The Wheat Gene TaVQ14 Confers Salt and Drought Tolerance in Transgenic Arabidopsis thaliana Plants

Abstract

Wheat is one of the most widely cultivated food crops worldwide, and the safe production of wheat is essential to ensure food security. Soil salinization and drought have severely affected the yield and quality of wheat. Valine-glutamine genes play important roles in abiotic stress response. This study assessed the effect of the gene TaVQ14 on drought and salt stresses resistance. Sequence analysis showed that TaVQ14 encoded a basic unstable hydrophobic protein with 262 amino acids. Subcellular localization showed that TaVQ14 was localized in the nucleus. TaVQ14 was upregulated in wheat seeds under drought and salt stress. Under NaCl and mannitol treatments, the percentage of seed germination was higher in Arabidopsis lines overexpressing TaVQ14 than in wild-type lines, whereas the germination rate was significantly lower in plants with a mutation in the atvq15 gene (a TaVQ14 homolog) than in WT controls, suggesting that TaVQ14 increases resistance to salt and drought stress in Arabidopsis seeds. Moreover, under salt and drought stress, Arabidopsis lines overexpressing TaVQ14 had higher catalase, superoxide dismutase, and proline levels and lower malondialdehyde concentrations than WT controls, suggesting that TaVQ14 improves salt and drought resistance in Arabidopsis by scavenging reactive oxygen species. Expression analysis showed that several genes responsive to salt and drought stress were upregulated in Arabidopsis plants overexpressing TaVQ14. Particularly, salt treatment increased the expression of AtCDPK2 in these plants. Moreover, salt treatment increased Ca²⁺ concentrations in plants overexpressing TaVQ14, suggesting that TaVQ14 enhances salt resistance in Arabidopsis seeds through calcium signaling. In summary, this study demonstrated that the heterologous expression of TaVQ14 increases the resistance of Arabidopsis seeds to salt and drought stress.

Keywords: TaVQ14; drought; expression analysis; salt; subcellular localization; wheat.

FIGURE 1

Phylogenetic analysis of TaVQ14 and its homologs. Homologs: Aegilops tauschii, AET3Gv20428900; Brachypodium distachyon, BRADI_2g10700v3; Hordeum vulgare, HORVU0Hr1G039840; Oryza glumipatula, OGLUM01G12770; Oryza sativa Indica Group, BGIOSGA001894; Oryza meridionalis, OMERI01G11190; Oryza meridionalis, OMERI01G11200; Oryza nivara, ONIVA01G13640; Oryza rufipogon, ORUFI01G12270; Oryza sativa Japonica Group, OsVQ1 (Os01g0278000); Setaria viridis, SEVIR_5G038600v2; Sorghum bicolor, SORBI_3003G131500; Triticum turgidum, TRITD3Av1G096170; Zea mays, Zm00001d040461.

FIGURE 2

Analysis of TaVQ14 expression by reverse-transcription quantitative PCR in wheat seeds subjected to drought and NaCl stress. *P < 0.05, **P < 0.01.

FIGURE 3

Nuclear localization of TaVQ14. The construct 35S:GFP:TaVQ14 and the control vector 1305 (35S:GFP) were transformed into Nicotiana tabacum leaves. The GFP signals in root cells were observed by confocal microscopy.

FIGURE 4

Germination phenotypes of TaVQ14 in transgenic Arabidopsis plants under salt stress. (A) Germination performance in TaVQ14-overexpressing and wild-type (WT) seeds grown on Murashige and Skoog medium containing 0, 100, or 150 mM of NaCl. (B) Rate of germination in transgenic and WT seeds. (C–L) Relative water content (C) and levels of catalase (D), proline (E), superoxide dismutase (F), malondialdehyde (G), Ascorbate Peroxidase (H), Ascorbic acid (I), Glutathion Reductases (J), L-Glutathione (K), and L-Glutathione oxidized (L) in transgenic and WT plants after salt treatment. Values are means ± SE (n = 3). *P < 0.05 **P < 0.01 (t-test). (M) Relative expression levels of salt-responsive genes in transgenic A. thaliana plants under normal salinity. Leaves of transgenic and WT plants were collected after salt stress. Y-axis: relative expression levels; X-axis: the time course of stress treatments; Error bars, 6 ± SE.

FIGURE 5

Germination phenotypes of TaVQ14 in transgenic Arabidopsis plants under drought stress. (A) Germination performance of TaVQ14-overexpressing and wild-type (WT) seeds on Murashige and Skoog medium containing 0, 150, or 300 mM of mannitol. (B) Rate of germination in transgenic and WT seeds. (C–L) Relative water content (C), and levels of catalase (D), proline (E), superoxide dismutase (F), malondialdehyde (G), Ascorbate Peroxidase (H), Ascorbic acid (I), Glutathion Reductases (J), L-Glutathione (K), and L-Glutathione oxidized (L) in transgenic and WT plants after drought treatment. Values are means ± SE (n = 3). *P < 0.05 **P < 0.01 (t-test). (M) Relative expression levels of drought-responsive genes in transgenic A. thaliana plants under normal water conditions. Leaves of transgenic and WT plants were collected after drought stress. Y-axis: relative expression levels; X-axis: the time course of stress treatments; Error bars, 6 ± SE.

FIGURE 6

Concentration of Na⁺, K⁺, and Ca²⁺ in transgenic Arabidopsis thaliana plants under salt and drought stress. (A) K⁺ ion content in transgenic Arabidopsis thaliana plants under salt and drought stress. (B) Na⁺ ion content in transgenic Arabidopsis thaliana plants under salt and drought stress. (C) Ca²⁺ ion content in transgenic Arabidopsis thaliana plants under salt and drought stress. (D) K⁺/Na⁺ in transgenic Arabidopsis thaliana plants under salt and drought stress. *P < 0.05, **P < 0.01.

FIGURE 7

Germination phenotypes of Arabidopsis thaliana seeds with a mutation in the gene atvq15, a TaVQ14 homolog, under salt and drought stress. (A) Germination performance in atvq15 mutant and wild-type (WT) seeds grown on Murashige and Skoog (MS) medium containing 0, 100, or 150 mM of NaCl. (B) Rate of germination in atvq15 mutant and WT seeds. (C) Germination performance in atvq15 mutant and WT seeds grown on MS medium supplemented with 0, 150, or 300 mM of mannitol. (D) Rate of germination in atvq15 mutant and WT seeds. Relative water content, and levels of catalase, proline, superoxide dismutase, malondialdehyde, Ascorbate Peroxidase, Ascorbic acid, Glutathion Reductases, L-Glutathione, and L-Glutathione oxidized in atvq14 and WT plants after salt treatment. Relative water content, and levels of catalase, proline, superoxide dismutase, malondialdehyde, Ascorbate Peroxidase, Ascorbic acid, Glutathion Reductases, L-Glutathione, and L-Glutathione oxidized in atvq14 and WT plants after drought treatment.