Abstract
The growth and development of maize roots are closely related to drought tolerance. In order to clarify the molecular mechanisms of drought tolerance between different maize (Zea mays L.) varieties at the protein level, the isobaric tags for relative and absolute quantitation (iTRAQ) quantitative proteomics were used for the comparative analysis of protein expression in the seedling roots of the drought-tolerant Chang 7-2 and drought-sensitive TS141 maize varieties under 20% polyethylene glycol 6000 (PEG 6000)-simulated drought stress. We identified a total of 7723 differentially expressed proteins (DEPs), 1243 were significantly differentially expressed in Chang 7-2 following drought stress, 572 of which were up-regulated and 671 were down-regulated; 419 DEPs were identified in TS141, 172 of which were up-regulated and 247 were down-regulated. In Chang 7-2, the DEPs were associated with ribosome pathway, glycolysis/gluconeogenesis pathway, and amino sugar and nucleotide sugar metabolism. In TS141, the DEPs were associated with metabolic pathway, phenylpropanoid biosynthesis pathway, and starch and sucrose metabolism. Compared with TS141, the higher drought tolerance of Chang 7-2 root system was attributed to a stronger water retention capacity; the synergistic effect of antioxidant enzymes; the strengthen cell wall; the osmotic stabilization of plasma membrane proteins; the effectiveness of recycling amino acid; and an improvement in the degree of lignification. The common mechanisms of the drought stress response between the two varieties included: The promotion of enzymes in the glycolysis/gluconeogenesis pathway; cross-protection against the toxicity of aldehydes and ammonia; maintenance of the cell membrane stability. Based on the proteome sequencing information, the coding region sequences of eight DEP-related genes were analyzed at the mRNA level by quantitative real-time PCR (qRT-PCR). The findings of this study can inform the future breeding of drought-tolerant maize varieties.
Highlights
Drought is a major abiotic stress that limits agricultural productivity and results in significant crop yield losses worldwide
We suggest that the high stability of the cell membrane in Chang 7-2 root system provide a normal cellular environment to cope with drought stress
Our results demonstrated that maize seedling roots possess a reactive oxygen species (ROS) scavenging system that responds to drought stress
Summary
Drought is a major abiotic stress that limits agricultural productivity and results in significant crop yield losses worldwide. Maize (Zea mays L.) is the primary grain product and feed crop in China, but it is sensitive to drought [1], which is an important limiting factor for maize yield. Drought impacts the entire growth cycle at the seedling stage [2], maize exhibits several important physiological responses, including decreased cell turgor [3], inhibited CO2 exchange, and decreased photosynthetic efficiency and chlorophyll contents under water stress [4,5]. Proteins execute cellular functions that directly affect crop growth and development, the proteome is constantly changing along with the types, functions, physiological states, environmental conditions, and pathological states of the cells. Proteomics is presently developing from qualitative to quantitative proteomics, and isobaric tags for relative and absolute quantitation (iTRAQ) is an accurate quantitative proteomics technique with high quantitative accuracy, high sensitivity, good repeatability, and high throughput [8]
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