Genome-wide analysis and expression profiling of DNA-binding with one zinc finger (Dof) transcription factor family in potato

Genome-Wide Identification and Functional Characterization of the Dof Family in Dendrobium officinale

The Dof gene family represents a class of plant-specific transcription factors that play crucial regulatory roles in various biological processes, including plant growth, development, and responses to abiotic stress. However, genome-wide identification and functional characterization of the Dof gene family remain unexplored in Dendrobium officinale. In this study, we performed a genome-wide identification and functional analysis of the DoDof gene family. A total of 28 Dof family members were identified and named DoDof1-28 based on genome annotation data. Phylogenetic analysis classified these genes into four major groups (A-D) and further subdivided them into nine subfamilies. Gene structure analysis revealed that most DoDofs lack introns, with no distinct specificity observed among different subfamilies and considerable diversity within the same subfamily. Sequence alignment analysis demonstrated that all DoDof proteins contain a conserved Dof domain consisting of 52 amino acids, which includes a C2-C2 zinc finger motif and a DNA-binding domain. MEME analysis revealed that the conserved motif composition exhibits a certain degree of conservation among DoDof proteins, but significant differences exist across subfamilies. Expression pattern analysis demonstrated that DoDofs have exhibited diverse expression profiles across different developmental stages, tissues, and under abiotic stresses (such as low temperature, salinity, and drought) in D. officinale, suggesting their potential roles in plant development and stress responses. Subcellular localization analysis indicated that DoDof15, DoDof22, and DoDof24 are localized exclusively in the nucleus. Yeast one-hybrid assays revealed that DoDof22 binds to the promoter of the ABA receptor DoPYL9, while DoDof15 and DoDof24 bind to the promoter of the bHLH transcription factor DobHLH68. These results suggest that DoDof proteins may regulate the growth, development, and stress response processes of D. officinale by binding to the promoters of target genes. This study provides critical insights into the functional roles of Dof transcription factors in Orchidaceae family and establishes a theoretical foundation for molecular breeding and stress resistance improvement in D. officinale.

Genome wide identification of Dof transcription factors in Carmine radish reveals RsDof33 role in cadmium stress and anthocyanin biosynthesis

Carmine radish (Raphanus sativus L.) is cultivated in Fuling, Chongqing, for its red color. Dof-TFs are critical in regulating plant growth, development, stress responses, and signal transduction.This work comprehensively examined the structure, evolution, and expression of the carmine radish Dof gene and its behavior under cadmium (Cd) stress. The radish genome has 59 RsDofs, which are divided into nine clusters (A: 8, B1: 10, B2: 10, C1: 3, C2.1: 5, C2.2: 4, C3: 11, D1: 4, and D2: 4). Phylogenetic tree analysis revealed significant Dof gene family resemblance between Arabidopsis thaliana and Brassica napus. Perhaps segment duplication resulted in RsDof gene family expansion. Cd stress-induced RsDof expression patterns were studied using an RNA-seq atlas and qRT-PCR. The majority of RsDofs were tissue-specific and Cd-sensitive. The involvement of RsDof genes in Cd stress response and anthocyanin synthesis was verified using qRT-PCR. RsDof33 is involved in Cd stress response and anthocyanin synthesis. A. thaliana overexpressed the recombinant fusion protein RsDof33-GFP, which was localized to the nucleus, resulting in fewer rosette leaves, delayed flowering, and higher anthocyanin concentration. RsDof33-expressing plants had significantly higher transcript levels of the auxin biosynthetic genes YUCCA (AtYUC2), auxin efflux carrier (AtPIN4), and AtKNAT2, which are involved in leaf shape development, as well as AtPAL, AtCHS, AtCHI, AtDFR, AtLDOX, and AtUF3GT. These findings indicate that RsDofs are critical to plant development and stress responses.

Identification and functional analysis of the Dof transcription factor genes in sugar beet

In this study, members of the BvDof transcription factor family were identified in the beet genome data (Beta vulgaris L.) Through systematic analysis, 22 BvDof family genes were found in the beet genome, and they were divided into nine groups by phylogenetic analysis. Fifteen members of the BvERF family were involved in the transition to rapid root tuber growth. There was a tandem replication during the generation of the Dof gene family in sugar beet. Bv1_zfms, Bv_ofna, Bv5_racn, and Bv6_augo may be involved in the regulation of secondary cambium development in the beet root tuber. Bv9_nood, Bv1_zfms, and Bv6_cdca may be related to the growth rate of root tubers. The results provide a reference for further elucidating the molecular mechanism of the BvDof transcription factor, which regulates the development of beet root tubers.

