PtAPX9-PtLTPG14 modulates the AsA-GSH cycle for lipid mechanisms in poplar

Abstract

Ascorbate peroxidase (APX) is an essential antioxidant enzyme participating in cellular homeostasis by scavenging reactive oxygen species (ROS). Nevertheless, few reports were involved in the roles of poplar APX in lipid mechanism, especially in lipid peroxidation. This study identified 11 PtAPX genes from the poplar genome, and PtAPXs were clustered into five clades. The exon/intron distribution and conserved motif analysis showed that PtAPXs exhibit a comparatively well-preserved gene structure and motif composition in the same Clade. Collinearity investigation indicated segmental duplication is considered the main duplication form during the evolutionary process of PtAPX genes. Also, the superoxide dismutase (SOD), monodehydroascorbate reductase (MDHAR), and glutathione-disulfide reductase (GSR) involved in the redox metabolism were discovered from the interaction network with PtAPXs. In addition, a series of transcription factors (TFs), such as MYB, bHLH, WRKY, and NAC, were identified from the TF network with PtAPX genes. Gene expression patterns revealed that PtAPXs have different expression levels in various tissues and organs and are significantly affected by various abiotic stresses, including ABA, NaCl, and H2O2. The luciferase (LUC) complementation assay gave new visions into the PtAPX9-PtLTPG14 complex participating in lipid metabolism, especially in lipid peroxidation, thus maintaining cellular homeostasis. These discoveries provided a novel perspective for further functional study on the roles of PtAPX9 in lipid metabolism and ROS scavenging system.