Abstract
BackgroundGRAS, an important family of transcription factors, have played pivotal roles in regulating numerous intriguing biological processes in plant development and abiotic stress responses. Since the sequencing of the sorghum genome, a plethora of genetic studies were mainly focused on the genomic information. The indepth identification or genome-wide analysis of GRAS family genes, especially in Sorghum bicolor, have rarely been studied.ResultsA total of 81 SbGRAS genes were identified based on the S. bicolor genome. They were named SbGRAS01 to SbGRAS81 and grouped into 13 subfamilies (LISCL, DLT, OS19, SCL4/7, PAT1, SHR, SCL3, HAM-1, SCR, DELLA, HAM-2, LAS and OS4). SbGRAS genes are not evenly distributed on the chromosomes. According to the results of the gene and motif composition, SbGRAS members located in the same group contained analogous intron/exon and motif organizations. We found that the contribution of tandem repeats to the increase in sorghum GRAS members was slightly greater than that of fragment repeats. By quantitative (q) RT-PCR, the expression of 13 SbGRAS members in different plant tissues and in plants exposed to six abiotic stresses at the seedling stage were quantified. We further investigated the relationship between DELLA genes, GAs and grain development in S. bicolor. The paclobutrazol treatment significantly increased grain weight, and affected the expression levels of all DELLA subfamily genes. SbGRAS03 is the most sensitive to paclobutrazol treatment, but also has a high response to abiotic stresses.ConclusionsCollectively, SbGRAs play an important role in plant development and response to abiotic stress. This systematic analysis lays the foundation for further study of the functional characteristics of GRAS genes of S. bicolor.
Highlights
GRAS, an important family of transcription factors, have played pivotal roles in regulating numerous intriguing biological processes in plant development and abiotic stress responses
The predicted subcellular localization results showed that 37 Sorghum bicolor GRAS (SbGRAS) proteins were located in the nuclear region, 24 in the cytoplasm, and 20 in the chloroplast (Additional file 1: Table S1).The number of GRAS Transcription factor (TF) in S. bicolor exceeded that in A. thaliana (32) and rice (57) [8], Cucumis sativus (37) [67], Vitis vinifera (52) [44] and Tartary buckwheat (47) [53], whereas there were fewer TFs than that in Malus x domestica (127) [46] and Populus trichocarpa (102) [68]
According to the topological structure of the tree and the classification method proposed by Cenci and Rouard [9], the 164 GRAS proteins in the phylogenetic tree were divided into 13 clades, consistent with the tree topology and previous classification of the GRAS taxonomic group in angiosperms [9], and indicating no loss of those proteins during S. bicolor’s evolution. These findings revealed that GRAS proteins within the reported subfamilies that are present in different plant species play a basic role in plant development and evolution, similar to those recently reported in previous studies on some other plant species, including Amborella trichopoda, Phoenix dactylifera, Vitis vinifera, Musa acuminata, Oryza sativa (Os). sativa, A. thaliana, Theobroma cacao and Coffea canephora [9]
Summary
GRAS, an important family of transcription factors, have played pivotal roles in regulating numerous intriguing biological processes in plant development and abiotic stress responses. The LHR I region has a putative nuclear localization signal near the C terminus, which has been confirmed in the DELLA protein and is similar to the amorphous SV40 (monkey virus) [14] The latter part of the LHR II domain contains the structure LXXLL (Leu-X-X-LeuLeu; X represents any amino acid), and it is conserved in over half of the GRAS proteins [15]. Cenci and Rouard [9] proposed that the GRAS family members in angiosperms include these eight subfamilies, and NSP 1, NSP2, DLT (DWARF AND LOW TILLERING), and other subfamilies Their names are based on the more representative genes in the subfamily, such as DELLA, HAM, DLT, LS, LISCL, PAT1, SCR, SCL3, SHR, and others [6,7,8]
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