Transcriptome and Proteome Analysis Identifies Salt Stress Response Genes in Bottle Gourd Rootstock-Grafted Watermelon Seedlings

Soil salinization poses a huge challenge to the development of agriculture and seriously decreases crop yield and quality. In recent years, grafting has become one of the key agronomic techniques used to enhance plant abiotic stress tolerance. In this study, we found that watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] grafted onto bottle gourd (Lagenaria siceraria Standl.) significantly enhanced salt tolerance. Transcriptome analysis revealed that a total of 8462 differentially expressed genes (DEGs) were identified, and the number of up- and down-regulated genes were 3207 and 5255, respectively. The DEGs in the bottle gourd rootstock-grafted plants were mainly involved in carbon metabolism, photosynthesis, and plant hormone signal transduction. Furthermore, proteome analysis identified 28 differently expressed proteins (DEPs) in bottle gourd rootstock-grafted plants under salt stress. These DEPs were closely associated with amino acid and protein synthesis, photosynthesis, mitochondrial metabolism and carbon metabolism, and stress defense. Combined transcriptome and proteome analyses showed that salt stress-responded genes in bottle gourd rootstock-grafted watermelon seedlings were mainly involved in plant hormone signal transduction, photosynthesis, and amino acid synthesis pathways.