Computational identification and systematic classification of novel GRAS genes in Isatis indigotica

Genome-wide analysis of the GRAS gene family in Liriodendron chinense reveals the putative function in abiotic stress and plant development

Introduction

GRAS genes encode plant-specific transcription factors that play essential roles in plant growth and development. However, the members and the function of the GRAS gene family have not been reported in Liriodendron chinense. L. chinense, a tree species in the Magnolia family that produces excellent timber for daily life and industry. In addition, it is a good relict species for plant evolution research.

Methods

Therefore, we conducted a genome-wide study of the LcGRAS gene family and identified 49 LcGRAS genes in L. chinense.

Results

We found that LcGRAS could be divided into 13 sub-groups, among which there is a unique branch named HAM-t. We carried out RNA sequencing analysis of the somatic embryos from L. chinense and found that LcGRAS genes are mainly expressed after heart-stage embryo development, suggesting that LcGRAS may have a function during somatic embryogenesis. We also investigated whether GRAS genes are responsive to stress by carrying out RNA sequencing (RNA-seq) analysis, and we found that the genes in the PAT subfamily were activated upon stress treatment, suggesting that these genes may help plants survive stressful environments. We found that PIF was downregulated and COR was upregulated after the transient overexpression of PATs, suggesting that PAT may be upstream regulators of cold stress.

Discussion

Collectively, LcGRAS genes are conserved and play essential roles in plant development and adaptation to abiotic stress.

Isatis indigotica: from (ethno) botany, biochemistry to synthetic biology

Isatis indigotica Fort. (Chinese woad) is a species with an ancient and well-documented history as an indigo dye and medicinal plant. It is often confused with Isatis tinctoria L. (European woad), a medicinal plant in Europe. Here, the differences between I. indigotica and I. tinctoria are systematically described. The usage development history, clinical applications and pharmacological activities, and chemical components of I. indigotica are also summarized. Lignans, indole alkaloids, and their corresponding derivatives have been identified as the major active ingredients of I. indigotica and are associated with anti-viral, anti-inflammatory, anti-cancer, and other health-promoting activities. Notable progress has been made in understanding the biosynthetic pathway and regulation mechanism of lignans and indole alkaloids in I. indigotica, the results from which should facilitate the process of targeted metabolic engineering or synthetic biology. Moreover, multiple biotechnology methods such as polyploid breeding and genetic engineering have been used with I. indigotica to result in, for example, greater yields, higher levels of bioactive component accumulation, and enhanced stress tolerance to salt, drought, and insects. Some issues require additional analyses, and suggestions for future research on I. indigotica are also discussed.

Genome-wide survey and expression analyses of the GRAS gene family in Brassica napus reveals their roles in root development and stress response

Genome-wide identification, classification, expression analyses, and functional characterization of GRAS genes in oil crop, Brassica napus, indicate their importance in root development and stress response. GRAS proteins are a plant-specific transcription factor gene family involved in tissues development and stress response. We classified 87 putative GRAS genes in the Brassica napus genome (BnGRASs) into 13 subfamilies by phylogenetic analysis. The C-terminal GRAS domains of Brassica napus (B. napus) proteins were less conserved among subfamilies, but were conserved within each subfamily. A series of analyses revealed that 89.7% of the BnGRASs did not have intron insertions, and 24 specific-motifs were found at the N-terminal. A highly conserved microRNA 171 (miRNA171) target was observed specifically in the HAM subfamily across land plants. A total of 868 pairs of interaction proteins were predicted, the primary of which were transcription factors involved in transcriptional regulation and signal transduction. Integrated comparative analysis of GRAS genes across 26 species of algae, mosses, ferns, gymnosperms, and angiosperms revealed that this gene family originated in early mosses and was classified into 19 subfamilies, 14 of which may have originated prior to bryophyte evolution. RNA-Seq analysis demonstrated that most BnGRASs were widely expressed in different tissues/organs at different stages in B. napus, and 24 BnGRASs were highly/specifically expressed in roots. Results from a qRT-PCR analysis suggested that two BnGRASs belonging to SCR and LISCL subfamilies potentially have important roles in the stress response of roots.

Genome-wide Identification, Classification, Expression and Duplication Analysis of GRAS Family Genes in Juglans regia L

Fifty-two GRAS genes are identified in walnut genome. Based on the evolutionary relationship and motif analysis, the walnut GRAS gene family was divided into eight subfamilies, and the sequence features analysis of JrGRAS proteins showed that the JrGRAS protein sequences were both conserved and altered during the evolutionary process. Gene duplication analysis indicated that seven GRAS genes in walnut have orthologous genes in other species, and five of them occurred duplicated events in walnut genome. Expression pattern analysis of the GRAS family genes in walnut showed that two JrGRAS genes (JrCIGRa-b and JrSCL28a) were differentially expressed between flower bud and leaf bud (p < 0.01), and two JrGRAS genes (JrCIGRa-b and JrSCL13b-d) were differentially expressed between the different development stages of flower buds transition (p < 0.01), besides, three hub genes (JrGAIa, JrSCL3f and JrSHRc) were identified by co-expression analysis, which suggested these GRAS genes may play an important role in regulating the development of apical meristem in walnut. This study laid a foundation for further understanding of the function of GRAS family genes in walnut.

