BackgroundAs a superfamily of transcription factors (TFs), the basic helix-loop-helix (bHLH) proteins have been characterized functionally in many plants with a vital role in the regulation of diverse biological processes including growth, development, response to various stresses, and so on. However, no systemic analysis of the bHLH TFs has been reported in Brachypodium distachyon, an emerging model plant in Poaceae.ResultsA total of 146 bHLH TFs were identified in the Brachypodium distachyon genome and classified into 24 subfamilies. BdbHLHs in the same subfamily share similar protein motifs and gene structures. Gene duplication events showed a close relationship to rice, maize and sorghum, and segment duplications might play a key role in the expansion of this gene family. The amino acid sequence of the bHLH domains were quite conservative, especially Leu-27 and Leu-54. Based on the predicted binding activities, the BdbHLHs were divided into DNA binding and non-DNA binding types. According to the gene ontology (GO) analysis, BdbHLHs were speculated to function in homodimer or heterodimer manner. By integrating the available high throughput data in public database and results of quantitative RT-PCR, we found the expression profiles of BdbHLHs were different, implying their differentiated functions.ConclusionOne hundred fourty-six BdbHLHs were identified and their conserved domains, sequence features, phylogenetic relationship, chromosomal distribution, GO annotations, gene structures, gene duplication and expression profiles were investigated. Our findings lay a foundation for further evolutionary and functional elucidation of BdbHLH genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-4044-4) contains supplementary material, which is available to authorized users.

MYB transcription factors are widespread in plants and play key roles in plant development. Although MYB transcription factors have been thoroughly characterized in many plants, genome-wide analysis of the MYB gene family has not yet been undertaken in Brachypodium distachyon. In this study, 122 BdMYB transcription factors were identified, comprising 85 MYB-R2R3, 34 MYB-related and three MYB-R1R2R3. Phylogenetic analysis showed that BdMYBs, OsMYBs and AtMYBs with similar functions were clustered in the same subgroup, and the phylogenetic relationships of BdMYB transcription factors were supported by highly conserved motifs and gene structures. Two cis-elements were found in the promoters of BdMYB genes. One is related to plant growth/development, the other is related to stress responses. Gene Ontology (GO) analysis indicated that most of the BdMYB genes are involved in various biological processes. The chromosome distribution pattern strongly indicated that genome-wide tandem and segment duplication mainly contributed to the expansion of the BdMYB gene family. Synteny analysis showed that 56, 58 and 61 BdMYB genes were orthologous to rice, maize and sorghum, respectively. We further demonstrated that BdMYB genes have evolved under strong purifying selection. The expression profiles indicated that most BdMYB genes might participate in floral development and respond to abiotic stresses. Additionally, 338 pairs of proteins were predicted to interact by constructing the interaction network. This work laid the foundation and provided clues for understanding the biological functions of these transcription factors.

Heat stress greatly affects plant growth/development and influences the output of crops. With the increased occurrence of extreme high temperature, the negative influence on cereal products from heat stress becomes severer and severer. It is urgent to reveal the molecular mechanism in response to heat stress in plants. In this research, we used RNA-seq technology to identify differentially expressed genes (DEGs) in leaves of seedlings, leaves and inflorescences at heading stage of Brachypodium distachyon, one model plant of grasses. Results showed many genes in responding to heat stress. Of them, the expression level of 656 DEGs were altered in three groups of samples treated with high temperature. Gene ontology (GO) analysis showed that the highly enriched DEGs were responsible for heat stress and protein folding. According to KEGG pathway analysis, the DEGs were related mainly to photosynthesis-antenna proteins, the endoplasmic reticulum, and the spliceosome. Additionally, the expression level of 454 transcription factors belonging to 49 gene families was altered, as well as 1,973 splicing events occurred after treatment with high temperature. This research lays a foundation for characterizing the molecular mechanism of heat stress response and identifying key genes for those responses in plants. These findings also clearly show that heat stress regulates the expression of genes not only at transcriptional level, but also at post-transcriptional level.

Background As one of the most important transcription factor families, GRAS proteins are involved in numerous regulatory processes, especially plant growth and development. However, they have not been systematically analyzed in Brachypodium distachyon , a new model grass. Results In this study, 48 BdGRAS genes were identified. Duplicated genes account for 41.7% of them and contribute to the expansion of this gene family. 33, 39, 35 and 35 BdGRAS genes were identified by synteny with their orthologs in rice, sorghum, maize and wheat genome, respectively, indicating close relationships among these species. Based on their phylogenic relationships to GRAS genes in rice and maize, BdGRAS genes can be divided into ten subfamilies in which members of the same subfamily showed similar protein sequences, conserved motifs and gene structures, suggesting possible conserved functions. Although expression variation is high, some BdGRAS genes are tissue-specific, phytohormones- or abiotic stresses-responsive, and they may play key roles in development, signal transduction pathways and stress responses. In addition, DELLA genes BdSLR1 and BdSLRL1 were functionally characterized to play a role in plant growth via the GA signal pathway, consistent with GO annotations and KEGG pathway analyses. Conclusions Systematic analyses of BdGRAS genes indicated that members of the same subfamily may play similar roles. This was supported by the conserved functions of BdSLR1 and BdSLRL1 in GA pathway. These results laid a foundation for further functional elucidation of BdGRAS genes, especially, BdSLR1 and BdSLRL1 . Electronic supplementary material The online version of this article (10.1186/s12864-019-5985-6) contains supplementary material, which is available to authorized users.

