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Preliminary study on the regulation of organ size and Sclerotinia sclerotiorum resistance by BnKIX8 in rapeseed (Brassica napus L.)

Luo Li-Ya,Ma Wu-Hui,Yang Long,Zhu Pei,Li Yan,Xu Ben-Bo,Zhang Xue-Kun,Xu Jin-Song*   

  1. College of Agronomy, Yangtze University / Key Laboratory of Green and Efficient Crop Production in the Middle Reaches of Yangtze River, Ministry of Agriculture and Rural Affairs / Hubei Key Laboratory of Waterlogging Disaster and Agricultural Use of Wetland, Jingzhou 434025, Hubei, China
  • Received:2026-03-02 Revised:2026-07-15 Accepted:2026-07-15 Published:2026-07-23
  • Supported by:
    This study was supported by the Major Projects of Agricultural Biology Breeding of China (2023ZD04042).

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Abstract: In crop production, high-yield potential and disease resistance are often difficult to synergistically improve. Exploring the functions and molecular mechanisms of BnKIX8 homologous copies in the growth, development, and Sclerotinia sclerotiorum resistance of Brassica napus is therefore of great significance for the coordinated improvement of single-plant yield and disease resistance. In this study, Arabidopsis thaliana AtKIX8 was used as the reference gene to identify BnKIX8 homologous copies in B. napus, and their expression patterns were analyzed. CRISPR-Cas9 technology was used to generate loss-of-function mutants of BnKIX8s. Their functions were clarified by comparing agronomic traits and S. sclerotiorum resistance between homozygous mutants and wild-type plants, and the underlying molecular mechanisms were preliminarily explored through transcriptome analysis. The results were as follows: (1) Four homologous copies of BnKIX8 were identified in B. napus. BnKIX8.A7 and BnKIX8.C7 were expressed at all 18 sampling points, with high expression levels in siliques and seeds, whereas no expression of BnKIX8.A1 or BnKIX8.C1 was detected. (2) Homozygous T-DNA-free single mutants, bnkix8.a7 and bnkix8.c7, and the double mutant bnkix8.a7bnkix8.c7 were successfully obtained through CRISPR-Cas9-mediated gene editing. Phenotypic analysis showed that, compared with the wild type, the bnkix8s mutants had significantly increased flower size, silique length, seed size, and 1000-seed weight, as well as significantly higher seed germination and vigor indices. The double mutant showed an additive phenotype, indicating functional redundancy between BnKIX8.A7 and BnKIX8.C7 in regulating rapeseed growth and development. (3) Evaluation of S. sclerotiorum resistance showed that, at 36 and 48 h post-inoculation, lesion areas in the bnkix8s mutants were significantly larger than those in the wild type, suggesting that BnKIX8.A7 and BnKIX8.C7 positively regulate resistance to S. sclerotiorum. (4) KEGG enrichment analysis of transcriptome data indicated that, under normal growth conditions, BnKIX8.A7 and BnKIX8.C7 may contribute to the growth–defense balance by influencing IAA and JA signal transduction pathways. At 24 h post-inoculation with S. sclerotiorum, BnKIX8.A7 and BnKIX8.C7 may participate in the resistance response by affecting α-linolenic acid metabolism and thiamine metabolism pathways. This study provides candidate pathways and genetic resources for further elucidating the functions of BnKIX8s and offers a theoretical basis for breeding high-yield and disease-resistant rapeseed varieties.

Key words: Brassica napus, BnKIX8, CRISPR-Cas9, Sclerotinia sclerotiorum, transcriptome

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