Sucrose mediates moderate salinity-promoted primary root growth in rapeseed

Soil salinization is an escalating global challenge that significantly hampers plant growth and agricultural yield. The root system can directly sense and respond to salinity, but little is known about how primary roots respond to salt stress in rapeseed. In most non-halophytes, moderate salt stress inhibits or does not affect the growth of primary root. Here, we surprisingly observed that moderate salt stress (50 mM NaCl) promotes the growth of primary root in rapeseed. In addition, rapeseed subjected to moderate salt stress accumulated less reactive oxygen species (ROS) and proline compared to plants subjected to high salt stress. Further transcriptomic analysis revealed that carbohydrate metabolism-related genes were predominantly enriched in differentially expressed genes (DEGs) under moderate salt stress, indicating that carbohydrate metabolites are involved in moderate salt stress-promoted primary root growth. Indeed, exogenous sucrose treatment restored the moderate salt stress-promoted primary root growth and changed the expression patterns of moderate salt stress responsive genes in rapeseed. This study reveals the specific response of primary root to moderate salt stress in rapeseed and further demonstrates that sucrose is responsible for promoting the primary root growth under moderate salt stress.