Growth-regulating Factor Family Research Articles

Molecular Mechanisms Regulating GRF Activity in Plant Growth, Development, and Environmental Responses.

Plants rely on complex regulatory mechanisms to ensure proper growth and development. As sessile organisms, these mechanisms must be flexible enough to adapt to changes in the environment. The GROWTH-REGULATING FACTORs (GRFs) are plant-specific transcription factors that act as a central hub controlling plant growth and development, offering promising biotechnological applications to enhance plant performance. Here, we analyze the complex molecular mechanisms that regulate GRF activity, and how their natural and synthetic variants can impact on plant growth and development. We describe the biological roles of the GRFs and examine how they regulate gene expression and contribute to the control of organ growth and the plant's response to a changing environment. This review focuses on the premise that unlocking their full biotechnological potential requires a thorough understanding of the various regulatory layers governing GRF activity, the functional divergence among GRF family members and the gene networks that they regulate.

Genome-wide identification of the GRF family in sweet orange (Citrus sinensis) and functional analysis of the CsGRF04 in response to multiple abiotic stresses

BackgroundCitrus is one of the most valuable fruits worldwide and an economic pillar industry in southern China. Nevertheless, it frequently suffers from undesirable environmental stresses during the growth cycle, which severely restricts the growth, development and yield of citrus. In plants, the growth-regulating factor (GRF) family of transcription factors (TF) is extensively distributed and plays an vital part in plant growth and development, hormone response, as well as stress adaptation. However, the systematic identification and functional analysis of GRF TFs in citrus have not been reported.ResultsHere, a genome-wide identification of GRF TFs was performed in Citrus sinensis, 9 members of CsGRFs were systematically identified and discovered to be scattered throughout 5 chromosomes. Subsequently, physical and chemical properties, phylogenetic relationships, structural characteristics, gene duplication events, collinearity and cis-elements of promoter were elaborately analyzed. In particular, the expression patterns of the CsGRF genes in response to multiple phytohormone and abiotic stress treatments were investigated. Predicated on this result, CsGRF04, which exhibited the most differential expression pattern under multiple phytohormone and abiotic stress treatments was screened out. Virus-induced gene silencing (VIGS) technology was utilized to obtain gene silenced plants for CsGRF04 successfully. After the three stress treatments of high salinity, low temperature and drought, the CsGRF04-VIGS lines showed significantly reduced resistance to high salinity and low temperature stresses, but extremely increased resistance to drought stress.ConclusionsTaken together, our findings systematically analyzed the genomic characterization of GRF family in Citrus sinensis, and excavated a CsGRF04 with potential functions under multiple abiotic stresses. Our study lay a foundation for further study on the function of CsGRFs in abiotic stress and hormone signaling response.

Identification, Evolution and Expression Analysis of GRF Family Reveals Their Involvement in Shoot Growth and Abiotic Stress Response in Moso Bamboo

Growth-regulating factors (GRFs) play an important role in regulating plant organ development, acting primarily as positive regulators of cell proliferation. However, research on the evolutionary history and expression patterns of the moso bamboo GRF family has been limited. In this study, a total of 24 GRFs have been identified in the Moso bamboo genome, and they have been categorized into four subfamilies. Estimation of the divergence time of paralogous gene pairs provided evidence supporting the significant contribution of recent whole-genome duplication events in the expansion of the GRF gene family. Sliding window analysis revealed that coding regions of a few PheGRFs, including the WRC and QLQ domains, may have undergone positive selection, possibly due to the redundant functions of paralogous genes. Coexpression network analysis further revealed the regulatory role of miR396 and various lncRNAs in controlling PheGRF expression. Based on the analysis of tissue-specific expression patterns using transcriptome sequencing, qRT-PCR results, and in situ hybridization, it was observed that most GRFs, particularly PheGRF6a and PheGRF9b, exhibited high levels of accumulation in the moso bamboo shoot. This suggests that the involvement of most PheGRF genes may be crucial for the growth and development of the bamboo shoot. A yeast two-hybrid screening revealed interactions between PheGRF9b and several proteins associated with plant growth and development, including PH02Gene11097.t1 (GIF3), PH02Gene37618.t (Phytochrome B), and PH02Gene01921.t3 (WD40). Based on transcriptome expression analysis, it was observed that a substantial number of PheGRFs exhibited significant variations under cold or drought stress treatments, and most of these genes were found to be downregulated, suggesting their role as abiotic stress-responsive genes. Our findings offer new insights into the GRF family of moso bamboo and provide some experimental evidence to support further gene functional validation research of PheGRF.

