Overexpression of CsPP2-A1 in cucumber enhanced salt tolerance by participating ABA-JA signaling pathway and antioxidant system

Phytolectin PP2 mainly exists in the phloem, and studies have shown that PP2 has the function of stress defense, especially against biotic harm brought from pests and diseases. According to the proteomic analysis of Cucumis sativus phloem sap in our previous research, a detected increased expression of PP2-A1 in cucumber in response to salinity indicated that PP2-A1 might be relevant to plant salt tolerance. In this paper, the expression of CsPP2-A1 assayed by qRT-PCR proved that the CsPP2-A1 could be induced in cucumber by a variety of biotic, abiotic, or phytohormones stresses. Moreover, the CsPP2-A1 gene was cloned and transferred into Arabidopsis and cucumber separately. The obtained CsPP2-A1 overexpressing (OE) Arabidopsis and cucumber phenotypically exhibited greater resistance to saline stress than the WT plants. Furthermore, the physiological experiments showed that the CsPP2-A1-OE plants possessed lower MDA contents and higher antioxidant enzyme activities (CAT, POD, and SOD) than wild-type (WT) plants. Meanwhile, transcriptome sequencing assay found that 2256 genes were differently expressed in CsPP2-A1-OE cucumber. Most of the differentially expressed genes (DEGs) were mainly enriched in the MAPK pathway, ABA, and JA signaling pathway and participated in stress adaptation and response. All the evidence indicated that CsPP2-A1 was engaged in plant salinity adaption and the salt tolerance enhancement might involve in the ABA-JA signaling pathway and the antioxidant system.