Abstract
BackgroundDrought is one of the major factors limiting global maize production. Exposure to long-term drought conditions inhibits growth and leads to yield losses. Although several drought-responsive genes have been identified and functionally analyzed, the mechanisms underlying responses to drought and water recovery treatments have not been fully elucidated. To characterize how maize seedling respond to drought stress at the transcriptional level, we analyzed physiological responses and differentially expressed genes (DEGs) in the inbred line B73 under water deficit and recovery conditions.ResultsThe data for relative leaf water content, leaf size, and photosynthesis-related parameters indicated that drought stress significantly repressed maize seedling growth. Further RNA sequencing analysis revealed that 6107 DEGs were responsive to drought stress and water recovery, with more down-regulated than up-regulated genes. Among the DEGs, the photosynthesis- and hormone-related genes were enriched in responses to drought stress and re-watering. Additionally, transcription factor genes from 37 families were differentially expressed among the three analyzed time-points. Gene ontology enrichment analyses of the DEGs indicated that 50 GO terms, including those related to photosynthesis, carbohydrate metabolism, oxidoreductase activities, nutrient metabolism and other drought-responsive pathways, were over-represented in the drought-treated seedlings. The content of gibberellin in drought treatment seedlings was decreased compared to that of control seedlings, while abscisic acid showed accumulated in the drought treated plants. The deep analysis of DEGs related to cell wall development indicated that these genes were prone to be down-regulated at drought treatment stage.ConclusionsMany genes that are differentially expressed in responses to drought stress and water recovery conditions affect photosynthetic systems and hormone biosynthesis. The identified DEGs, especially those encoding transcription factors, represent potential targets for developing drought-tolerant maize lines.
Highlights
Drought is one of the major factors limiting global maize production
Physiological responses to drought stress and water recovery To investigate the physiological responses of maize seedlings to water deficit and recovery, the phenotypic traits, including relative water content (RWC) and leaf length, were evaluated at the following three time-points: 3 and 6 days after initiating the drought treatment and after a 1-day water recovery period (Fig. 1a-c)
We describe the results of our comprehensive investigation regarding physiological responses and gene expression patterns in plants treated with drought stress and a water recovery period
Summary
Drought is one of the major factors limiting global maize production. Exposure to long-term drought conditions inhibits growth and leads to yield losses. To characterize how maize seedling respond to drought stress at the transcriptional level, we analyzed physiological responses and differentially expressed genes (DEGs) in the inbred line B73 under water deficit and recovery conditions. Maize seedlings growing under water stress conditions exhibit several important physiological responses, including decreased cell turgor [7, 16], leaf rolling [17], inhibited CO2 exchange and decreased photosynthetic efficiency and chlorophyll contents [1, 18, 19]. The photosynthetic and gas exchange responses are the most sensitive to water deficits [20], and maintaining relatively high photosynthetic activity levels may enhance plant drought tolerance. Over-expression of heat shock transcription factor (TF) HSFA9 may increase water deficit tolerance by protecting the photosynthetic complex in seedlings of tobacco [21]. A high-throughput identification of photosystem-associated genes and a clarification of the relationship between these genes and drought stress responses are required
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