Transcriptome Analysis of Tolerant and Susceptible Maize Genotypes Reveals Novel Insights about the Molecular Mechanisms Underlying Drought Responses in Leaves.

Joram Kiriga Waititu,Xingen Zhang,Chunyi Zhang,Tianci Chen,Huan Wang,Yang Zhao

doi:10.3390/ijms22136980

Abstract

Maize (Zea mays L.) is the most essential food crop in the world. However, maize is highly susceptible to drought stress, especially at the seedling stage, and the molecular mechanisms underlying drought tolerance remain elusive. In this study, we conducted comparative transcriptome and physiological analyses of drought-tolerant (CML69) and susceptible (LX9801) inbred lines subjected to drought treatment at the seedling stage for three and five days. The tolerant line had significantly higher relative water content in the leaves, as well as lower electrolyte leakage and malondialdehyde levels, than the susceptible line. Using an RNA-seq-based approach, we identified 10,084 differentially expressed genes (DEGs) with 6906 and 3178 DEGs been annotated and unannotated, respectively. Two critical sets of drought-responsive DEGs, including 4687 genotype-specific and 2219 common drought-responsive genes, were mined out of the annotated DEGs. The tolerant-line DEGs were predominantly associated with the cytoskeleton, cell wall modification, glycolysis/gluconeogenesis, transport, osmotic regulation, drought avoidance, ROS scavengers, defense, and transcriptional factors. For the susceptible line, the DEGs were highly enriched in the photosynthesis, histone, and carbon fixation pathways. The unannotated DEGs were implicated in lncRNAs, including 428 previously reported and 22% putative TE-lncRNAs. There was consensus on both the physiological response and RNA-seq outcomes. Collectively, our findings will provide a comprehensive basis of the molecular networks mediating drought stress tolerance of maize at the seedling stage.

Highlights

Drought is one of the most important abiotic stresses threatening worldwide agricultural production and food safety [1,2,3]
No significant difference was observed in the relative water content (RWC), the relative electrolyte leakage (REL), and leaf malondialdehyde (MDA) content between LX9801 and CML69 at well-watered conditions (Figure 1D–F)
The REL and MDA content was significantly higher in the susceptible line than the tolerant line at both drought stress conditions (Figure 1E,F, respectively)

Summary

Introduction

Drought is one of the most important abiotic stresses threatening worldwide agricultural production and food safety [1,2,3]. On average, it reduces global cereal production by 10.1% and affects 64% of the worldwide land area [4,5]. Water scarcity is anticipated to worsen, with a much more significant impact on the physiological status and productivity of major crops expected in the coming decades [7]. Maize (Zea mays L.) is an important food crop surpassing rice and wheat since 2012 [8] Understanding drought tolerance mechanisms in crops and developing drought-tolerant varieties is critical for maintaining crop yields under drought conditions.

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Conclusion