Fig. 4

The interaction among ABA, auxin, and GA in regulating strawberry and tomato fruit development. A A diagram of strawberry fruit illustrating the regulatory mechanism during fruit ripening. In the achene, the expression of ABA biosynthesis gene (FaNCED6) increases, and the expression of ABA metabolism gene (FaCYP707A4, FaCYP722A) decreases, which resulted in a high ABA level. On the other hand, the expression of FaPIN2/3/5 and FaYUC1/2/10/11 decreases, which resulted in a reduced auxin and GA level. The feedforward loop of ABA level was activated, and the ripening related transcription factors (MYB79, MYB10) were activated to ensure fruit firmness and anthocyanin biosynthesis. As fruit ripens, JA level accumulates to ensure flavor formation. B In tomato, seeds are the site of auxin production. Auxin was also transported to the surrounding tissues to stimulate fruit growth. However, during fruit ripening, SlEIN3 and SlTAGL1, activate ethylene production and form a positive feedback circuit. SlEIN3 and SlTAGL1 form a complex and promote fruit ripening by regulating transcription factors SlCRTISO, SlPL, SlEXP1, SlCEL2 etc. On the other hand, the expression of SlCRTISO, SlPL, SlEXP1 and SlCEL2 is also related to ethylene production. However, whether there is a direct regulation is not clear. Adapted from (Kang et al. 2013a; Liao et al. 2018; Cao et al. 2020; Chen et al. 2020; Li et al. 2022)