Transcriptome Analyses in Different Cucumber Cultivars Provide Novel Insights into Drought Stress Responses.

Min Wang,Biao Jiang,Zhaojun Liang,Yu’E Lin,Xiaoming He,Wenrui Liu,Qingwu Peng

doi:10.3390/ijms19072067

Abstract

Drought stress is one of the most serious threats to cucumber quality and yield. To gain a good understanding of the molecular mechanism upon water deficiency, we compared and analyzed the RNA sequencing-based transcriptomic responses of two contrasting cucumber genotypes, L-9 (drought-tolerant) and A-16 (drought-sensitive). In our present study, combining the analysis of phenotype, twelve samples of cucumber were carried out a transcriptomic profile by RNA-Seq under normal and water-deficiency conditions, respectively. A total of 1008 transcripts were differentially expressed under normal conditions (466 up-regulated and 542 down-regulated) and 2265 transcripts under drought stress (979 up-regulated and 1286 down-regulated). The significant positive correlation between RNA sequencing data and a qRT-PCR analysis supported the results found. Differentially expressed genes (DEGs) involved in metabolic pathway and biosynthesis of secondary metabolism were significantly changed after drought stress. Several genes, which were related to sucrose biosynthesis (Csa3G784370 and Csa3G149890) and abscisic acid (ABA) signal transduction (Csa4M361820 and Csa6M382950), were specifically induced after 4 days of drought stress. DEGs between the two contrasting cultivars identified in our study provide a novel insight into isolating helpful candidate genes for drought tolerance in cucumber.

Highlights

Drought stress generally occurs when soil water is deficient, leading to a continuous loss of water by transpiration or evaporation [1]
There were no difference of malondialdehyde (MDA) and the enzyme superoxide dismutase (SOD) between L-9 and A-16 before drought, while A-16 presented a prominent increase of MDA and significant decrease of SOD at the 4th day after drought treatment (Figure 1D,E)
The results showed that there was a strong positive correlation between the RNA-seq and Quantitative Real-Time PCR (qRT-PCR) result (Figure 5), which indicated the accuracy of the RNA-seq data

Summary

Introduction

Drought stress generally occurs when soil water is deficient, leading to a continuous loss of water by transpiration or evaporation [1]. A key limiting factor in plant growth and development, impacts plant elongation and expansion growth [2,3]. Carbon monoxide (CO) is involved in hydrogen gas (H2)-induced adventitious root development under stimulated drought stress and alleviates oxidative damage by altering relative physiological index [12]. CsCER1 is involved in the fruit cuticle synthesis, and overexpressing the gene has been shown to improve the drought tolerance under water-deficiency conditions [13]. Applied hydrogen peroxide could considerably enhance the cucumber drought resistance by increasing the plant’s antioxidative defense system and its capacity for osmotic adjustment [14]. Tobacco PR-2d promoter/uidA (GUS) gene is induced in transgenic cucumber and improves the response to biotic and abiotic stimuli [15]

Methods

Results

Conclusion