iTRAQ-based quantitative proteomic analysis reveals new metabolic pathways responding to chilling stress in maize seedlings.

Unlabelled: To date, transcriptome profile analysis of maize seedlings in response to cold stress have been well documented; however, changes in protein species abundance of maize seedlings in response to cold stress are still unknown. Herein, leaves from the maize inbred line W9816 (a cold-resistance genotype) were harvested at three-leaf stage, and were used to identify the differential abundance protein species (DAPS) between chilling stress (4°C) and control conditions (25°C). iTRAQ-based quantitative proteomic were used in this study. As a result, 173 DAPS were identified after chilling stress. Bioinformatic analysis showed that 159 DAPS were annotated in 38 Gene Ontology functional groups, 108 DAPS were classified into 20 clusters of orthologous groups of protein categories, 99 DAPS were enrichment in KEGG pathways. Antioxidants assays validated that the iTRAQ results were reliable. Based on functional analysis, we concluded that the adaptive response of maize seedlings to chilling stress might be related to alleviation of photodamage caused by the over-energized state of thylakoid membrane, more energy produced through glycolysis, increased abundance of stress-responsive protein species, and improvement in the overall ability to scavenge ROS. Posttranscriptional regulation and posttranslational modifications also play important roles for maize to adapt to chilling stress.

Biological Significance: The major challenge for maize breeders is the complexity of the response to chilling stress. Although extensive researches have been focus on maize chilling stress using segregating populations, epigenetics, transcriptomics, molecular biology, however, the molecular mechanism of chilling stress in maize remains to be further elucidated. In the present paper, a differential proteomic analysis was performed and the results revealed the adaptive response of maize seedlings to chilling stress might be related to alleviation of photodamage caused by the over-energized state of thylakoid membrane, more energy produced through glycolysis, increased abundance of stress-responsive protein species, improvement in the overall ability to scavenge ROS, including detoxifying enzymes and antioxidants. Posttranscriptional regulation and posttranslational modifications also play important roles for maize to adapt to chilling stress. This approach identified new protein species involved in posttranslational modifications, signal transduction, lipid metabolism, inorganic ion transport and metabolism and other biological processes that were not previously known to be associated with chilling stress response.