Genome-Wide Identification of Barley ABC Genes and Their Expression in Response to Abiotic Stress Treatment

Abstract

Adenosine triphosphate-binding cassette transporters (ABC transporters) participate in various plant growth and abiotic stress responses. In the present study, 131 ABC genes in barley were systematically identified using bioinformatics. Based on the classification method of the family in rice, these members were classified into eight subfamilies (ABCA-ABCG, ABCI). The conserved domain, amino acid composition, physicochemical properties, chromosome distribution, and tissue expression of these genes were predicted and analyzed. The results showed that the characteristic motifs of the barley ABC genes were highly conserved and there were great diversities in the homology of the transmembrane domain, the number of exons, amino acid length, and the molecular weight, whereas the span of the isoelectric point was small. Tissue expression profile analysis suggested that ABC genes possess non-tissue specificity. Ultimately, 15 differentially expressed genes exhibited diverse expression responses to stress treatments including drought, cadmium, and salt stress, indicating that the ABCB and ABCG subfamilies function in the response to abiotic stress in barley.

Keywords: ABC gene family; abiotic stress; barley; gene expression.

Figure 1

Unrooted Neighbor-Joining tree constructed with ABC proteins of Hordeum vulgare L. (HORVV) and Oryza sativa L. (ORYSJ). The domains clustered into eight subgroups (ABCA-ABCG, ABCI). Different colored shadings indicated eight ABC transporter subfamilies. The red branch is barley, and the black branch is rice.

Figure 2

Mapping of the HvABC genes on Hordeum vulgare L. chromosomes. The chromosome number is indicated at the top of each chromosome. Three putative HvABC genes could not be localized on a specific chromosome.

Figure 3

Conserve amino acid in seven motifs of ABC gene family in barley. Motif analysis and the sequence logos was performed using MEME website.

Figure 4

Heatmap showing the expression pattern of HvABC genes in developmental stages and tissues, including ROO1 (Roots from seedings), ROO2 (Roots), LEA (Shoots from seedings), ETI (Etiolated seeding, dark cond), INF2 (Developing inflorescences), PAL (Dissected inflorescences), LEM/LOD/RAC (inflorescences, lemma/lodicule/rachis), NOD (Developing tillers), CAR5/CAR15 (Developing grain, 5 DAP/15 DAP), EPI (Epidermal strips), SEN (Senescing leaves). The combined phylogenetic trees of HvABCs genes on the left panel. The scale bar at the top represents relative expression value. Red denotes high expression levels, and green denotes low expression levels.

Figure 5

qRT-PCR analysis of 15 HvABC genes in response to (A) 50 μmol·L⁻¹ CdCl₂ (B) 200 mmol·L⁻¹ NaCl (C) 20% PEG6000. columns in black represent CK, columns in gray represent abiotic stress. ANOVA and LSD was used to test significance. Asterisks indicate the corresponding gene significantly up- or down-regulated compared with the untreated control (* p < 0.05, ** p < 0.01, *** p < 0.001) Data are the means of three replicates with standard errors represented by bars.