J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (5): 1241-1261.DOI: 10.1111/jipb.13439

• Molecular Physiology • Previous Articles     Next Articles

Sorbitol induces flower bud formation via the MADS‐box transcription factor EjCAL in loquat

Hong‐Xia Xu1, Dong Meng2,3, Qing Yang2,3, Ting Chen2,3, Meng Qi2,3, Xiao‐Ying Li1, Hang Ge1 and Jun‐Wei Chen1*   

  1. 1. Institute of Horticulture, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China;
    2. Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing 100000, China;
    3. College of Forestry, Beijing Forestry University, Beijing 100083, China
    *Correspondence: Jun‐Wei Chen (chenjunwei@zaas.ac.cn)
  • Received:2022-07-17 Accepted:2022-12-19 Online:2023-02-21 Published:2023-05-01

Abstract: Sorbitol is an important signaling molecule in fruit trees. Here, we observed that sorbitol increased during flower bud differentiation (FBD) in loquat (Eriobotrya japonica Lindl.). Transcriptomic analysis suggested that bud formation was associated with the expression of the MADS‐box transcription factor (TF) family gene, EjCAL. RNA fluorescence in situ hybridization showed that EjCAL was enriched in flower primordia but hardly detected in the shoot apical meristem. Heterologous expression of EjCAL in Nicotiana benthamiana plants resulted in early FBD. Yeast‐one‐hybrid analysis identified the ERF12 TF as a binding partner of the EjCAL promoter. Chromatin immunoprecipitation‐PCR confirmed that EjERF12 binds to the EjCAL promoter, and β‐glucuronidase activity assays indicated that EjERF12 regulates EjCAL expression. Spraying loquat trees with sorbitol promoted flower bud formation and was associated with increased expression of EjERF12 and EjCAL. Furthermore, we identified EjUF3GaT1 as a target gene of EjCAL and its expression was activated by EjCAL. Function characterization via overexpression and RNAi reveals that EjUF3GaT1 is a biosynthetic gene of flavonoid hyperoside. The concentration of the flavonoid hyperoside mirrored that of sorbitol during FBD and exogenous hyperoside treatment also promoted loquat bud formation. We identified a mechanism whereby EjCAL might regulate hyperoside biosynthesis and confirmed the involvement of EjCAL in flower bud formation in planta. Together, these results provide insight into bud formation in loquat and may be used in efforts to increase yield.

Key words: EjCAL, flower bud differentiation, hyperoside, loquat, sorbitol

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