The Aldehyde Dehydrogenase Superfamily in Brassica napus L.: Genome-Wide Identification and Expression Analysis Under Low-Temperature Conditions

The Aldehyde Dehydrogenase (ALDH) superfamily comprises a group of NAD⁺ or NADP⁺-dependent enzymes that play essential roles in responding to abiotic stresses in plants. In <i>Brassica napus</i> L., however, the increasing frequency of extremely low temperatures during winter in recent years has significantly affected both yield and quality. This study conducted a genome-wide screening of <i>ALDH</i> superfamily genes, analyzing their gene structures, evolutionary relationships, protein physicochemical properties, and expression patterns under low-temperature stress to explore the function of the <i>ALDH</i> superfamily gene in cold tolerance in <i>Brassica napus</i> L. A total of six <i>BnALDH</i> genes with significant differences in expression levels were verified utilizing quantitative real-time polymerase chain reaction (qRT-PCR), revealing that <i>BnALDH11A2</i>, <i>BnALDH7B2</i>, <i>BnALDH3F5</i>, <i>BnALDH12A3</i>, <i>BnALDH2B6</i>, and <i>BnALDH7B3</i> all exhibited higher expression in cold-tolerant material 24W233 compared with cold-sensitive material 24W259. Additionally, a single nucleotide polymorphism (SNP) in the <i>BnALDH11A2</i> promoter region shows differences between the cold-tolerant (24W233) and the cold-sensitive (24W259) <i>Brassica napus</i> varieties, and it may be associated with the cold tolerance of these two varieties. This comprehensive analysis offers valuable insights into the role of <i>ALDH</i> family genes in low-temperature stress adaptation in <i>Brassica napus</i> and offers genetic resources for the development of novel cold-tolerant cultivars.