Abstract
To unravel the molecular mechanisms underpinning maize (Zea mays L.) drought stress tolerance, we conducted comprehensive comparative transcriptome and physiological analyses of drought-tolerant YE8112 and drought-sensitive MO17 inbred line seedlings that had been exposed to drought treatment for seven days. Resultantly, YE8112 seedlings maintained comparatively higher leaf relative water and proline contents, greatly increased peroxidase activity, but decreased malondialdehyde content, than MO17 seedlings. Using an RNA sequencing (RNA-seq)-based approach, we identified a total of 10,612 differentially expressed genes (DEGs). From these, we mined out four critical sets of drought responsive DEGs, including 80 specific to YE8112, 5140 shared between the two lines after drought treatment (SD_TD), five DEGs of YE8112 also regulated in SD_TD, and four overlapping DEGs between the two lines. Drought-stressed YE8112 DEGs were primarily associated with nitrogen metabolism and amino-acid biosynthesis pathways, whereas MO17 DEGs were enriched in the ribosome pathway. Additionally, our physiological analyses results were consistent with the predicted RNA-seq-based findings. Furthermore, quantitative real-time polymerase chain reaction (qRT-PCR) analysis and the RNA-seq results of twenty representative DEGs were highly correlated (R2 = 98.86%). Crucially, tolerant line YE8112 drought-responsive genes were predominantly implicated in stress signal transduction; cellular redox homeostasis maintenance; MYB, NAC, WRKY, and PLATZ transcriptional factor modulated; carbohydrate synthesis and cell-wall remodeling; amino acid biosynthesis; and protein ubiquitination processes. Our findings offer insights into the molecular networks mediating maize drought stress tolerance.
Highlights
Drought remains the primary abiotic constraint to plant growth and development, as well as crop productivity [1,2]), accounting for approximately 70% potential yield loss worldwide, largely owing to climate change [3,4]
Results of the malondialdehyde (MDA) content showed that the parameter increased with the increasing number of stress exposure days, starting from day one in sensitive line MO17 and day three in tolerant line in YE8112
Our results have shown that divergent responses to drought stress exist between YE8112 and MO17 inbred lines, and that there was coherence between the physiological characterization and transcriptome profiling data of the two lines
Summary
Drought remains the primary abiotic constraint to plant growth and development, as well as crop productivity [1,2]), accounting for approximately 70% potential yield loss worldwide, largely owing to climate change [3,4]. Yield loss emanating from seedling-stage-drought-stress is of major concern in arid and semi-arid areas, such as Hebei Province in Northern China, where maize often experience moisture deficit stress in spring and early summer, thereby threatening germination and seedling growth [10]. Moisture deficit at the seedling phase will hamper early crop establishment and negatively impact on plants’ grain yield potential, as a consequence of premature tasseling and a prolonged anthesis-silk interval [12]. Untying the molecular basis of maize seedling-stage drought response, in order to improve early crop establishment in such arid and semi-arid drought-prone regions, remains pertinent in maize breeding programs [3]
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