Ectopic expression of HvbHLH132 from hulless barley reduces cold tolerance in transgenic Arabidopsis thaliana

KEY MESSAGE

Overexpression of HvbHLH132 from hulless barley impairs in chilling and freezing tolerance at the seedlings stage in Arabidopsis thaliana The basic helix-loop-helix (bHLH) transcription factors (TF) are ubiquitously existed in eukaryote and play crucial roles in numerous biological processes. However, the characterization of their members and functions in hulless barley remains limited. Here, we conducted a genome-wide identification of the HvbHLH gene family and assessed the role of HvbHLH132 in cold stress tolerance. We identified 141 HvbHLH genes, which were categorized into twelve subfamilies. Subcellular localization predictions indicated that the majority of HvbHLH proteins were localized in the nucleus. cis-Acting element analysis revealed that the promoter regions of the HvbHLH family contain diverse elements associated with various biological processes. Expression profiling of the 141 HvbHLH genes in two extreme varieties revealed that HvbHLH132 was significantly induced and exhibited substantial differential expression under cold stress. Analyses of subcellular localization and transactivation activity confirmed that HvbHLH132 specifically localized in the nucleus and contributed to transcriptional activation. Furthermore, overexpression of HvbHLH132 in Arabidopsis resulted in impaired chilling and freezing tolerance at the seedling stage, leading to biochemical changes unfavorable for freezing stress. Additionally, the expression of some cold-responsive genes (COR) genes was significantly less induced compared to wild type under freezing stress. This study provides comprehensive insight into the HvbHLH gene family and reveals a critical role of HvbHLH132 in regulating cold tolerance in plants.

Exploring CDF gene family in wild potato under salinity stress unveils promising candidates for developing climate-resilient crops

The DNA-binding with one finger (Dof) gene family is a class of plant-specific transcription factors involved in diverse biological processes, including response to biotic and abiotic stresses. Members of this family have been reported in the cultivated potato Solanum tuberosum, but clues to the roles of several Dof genes are still lacking. Potato wild relatives represent a genetic reservoir for breeding as they could provide useful alleles for adaptation to the environment and tolerance to biotic and abiotic stresses. We performed an in silico analysis to identify genes belonging to the Dof family in the wild potato S. commersonii, confirming that the identified Dof genes can be grouped in four classes (A, B, C, D), as reported for cultivated potato. A special focus was dedicated to Cycling Dof Factors (CDFs), which play a crucial role in plant responses to abiotic stresses. Analysis of available RNA-seq data confirmed CDF genes as regulated by stresses and often in a tissue specific manner. To ascertain their involvement in the stress response, S. tuberosum and S. commersonii plantlets growing in vitro were subjected to salt stress (80mM NaCl) for short (2 days) and prolonged (7 days) times. Analysis of phenotypic traits and qRT-PCR expression profiles of target CDF genes in aerial and root tissues showed differences between the two species. In addition, after saline treatment, changes in total phenols, proline, and malondialdehyde suggested a diverse perception of saline stress in S. commersonii vs. S. tuberosum. Overall, this study provided useful clues to the involvement of CDF genes in salt response and promoted the identification of potential candidate genes for further functional studies.

Identification and Characterization of the DOF Gene Family in Phoebe bournei and Its Role in Abiotic Stress-Drought, Heat and Light Stress

Phoebe bournei is a second-class endangered and protected species unique to China, and it holds significant ecological and economic value. DNA binding one zinc finger (Dof) transcription factors are plant-specific regulators. Numerous studies have demonstrated that Dof genes are involved in plant growth, development and responses to abiotic stress. In this study, we identified and analyzed 34 PbDof gene members at the whole-genome level. The results indicated that the 34 PbDof genes were unevenly distributed across 12 chromosomes. We utilized the Dof genes from Arabidopsis thaliana and P. bournei to construct a phylogenetic tree and categorized these genes into eight subgroups. In the collinearity analysis, there were 16 homologous gene pairs between AtDof and PbDof and nine homologous gene pairs between ZmDof and PbDof. We conducted a cis-acting element analysis and found that cis-acting elements involved in light response were the most abundant in PbDof genes. Through SSR site prediction, we analyzed that the evolution level of Dof genes is low. Additionally, we assessed the expression profiles of eight PbDof genes under high temperature, drought, and light stress using qRT-PCR. In particular, PbDof08 and PbDof16 are significantly upregulated under the three stresses. This study provides foundational information for PbDof genes and offers new insights for further research on the mechanism of Dof transcription factors responding to stress, as well as the adaptation of P. bournei to environmental changes.

Genome-wide identification and molecular evolution of Dof transcription factors in Cyperus esculentus

Dof transcription factor family in Cyperus esculentus genome was identified and analyzed using bioinformatics. The analysis results revealed that C.esculentus genome contains 29 Dof genes (CesDof), all of which are located in the nucleus according to subcellular localization prediction. CesDof proteinrs have a range of 124 to 512 amino acids, with most being basic proteins. Their secondary structure was mainly irregular curl. The promoter sequence of CesDof genes contains cis-acting elements that respond to light, drought, hormones, low temperature, and circadian rhythm. Codon preference analysis showed that CesDof genes' codon preference ends in T/A. Collinearity analysis revealed that C.esculentus had three pairs of collinear CesDof genes. Additionally, there were 15 pairs of collinear genes between C.esculentus and Arabidopsis thaliana. The genetic relationship between C.esculentus and Rhynchospora pubera was found to be the closest. Phylogenetic tree analysis revealed that 29 CesDof genes of C.esculentus can be classified into 4 subgroups. Additionally, 144 miRNAs were predicted to target these CesDof genes. Furthermore, protein interaction analysis indicated that 15 Dof proteins in C.esculentus had interactions. The qRT-PCR verification results of drought stress and salt stress treatment experiments showed that most CesDof genes were involved in drought stress and salt stress responses, and the gene expression trends under drought stress and salt stress conditions were consistent. These results lay a theoretical foundation for further studying the molecular functions of Dof gene family in C.esculentus and its molecular mechanisms in regulating the life activities of C.esculentus.

