Physiological and proteomic insights into cold tolerance mechanism in two contrasting maize genotypes

Low temperature is one of the key abiotic stresses that affects plant growth, development, yield and quality. To elucidate the possible mechanisms of cold tolerance in maize (Zea mays), three-leaf stage seedlings of two cold-tolerant contrasting genotypes, MT19 (a cold-tolerant genotype) and MS19 (a cold-sensitive genotype), were subject to cold stress (4°C) for 4 d. Then the physiological responses were investigated and the proteome of leaves was analyzed by isobaric tags for relative and absolute quantitation (iTRAQ) approach. Cold stress significantly reduced the growth of both genotypes. However, MT19 exhibited stronger antioxidant capacity, synthesized more osmotic regulatory substances, and had a lower level of membrane lipid peroxidation in response to cold stress compared to MS19. Proteomics analysis revealed that 241 differentially abundant proteins (DAPs) were identified in MT19 but only 108 DAPs were identified in MS19 in response to cold stress. Based on the DAPs, complex protein-protein interactions were observed in MT19. And the DAPs involved in plant defense, fatty acid metabolism and protein synthesis were significantly increased in MT19 response to cold stress. These results indicated that increasing of antioxidant and defense proteins, enhancing fatty acid metabolism were critical for the cold-tolerant maize resistant to cold stress. This study provides a comprehensive landscape at the cold-responsive physiological and proteomics in maize seedlings and insights into unraveling the molecular mechanism of maize resistant to cold stress.