Transcriptomic and metabolomic analyses reveals the importance of ethylene networks in mulberry fruit ripening

Mulberry (Morus alba L.) is a climacteric and highly perishable fruit. Ethylene has been considered to be an important trigger of fruit ripening process. However the role of ethylene in mulberry fruit ripening process remains unclear. In this study, an integrative analysis of metabolome and transcriptome data acquired from mulberry fruit along with the physiological changes that accompany the fruit ripening processes were analyzed. This study unveil changes in the accumulation of specific metabolites at different stages of fruit development and ripening process were strongly correlated with transcriptional changes as well as the underlying physiological changes and development of taste conferring biomolecules. Mulberry fruit ripening was highly associated with endogenous ethylene production and further exogenous ethylene application assisted the ripening process. Transcriptomic analysis revealed that diverse ripening-related genes involved in sugar and anthocyanin biosynthesis and cell wall modification pathway genes were differentially expressed. Network analysis of transcriptomic and metabolomic data have shown that,many transcription factors and ripening-related genes are involved and among which ethylene-responsive transcription factor 3 (MaERF3) plays a crucial role in ripening process. Further the role of MaERF3 in ripening process was experimentally proven in a transient overexpression assay in apple. Altogether our study shows that ethylene plays a vital role in modulating mulberry fruit ripening. The implications of this study in the genetic manipulation of mulberry fruit for effective breeding and better post-harvest management are discussed.