Integrated transcriptome and metabolome analysis of salinity tolerance in chrysanthemum polyploids

Autopolyploids frequently exhibit improved tolerance to salt stress, and several studies have reported on the molecular mechanisms of salt tolerance in them. However, it's unclear if the salt - tolerance molecular mechanisms of autopolyploids in the same genus are consistent. In this experiment, chrysanthemum autopolyploids wilted less than parents under NaCl. After a 4-hour salt treatment, the activities of peroxidase, superoxide dismutase, and catalase in aututetraploid Chrysanthemum lavandulifolium (Fisch. ex Trautv.) Makino were 1.25, 1.31, and 1.23 times higher than in diploid, respectively. Similarly, autooctoploid Gongju [ C. morifolium (Ramat) Tzvel.] exhibited greater antioxidant enzyme activities than their tetraploid counterparts. Through transcriptome and metabolome analysis, we found that tetraploid C . lavandulifolium showed significant enrichment of differentially expressed genes and metabolites in glycerophospholipid metabolism, phenylalanine metabolism, and flavonoid/flavonol biosynthesis pathways compared to diploid C . lavandulifolium . In contrast, between tetraploid and autooctoploid Gongju, differentially expressed genes and metabolites were mainly enriched in terpenoid backbone biosynthesis, purine metabolism, and ABC transporter-related pathways. At the level of hormone regulation, the autooctoploid Gongju significantly upregulated the metabolic synthesis of abscisic acid (ABA) and jasmonic acid (JA), as well as the expression of downstream salt-tolerance-related genes, compared with the tetraploid. In contrast, the aututetraploid C . lavandulifolium significantly upregulated ABA biosynthesis and the expression of downstream salt-tolerance-related genes compared with the diploid. This reveals the differentiation in salt tolerance regulatory networks among autopolyploids of the genus Chrysanthemum . This distinction provides a foundation for the accurate selection of target genes aimed at enhancing salt tolerance in polyploid Chrysanthemumu • Polyploids chrysanthemum exhibit stronger tolerance to salt stress than their parents. • Octoploid Gongju enhances salt tolerance via ABA, JA, and antioxidant enzyme systems. • Tetraploid C. lavandulifolium enhances salt tolerance via ABA and antioxidant enzymes.