Genome-wide identification, phylogeny, and expression analysis of GRF transcription factors in pineapple (Ananas comosus).

Pineapple is the only commercially grown fruit crop in the Bromeliaceae family and has significant agricultural, industrial, economic, and ornamental value. GRF (growth-regulating factor) proteins are important transcription factors that have evolved in seed plants (embryophytes). They contain two conserved domains, QLQ (Gln, Leu, Gln) and WRC (Trp, Arg, Cys), and regulate multiple aspects of plant growth and stress response, including floral organ development, leaf growth, and hormone responses. The GRF family has been characterized in a number of plant species, but little is known about this family in pineapple and other bromeliads. We identified eight GRF transcription factor genes in pineapple, and phylogenetic analysis placed them into five subfamilies (I, III, IV, V, VI). Segmental duplication appeared to be the major contributor to expansion of the AcGRF family, and the family has undergone strong purifying selection during evolution. Relative to that of other gene families, the gene structure of the GRF family showed less conservation. Analysis of promoter cis-elements suggested that AcGRF genes are widely involved in plant growth and development. Transcriptome data and qRT-PCR results showed that, with the exception of AcGRF5, the AcGRFs were preferentially expressed in the early stage of floral organ development and AcGRF2 was strongly expressed in ovules. Gibberellin treatment significantly induced AcGRF7/8 expression, suggesting that these two genes may be involved in the molecular regulatory pathway by which gibberellin promotes pineapple fruit expansion. AcGRF proteins appear to play a role in the regulation of floral organ development and the response to gibberellin. The information reported here provides a foundation for further study of the functions of AcGRF genes and the traits they regulate.

Comprehensive evolutionary analysis of growth-regulating factor gene family revealing the potential molecular basis under multiple hormonal stress in Gramineae crops.

Growth-regulating factors (GRFs) are plant-specific transcription factors that contain two highly conserved QLQ and WRC domains, which control a range of biological functions, including leaf growth, floral organ development, and phytohormone signaling. However, knowledge of the evolutionary patterns and driving forces of GRFs in Gramineae crops is limited and poorly characterized. In this study, a total of 96 GRFs were identified from eight crops of Brachypodium distachyon, Hordeum vulgare, Oryza sativa L. ssp. indica, Oryza rufipogon, Oryza sativa L. ssp. japonica, Setaria italic, Sorghum bicolor and Zea mays. Based on their protein sequences, the GRFs were classified into three groups. Evolutionary analysis indicated that the whole-genome or segmental duplication plays an essential role in the GRFs expansion, and the GRFs were negatively selected during the evolution of Gramineae crops. The GRFs protein function as transcriptional activators with distinctive structural motifs in different groups. In addition, the expression of GRFs was induced under multiple hormonal stress, including IAA, BR, GA3, 6BA, ABA, and MeJ treatments. Specifically, OjGRF11 was significantly induced by IAA at 6h after phytohormone treatment. Transgenic experiments showed that roots overexpressing OjGRF11 were more sensitive to IAA and affect root elongation. This study will broaden our insights into the origin and evolution of the GRF family in Gramineae crops and will facilitate further research on GRF function.

Genome-wide identification of BcGRF genes in flowering Chinese cabbage and preliminary functional analysis of BcGRF8 in nitrogen metabolism.