Genome-wide identification and expression analysis of the Dof gene family reveals their involvement in hormone response and abiotic stresses in sunflower (Helianthus annuus L.)

DNA binding with one finger (Dof), plant-specific zinc finger transcription factors, can participate in various physiological and biochemical processes during the life of plants. As one of the most important oil crops in the world, sunflower (Helianthus annuus L.) has significant economic and ornamental value. However, a systematic analysis of H. annuus Dof (HaDof) members and their functions has not been extensively conducted. In this study, we identified 50 HaDof genes that are unevenly distributed on 17 chromosomes of sunflower. We present a comprehensive overview of the HaDof genes, including their chromosome locations, phylogenetic analysis, and expression profile characterization. Phylogenetic analysis classified the 366 Dof members identified from 11 species into four groups (further subdivided into nine subfamilies). Segmental duplications are predominantly contributed to the expansion of sunflower Dof genes, and all segmental duplicate gene pairs are under purifying selection due to strong evolutionary constraints. Furthermore, we observed differential expression patterns for HaDof genes in normal tissues as well as under hormone treatment or abiotic stress conditions by analyzing RNA-seq data from previous studies and RT-qPCR data in our current study. The expression of HaDof04 and HaDof43 were not detected in any samples, which implied that they may be gradually undergoing pseudogenization process. Some HaDof genes, such as HaDof25 and HaDof30, showed responsiveness to exogenous plant hormones, such as kinetin, brassinosteroid, auxin or strigolactone, while others like HaDof15 and HaDof35 may participate in abiotic stress resistance of sunflower seedling. Our study represents the initial step towards understanding the phylogeny and expression characterization of sunflower Dof family genes, which may provide valuable reference information for functional studies on hormone response, abiotic stress resistance, and molecular breeding in sunflower and other species.

CmDOF18 positively regulates salinity tolerance in Chrysanthemum morifolium by activating the oxidoreductase system

BACKGROUND

Chrysanthemum, one of the four major cut flowers all over the world, is very sensitive to salinity during cultivation. DNA binding with one finger (DOF) transcription factors play important roles in biological processes in plants. The response mechanism of CmDOF18 from chrysanthemum to salt stress remains unclear.

RESULTS

In this study, CmDOF18 was cloned from Chrysanthemum morifolium, and its expression was induced by salinity stress. The gene encodes a 291-amino acid protein with a typical DOF domain. CmDOF18 was localized to the nucleus in onion epidermal cells and showed transcriptional activation in yeast. CmDOF18 transgenic plants were generated to identify the role of this gene in resistance to salinity treatment. Chrysanthemum plants overexpressing CmDOF18 were more resistant to salinity stress than wild-type plants. Under salinity stress, the malondialdehyde content and leaf electrolyte conductivity in CmDOF18-overexpressing transgenic plants were lower than those in wild-type plants, while the proline content, chlorophyll content, superoxide dismutase activity and peroxidase activity were higher than those in wild-type plants. The opposite findings were observed in gene-silenced plants compared with wild-type plants. The gene expression levels of oxidoreductase increased in CmDOF18-overexpressing transgenic plants but decreased in CmDOF18-SRDX gene-silenced transgenic plants.

CONCLUSION

In summary, we analyzed the function of CmDOF18 from chrysanthemum, which may regulate salinity stress in plants, possibly due to its role in the regulation of oxidoreductase.

Molecular characterization and evolutionary relationships of DOFs in four cherry species and functional analysis in sweet cherry

The DOF (DNA binding with one finger) has multiple functions in plants. However, it has received little attention in the research field of cherries. In this study, the evolutionary relationship and molecular characterization of DOF in four cherry species were analyzed, revealing its expression pattern in sweet cherry. There are 23 members in Prunus avium cv. 'Tieton', 88 in Prunus cerasus, 53 in Cerasus × yedoensis, and 27 in Cerasus serrulata. Most of these genes are intron-less or non-intron, with a conserved C2-C2 domain. Due to heterozygosity and chromosomal ploidy, whole-genome duplication (WGD) events occur to varying degrees, and DOF genes are contracted during evolution. Furthermore, these genes are affected by purifying selection pressure. Under low-temperature treatment, the expression of PavDOF2 and PavDOF18 were significantly up-regulated, while that of PavDOF16 is significantly down-regulated. The expression of PavDOF9, PavDOF12, PavDOF14, PavDOF16, PavDOF17, PavDOF18, and PavDOF19 exhibits an increasing trend during flower development and varies during sweet cherry fruit development. PavDOF1, PavDOF8, PavDOF9, and PavDOF15 are localized in the nucleus but is not transcriptionally active. The findings systemically demonstrate the molecular characteristics of DOF in different cherry varieties, providing a basis for further research on the functions of these genes.

