Physiological and Transcriptomic Insights into Mechanisms of Salt Tolerance in the Leaves and Roots of the Halophyte Suaeda japonica Makino Under High Salinity Stress
Shinta Shinta, Kristine Mae Y. Bentoy, Anisa Nazera Fauzia, Mami Nampei, Nguyen Manh Linh, Akihiro Ueda
Abstract
Abstract Suaeda japonica Makino, a succulent euhalophyte from the Chenopodiaceae family, grows naturally in Japan and is presumed to exhibit high salt tolerance. However, the molecular mechanisms underlying its salinity tolerance remain poorly understood. This study aimed to examine the physiological responses of S. japonica to varying NaCl concentrations, perform transcriptome profiling of its leaves and roots under 600 mM NaCl exposure, and identify key genes involved in salt tolerance. S. japonica exhibited remarkable tolerance to extreme salinity levels of up to 600 mM for 28 days. Physiological analysis revealed that salinity stress led to increased Na + , soluble sugars, and proline; increased antioxidant enzyme activities; and decreased malondialdehyde (MDA) concentrations in the leaves, indicating a protective role for osmotic regulation, reactive oxygen species (ROS) scavenging, and protection of cellular macromolecules in S. japonica under high salinity. De novo RNA-seq analysis detected 8695 and 9424 differentially expressed genes (DEGs) in the leaves and roots, respectively. Salinity-responsive transcription factors including bHLH, AP2-EREBP, bZIP, WRKY, NAC, HSF, and MYB have been identified. Additionally, DEGs related to the ABA signaling pathway, ion channels/transporters, Ca 2+ signaling, aquaporins, ABC transporters, starch and sucrose metabolism, proline biosynthesis, LEA proteins, and ROS scavenging were significantly expressed in both the leaves and roots, suggesting that these may be the major protective mechanisms to high salinity stress in S. japonica . This study provides a new perspective on the molecular mechanisms underlying salinity tolerance in S. japonica and establishes a foundation for future research.