Growth-regulating factors (GRFs) are a unique family of transcription factors with well-characterized functions in plant growth and development. However, few studies have evaluated their roles in the absorption and assimilation of nitrate. In this study, we characterized the GRF family genes of flowering Chinese cabbage (Brassica campestris), an important vegetable crop in South China. Using bioinformatics methods, we identified BcGRF genes and analyzed their evolutionary relationships, conserved motifs, and sequence characteristics. Through genome-wide analysis, we identified 17 BcGRF genes distributed on seven chromosomes. A phylogenetic analysis revealed that the BcGRF genes could be categorized into five subfamilies. RT-qPCR analysis showed that BcGRF1, 8, 10, and 17 expression clearly increased in response to nitrogen (N) deficiency, particularly at 8 h after treatment. BcGRF8 expression was the most sensitive to N deficiency and was significantly correlated with the expression patterns of most key genes related to N metabolism. Using yeast one-hybrid and dual-luciferase assays, we discovered that BcGRF8 strongly enhances the driving activity of the BcNRT1.1 gene promoter. Next, we investigated the molecular mechanism by which BcGRF8 participates in nitrate assimilation and N signaling pathways by expressing it in Arabidopsis. BcGRF8 was localized in the cell nucleus and BcGRF8 overexpression significantly increased the shoot and root fresh weights, seedling root length, and lateral root number in Arabidopsis. In addition, BcGRF8 overexpression considerably reduced the nitrate contents under both nitrate-poor and -rich conditions in Arabidopsis. Finally, we found that BcGRF8 broadly regulates genes related to N uptake, utilization, and signaling. Our results demonstrate that BcGRF8 substantially accelerates plant growth and nitrate assimilation under both nitrate-poor and -rich conditions by increasing the number of lateral roots and the expression of genes involved in N uptake and assimilation, providing a basis for crop improvement.

Genome-wide identification of growth-regulating factor transcription factor family related to leaf and stem development in alfalfa.

Growth-regulating factors (GRFs) play crucial roles in plant growth and stress response. To date, there have been no reports of the analysis and identification of the GRF transcription factor family in alfalfa. In this study, we identified 27 GRF family members from alfalfa (Medicago sativa L.) “Xinjiang Daye”, and analyzed their physicochemical properties. Based on phylogenetic analysis, these MsGRFs were divided into five subgroups, each with a similar gene structure and conserved motifs. MsGRFs genes are distributed on 23 chromosomes, and all contain QLQ and WRC conserved domains. The results of the collinearity analysis showed that all MsGRFs are involved in gene duplication, including multiple whole-genome duplication or segmental duplication and a set of tandem duplication, indicating that large-scale duplication is important for the expansion of the GRF family in alfalfa. Several hormone-related and stress-related cis-acting elements have been found in the promoter regions of MsGRFs. Some MsGRFs were highly expressed in young leaves and stems, and their expression decreased during development. In addition, the leaf size of different varieties was found to vary, and MsGRF1 to 4, MsGRF18 to 20, and MsGRF22 to 23 were differentially expressed in large and small leaf alfalfa varieties, suggesting that they are critical in the regulation of leaf size. The results of this study can benefit further exploration of the regulatory functions of MsGRFs in growth and development, and can identify candidate genes that control leaf size development.

Genome-Wide Identification and Structural Characterization of Growth-Regulating Factors (GRFs) in Actinida eriantha and Actinidia chinensis.

Growth-regulating factors (GRFs) encode plant-specific transcription factors that play a vital role in regulation of plant growth, development, and stress response. Although GRFs have been identified in various plants, there is no reported work available in Actinidia (commonly known as kiwifruit) so far. In the present study, we identified 22 GRF genes on A. chinensis (hereafter A. chinensis is referred to as Ac, and GRF genes in A. chinensis are referred to as AcGRF) distributed on 17 chromosomes and one contig, and 26 GRF genes in A. eriantha (hereafter A. eriantha is referred to as Ae, and GRF genes in A. eriantha are referred to as AeGRF) distributed on 21 chromosomes. Phylogenetic analysis showed that kiwifruit GRF proteins were clustered into five distinct groups. Additionally, kiwifruit GRFs showed motif composition and gene structure similarities within the same group. Synteny analysis showed that whole-genome duplication played a key role in the expansion of the GRF family in kiwifruit. The higher expression levels of kiwifruit GRFs in young tissues and under stress conditions indicated their regulatory role in kiwifruit growth and development. We observed two genes in Ae (AeGRF6.1, AeGRF6.2) and two genes in Ac (AcGRF6.1, AeGRF6.2) significantly upregulated in different RNA-seq datasets. The presence of conserved protein structures and cis-regulatory elements caused functional divergence in duplicated gene pairs. The subcellular localization indicated the presence of kiwifruit GRFs in the nucleus of the plant cell. Protein-protein interaction analysis predicted AtGIF protein orthologs for AcGRFs and AeGRFs. Taken together, we systematically analyzed the characterization of kiwifruit GRF family members for their potential role in kiwifruit development and Pseudomonas syringae pv. actinidiae (Psa.) invasion response. Further functional studies of kiwifruit GRFs in plant growth, development, and stress response will provide valuable insights for kiwifruit breeders.

