Abstract: 【Objective】 To elucidate the molecular mechanism by which Brassica napus responds to long-term waterlogging stress at the seedling stage,and to screen for relevant important metabolic pathways and core genes. 【Methods】 The waterlogging-sensitive B. napus inbred line YZ59 was used as the research object. Seedling leaves under normal growth and under 7 d of waterlogging stress were subjected to transcriptome sequencing. Differentially expressed genes were screened,followed by GO （gene ontology） and KEGG （Kyoto encyclopedia of genes and genomes） enrichment analyses. 【Results】 A total of 3 085 differentially expressed genes were identified between the normal growth leaves and the 7 d waterlogged leaves,including 2 313 upregulated genes and 772 downregulated genes;among the 3 085 differentially expressed genes,312 transcription factors were identified,with 206 upregulated and 106 downregulated. The bHLH family transcription factors showed the largest number of upregulated genes （30）,while the MYB family transcription factors showed the largest number of downregulated genes （20）. GO enrichment analysis indicated that the differentially expressed genes were mainly enriched in the three primary categories：molecular function,cellular component,and biological process;the highest number of differentially expressed genes enriched in the fourth-level terms were DNA binding and RNA binding. KEGG enrichment analysis showed that differentially expressed genes were primarily enriched in the plant hormone signal transduction pathway,the MAPK signaling pathway,and the plant-pathogen interaction pathway;the vast majority of genes in the MAPK signaling pathway and the plant-pathogen interaction pathway were upregulated;in the plant hormone signal transduction pathway,both upregulated and downregulated genes were present,but the former outnumbered the latter. Separate analysis of the starch and sucrose metabolism pathway,as well as the glycolysis and gluconeogenesis pathways,revealed that many key genes were differentially expressed,with upregulation predominating. Long-term waterlogging promoted the conversion of D-glucose to D-glucose-6-phosphate and the conversion of D-fructose to D-fructose-6-phosphate,as well as the synthesis of trehalose,to maintain normal cellular life activities in the seedling B. napus;long-term waterlogging also accelerated the process of energy release through glycolysis and promoted the interconversion among acetate,acetaldehyde,and ethanol in the organism. 【Conclusion】 The response of seedling B. napus to long-term waterlogging stress is dominated by gene upregulation,with bHLH and MYB transcription factor families being the key regulatory factors;the glycolysis process plays a crucial role in the response of seedling B. napus to long-term waterlogging stress.

Key words: Brassica napus, Waterlogging stress, Transcriptome sequencing, bHLH transcription factor, MYB transcription factor, Enrichment analysis