MicroRNA156-SPL13B Module Induces Parthenocarpy Through the Gibberellin Pathway

Fruit development typically follows pollination and fertilisation. However, parthenocarpy, the formation of seedless fruits, represents an alternative pathway. The fruit that grows from the ovary under unpollinated and/or unfertilised conditions is termed parthenocarpic. This trait is not only desirable to consumers but also contributes to yield stability under adverse environmental conditions. In this study, we demonstrate that overexpression of miR156h regulates parthenocarpy under unpollinated conditions via a gibberellic acid (GA)-dependent pathway. MdSPL13B was found to be involved in MdmiR156h-modulated GA accumulation and parthenocarpy through directly binding to the promoters of MdKO, MdKAO2 and MdGA20ox. Furthermore, MdSPL13B was able to indirectly promote GA deactivation by binding to the promoter of MdMSI1, which mediates the histone modification of MdGA2ox8 and MdSPY. This study provides novel insight into the miR156-SPL-GA regulatory module in parthenocarpy.