Genome-wide analysis of autophagy-related gene family and PagATG18a enhances salt tolerance by regulating ROS homeostasis in poplar

Autophagy is the process by which intracellular components are delivered to lysosomes or vacuoles for degradation and recycling, which can promote the tolerance of organisms to biotic/abiotic stresses. However, autophagy-related genes (ATG) are not well studied in woody plants. Here, 48 ATG genes were identified in the poplar genome and divided into 14 subfamilies according to the phylogenetic tree. Collinearity analysis showed that 26 pairs of genes were derived by segmental duplication in poplars. The isogenous gene pairs of the ATG family between P. trichocarpa and other six species were analyzed by synteny analysis. Moreover, the ATG promoters contain a large number of phytohormone response elements and stress-response elements. Both phytohormone and salt treatments can induce the expression of PagATG18 subfamily genes. Overexpression of PagATG18a significantly improved the salt tolerance of poplar and reducing the oxidative damage of the membrane. Further research verified that PagATG18a interacted with the light-harvesting complex LHCB1 and APX2, indicating PagATG18a might be involved in regulating photosynthesis and antioxidant activity under stress. This study provides valuable information for further research on the functional characteristics of ATG genes in poplar and the theoretical basis for poplar stress resistance breeding.