Response Mechanisms to Flooding Stress in Mulberry Revealed by Multi-Omics Analysis

Abiotic stress, including flooding, seriously affects the normal growth and development of plants. Mulberry (Morus alba), a species known for its flood resistance, is cultivated worldwide for economic purposes. The transcriptomic analysis has identified numerous differentially expressed genes (DEGs) involved in submergence tolerance in mulberry plants. However, a comprehensive analyses of metabolite types and changes under flooding stress in mulberry remain unreported. A non-targeted metabolomic analysis utilizing liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted to further investigate the effects of flooding stress on mulberry. A total of 1,169 metabolites were identified, with 331 differentially accumulated metabolites (DAMs) exhibiting up-regulation in response to flooding stress and 314 displaying down-regulation. Pathway enrichment analysis identified significant modifications in many metabolic pathways due to flooding stress, including amino acid biosynthesis and metabolism and flavonoid biosynthesis. DAMs and DEGs are significantly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for amino acid, phenylpropanoid and flavonoid synthesis. Furthermore, metabolites such as methyl jasmonate, sucrose, and D-mannose 6-phosphate accumulated in mulberry leaves post-flooding stress. Therefore, genes and metabolites associated with these KEGG pathways are likely to exert a significant influence on mulberry flood tolerance. This study makes a substantial contribution to the comprehension of the underlying mechanisms implicated in the adaptation of mulberry plants to submergence.