Functional characterisation of Dof gene family and expression analysis under abiotic stresses and melatonin-mediated tolerance in pitaya (Selenicereus undatus)

DNA binding proteins with one finger (Dof ) transcription factors are essential for seed development and defence against various biotic and abiotic stresses in plants. Genomic analysis of Dof has not been determined yet in pitaya (Selenicereus undatus ). In this study, we have identified 26 Dof gene family members, renamed as HuDof-1 to HuDof-26 , and clustered them into seven subfamilies based on conserved motifs, domains, and phylogenetic analysis. The gene pairs of Dof family members were duplicated by segmental duplications that faced purifying selection, as indicated by the K a /K s ratio values. Promoter regions of HuDof genes contain many cis -acting elements related to phytohormones including abscisic acid, jasmonic acid, gibberellin, temperature, and light. We exposed pitaya plants to different environmental stresses and examined melatonin's influence on Dof gene expression levels. Signifcant expression of HuDof -2 and HuDof -6 were observed in different developmental stages of flower buds, flowers, pericarp, and pulp. Pitaya plants were subjected to abiotic stresses, and transcriptome analysis was carried out to identify the role of Dof gene family members. RNA-sequencing data and reverse transcription quantitative PCR-based expression analysis revealed three putative candidate genes (HuDof -1, HuDof -2, and HuDof -8), which might have diverse roles against the abiotic stresses. Our study provides a theoretical foundation for functional analysis through traditional and modern biotechnological tools for pitaya trait improvement.

Assessing small RNA profiles in potato diploid hybrid and its resynthesized allopolyploid reveals conserved abundance with distinct genomic distribution

KEY MESSAGE

The shock produced by the allopolyploidization process on a potato interspecific diploid hybrid displays a non-random remobilization of the small RNAs profile on a variety of genomic features. Allopolyploidy, a complex process involving interspecific hybridization and whole genome duplication, significantly impacts plant evolution, leading to the emergence of novel phenotypes. Polyploids often present phenotypic nuances that enhance adaptability, enabling them to compete better and occasionally to colonize new habitats. Whole-genome duplication represents a genomic "shock" that can trigger genetic and epigenetic changes that yield novel expression patterns. In this work, we investigate the polyploidization effect on a diploid interspecific hybrid obtained through the cross between the cultivated potato Solanum tuberosum and the wild potato Solanum kurtzianum, by assessing the small RNAs (sRNAs) profile of the parental diploid hybrid and its derived allopolyploid. Small RNAs are key components of the epigenetic mechanisms involved in silencing by RNA-directed DNA Methylation (RdDM). A sRNA sequencing (sRNA-Seq) analysis was performed to individually profile the 21 to 22 nucleotide (21 to 22-nt) and 24-nt sRNA size classes due to their unique mechanism of biogenesis and mode of function. The composition and distribution of different genomic features and differentially accumulated (DA) sRNAs were evaluated throughout the potato genome. We selected a subset of genes associated with DA sRNAs for messenger RNA (mRNA) expression analysis to assess potential impacts on the transcriptome. Interestingly, we noted that 24-nt DA sRNAs that exclusively mapped to exons were correlated with differentially expressed mRNAs between genotypes, while this behavior was not observed when 24-nt DA sRNAs were mapped to intronic regions. These findings collectively emphasize the nonstochastic nature of sRNA remobilization in response to the genomic shock induced by allopolyploidization.

Morphological, physio-biochemical, and molecular indications of heat stress tolerance in cucumber

Global warming is a critical challenge limiting crop productivity. Heat stress during cucumber growing stages caused deterioration impacts on the flowering, fruit, and yield stages. In this study, "inbred line 1 and hybrid P1 × P2" (heat-tolerant) and "Barracuda" (heat-sensitive) were utilized to determine the heat tolerance in summer season. The heat injury index was used to exhibit the heat tolerance performance. The heat injury index for heat tolerant (HT) genotypes, on leaves (HIIL%) and female flowers (HIIF%), was less than 25 and 15 % in HT, compared to heat sensitive (HS) was more than 75 and 85%, respectively. Moreover, the content of leaf chlorophyll, proline, brassinosteroid (BRs), abscisic acid content (ABA), the activity of catalase (CAT, EC 1.11. 1.6), peroxidase (POD, EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) increased with the heat stress responses in HT plants. Expression pattern analyses of eight genes, related to POD (CSGY4G005180 and CSGY6G015230), SOD (CSGY4G010750 and CSGY1G026400), CAT (CsGy4G025230 and CsGy4G025240), and BR (CsGy6G029150 and CsGy6G004930) showed a significant increase in HT higher than in HS plants. This study furnishes valuable markers for heat tolerance genotypes breeding in cucumber and provides a basis for understanding heat-tolerance mechanisms.

