Na2CO3-responsive mechanism insight from quantitative proteomics and SlRUB gene function in Salix linearistipularis seedlings.

Mongolian willow (Salix linearistipularis) is a naturally occurring woody dioecious plant in the saline soils of northeastern China that has a high tolerance to alkaline salts. Although transcriptomics studies have identified a large number of salinity-responsive genes, the mechanism of salt tolerance in Mongolian willow is not clear. Here, we found that in response to Na2CO3 stress, Mongolian willow regulates osmotic homeostasis by accumulating proline and soluble sugars, and scavenges ROS by antioxidant enzymes and non-enzymatic antioxidants. Our quantitative proteomics study identified 154 salt-sensitive proteins mainly involved in maintaining the stability of the photosynthetic system and ROS homeostasis to cope with Na2CO3 stress. Among them, Na2CO3-induced rubredoxin (RUB) was predicted to be associated with 122 proteins for modulation of these processes. The chloroplast-localized SlRUB was highly expressed in leaves and significantly induced under Na2CO3 stress. Phenotypic analysis of overexpression, mutation, and complementation materials of RUB in Arabidopsis suggests that SlRUB is critical for the regulation of photosynthesis, ROS scavenging, and other metabolisms in the seedlings of Mongolian willow to cope with Na2CO3 stress. This provides more clues to better understand the alkali-responsive mechanism and RUB functions in the woody Mongolian willow.