Myelocytomatosis oncogenes (MYC) transcription factors (TFs) belong to basic helix-loop-helix (bHLH) TF family and have a special bHLH_MYC_N domain in the N-terminal region. Presently, there is no detailed and systematic analysis of MYC TFs in wheat, rice, and Brachypodium distachyon. In this study, 26 TaMYC, 7 OsMYC, and 7 BdMYC TFs were identified and their features were characterized. Firstly, they contain a JAZ interaction domain (JID) and a putative transcriptional activation domain (TAD) in the bHLH_MYC_N region and a BhlH region in the C-terminal region. In some cases, the bHLH region is followed by a leucine zipper region; secondly, they display tissue-specific expression patterns: wheat MYC genes are mainly expressed in leaves, rice MYC genes are highly expressed in stems, and B. distachyon MYC genes are mainly expressed in inflorescences. In addition, three types of cis-elements, including plant development/growth-related, hormone-related, and abiotic stresses-related were identified in different MYC gene promoters. In combination with the previous studies, these results indicate that MYC TFs mainly function in growth and development, as well as in response to stresses. This study laid a foundation for the further functional elucidation of MYC genes.

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By regulating the pre-mRNA splicing of other genes and themselves, plant serine/arginine-rich (SR) proteins play important roles in development and in response to abiotic stresses. Presently, the functions of most plant SR protein genes remain unclear. Wheat (Triticum aestivum) and Brachypodium distachyon are closely related species. In this study, 40 TaSR and 18 BdSR proteins were identified respectively, and they were classified into seven subfamilies: SR, RS, SCL, RSZ, RS2Z, SC35, and SR45. Similar to Arabidopsis and rice SR protein genes, most TaSR and BdSR protein genes are expressed extensively. Surprisingly, real-time polymerase chain reaction (RT-PCR) analyses showed that no alternative splicing event was found in TaSR protein genes, and only six BdSR protein genes are alternatively spliced genes. The detected alternatively spliced BdSR protein genes and transcripts are much fewer than in Arabidopsis, rice, maize, and sorghum. In the promoter regions, 92 development-related, stress-related, and hormone-related cis-elements were detected, indicating their functions in development and in response to environmental stresses. Meanwhile, 19 TaSR and 16 BdSR proteins were predicted to interact with other SR proteins or non-SR proteins, implying that they are involved in other functions in addition to modulating pre-mRNA splicing as essential components of the spliceosome. These results lay a foundation for further analyses of these genes.

Background Plant Trihelix transcription factors, specifically bind to GT elements and play important roles in plant physiology and development. Wheat is a main cereal crop. Brachypodium distachyon is a close relative of wheat and has been described as a new model species for studying of grass functional genomics. Presently, little is known about wheat and B. distachyon Trihelix genes. Results In 51 species, 2387 Trihelix genes were identified, including 80 wheat Trihelix genes and 27 B. distachyon Trihelix genes. Consistent with the results of previous studies, these genes were classified into five subfamilies: GT-1, GT-2, SIP1, GTγ, and SH4. Members of the same subfamily shared similar gene structures and common motifs. Most TaGT and BdGT genes contained many kinds of cis -elements, such as development-, stress-, and phytohormone-related cis -acting elements. Additionally, 21 randomly selected TaGT genes were mainly expressed in the roots and flowers, while the expression of 19 selected BdGT genes was constitutive. These results indicate that the roles of Trihelix genes in wheat and B. distachyon might have diversified during the evolutionary process. The expression of the most selected TaG T and BdGT genes was down-regulated when exposed to low temperatures, NaCl, ABA, and PEG, implying that TaGT and BdGT genes negatively respond to abiotic stress. On the contrary, the expression of some genes was up-regulated under heat stress. Conclusions Trihelix genes exist extensively in plants and have many functions. During the evolutionary process, this gene family expanded and their functions diversified. As a result, the expression pattern and functions of members of the same family might be different. This study lays a foundation for further functional analyses of TaGT and BdGT genes. Electronic supplementary material The online version of this article (10.1186/s12864-019-5494-7) contains supplementary material, which is available to authorized users.