Comparative proteomic analysis of parasitic loranthus seeds exposed to dehydration stress

Abstract

Parasitic loranthus [Taxillus chinensis (DC.) Danser] is an important medicinal plant that produces recalcitrant seeds that are sensitive to dehydration. Desiccation tolerance is critical for the survival of recalcitrant seeds in low-moisture environments. Clarifying how these seeds respond to desiccation is important for long-term conservation. Thus, the viability, germination, microstructure, and antioxidant enzyme activities of dehydrated parasitic loranthus seeds were investigated. Diverse organelles were degraded or deformed during dehydration treatments. Additionally, superoxide dismutase and catalase activities gradually decreased in response to desiccation stress. A proteomic analysis involving TMT-labeling and LC–MS/MS were performed. A total of 1479 proteins were identified, of which 141 were differentially expressed proteins (DEPs) at 16 and 36 h after initiating the dehydration treatments. A functional annotation based on gene ontology revealed that the DEPs were mainly localized in chloroplasts and were related to energy metabolism, responses to stimuli, and the regulation of biological processes. A KEGG pathway enrichment analysis determined that several of the identified proteins were associated with signal transductions, photosynthesis, and glycolysis/gluconeogenesis. The results suggest that the efficient removal of excessive ROS amounts may be crucial for promoting parasitic loranthus seed germination under dehydration stress conditions. A series of candidate dehydration stress-related proteins were identified and may be relevant for enhancing the dehydration tolerance of the recalcitrant seeds. To the best of our knowledge, this is the first study to elucidate the possible molecular mechanisms underlying the sensitivity of recalcitrant parasitic loranthus seeds to dehydration via a proteomic analysis involving TMT-labeling.