Construction and analysis of degradome-dependent microRNA regulatory networks in soybean

BACKGROUND

Usually the microRNA (miRNA)-mediated gene regulatory network (GRN) is constructed from the investigation of miRNA expression profiling and target predictions. However, the higher/lower expression level of miRNAs does not always indicate the higher/lower level of cleavages and such analysis, thus, sometimes ignores the crucial cleavage events. In the present work, the degradome sequencing data were employed to construct the complete miRNA-mediated gene regulatory network in soybean, unlike the traditional approach starting with small RNA sequencing data.

RESULTS

We constructed the root-, cotyledon-, leaf- and seed-specific miRNA regulatory networks with the degradome sequencing data and the forthcoming verification of miRNA profiling analysis. As a result, we identified 205 conserved miRNA-target interactions (MTIs) involved with 6 conserved gma-miRNA families and 365 tissue-specific MTIs containing 24 root-specific, 45 leaf-specific, 63 cotyledon-specific and 225 seed-specific MTIs. We found a total of 156 miRNAs in tissue-specific MTIs including 18 tissue-specific miRNAs, however, only 3 miRNAs have consistent tissue-specific expression. Our study showed the degradome-dependent miRNA regulatory networks (DDNs) in four soybean tissues and explored their conservations and specificities.

CONCLUSIONS

The construction of DDNs may provide the complete miRNA-Target interactions in certain plant tissues, leading to the identification of the conserved and tissue-specific MTIs and sub-networks. Our work provides a basis for further investigation of the roles and mechanisms of miRNA-mediated regulation of tissue-specific growth and development in soybean.

Identification and expression of GRAS family genes in maize (Zea mays L.)

GRAS transcriptional factors have diverse functions in plant growth and development, and are named after the first three transcription factors, namely, GAI (GIBBERELLIC ACID INSENSITIVE), RGA (REPRESSOR OF GAI) and SCR (SCARECROW) identified in this family. Knowledge of the GRAS gene family in maize remains was largely unknown, and their characterization is necessary to understand their importance in the maize life cycle. This study identified 86 GRAS genes in maize, and further characterized with phylogenetics, gene structural analysis, genomic loci, and expression patterns. The 86 GRAS genes were divided into 8 groups (SCL3, HAM, LS, SCR, DELLA, SHR, PAT1 and LISCL) by phylogenetic analysis. Most of the maize GRAS genes contain one exon (80.23%) and closely related members in the phylogenetic tree had similar structure and motif composition. Different motifs especially in the N-terminus might be the sources of their functional divergence. Segmental- and tandem-duplication occurred in this family leading to expansion of maize GRAS genes and the expression patterns of the duplicated genes in the heat map according to the published microarray data were very similar. Quantitative RT-PCR (qRT-PCR) results demonstrated that the expression level of genes in different tissues were different, suggesting their differential roles in plant growth and development. The data set expands our knowledge to understanding the function of GRAS genes in maize, an important crop plant in the world.

Genome-wide characterization of GRAS family genes in Medicago truncatula reveals their evolutionary dynamics and functional diversification

The GRAS gene family is a large plant-specific family of transcription factors that are involved in diverse processes during plant development. Medicago truncatula is an ideal model plant for genetic research in legumes, and specifically for studying nodulation, which is crucial for nitrogen fixation. In this study, 59 MtGRAS genes were identified and classified into eight distinct subgroups based on phylogenetic relationships. Motifs located in the C-termini were conserved across the subgroups, while motifs in the N-termini were subfamily specific. Gene duplication was the main evolutionary force for MtGRAS expansion, especially proliferation of the LISCL subgroup. Seventeen duplicated genes showed strong effects of purifying selection and diverse expression patterns, highlighting their functional importance and diversification after duplication. Thirty MtGRAS genes, including NSP1 and NSP2, were preferentially expressed in nodules, indicating possible roles in the process of nodulation. A transcriptome study, combined with gene expression analysis under different stress conditions, suggested potential functions of MtGRAS genes in various biological pathways and stress responses. Taken together, these comprehensive analyses provide basic information for understanding the potential functions of GRAS genes, and will facilitate further discovery of MtGRAS gene functions.