute of Forestry, Chinese Academy of Forestry Beijing 100091
    2. Co-innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University Nanjing 210037
  • Received:2025-09-17 Revised:2025-12-13 Online:2026-06-10 Published:2026-06-13
  • Contact: Guodong Rao E-mail:rgd@caf.ac.cn

Abstract:

Objective: This study aims to generate tetraploid olive plants, analyze their phenotypic differences from wild-type diploids, and explore the genetic regulatory mechanism underlying the cell enlargement phenotype in the tetraploids. Method: Tetraploid induction was performed using a colchicine and oryzalin mixture via a droplet application. Ploidy was rapidly identified by flow cytometry. Karyotype analysis was performed using improved phenol fuchsin staining. Leaf cross-sections of tetraploid plants were made using vibratome sectioning, and observed after toluidine blue staining. Leaf epidermal cells of tetraploids were examined by PI staining. Gene expression profiling and differentially expressed genes (DEGs) enrichment analysis of leaves of different ploidy plants were conducted using the Illumina platform. Based on the T2T high-quality olive genome, EXP gene family members were identified and characterized using Blastp, HMM, ProtParam, Cello version 2.5, MEGA11, AlphaFold3.0, SAVES, and PyMOL, and their expression patterns were further elucidated. Result: A total of 23 tetraploid olive plants were obtained, with an induction efficiency of 24.46%. Compared to diploids, tetraploids exhibited a cell enlargement phenotype, with significantly enlarged epidermal cells and stomata (P<0.000 1). RNA-seq identified 4 743 DEGs (2 371 up-regulated and 2 372 down-regulated). Through differential gene expression analysis, the auxin signaling pathway closely associated with cell enlargement was significantly enriched. Two markedly upregulated EXP members were identified and further validated by qRT-PCR. A comprehensive genome-wide analysis of the EXP gene family was completed. Conclusion: The EXP gene family is closely associated with tetraploid cell enlargement, laying a foundation for further exploration of the gigas phenotype in polyploids in the future.

Key words: Olea europaea, polyploid, cell enlargement, transcriptome, EXP gene family

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