MdGATA15 regulates MdANR to promote the synthesis of procyanidin and enhance the sunburn resistance of apple fruit

• The key transcription factor GATA15, involved in the flavonoid biosynthesis pathway, was identified based on transcriptomic data. • Apple peels overexpressing MdGATA15 TF were less sunburned. • The overexpression of MdGATA15 TF resulted in a significant increase in procyanidin content. • The MdGATA15 protein specifically binds to the ANR promoter, a crucial gene involved in procyanidin biosynthesis, thereby enhancing the transcriptional activation of procyanidin expression. Bagging apples can enhance fruit appearance and quality by reducing pest and disease damage. However, upon removal of the fruit bag, apples become susceptible to photodamage and heat stress, potentially resulting in sunburn symptoms. In this study, we examined ‘Ruixiang Hong’ apples post-bag removal and observed that mild photodamage preserved the cellular structure of pericarp tissue and showed low antioxidant enzyme activity. In contrast, severe injury led to cellular disorganization and dehydration in the pericarp, triggering increased antioxidant enzyme activity as a protective response. We identified a transcription factor (TF), MdGATA15, from previous transcriptomic and metabolomic datasets that appeared relevant to sunburn mitigation. To elucidate the role of MdGATA15 in sunburn response, we introduced this TF into plants through both transient and stable transformation methods. Subsequently, we measured flavonoid content after exposing the plants to intense light and high temperature. All three sets of transgenic materials exhibited increased content of most flavonoids in the overexpression plants compared with the control, with a significant increase in procyanidin content. Further analysis revealed that MdGATA15 bound to the promoter of MdANR , a key gene involved in procyanidin biosynthesis, thereby upregulating anthocyanin expression. These findings suggest that MdGATA15 may alleviate sunburn symptoms in apple peels.