Comprehensive Analysis for GRF Transcription Factors in Sacred Lotus (Nelumbo nucifera).

Sacred lotus (Nelumbo nucifera) is an aquatic perennial plant with essential food, ornamental, and pharmacological value. Growth-regulating factor (GRF) is a transcription factor (TF) family that plays an important role in regulating the growth and development of plants. In this study, a comprehensive analysis of the GRF family in N. nucifera was performed, and its role in N. nucifera development was studied. A total of eight GRF genes were identified in the N. nucifera genome. Phylogenetic analysis divided the 38 GRF genes into six clades, while the NuGRFs only contained five clades. The analyses of gene structures, motifs, and cis-acting regulatory elements of the GRF gene family were performed. In addition, the chromosome location and collinearity were analyzed. The expression pattern based on transcriptomic data and real-time reverse transcription-quantitative PCR (qRT-PCR) revealed that the GRF genes were expressed in multiple organs and were abundant in actively growing tissues, and the expression levels decreased as the age of N. nucifera increased. Then, 3D structures of the NuGRF proteins were predicted by homology modeling. Finally, the subcellular localization of GRF1 was ascertained in the tobacco leaf through a vector. Therefore, this study provides a comprehensive overview of the GRF TF family in N. nucifera.

Genome-wide identification and analysis of GRF (growth-regulating factor) gene family in Camila sativa through in silico approaches

ObjectiveGRFs (growth-regulating factors) are transcription factors that significantly influence plant development and stress response. In the present study, genome-wide discovery and analysisof the CsGRF family and its significant roles in Camelina sativa development was done utilizing model GRF genes of Arabidopsis thaliana that are available in the public domain databases. MethodsGene structure analysis, exon and intron structures, phylogenetic analysis, mapping of various GRF genes on the chromosome's distribution, conserved domain analysis, and synteny analysis will be systematically categorized. Investigation of cis-regulatory elements will also be carried out using various bioinformatic approaches. ResultsIn the C. sativa genome, 19 GRF gene members and 4 GRF variants were found using publicly available genomic data. The encoding regions of GRF1, GRF2, GRF2A, and GRF8 were similar and maximal, i.e., 2046 bp, which encodes 555 amino acids, followed by GRF2. C. sativa has the most GRF gene representatives, scattered throughout six chromosomes, and appears to have 3 to 4 protein-coding regions. GRF is involved in biological processes (44.7%), molecular activities (50%), and cellular functions(24.6%). The molecular weights of GRF proteins range from 29.57 to 61.57 kDa. The majority of GRF proteins have a theoretical PI between 7.0 and 9.42. All CsGRFshave preserved QLQ and WRC (Trp, Arg, Cys) domains. All C. sativa proteins have SNH and QG (Gln, Gly) domains. The motif composition and gene structure of CsGRFs from the same sub-group were similar. In the analysis of conserved domains, the motifs of CsGRF genes were highly conserved. According to synteny investigations, large-scale duplications played a significant role in expanding the CsGRF family. ConclusionsOur findings will help tounderstand the functions of the GRF family in the evolutionary and physiological aspects of C. sativa and provide a future direction for novel work to improve crop productivity. Identifying single-gene families in multiple plant species is best to enhance crop productivity, growth, and development.

Identification, Molecular Characteristics, and Evolution of GRF Gene Family in Foxtail Millet (Setaria italica L.).

Growth-regulating factor (GRF) is a multigene family that plays a vital role in the growth and development of plants. In the past, the GRF family of many plants has been studied. However, there is not a report about identification and evolution of GRF in foxtail millet (Setaria italia). Here, we identified 10 GRF genes in foxtail millet. Seven (70.00%) were regulated by Sit-miR396, and there were 19 optimal codons in GRFs of foxtail millet. Additionally, we found that WGD or segmental duplication have affected GRFs in foxtail millet between 15.07 and 45.97 million years ago. Regarding the GRF gene family of land plants, we identified a total of 157 GRF genes in 15 representative land plants. We found that GRF gene family originated from Group E, and the GRF gene family in monocots was gradually shrinking. Also, more loss resulted from the small number of GRF genes in lower plants. Exploring the evolution of GRF and functional analysis in the foxtail millet help us to understand GRF better and make a further study about the mechanism of GRF. These results provide a basis for the genetic improvement of foxtail millet and indicate an improvement of the yield.

