Hydrogen Peroxide Response in Leaves of Poplar (Populus simonii × Populus nigra) Revealed from Physiological and Proteomic Analyses

Hydrogen peroxide (H(2)O(2)) is one of the most abundant reactive oxygen species (ROS), which plays dual roles as a toxic byproduct of cell metabolism and a regulatory signal molecule in plant development and stress response. Populus simonii × Populus nigra is an important cultivated forest species with resistance to cold, drought, insect and disease, and also a key model plant for forest genetic engineering. In this study, H(2)O(2) response in P. simonii × P. nigra leaves was investigated using physiological and proteomics approaches. The seedlings of 50-day-old P. simonii × P. nigra under H(2)O(2) stress exhibited stressful phenotypes, such as increase of in vivo H(2)O(2) content, decrease of photosynthetic rate, elevated osmolytes, antioxidant accumulation, as well as increased activities of several ROS scavenging enzymes. Besides, 81 H(2)O(2)-responsive proteins were identified in the poplar leaves. The diverse abundant patterns of these proteins highlight the H(2)O(2)-responsive pathways in leaves, including 14-3-3 protein and nucleoside diphosphate kinase (NDPK)-mediated signaling, modulation of thylakoid membrane structure, enhancement of various ROS scavenging pathways, decrease of photosynthesis, dynamics of proteins conformation, and changes in carbohydrate and other metabolisms. This study provides valuable information for understanding H(2)O(2)-responsive mechanisms in leaves of P. simonii × P. nigra.