Waterlogging-responsive Genes Revealed by Transcriptome Sequencing in Leaves of Two Crabapple Species with Contrasting Waterlogging Tolerance

Crabapples ( Malus sp.) are ornamental woody plants that belong to the Rosaceae family. Flooding has severely hampered the growth and development of crabapple, and little is known about the molecular responses of crabapple to waterlogging tolerance. Cuttings of waterlogging-tolerant Malus hupehensis and waterlogging-intolerant Malus halliana received flooding treatment of 30 days and regular planting, respectively. Using transcriptome sequencing, we isolated 5703 and 2735 waterlogging-responsive genes from waterlogging-treated M. hupehensis and M. halliana leaves. Among these differentially expressed genes (DEGs), only 746 were shared by both. Several variables may explain the greater waterlogging tolerance of M. hupehensis : there were more waterlogging response genes related to carbohydrate and energy metabolism; signal transduction; antioxidation; lipid metabolism; protein and amino acid metabolism; and polysaccharide, cell wall, and cytoskeleton metabolism pathway in the waterlogged leaves of M. hupehensis than in M. halliana. In particular, the number of DEGs related to anaerobic metabolism, fatty acid metabolism, protein phosphorylation and dephosphorylation, γ -aminobutyric acid metabolism and cellulase, pectinase metabolism pathway in the flooded leaves of M. hupehensis was more than that in M. halliana. The alterations in gene expression patterns of the two crabapple species induced by waterlogging varied substantially. These outcomes pave the way for further studies into the functions of genes that may be involved in waterlogging tolerance in crabapples.