Identification of alkaline salt tolerance genes in Brassica napus L. by transcriptome analysis

Abstract BackgroundSoil salt alkalization is one major abiotic factor reducing the productivity of crops worldwide, including rapeseed (Brassica napus L.), an indispensable oil crop and vegetable. The mechanism studies of alkali-salt-tolerance are helpful for the breeding of high resistant varieties and the expansion of the planting area. However, the study of the alkaline salt tolerance mechanism in rapeseed is limited. This study aimed to identify candidate genes related to the regulation of alkali salt tolerance in B. napus. ResultsIn the current study, B. napus line 2205 exhibited stronger tolerance to alkaline salt than B. napus line 1423. In line 2205, the lesser plasma membrane damage index, the accumulated osmotic adjustment substances, and higher antioxidant enzyme activities were contributed to alkaline tolerance. Ultrastructure observation found that the mesophyll cells of line 2205 had higher integrity compared with line 1423, further confirming that line 2205 suffered a lesser injury under alkali-salt stress. Transcriptome analysis showed that more genes responded to alkaline salt in line 2205, and the expressions of respective specific response genes were different in these two cultivars. The expression level of the line-1423-specific-response genes was lower in line 2205, which were primarily annotated to the cytosol, spliceosome, and ubiquitin-mediated proteolysis, whereas most of the specific response genes in line 2205 had a higher expression, which were mainly enriched in carbohydrate metabolism, photosynthetic processes, ROS regulating, and response to salt stress. It can be seen that the tolerance to alkaline salt is attributed to the high expression of some genes in these pathways. Based on these results, twelve cross-differentially expressed genes, including BnMDH2, BnGAPCs, BnACO1, BnGOXs, and BnGGTAs, were proposed as candidate genes for regulating alkali-salt tolerance in rapeseed.ConclusionsThe present study demonstrates that tolerant rapeseed exhibits superior physiological indicators and actively mobilizes genes involved in energy metabolism and ROS-related pathways to resist undesirable adverse signals from alkaline salts. The candidate genes provide reliable clues for further analysis of the resistance mechanism of rapeseed.