Genome-wide and transcriptome-wide identification of the APX gene family in rapeseed (Brassica napus L.) and their expression features under low temperature stress

Ascorbate peroxidase (APX) is a crucial H₂O₂ scavenger that utilizes ascorbic acid as an electron donor and plays a significant role in plant stress resistance. This study aims to identify and characterize the Brassica napus L. APX gene family through genome and transcriptome sequencing, while also revealing their expression profile under low-temperature stress via transcriptome and proteome analysis. The results indicate the presence of 18 genes with three different conserved domains distributed in Brassica napus L., which can be classified into three major branches based on phylogenetic analysis. Eleven members were predicted to have the low-temperature response component (LTR). Most APX genes exhibit up-regulated transcriptional expression under low temperature stress, particularly APX2, APX4, APX12, and APX18. In terms of proteomics data, only six members (APX2, APX4, APX8, APX12, APX17, and APX18) showed temporal specificity in their expression patterns. Therefore, this study provides valuable insights into the complexity of the APX family in the functional characterization of its genes for future research.