Expression pattern of salt tolerance-related genes in Aegilops cylindrica

Abstract

Aegilops cylindrica, a salt-tolerant gene pool of wheat, is a useful plant model for understanding mechanism of salt tolerance. A salt-tolerant USL26 and a salt-sensitive K44 genotypes of A. cylindrica, originating from Uremia Salt Lake shores in Northwest Iran and a non-saline Kurdestan province in West Iran, respectively, were identified based on screening evaluation and used for this work. The objective of the current study was to investigate the expression patterns of four genes related to ion homeostasis in this species. Under treatment of 400 mM NaCl, USL26 showed significantly higher root and shoot dry matter levels and K⁺ concentrations, together with lower Na⁺ concentrations than K44 genotype. A. cylindrica HKT1;5 (AecHKT1;5), SOS1 (AecSOS1), NHX1 (AecNHX1) and VP1 (AecVP1) were partially sequenced to design each gene specific primer. Quantitative real-time PCR showed a differential expression pattern of these genes between the two genotypes and between the root and shoot tissues. Expressions of AecHKT1;5 and AecSOS1 was greater in the roots than in the shoots of USL26 while AecNHX1 and AecVP1 were equally expressed in both tissues of USL26 and K44. The higher transcripts of AecHKT1;5 in the roots versus the shoots could explain both the lower Na⁺ in the shoots and the much lower Na⁺ and higher K⁺ concentrations in the roots/shoots of USL26 compared to K44. Therefore, the involvement of AecHKT1;5 in shoot-to-root handover of Na⁺ in possible combination with the exclusion of excessive Na⁺ from the root in the salt-tolerant genotype are suggested.

Keywords: HKT1;5; NHX1; SOS1; Salinity; Sodium exclusion.

Fig. 1

Biplot of 44 genotypes of A. cylindrica (1–44) and physiological traits (vectors) affected by 400 mM NaCl for 4 weeks. The PC1 and PC2 explain 53.4 and 31.5% of the total variations, respectively. Traits abbreviations: STi: salt tolerance index, rNa: root Na⁺, rK: root K⁺, rK/Na: root K⁺/Na⁺, sNa: shoot Na⁺, sK: shoot K⁺, sK/Na: shoot K⁺/Na⁺, rDW: root dry matter, sDW: shoot dry matter; MDA: shoot malondialdehyde, H₂O₂: shoot hydrogen peroxide and Car: shoot carbohydrate

Fig. 2

Phylogenetic tree based on nucleotide sequences, showing the relation of a AecHKT1;5, b AecSOS1, c AceNHX1 and d AecVP1to the correspondences of members of the genus Triticum spp. and the species Aegilops tauschii, Hordeum vulgare, Oryza sativa, Zea mays, Brachypodium distachyon, Setaria italica and other

Fig. 3

Expression analysis of the AecHKT1;5 gene in a root and b shoot tissues of A. cylindrica tolerant (USL26) and sensitive (K44) genotypes. Bars represent means ± SE and bars headed by the same letter represent not significantly different at P < 0.05

Fig. 4

Expression analysis of the AecSOS1 gene in a root and b shoot tissues of A. cylindrica tolerant (USL26) and sensitive (K44) genotypes. Bars represent means ± SE and bars headed by the same letter represent not significantly different at P < 0.05

Fig. 5

Expression analysis of the AecNHX1 gene in a root and b shoot tissues of A. cylindrica tolerant (USL26) and sensitive (K44) genotypes. Bars represent means ± SE and bars headed by the same letter represent not significantly different at P < 0.05

Fig. 6

Expression analysis of AecVP1 gene in a root and b shoot tissues of A. cylindrica tolerant (USL26) and sensitive (K44) genotypes. Bars represent means ± SE and bars headed by the same letter represent not significantly different at P < 0.05