Abstract
Drought stress is the major abiotic factor threatening maize (Zea mays L.) yield globally. Therefore, revealing the molecular mechanisms fundamental to drought tolerance in maize becomes imperative. Herein, we conducted a comprehensive comparative analysis of two maize inbred lines contrasting in drought stress tolerance based on their physiological and proteomic responses at the seedling stage. Our observations showed that divergent stress tolerance mechanisms exist between the two inbred-lines at physiological and proteomic levels, with YE8112 being comparatively more tolerant than MO17 owing to its maintenance of higher relative leaf water and proline contents, greater increase in peroxidase (POD) activity, along with decreased level of lipid peroxidation under stressed conditions. Using an iTRAQ (isobaric tags for relative and absolute quantification)-based method, we identified a total of 721 differentially abundant proteins (DAPs). Amongst these, we fished out five essential sets of drought responsive DAPs, including 13 DAPs specific to YE8112, 107 specific DAPs shared between drought-sensitive and drought-tolerant lines after drought treatment (SD_TD), three DAPs of YE8112 also regulated in SD_TD, 84 DAPs unique to MO17, and five overlapping DAPs between the two inbred lines. The most significantly enriched DAPs in YE8112 were associated with the photosynthesis antenna proteins pathway, whilst those in MO17 were related to C5-branched dibasic acid metabolism and RNA transport pathways. The changes in protein abundance were consistent with the observed physiological characterizations of the two inbred lines. Further, quantitative real-time polymerase chain reaction (qRT-PCR) analysis results confirmed the iTRAQ sequencing data. The higher drought tolerance of YE8112 was attributed to: activation of photosynthesis proteins involved in balancing light capture and utilization; enhanced lipid-metabolism; development of abiotic and biotic cross-tolerance mechanisms; increased cellular detoxification capacity; activation of chaperones that stabilize other proteins against drought-induced denaturation; and reduced synthesis of redundant proteins to help save energy to battle drought stress. These findings provide further insights into the molecular signatures underpinning maize drought stress tolerance.
Highlights
Maize (Zea mays L.) is one of the world’s most agro-economically important crops because of its raw material use in the food, feed, and biofuel production for humans and animals [1,2,3]
Our results have shown that divergent stress tolerance mechanisms exist between the two lines at the seedling stage
Both qualitative and quantitative differences, at physiological and proteomic levels, showed that YE8112 is comparatively more tolerant to drought stress than MO17 owing to its maintenance of higher Relative water content (RWC) and proline contents, higher increase in POD enzyme activity, along with decreased level of lipid peroxidation under stressed conditions
Summary
Maize (Zea mays L.) is one of the world’s most agro-economically important crops because of its raw material use in the food, feed, and biofuel production for humans and animals [1,2,3] It is under severe threat from various abiotic stresses including drought, salinity, cold, heat, and flooding [4,5,6,7,8]. In order to study maize drought stress responses at the protein level, we have employed an iTRAQ-based quantitative strategy to perform proteome profiling of two contrasting maize inbred lines (drought-tolerant YE8112 and drought-sensitive MO17) at the seedling stage. We evaluated some physiological responses of these two inbred lines under drought stress, and the results of this study provide further insights into the drought stress tolerance signatures in maize
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