OsSSID6 Negatively Regulates Salt Stress Tolerance in Rice (Oryza Sativa L.) via Metabolic Pathways and ROS Scavenging

Soil salinization is becoming a huge threat to reducing productivity of rice (Oryza sativa L.) around the world. Previous studies have found that some Domain of unknown function (DUF) proteins play an essential role in the growth and development of plants. The DUF936 family is reported to respond to abiotic stresses, but the specific molecular mechanisms of its members remain elusive. In this study, OsSSID6 (Salt-Stress Induced DUF936 protein) is found at the cell membrane and the protein's expression could be affected by several abiotic stresses. The CRISPR/Cas9 knockout lines increased salt tolerance in rice, whereas the overexpression lines showed more sensitivity. And meanwhile the similar changes of ROS-scavenging capacity were observed both in knockout and overexpression lines. Transcriptome analysis identified that the expression of genes linked to multiple metabolic pathways, including phenylpropanoid and flavonoid biosynthesis, and stress response, was significantly up-regulated in KO lines. Our findings reveal that OsSSID6 gene modulates rice salt stress tolerance by orchestrating a network of metabolic pathways, including those involved in the reactive oxygen species (ROS) scavenging system, phenylpropanoid and flavonoid biosynthesis and stress response-related mechanism. sThese results provide important information for engineering salt-tolerant crops.