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. 2019 Feb 14;10(2):142.
doi: 10.3390/genes10020142.

Overexpression of StDREB2 Transcription Factor Enhances Drought Stress Tolerance in Cotton (Gossypium barbadense L.)

Mohamed A El-Esawi  1 , Aisha A Alayafi  2
Affiliations

Overexpression of StDREB2 Transcription Factor Enhances Drought Stress Tolerance in Cotton (Gossypium barbadense L.)

Mohamed A El-Esawi et al. Genes (Basel). .

Abstract

Drought stress significantly restricts plant growth and crop productivity. Cotton is the most important textile fiber and oilseed crop worldwide, and its cultivation is affected by drought stress, particularly in dry regions. Improving cotton tolerance to drought stress using the advanced genetic engineering technologies is a promising strategy to maintain crop production and fiber quality and meet the increasing worldwide fiber and oil demand. Dehydration-responsive element binding (DREB) transcription factors play a main role in regulating stresses-tolerance pathways in plant. This study investigated whether potato DREB2 (StDREB2) overexpression can improve drought tolerance in cotton. StDREB2 transcription factor was isolated and overexpressed in cotton. Plant biomass, boll number, relative water content, soluble sugars content, soluble protein content, chlorophyll content, proline content, gas-exchange parameters, and antioxidants enzymes (POD, CAT, SOD, GST) activity of the StDREB2-overexpressing cotton plants were higher than those of wild type plants. By contrast, the contents of malondialdehyde, hydrogen peroxide and superoxide anion of StDREB2-overexpressing transgenic plants were significantly lower than that of the wild type plants. Moreover, the transgenic cotton lines revealed higher expression levels of antioxidant genes (SOD, CAT, POD, GST) and stress-tolerant genes (GhERF2, GhNAC3, GhRD22, GhDREB1A, GhDREB1B, GhDREB1C) compared to wild-type plants. Taken together, these findings showed that StDREB2 overexpression augments drought stress tolerance in cotton by inducing plant biomass, gas-exchange characteristics, reactive oxygen species (ROS) scavenging, antioxidant enzymes activities, osmolytes accumulation, and expression of stress-related genes. As a result, StDREB2 could be an important candidate gene for drought-tolerant cotton breeding.

Keywords: StDREB2; antioxidants; drought; genes expression; osmolytes; transgenic cotton.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Molecular analyses and survival rate of cotton lines. StDREB2 expression in T0 (A) and T3 (B) transgenic cotton lines using qRT-PCR. Survival rate of the wild type and transgenic lines following 12-day recovery after drought treatment (C).
Figure 2
Figure 2
Root dry weight (g/plant) (A), shoot dry weight (g/plant) (B), boll number per plant (C), and relative water content (%) (D) of wild-type and StDREB2-overexpressing cotton lines under normal and drought conditions. WAS represents week after drought stress. Data represent means ± SE (n = 5). Same letters on columns tops denote non-significant differences (p ≤ 0.05).
Figure 3
Figure 3
Chlorophyll content (mg g−1 FW) (A), soluble protein content (mg g−1 FW) (B), soluble sugar content (mg g−1 FW) (C), and proline content (µg g−1 FW) (D) of wild type and StDREB2-overexpressing cotton under normal and drought conditions. FW represents fresh weight. Data are means ± SE (n = 5). Same letters on columns denote non-significant differences (p ≤ 0.05).
Figure 4
Figure 4
Photosynthetic rate (Pn, μmol m2 s−1) (A), stomatal conductance (gs, mol m2 s−1) (B), and transpiration rate (E, mmol m2 s−1) (C) of wild type and StDREB2-overexpressing cotton lines under normal and drought conditions. WAS represents week after drought stress. Data represent means ± SE (n = 5). Same letters on columns tops denote non-significant differences (p ≤ 0.05).
Figure 5
Figure 5
Hydrogen peroxide (H2O2, µmol g−1 FW) content (A), superoxide anion (O2.−, mm g−1 FW) content (B), and lipid peroxidation (MDA, µmol g−1 FW) level (C) of the wild type and StDREB2-overexpressing cotton lines under normal and drought conditions. WAS represents week after drought stress. Data represent means ± SE (n = 5). Same letters on columns tops denote non-significant differences (p ≤ 0.05).
Figure 6
Figure 6
Activities of catalase (CAT) (A), superoxide dismutase (SOD) (B), peroxidase (POD) (C), and glutathione-S-transferase (GST) (D) in wild type and StDREB2-overexpressing cotton lines under normal and drought conditions. WAS represents week after drought stress. Data represent means ± SE (n = 5). Same letters on columns tops denote non-significant differences (p ≤ 0.05).
Figure 7
Figure 7
Expression levels of CAT (A), SOD (B), POD (C), and GST (D) genes in the wild type and StDREB2-overexpressing cotton lines under normal and drought conditions. Data represent means ± SE (n = 5). Same letters on columns tops denote non-significant differences (p ≤ 0.05).
Figure 8
Figure 8
Expression levels of GhERF2 (A), GhNAC3 (B), GhRD22 (C), GhDREB1A (D), GhDREB1B (E), and GhDREB1C (F) genes in the wild type and StDREB2-overexpressing cotton lines under normal and drought conditions. Data represent means ± SE (n = 5). Same letters on columns tops denote non-significant differences (p ≤ 0.05).
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