Transcriptomics Analyses Reveal Wheat Responses to Drought Stress during Reproductive Stages under Field Conditions

Abstract

Drought is a major abiotic stress that limits wheat production worldwide. To ensure food security for the rapidly increasing world population, improving wheat yield under drought stress is urgent and relevant. In this study, an RNA-seq analysis was conducted to study the effect of drought on wheat transcriptome changes during reproductive stages under field conditions. Our results indicated that drought stress during early reproductive periods had a more severe impact on wheat development, gene expression and yield than drought stress during flowering. In total, 115,656 wheat genes were detected, including 309 differentially expressed genes (DEGs) which responded to drought at various developmental stages. These DEGs were involved in many critical processes including floral development, photosynthetic activity and stomatal movement. At early developmental stages, the proteins of drought-responsive DEGs were mainly located in the nucleus, peroxisome, mitochondria, plasma membrane and chloroplast, indicating that these organelles play critical roles in drought tolerance in wheat. Furthermore, the validation of five DEGs confirmed their responsiveness to drought under different genetic backgrounds. Functional verification of DEGs of interest will occur in our subsequent research. Collectively, the results of this study not only advanced our understanding of wheat transcriptome changes under drought stress during early reproductive stages but also provided useful targets to manipulate drought tolerance in wheat at different development stages.

Keywords: DEGs; RNA-seq; developmental stages; drought; wheat.

Figure 1

The developmental stages of plants used for tissue collection and RNA-seq analysis. T4: pistil and stamen differentiation stage; T5: anther differentiation stage; T6: tetrad stage; T8: early flowering stage; and T9: grain formation stage.

Figure 2

Profile of relative soil water content (RSWC) during wheat growth. T: time point.

Figure 3

PCA displaying the intrinsic biological variation among samples. Group A: samples from block A. Group D: samples from Block D. The three trilaterals or roundness in each ellipse represents three biological replicates at the same time point (development stage).

Figure 4

Heatmap of 226 drought-responsive genes at T4 (pistil and stamen differentiation stage) based on fpkm values for each gene. The color scale of blue (low), yellow (medium), and red (high) represents the transcriptome levels of differentially expressed genes. The predicted subcellular location of 100 proteins from 226 genes was located mainly in the plasma membrane, vacuole and endoplasmic reticulum.

Figure 5

Venn diagrams showing the common genes at different time points. T4 (blue): pistil and stamen differentiation stage; T5 (yellow): anther differentiation stage; T6 (green): tetrad stage.

Figure 6

Comparison of the log2 fold change of 21 selected transcripts using RNA-seq and RT-qPCR.

Figure 7

Drought-related physiological traits in Hanmai 9 and Cangmai 6001. Data are mean ± standard deviation of three trials. ^*p < 0.05; ^**p < 0.01.

Figure 8

RT-qPCR validation of selected genes in Hanmai 9 and Cangmai 6001. Data are mean ± standard deviation of three trials. ^*p < 0.05; ^**p < 0.01.