Genome-wide characterization of JASMONATE-ZIM DOMAIN transcription repressors in wheat (Triticum aestivum L.)

Abstract

Background: The JASMONATE-ZIM DOMAIN (JAZ) repressor family proteins are jasmonate co-receptors and transcriptional repressor in jasmonic acid (JA) signaling pathway, and they play important roles in regulating the growth and development of plants. Recently, more and more researches on JAZ gene family are reported in many plants. Although the genome sequencing of common wheat (Triticum aestivum L.) and its relatives is complete, our knowledge about this gene family remains vacant.

Results: Fourteen JAZ genes were identified in the wheat genome. Structural analysis revealed that the TaJAZ proteins in wheat were as conserved as those in other plants, but had structural characteristics. By phylogenetic analysis, all JAZ proteins from wheat and other plants were clustered into 11 sub-groups (G1-G11), and TaJAZ proteins shared a high degree of similarity with some JAZ proteins from Aegliops tauschii, Brachypodium distachyon and Oryza sativa. The Ka/Ks ratios of TaJAZ genes ranged from 0.0016 to 0.6973, suggesting that the TaJAZ family had undergone purifying selection in wheat. Gene expression patterns obtained by quantitative real-time PCR (qRT-PCR) revealed differential temporal and spatial regulation of TaJAZ genes under multifarious abiotic stress treatments of high salinity, drought, cold and phytohormone. Among these, TaJAZ7, 8 and 12 were specifically expressed in the anther tissues of the thermosensitive genic male sterile (TGMS) wheat line BS366 and normal control wheat line Jing411. Compared with the gene expression patterns in the normal wheat line Jing411, TaJAZ7, 8 and 12 had different expression patterns in abnormally dehiscent anthers of BS366 at the heading stage 6, suggesting that specific up- or down-regulation of these genes might be associated with the abnormal anther dehiscence in TGMS wheat line.

Conclusion: This study analyzed the size and composition of the JAZ gene family in wheat, and investigated stress responsive and differential tissue-specific expression profiles of each TaJAZ gene in TGMS wheat line BS366. In addition, we isolated 3 TaJAZ genes that would be more likely to be involved in the regulation of abnormal anther dehiscence in TGMS wheat line. In conclusion, the results of this study contributed some novel and detailed information about JAZ gene family in wheat, and also provided 3 potential candidate genes for improving the TGMS wheat line.

Keywords: Anther dehiscence; Gene expression; JASMONATE-ZIM DOMAIN; Phylogenetic analysis; Thermo sensitive genic male sterile (TGMS).

Fig. 1

Phylogenetic relationship and motif structure of wheat JAZ proteins. a The phylogenetic tree of TaJAZ proteins constructed from a complete alignment of 34 wheat JAZ proteins using MEGA 6.0 by the neighbor-joining method with 1000 bootstrap replicates. Bootstrap scores are indicated on the nodes and the 14 members of TaJAZ, most of which contain duplicated genes, are indicated by yellow or pink block. b Domain distribution of TaJAZ proteins were investigated using the MEME web server. Color blocks represent the position of motifs on corresponding proteins. c The consensus sequence of TIFY and Jas motif from wheat JAZ proteins. The relative position of each motif can be determined using the scale below

Fig. 2

Chromosome distribution of JAZ gene family in wheat. Red dots on the chromosomes indicate the position of centromeres. The red arrows next to gene names show the direction of transcription. The position of each gene could be estimated using the left scale

Fig. 3

Exon-intron structures of TaJAZ genes. Exons are represented by blank boxes and introns by blank lines. The sizes of exons and introns could be estimated using the scale below

Fig. 4

Phylogenetic relationship of JAZ proteins among wheat and other species. The full-length amino acid sequences of 34 T. aestivum, 6 S. moellendorffii, 12 A. thaliana, 15 O. sativa, 7 P. patens, 6 maize, 15 B. distachyon, 15 S. bicolor, 13 P. sitchensis, 8 Ae. tauschii and 7 H. brasiliensis genes were aligned by using ClustalX and the phylogenetic tree was constructed using MEGA 6.0 by the neighbor-joining method with 1000 bootstrap replicates. Each TaJAZ protein is indicated by a red dot. Two major groups, group I and II, are represented by the red and blue, respectively

Fig. 5

Expression heat maps of 14 TaJAZ genes under 5 phytohormone (MeJA, ABA, GA, IAA and SA), drought, salt and cold treatments in TGMS wheat line. qRT-PCR strategy was used to analyze the relative expression level of each TaJAZ gene. The expression level of wheat actin was used as the internal control to standardize the RNA samples for each reaction, and the expression at 0 h was set as 1 (data not show). The data are from three biological replicates

Fig. 6

Expression patterns of TaJAZ genes during the whole heading stage. A a, b the phenotype of anther dehiscence in conventional wheat line Jing411; c, d the phenotype of anther dehiscence in TGMS wheat line BS366. Scale bars: a, c = 4 mm, b = 2 mm, d = 1 mm. B the schematic diagram of 6 stages during the whole heading period and the size of corresponding anther in each heading stage. Scale bars = 2 mm. C the relative expression patterns of TaJAZ genes in each heading stage. qRT-PCR was used to analyze the relative expression level of each TaJAZ gene. F1–F6 represent 6 stages during the whole heading period. The expression level of wheat actin was used as the internal control to standardize the RNA samples for each reaction, and the expression in stage 1 was set as 1. The data are from three biological replicates, and error bars represent the standard error

Fig. 7

Real-time PCR analysis of TaJAZ genes in 6 wheat tissues in heading stage 6. The expression level of wheat actin was used as the internal control to standardize the RNA samples for each reaction, and the expression in the root was set as 1. The data are from three biological replicates, and error bars represent the standard error