Characterization of Dof Transcription Factors and the Heat-Tolerant Function of PeDof-11 in Passion Fruit (Passiflora edulis)

Abiotic stress is the focus of passion fruit research since it harms the industry, in which high temperature is an important influencing factor. Dof transcription factors (TFs) act as essential regulators in stress conditions. TFs can protect against abiotic stress via a variety of biological processes. There is yet to be published a systematic study of the Dof (PeDof) family of passion fruit. This study discovered 13 PeDof family members by using high-quality genomes, and the members of this characterization were identified by bioinformatics. Transcriptome sequencing and qRT-PCR were used to analyze the induced expression of PeDofs under high-temperature stress during three periods, in which PeDof-11 was significantly induced with high expression. PeDof-11 was then chosen and converted into yeast, tobacco, and Arabidopsis, with the findings demonstrating that PeDof-11 could significantly respond to high-temperature stress. This research lays the groundwork for a better understanding of PeDof gene regulation under high-temperature stress.

Genome-wide identification and functional analysis of ICE genes reveal that Gossypium thurberi "GthICE2" is responsible for cold and drought stress tolerance

Cold stress has been found to have a negative impact on cotton growth and annual production. To address this issue, the utilization of cold-tolerant gene resources from wild species of Gossypium is crucial for genetic improvements in cultivated cotton. ICE (inducer of CBF expression) are the key regulators of cold tolerance in plants, however, there is relatively little information on ICE genes in cotton. Herein, we performed comprehensive bioinformatics analyses of the ICE gene family in eight cotton species. Phylogenetic analysis showed that 52 ICE genes were clustered into four subgroups. Cis-regulatory elements analysis suggests that the expression of ICE genes might be regulated by light, plant hormones, and various environment stresses. Higher expression of GthICE2 was observed in leaves as compared to roots and stems, in response to cold, drought, and exogenous hormone ABA. Furthermore, overexpression of GthICE2 in A. thaliana led to higher germination and survival rates, longer root length, lower ion leakage, and induction under cold and drought stress. Histochemical staining showed that oxidative damage in transgenic lines was much lower compared to wild-type plants. Lower MDA contents and higher SOD and POD activities were observed in overexpressed plants. Y1H and LUC assays revealed that GthICE2 might activate the expression of GthCBF4, a cold-responsive gene, by connecting with the MYC cis-element present in the promoter of GthCBF4. GthICE2 confers cold and drought stress tolerance in cotton. Our findings add significantly to the existing knowledge regarding cold stress tolerance and helps to elucidate cold response mechanisms in cotton.

Genome-wide survey and expression analysis of Dof transcription factor family in sweetpotato shed light on their promising functions in stress tolerance

DNA-binding with one finger (Dof) transcription factors play a crucial role in plant abiotic stress regulatory networks, although massive Dofs have been systematically characterized in plants, they have not been identified in the hexaploid crop sweetpotato. Herein, 43 IbDof genes were detected to be disproportionally dispersed across 14 of the 15 chromosomes of sweetpotato, and segmental duplications were discovered to be the major driving force for the expansion of IbDofs. The collinearity analysis of IbDofs with their related orthologs from eight plants revealed the potential evolutionary history of Dof gene family. Phylogenetic analysis displayed that IbDof proteins were assigned into nine subfamilies, and the regularity of gene structures and conserved motifs was consistent with the subgroup classification. Additionally, five chosen IbDof genes were shown to be substantially and variably induced under various abiotic conditions (salt, drought, heat, and cold), as well as hormone treatments (ABA and SA), according to their transcriptome data and qRT-PCR experiments. Consistently, the promoters of IbDofs contained a number of cis-acting elements associated with hormone and stress responses. Besides, it was noted that IbDof2 had transactivation activity in yeasts, while IbDof-11/-16/-36 did not, and protein interaction network analysis and yeast two-hybrid experiments revealed a complicated interaction connection amongst IbDofs. Collectively, these data lay a foundation for further functional explorations of IbDof genes, especially with regards to the possible application of multiple IbDof members in breeding the tolerant plants.

DOF transcription factors: Specific regulators of plant biological processes

Plant biological processes, such as growth and metabolism, hormone signal transduction, and stress responses, are affected by gene transcriptional regulation. As gene expression regulators, transcription factors activate or inhibit target gene transcription by directly binding to downstream promoter elements. DOF (DNA binding with One Finger) is a classic transcription factor family exclusive to plants that is characterized by its single zinc finger structure. With breakthroughs in taxonomic studies of different species in recent years, many DOF members have been reported to play vital roles throughout the plant life cycle. They are not only involved in regulating hormone signals and various biotic or abiotic stress responses but are also reported to regulate many plant biological processes, such as dormancy, tissue differentiation, carbon and nitrogen assimilation, and carbohydrate metabolism. Nevertheless, some outstanding issues remain. This article mainly reviews the origin and evolution, protein structure, and functions of DOF members reported in studies published in many fields to clarify the direction for future research on DOF transcription factors.

