Transcriptome profiling comparison between the salt sensitive and tolerant cultivars of sweet potato reveals the key regulatory pathways in response to high salt stress

Sweet potato ( Ipomoea batatas (L.) Lam.) is an important food crop with high nutritional and economic value. However, the mechanism regulating the resistance of different sweet potato varieties to salt stress is unclear. Here, a systematic was conducted with the salt sensitive variety YS25 and salt tolerant variety FMG in response to salt stress. Phenotypic and physiochemical analyses demonstrated that under salt stress condition, the growth of FMG was less affected. It showed more vigorous growth, accompanied with less chlorophyll loss and sodium, malondialdehyde (MDA) and H ₂ O ₂ accumulation, than did YS25. It also showed higher soluble sugar content and superoxide dismutase (SOD), guaiacol peroxidase (POD) and catalase (CAT) enzymatic activity. Further transcriptomic analyses respectively identified 7370 and 7068 differential expression genes (DEGs) in YS25 and FMG. Gene ontology (GO) term analyses revealed that they were significantly rich in the terms of "biological processes" and "molecular functions". Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses showed that DEGs in the salt tolerant variety FMG were significantly enriched in the zeatin biosynthesis pathway, the starch and sucrose metabolis pathway, the galactose metabolis pathway, the nitrogen metabolis pathway and the flavonoid biosynthesis pathway. Expressions of the key genes in these regulatory pathways were further confirmed with quantitative real-time polymerase chain reaction (qRT-PCR) assays in the salt sensitive sweet potato cultivar XGH and the salt tolerant cultivar QT. Our studies provide a novel approach to the mining of new gene targets usable for breeding of salt tolerant sweet potato.