REM Gene Family in Sugar Beet and Functional BvREM12 in Salt Stress Tolerance
Soil salinization acts as a major abiotic stress and severely hampers global agricultural productivity. Elucidating the molecular mechanisms underlying plant salt tolerance is of great significance for crop improvement. Remorin (REM) proteins are plant-specific membrane marker proteins that play a key role in stress signaling; however, their function in the salt tolerance response of sugar beet remains unclear. In this study, 14 BvREM gene family members were identified. Phylogenetic analysis revealed that this family can be divided into five subgroups and exhibits significant interspecies collinearity with Arabidopsis. Transcriptomic analysis showed that several BvREM genes were up-regulated under salt stress, with BvREM12 displaying greater expression fold change than most other family members. Using sugar beet line M14 as the gene resource material, we explored the potential function and proposed a working regulatory model for candidate gene BvREM12 in salt stress response. Subcellular localization results indicated that the BvREM12 protein is localized to the cell membrane and nucleus. Overexpression of BvREM12 significantly increased biomass accumulation in Arabidopsis, elevated antioxidant enzyme activities, decreased MDA levels, and increased proline content; a high K+/Na+ ratio was maintained, whilst Ca2+ levels were significantly higher than in the Col-0. Furthermore, qRT-PCR analysis revealed that several key salt-responsive genes were significantly up-regulated under salt stress. In summary, BvREM12 integrates the ‘Ca2+-SOS3-SOS2-SOS1’ signaling pathway with the ‘H+-ATPase-AKT1’ ion transport system to synergistically regulate Na+ efflux and K+ influx, thereby maintaining cellular ion homeostasis and redox balance, and significantly enhancing the plant salt tolerance. This study systematically characterized the sugar beet BvREM gene family and functionally dissected BvREM12. Different from previous studies on REM proteins mainly focusing on ROS scavenging at plasma membrane nanodomains, our work reveals that BvREM12, which is dual-localized to the plasma membrane and nucleus, coordinates the Ca2+-dependent SOS signaling cascade and H+-ATPase-AKT1 ion transport system to jointly maintain ion homeostasis and redox balance under salt stress. This work provides candidate genes and a mechanistic reference for molecular breeding of salt-tolerant sugar beet.