Genome-Wide Identification of the DOF Gene Family Involved in Fruitlet Abscission in Areca catechu L

Fruitlet abscission frequently occurs in Areca catechu L. and causes considerable production loss. However, the inducement mechanism of fruitlet abscission remains mysterious. In this study, we observed that the cell architecture in the abscission zone (AZ) was distinct with surrounding tissues, and varied obviously before and after abscission. Transcriptome analysis of the “about-to-abscise” and “non-abscised” AZs were performed in A. catechu, and the genes encoding the plant-specific DOF (DNA-binding with one finger) transcription factors showed a uniform up-regulation in AZ, suggesting a role of the DOF transcription in A. catechu fruitlet abscission. In total, 36 members of the DOF gene family distributed in 13 chromosomes were identified from the A. catechu genome. The 36 AcDOF genes were classified into nine subgroups based on phylogenic analysis. Six of them showed an AZ-specific expression pattern, and their expression levels varied according to the abscission process. In total, nine types of phytohormone response cis-elements and five types of abiotic stress related cis-elements were identified in the promoter regions of the AcDOF genes. In addition, histochemical staining showed that lignin accumulation of vascular bundles in AZ was significantly lower than that in pedicel and mesocarp, indicating the specific characteristics of the cell architecture in AZ. Our data suggests that the DOF transcription factors might play a role in fruitlet abscission regulation in A. catechu.

Genome-wide identification, phylogenetic and expression pattern analysis of Dof transcription factors in blueberry (Vaccinium corymbosum L.)

Background

DNA binding with one finger (Dof) proteins are plant-specific transcription factor (TF) that plays a significant role in various biological processes such as plant growth and development, hormone regulation, and resistance to abiotic stress. The Dof genes have been identified and reported in multiple plants, but so far, the whole genome identification and analysis of Dof transcription factors in blueberry (Vaccinium corymbosum L.) have not been reported yet.

Methods

Using the Vaccinium genome, we have identified 51 VcDof genes in blueberry. We have further analyzed their physicochemical properties, phylogenetic relationships, gene structure, collinear analysis, selective evolutionary pressure, cis-acting promoter elements, and tissue and abiotic stress expression patterns.

Results

Fifty-one VcDof genes were divided into eight subfamilies, and the genes in each subfamily contained similar gene structure and motif ordering. A total of 24 pairs of colinear genes were screened; VcDof genes expanded mainly due to whole-genome duplication, which was subjected to strong purifying selection pressure during the evolution. The promoter of VcDof genes contains three types of cis-acting elements for plant growth and development, phytohormone and stress defense responsiveness. Expression profiles of VcDof genes in different tissues and fruit developmental stages of blueberry indicated that VcDof2 and VcDof45 might play a specific role in anthesis and fruit growth and development. Expression profiles of VcDof genes in different stress indicated that VcDof1, VcDof11, and VcDof15 were highly sensitive to abiotic stress. This study provides a theoretical basis for further clarifying the biological function of Dof genes in blueberry.

Genome-Wide Identification of DNA Binding with One Finger (Dof) Gene Family in Tartary Buckwheat (Fagopyrum tataricum) and Analysis of Its Expression Pattern after Exogenous Hormone Stimulation

Simple Summary

A number of studies have demonstrated that DNA binding with one finger (Dof) proteins are involved in multiple biological processes. In the present study, Dof genes or proteins in Tartary buckwheat (FtDofs) were systematically analysed, including their physical properties, phylogenetic relationships, structure, motif composition, cis-acting elements present in promoter regions, chromosomal distribution, gene duplication events, syntenic relationships, expression patterns in different tissues and different fruit developmental stages and responses to exogenous hormone stimulation. The results indicated that the expansion of FtDofs was mainly due to segmental duplication. The tissue-specific expression patterns of FtDofs and their positive responses to exogenous hormone stimulation suggest that they play important roles in the growth and development of Tartary buckwheat as well as in the adaptation to environmental changes. Collectively, this study lays a foundation for further exploration of the function of FtDof genes in Tartary buckwheat.

Abstract

DNA binding with one finger (Dof) proteins have been proven to be involved in multiple biological processes. However, genome-wide identification of the Dof gene family has not been reported for Tartary buckwheat (Fagopyrum tataricum). In this study, 35 FtDof proteins were identified, and they could be divided into nine phylogenetic subgroups. Proteins within the same subgroup had similar gene structure and motif composition. Moreover, abundant cis-acting elements were present in the promoter regions of FtDof genes. Segmental duplication was the primary driving force for the evolution of the FtDof gene family. Synteny analysis indicated that Tartary buckwheat was closer to dicotyledons, and more orthologous Dof genes existed among them. The expression pattern of FtDofs in different tissues and at different fruit developmental stages varied. Different tissues contained several genes that were specifically expressed. FtDof expression was mainly upregulated under methyl jasmonate treatment and downregulated under other hormone treatments. Taken together, FtDofs may play important roles in the growth and development of Tartary buckwheat and in response to abiotic and biotic stresses. Therefore, the genome-wide identification and expression pattern analysis of the Tartary buckwheat Dof gene family lays a foundation for further exploration of the functional characteristics of FtDofs in the future.

