Abstract
The economically important DT2008 and the model Williams 82 (W82) soybean cultivars were reported to have differential drought-tolerant degree to dehydration and drought, which was associated with root trait. Here, we used 66K Affymetrix Soybean Array GeneChip to compare the root transcriptomes of DT2008 and W82 seedlings under normal, as well as mild (2 h treatment) and severe (10 h treatment) dehydration conditions. Out of the 38172 soybean genes annotated with high confidence, 822 (2.15%) and 632 (1.66%) genes showed altered expression by dehydration in W82 and DT2008 roots, respectively, suggesting that a larger machinery is required to be activated in the drought-sensitive W82 cultivar to cope with the stress. We also observed that long-term dehydration period induced expression change of more genes in soybean roots than the short-term one, independently of the genotypes. Furthermore, our data suggest that the higher drought tolerability of DT2008 might be attributed to the higher number of genes induced in DT2008 roots than in W82 roots by early dehydration, and to the expression changes of more genes triggered by short-term dehydration than those by prolonged dehydration in DT2008 roots vs. W82 roots. Differentially expressed genes (DEGs) that could be predicted to have a known function were further analyzed to gain a basic understanding on how soybean plants respond to dehydration for their survival. The higher drought tolerability of DT2008 vs. W82 might be attributed to differential expression in genes encoding osmoprotectant biosynthesis-, detoxification- or cell wall-related proteins, kinases, transcription factors and phosphatase 2C proteins. This research allowed us to identify genetic components that contribute to the improved drought tolerance of DT2008, as well as provide a useful genetic resource for in-depth functional analyses that ultimately leads to development of soybean cultivars with improved tolerance to drought.
Highlights
Soybean (Glycine max L.) has been regarded as one of the major legume crops worldwide with multibillion dollars in value
The relative water content (RWC) of dehydrated plants was measured during dehydration treatment, and the values were 70.2 and 75.8% for Williams 82 (W82) and DT2008, respectively, at 2 h, whereas the respective values at 10 h of dehydration were 18.1 and 40% (Figure 1B), indicating the mild and severe stress intensities
This experimental design allowed us to identify (i) dehydration-responsive genes in each cultivar in a time-course manner (W-D2/wellwatered control h (W-C) and WD10/W-C; dehydrated 2 h (DT-D2)/DT-C and dehydrated 10 h (DT-D10)/DT-C), as well as (ii) genes involved in regulatory network that regulates differential root trait (DT-C/W-C, DT-D2/ W82 dehydrated 2 h (W-D2), and DT-D10/W82 dehydrated 10 h (W-D10)), thereby potentially contributing to higher drought tolerance of DT2008 relative to W82
Summary
Soybean (Glycine max L.) has been regarded as one of the major legume crops worldwide with multibillion dollars in value. In recent years, scientific community has paid a great attention to research toward understanding of mechanisms underlying soybean responses to drought, leading to development of improved drought-tolerant soybean cultivars (Tran and Mochida, 2010; Thao and Tran, 2012; Hossain et al, 2013; Deshmukh et al, 2014). Identification of quantitative trait loci and genes involved in determination of root traits has been regarded as an important task of research community that has interest in elucidation of molecular mechanisms regulating plant responses to drought (Manavalan et al, 2009; Comas et al, 2013; Thao et al, 2013; Satbhai et al, 2015). The results of this study will enable us to identify dehydration-responsive genes in soybean roots and understand the genetic network underlying the differential drought tolerability of W82 and DT2008, as well as provide us with a list of promising candidate genes that hold potential application in development of improved drought-tolerant transgenic soybean varieties through genetic engineering
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