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. 2020 Nov 12;21(1):792.
doi: 10.1186/s12864-020-07175-9.

Genome-wide identification of R2R3-MYB family in wheat and functional characteristics of the abiotic stress responsive gene TaMYB344

Qiuhui Wei  1 , Rong Chen  2 , Xin Wei  2 , Yuheng Liu  2 , Shujuan Zhao  2 , Xiaopu Yin  3 , Tian Xie  4
Affiliations

Genome-wide identification of R2R3-MYB family in wheat and functional characteristics of the abiotic stress responsive gene TaMYB344

Qiuhui Wei et al. BMC Genomics. .

Abstract

Background: MYB superfamily is one of the most abundant families in plants, which plays important roles in plant growth, development, and productivity. However, to date, researches on MYBs in wheat (Triticum aestivum L.) are scattered mostly, not comprehensive.

Results: In this study, a total of 393 R2R3-MYBs and 12 R1R2R3-MYBs were identified and analyzed including gene structure, chromosomal distribution, synteny relationship, and evolutionary relationship. Then, 29 clusters tandem duplication and 8 clusters segmental duplication genes were discovered. The expression profile of the identified genes under abiotic and biotic stress was analyzed using RNA-seq data. Based on expression patterns analysis, we screened many candidate genes involved in plant response to abiotic and biotic stress. Among them, the functional characteristics of TaMYB344 were further studied. TaMYB344 was localized in the nucleus and functioned as a weak transcriptional activator. We demonstrated that TaMYB344-overexpressing transgenic tobacco plants had enhanced tolerance to drought, heat, and high salt stress.

Conclusions: In this study, 393 R2R3-MYBs and 12 R1R2R3-MYBs in wheat were systemically identified and analyzed. Differential expression analysis indicated that many R2R3-MYBs were involved in abiotic and biotic stress response. We identified a potential candidate gene TaMYB344, overexpression of which in tobacco plants enhanced drought, heat, and salt stress tolerance. These results will provide abundant molecular data for breeding new varieties of wheat in the future.

Keywords: Abiotic stress; Expression pattern; Genome; MYB family; Wheat.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Distribution of 405 TaMYBs on 21 wheat chromosomes. a Numbers of TaMYBs on each wheat chromosome. b-d Relative position of TaMYBs distribution on 21 wheat chromosomes. The picture was drawn by MapInspect. Tandem duplication genes are marked by red boxes, and segmental duplication genes are marked by red lines and dots
Fig. 2
Fig. 2
Syntenic relationship of TaR2R3-MYBs in wheat genome A/B/D. The positions of all the TaR2R3-MYBs are depicted in the three subgenomes of wheat. The different color lines indicate the synteny of TaR2R3-MYBs among genome A/B/D. The picture was drawn with TB tools
Fig. 3
Fig. 3
Phylogenetic tree of R2R3-MYBs in wheat and Arabidopsis. The sequences contain 393 TaR2R3-MYBs in wheat and 126 AtR2R3-MYBs in Arabidopsis. All R2R3-MYBs were divided into 9 clusters (C1-C9). S1-S25 represent the previous functional classification of 126 AtR2R3-MYBs in Arabidopsis [2]. The picture was generated by using MEGA 7 software coupled with Neighbor-Joining method with a bootstrap of 1000 replicates
Fig. 4
Fig. 4
Expression profiles of TaR2R3-MYB genes in different tissues. Row coordinate meanings are as following: Grain_Z71, _Z75 and _Z85: grains at 2, 15, and 30 days post anthesis (dpa) stages, respectively; Leaf_Z10, _Z23, and _Z71: leaf at seedling stage, flag leaf at tillering stage, and leaf at 2 dpa stage; Root_Z10, _Z13, and _Z39: roots at seedling, three leaf, and flag leaf stages, respectively; Spike_Z32, _Z39, and _Z65: spikes at two-node, flag leaf, and anthesis stages, respectively; Stem_Z30, _Z32, and _Z65: stems at 1 cm spike, two-node, and anthesis stages, respectively. Heatmap was created by R program based on the data of the transcript per million (TPM) values which were normalized with Z-score method. The red and blue cells respectively represent highest and lowest expression level
Fig. 5
Fig. 5
Expression profiles of TaR2R3-MYB genes under drought/heat treatment. Row coordinate meaning are as follows: DH_1 and DH_6: drought and heat stress at 1 and 6 h post stress (hps), respectively; H_1, and H_6: heat stress at 1 and 6 hps, respectively; D_1 and D_6: drought stress at 1 and 6 hps, respectively. Heatmap was created by R program based on the data of the transcript per million (TPM) values which were normalized with Z-score method. The red and blue cells respectively represent highest and lowest expression level
Fig. 6
Fig. 6
Expression profiles of four selected TaMYB genes under drought stress. Dark gray columns represent the transcript per million (TPM) values from RNA-seq data, which reflect the expression level; Gray columns represent the result of qRT-PCR experiments. Asterisks indicate significant difference (*P < 0.05; **P < 0.01)
Fig. 7
Fig. 7
Functional characterization of TaMYB344 in transgenic tobacco plants under different abiotic stress. a Expression patterns of TaMYB344 in 14-day-old wheat seedlings after treatment with 20% PEG6000. b, c Phenotypes and survival rates of WT, VC, and OE lines (OE2, OE3, and OE10) after drought treatment. d Stomatal aperture after dehydration treatment. e Width/length ratios of stomata. f Germination ratios of WT and OE lines after heat treatment. g, h Phenotype of WT and OE lines after heat treatment. i Expression patterns of TaMYB344 in 14-day-old wheat seedlings after treatment with 200 mM NaCl. j Phenotype of WT, VC, and OE lines after salt treatment. At least three independent biological replicates were performed. Vertical bars refer to ±SE (n = 3). Asterisks indicate significant difference (*P < 0.05; **P < 0.01)
Fig. 8
Fig. 8
Subcellular localization and transcriptional activity analysis of TaMYB344. a Subcellular localization of TaMYB344. Recombinant ubiqutin:: TaMYB344-GFP and control vector ubiquitin::GFP were respectively transformed into onion epidermal cells and observed with fluorescence microscopy. b Transactivation activity of TaMYB344 in yeast. Schematic diagrams illustrate the different portions of TaMYB344 ORF. Recombinant were transformed into yeast strain AH109, and the transformants were screened by SD/−Trp, SD/−Trp/−His+X-a-gal, and SD/−Trp/−His/−Ade + X-a-gal media. At least three independent biological replicates were performed
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