Genome-wide identification of DCL, AGO and RDR gene families and their associated functional regulatory elements analyses in banana (Musa acuminata)

RNA silencing is mediated through RNA interference (RNAi) pathway gene families, i.e., Dicer-Like (DCL), Argonaute (AGO), and RNA-dependent RNA polymerase (RDR) and their cis-acting regulatory elements. The RNAi pathway is also directly connected with the post-transcriptional gene silencing (PTGS) mechanism, and the pathway controls eukaryotic gene regulation during growth, development, and stress response. Nevertheless, genome-wide identification of RNAi pathway gene families such as DCL, AGO, and RDR and their regulatory network analyses related to transcription factors have not been studied in many fruit crop species, including banana (Musa acuminata). In this study, we studied in silico genome-wide identification and characterization of DCL, AGO, and RDR genes in bananas thoroughly via integrated bioinformatics approaches. A genome-wide analysis identified 3 MaDCL, 13 MaAGO, and 5 MaRDR candidate genes based on multiple sequence alignment and phylogenetic tree related to the RNAi pathway in banana genomes. These genes correspond to the Arabidopsis thaliana RNAi silencing genes. The analysis of the conserved domain, motif, and gene structure (exon-intron numbers) for MaDCL, MaAGO, and MaRDR genes showed higher homogeneity within the same gene family. The Gene Ontology (GO) enrichment analysis exhibited that the identified RNAi genes could be involved in RNA silencing and associated metabolic pathways. A number of important transcription factors (TFs), e.g., ERF, Dof, C2H2, TCP, GATA and MIKC_MADS families, were identified by network and sub-network analyses between TFs and candidate RNAi gene families. Furthermore, the cis-acting regulatory elements related to light-responsive (LR), stress-responsive (SR), hormone-responsive (HR), and other activities (OT) functions were identified in candidate MaDCL, MaAGO, and MaRDR genes. These genome-wide analyses of these RNAi gene families provide valuable information related to RNA silencing, which would shed light on further characterization of RNAi genes, their regulatory elements, and functional roles, which might be helpful for banana improvement in the breeding program.

Volatile Compounds From Bacillus, Serratia, and Pseudomonas Promote Growth and Alter the Transcriptional Landscape of Solanum tuberosum in a Passively Ventilated Growth System

The interaction of an array of volatile organic compounds (VOCs) termed bacterial volatile compounds (BVCs) with plants is now a major area of study under the umbrella of plant-microbe interactions. Many growth systems have been developed to determine the nature of these interactions in vitro. However, each of these systems have their benefits and drawbacks with respect to one another and can greatly influence the end-point interpretation of the BVC effect on plant physiology. To address the need for novel growth systems in BVC-plant interactions, our study investigated the use of a passively ventilated growth system, made possible via Microbox^® growth chambers, to determine the effect of BVCs emitted by six bacterial isolates from the genera Bacillus, Serratia, and Pseudomonas. Solid-phase microextraction GC/MS was utilized to determine the BVC profile of each bacterial isolate when cultured in three different growth media each with varying carbon content. 66 BVCs were identified in total, with alcohols and alkanes being the most abundant. When cultured in tryptic soy broth, all six isolates were capable of producing 2,5-dimethylpyrazine, however BVC emission associated with this media were deemed to have negative effects on plant growth. The two remaining media types, namely Methyl Red-Voges Proskeur (MR-VP) and Murashige and Skoog (M + S), were selected for bacterial growth in co-cultivation experiments with Solanum tuberosum L. cv. ‘Golden Wonder.’ The BVC emissions of Bacillus and Serratia isolates cultured on MR-VP induced alterations in the transcriptional landscape of potato across all treatments with 956 significantly differentially expressed genes. This study has yielded interesting results which indicate that BVCs may not always broadly upregulate expression of defense genes and this may be due to choice of plant-bacteria co-cultivation apparatus, bacterial growth media and/or strain, or likely, a complex interaction between these factors. The multifactorial complexities of observed effects of BVCs on target organisms, while intensely studied in recent years, need to be further elucidated before the translation of lab to open-field applications can be fully realized.

Expression profiling of the Dof gene family under abiotic stresses in spinach

DNA-binding with one finger (Dof) are plant-specific transcription factors involved in numerous pathways of plant development, such as abiotic stresses responses. Although genome-wide analysis of Dof genes has been performed in many species, but these genes in spinach have not been analyzed yet. We performed a genome-wide analysis and characterization of Dof gene family in spinach (Spinacia oleracea L.). Twenty-two Dof genes were identified and classified into four groups with nine subgroups, which was further corroborated by gene structure and motif analyses. Ka/Ks analysis revealed that SoDofs were subjected to purifying selection. Using cis-acting elements analysis, SoDofs were involved in plant growth and development, plant hormones, and stress responses. Expression profiling demonstrated that SoDofs expressed in leaf and inflorescence, and responded to cold, heat, and drought stresses. SoDof22 expressed the highest level in male flowers and under cold stress. These results provided a genome-wide analysis of SoDof genes, their gender- and tissue-specific expression, and response to abiotic stresses. The knowledge and resources gained from these analyses will benefit spinach improvement.