Genome-wide analysis of growth-regulating factors (GRFs) in Triticum aestivum.

The Growth-Regulating Factor (GRF) family encodes a type of plant-specific transcription factor (TF). GRF members play vital roles in plant development and stress response. Although GRF family genes have been investigated in a variety of plants, they remain largely unstudied in bread wheat (Triticum aestivum L.). The present study was conducted to comprehensively identify and characterize the T. aestivum GRF (TaGRF) gene family members. We identified 30 TaGRF genes, which were divided into four groups based on phylogenetic relationship. TaGRF members within the same subgroup shared similar motif composition and gene structure. Synteny analysis suggested that duplication was the dominant reason for family member expansion. Expression pattern profiling showed that most TaGRF genes were highly expressed in growing tissues, including shoot tip meristems, stigmas and ovaries, suggesting their key roles in wheat growth and development. Further qRT-PCR analysis revealed that all 14 tested TaGRFs were significantly differentially expressed in responding to drought or salt stresses, implying their additional involvement in stress tolerance of wheat. Our research lays a foundation for functional determination of TaGRFs, and will help to promote further scrutiny of their regulatory network in wheat development and stress response.

Molecular evolution and diversification of the GRF transcription factor family.

- Growth Regulating Factors (GRFs) comprise a transcription factor family with important functions in plant growth and development. They are characterized by the presence of QLQ and WRC domains, responsible for interaction with proteins and DNA, respectively. The QLQ domain is named due to the similarity to a protein interaction domain found in the SWI2/SNF2 chromatin remodeling complex. Despite the occurrence of the QLQ domain in both families, the divergence between them had not been further explored. Here, we show evidence for GRF origin and determined its diversification in angiosperm species. Phylogenetic analysis revealed 11 well-supported groups of GRFs in flowering plants. These groups were supported by gene structure, synteny, and protein domain composition. Synteny and phylogenetic analyses allowed us to propose different sets of probable orthologs in the groups. Besides, our results, together with functional data previously published, allowed us to suggest candidate genes for engineering agronomic traits. In addition, we propose that the QLQ domain of GRF genes evolved from the eukaryotic SNF2 QLQ domain, most likely by a duplication event in the common ancestor of the Charophytes and land plants. Altogether, our results are important for advancing the origin and evolution of the GRF family in Streptophyta.

Cloning and Primary Functional Analysis of <i>PeGRF1</i> in <i>Phyllostachys edulis</i>

To explore the role of Growth regulating-factor (GRF) in the growth of bamboo shoots, one GRF gene was isolated from moso bamboo ( Phyllostachys edulis ) by RT-PCR. Bioinformatics methods were used for gene sequence analysis, and the expression pattern of the GRF gene in bamboo shoots at different development stages was analyzed by qRT-PCR. Simultaneously, ectopic expression in Arabidopsis was conducted to validate the gene function. The result showed that the isolated gene from moso bamboo was 1 164 bp, encoding 387 amino acids, which was named as PeGRF1 . Protein sequence analysis showed that PeGRF1 had the complete typical domains (WRC and QLQ) of GRF family. The phylogenetic analysis demonstrated that PeGRF1 were clustered closer to the GRFs of monocotyledonous plants such as Oryza sativa , indicating they had close relationship. PeGRF1 expressed predominantly in young bamboo shoots. Meanwhile, the expression level of PeGRF1 was significantly higher during rapid growth stage than that during slow growth stage of bamboo shoots, and the expression level of PeGRF1 in the upper and middle of bamboo shoots was significantly higher than that in the base. Overexpression of PeGRF1 could increase the plant height of transgenic Arabidopsis . Taken together, our results demonstrated that PeGRF1 was involved in development of bamboo shoots, which provided references for elucidating the biological functions of GRF genes in bamboo.

Genome-wide identification of growth-regulating factors in moso bamboo (Phyllostachys edulis): in silico and experimental analyses.

Growth-regulating factor (GRF), a small plant-specific transcription factor (TF) family, is extensively involved in the regulation of growth and developmental processes. However, the GRF family has not been comprehensively studied in moso bamboo (Phyllostachys edulis), a typical non-timber forest member. Here, 18 GRF genes were identified and characterized from the moso bamboo genome, and they clustered into three subfamilies (A, B and C). PeGRF genes were analyzed to determine their gene structures, conserved motifs and promoter. The non-synonymous/synonymous substitution ratios of paralogous and orthologous were less than 1, indicating that the GRF family mainly experienced purifying selection during evolution. According to the analysis of tissue-specific expression patterns, the participation of moso bamboo GRFs might be required during the formation and development of these five tissues. Moreover, PeGRF proteins might be involved in the regulation of plant development in biological processes. The qRT-PCR analysis demonstrated that PeGRF genes played essential roles in combating hormonal stresses and they might be involved in hormone regulation. PeGRF11, a nuclear localized protein as assessed by a subcellular localization assay, could interact with PeGIF3 in yeast and in planta according to yeast two-hybridization and bimolecular fluorescence complementation assays (BiFC) assays. But PeGRF11, as a TF, had no transcriptional activity in yeast. These results provide useful information for future functional research on the GRF genes in moso bamboo.

Genome-wide identification of GRF transcription factors in soybean and expression analysis of GmGRF family under shade stress

BackgroundThe Growth-regulating factor (GRF) family encodes plant-specific transcription factors which contain two conserved domains, QLQ and WRC. Members of this family play vital roles in plant development and stress response processes. Although GRFs have been identified in various plant species, we still know little about the GRF family in soybean (Glycine max).ResultsIn the present study, 22 GmGRFs distributed on 14 chromosomes and one scaffold were identified by searching soybean genome database and were clustered into five subgroups according to their phylogenetic relationships. GmGRFs belonging to the same subgroup shared a similar motif composition and gene structure. Synteny analysis revealed that large-scale duplications played key roles in the expansion of the GmGRF family. Tissue-specific expression data showed that GmGRFs were strongly expressed in growing tissues, including the shoot apical meristems, developing seeds and flowers, indicating that GmGRFs play critical roles in plant growth and development. On the basis of expression analysis of GmGRFs under shade conditions, we found that all GmGRFs responded to shade stress. Most GmGRFs were down-regulated in soybean leaves after shade treatment.ConclusionsTaken together, this research systematically analyzed the characterization of the GmGRF family and its primary roles in soybean development and shade stress response. Further studies of the function of the GmGRFs in the growth, development and stress tolerance of soybean, especially under shade stress, will be valuable.

Genome-wide identification and expression analysis of GRF genes regulating apple tree architecture

Growth-regulating factor (GRF) proteins comprise a family of plant-specific transcription factors that play crucial roles in regulating plant architecture. However, information pertaining to the GRF gene family in apple (Malus × domestica) is limited. In the present study, 16 GRF family members were identified in the apple genome, and nine were predicted to be putative targets of apple microRNA396 (miR396). Phylogenetic and synteny analyses of MdGRF genes indicated that gene duplication events have likely contributed to the expansion and evolution of MdGRFs. Moreover, several pairs of MdGRF/AtGRF homologs were identified. The tissue-specific expression patterns of MdmiR396–MdGRF genes in different tissues and in the ArrayExpress database were subsequently characterized. The analyses indicated that they had opposing functions. Exogenous brassinolide, gibberellic acid, 1-naphthylacetic acid, and 6-benzylaminopurine increased primary shoot lengths and diameters, and elevated the expression levels of several MdGRF genes. The expression levels of MdmiR396 and MdGRF genes were reduced in the standard cultivar “Nagafu 2” compared with its short branch spur-type bud mutation “Yanfu 6,” and in the standard graft combination Nagafu 2/Nagafu 2 compared with the dwarfing graft combination Nagafu 2/“Malling 9.” Thus, MdmiR396-MdGRF may be involved in the regulation of apple tree size in response to hormone signals and in different apple varieties and grafting combinations. This work provides a basis for further functional research on MdmiR396-MdGRFs and their potential involvement in the regulation of apple tree architecture.

Characterization and expression analysis of growth regulating factor (GRF) family genes in cucumber

The growth regulating factor (GRF) family is a conserved class of transcription factors involved in various biological processes in plants. However, there have been only a few studies of the GRF family genes in cucumber, Cucumis sativus (Cs). In this study, we identified and characterized 8 CsGRF genes in cucumber. Two highly conserved domains, QLQ and WRC, were identified to be present in all CsGRF proteins. In addition, three less conserved domains (FFD, TQL, and GGPL) were also detected in some CsGRF members. Based on phylogenetic analysis, the GRF genes from cucumber, Arabidopsis, tomato, rice and maize could be classified into 10 groups, and CsGRFs were clustered closer with the GRF genes from dicots (Arabidopsis and tomato) than with those from monocots (rice and maize). Promoter analysis revealed that the CsGRF genes were involved in cucumber growth and development as well as in responses to various hormones and stresses. Transcriptome data showed that the CsGRF genes have distinct expression patterns in different tissues, especially in ovaries and leaves. Expression profiling analysis indicated that all CsGRF genes were responsive to salt and drought stress treatments. These results demonstrate that the cucumber GRF gene family may function in organ development and plant stress responses.

UV-B Inhibits Leaf Growth through Changes in Growth Regulating Factors and Gibberellin Levels.

Ultraviolet-B (UV-B) radiation affects leaf growth in a wide range of species. In this work, we demonstrate that UV-B levels present in solar radiation inhibit maize (Zea mays) leaf growth without causing any other visible stress symptoms, including the accumulation of DNA damage. We conducted kinematic analyses of cell division and expansion to understand the impact of UV-B radiation on these cellular processes. Our results demonstrate that the decrease in leaf growth in UV-B-irradiated leaves is a consequence of a reduction in cell production and a shortened growth zone (GZ). To determine the molecular pathways involved in UV-B inhibition of leaf growth, we performed RNA sequencing on isolated GZ tissues of control and UV-B-exposed plants. Our results show a link between the observed leaf growth inhibition and the expression of specific cell cycle and developmental genes, including growth-regulating factors (GRFs) and transcripts for proteins participating in different hormone pathways. Interestingly, the decrease in the GZ size correlates with a decrease in the concentration of GA19, the immediate precursor of the active gibberellin, GA1, by UV-B in this zone, which is regulated, at least in part, by the expression of GRF1 and possibly other transcription factors of the GRF family.

Genome-wide in silico identification, characterization and transcriptional analysis of the family of growth-regulating factors in common bean (Phaseolus vulgaris L.) subjected to polyethylene glycol-induced drought stress

According to most recent findings, growth regulating factors (GRFs) are plant-specific transcription factors (TFs) that play important roles in many processes, including abiotic and biotic stress response mechanisms. Completion of the common bean (Phaseolus vulgaris) genome project has provided researchers with the opportunity to identify all GRF genes in this species. With this aim, a genome-wide in silico study was performed and 10 GRF proteins (called PhvGRFs) were identified in the common bean genome. Conserved and mandatory motifs (QLQ and WRC) were confirmed in all identified PhvGRFs and two segmental duplication events were determined. Most of the PhvGRFs were found to be more similar to Arabidopsis thaliana GRFs than to Zea mays GRFs in a phylogenetic tree. According to the expression analysis of 10 PhvGRFs, inversely related expression patterns were observed in the roots of Yakutiye and Zulbiye cultivars based on their capacity to adopt to drought stress. After drought treatment of the Zulbiye cultivar, a drought-sensitive common bean cultivar, PhvGRF1, PhvGRF2, PhvGRF3, PhvGRF5, PhvGRF6, PhvGRF9 and PhvGRF10 genes were upregulated 2- to 4-fold in root tissues, as compared to the untreated control. The trend of PhvGRF1, PhvGRF2, PhvGRF3, PhvGRF5, PhvGRF6, PhvGRF7, PhvGRF9 and PhvGRF10 genes showed a consistent decline of 2- to 6-fold in root tissues of the drought-tolerant Yakutiye cultivar subjected to 24 h of drought stress. We demonstrated that the expression patterns of the identified PhvGRFs correlated with the drought-stress response in a cultivar-specific manner in the common bean. We suggest that members of the GRF family can also be used for genetic engineering applications in the common bean.