Genome-Wide Analysis and Expression Profiles of the Dof Family in Cleistogenes songorica under Temperature, Salt and ABA Treatment

The DNA-binding with one zinc finger (Dof) family of plant-specific transcription factors has a variety of important functions in gene transcriptional regulation, development, and stress responses. However, the structure and expression patterns of Dof family have not been identified in Cleistogenes songorica, which is an important xerophytic and perennial gramineous grass in desert grassland. In this study, 50 Dof genes were identified in C. songorica and could be classified into four groups. According to genome-wide analysis, 46 of 50 Dof genes were located on 20 chromosomes, and the gene structure and conserved protein motif of these proteins were analyzed. In addition, phylogenetic analysis of Dof genes in C. songorica, Arabidopsis thaliana, Oryza sativa, and Brachypodium distachyon estimated the evolutionary relationships, and these genes were grouped into seven clusters. Moreover, the expression profiles of these Dof genes in C. songorica were analyzed in response to high/low temperature, salinity, and ABA treatments. These results will provide valuable information for future studies on gene classification, cloning, and functional characterization of this family in C. songorica.

Transcriptomic analysis of grapevine Dof transcription factor gene family in response to cold stress and functional analyses of the VaDof17d gene

Dof genes enhance cold tolerance in grapevine and VaDof17d is tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides. DNA-binding with one finger (Dof) proteins comprise a large family that plays important roles in the regulation of abiotic stresses. No in-depth analysis of Dof genes has been performed in the grapevine. In this study, we analyzed a total of 25 putative Dof genes in grapevine at genomic and transcriptomic levels, compiled expression profiles of 11 selected VaDof genes under cold stress and studied the potential function of the VaDof17d gene in grapevine calli. The 25 Dof proteins can be classified into four phylogenetic groups. RNA-seq and qRT-PCR results demonstrated that a total of 11 VaDof genes responded to cold stress. Comparative mRNA sequencing of 35S::VaDof17d grape calli showed that VaDof17d was tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides (RFOs), as observed by the up-regulation of galactinol synthase (GolS) and raffinose synthase genes. We found that the Dof17d-ED (CRISPR/Cas9-mediated mutagenesis of Dof17d-ED) mutant had low cold tolerance with a decreased RFOs level during cold stress. These results formed the fundamental knowledge for further analysis of the biological roles of Dof genes in the grapevine's adaption to cold stresses.

In silico identification and characterization of AGO, DCL and RDR gene families and their associated regulatory elements in sweet orange (Citrus sinensis L.)

RNA interference (RNAi) plays key roles in post-transcriptional and chromatin modification levels as well as regulates various eukaryotic gene expressions which are involved in stress responses, development and maintenance of genome integrity during developmental stages. The whole mechanism of RNAi pathway is directly involved with the gene-silencing process by the interaction of Dicer-Like (DCL), Argonaute (AGO) and RNA-dependent RNA polymerase (RDR) gene families and their regulatory elements. However, these RNAi gene families and their sub-cellular locations, functional pathways and regulatory components were not extensively investigated in the case of economically and nutritionally important fruit plant sweet orange (Citrus sinensis L.). Therefore, in silico characterization, gene diversity and regulatory factor analysis of RNA silencing genes in C. sinensis were conducted by using the integrated bioinformatics approaches. Genome-wide comparison analysis based on phylogenetic tree approach detected 4 CsDCL, 8 CsAGO and 4 CsRDR as RNAi candidate genes in C. sinensis corresponding to the RNAi genes of model plant Arabidopsis thaliana. The domain and motif composition and gene structure analyses for all three gene families exhibited almost homogeneity within the same group members. The Gene Ontology enrichment analysis clearly indicated that the predicted genes have direct involvement into the gene-silencing and other important pathways. The key regulatory transcription factors (TFs) MYB, Dof, ERF, NAC, MIKC_MADS, WRKY and bZIP were identified by their interaction network analysis with the predicted genes. The cis-acting regulatory elements associated with the predicted genes were detected as responsive to light, stress and hormone functions. Furthermore, the expressed sequence tag (EST) analysis showed that these RNAi candidate genes were highly expressed in fruit and leaves indicating their organ specific functions. Our genome-wide comparison and integrated bioinformatics analyses provided some necessary information about sweet orange RNA silencing components that would pave a ground for further investigation of functional mechanism of the predicted genes and their regulatory factors.

Genome-Wide Identification and Expression Analysis of the Dof Gene Family in Medicago sativa L. Under Various Abiotic Stresses

The Dof transcription factor is a plant-specific transcriptional regulator that plays important roles in plant development and acts as a mediator in plant external stress responses. However, Dofs have previously been identified in several plants but not in alfalfa (Medicago sativa L.), one of the most widely cultivated forage legumes. In the present study, a total of 40 MsDof genes were identified, and the phylogenetic reconstruction, classification, conserved motifs, and expression patterns under abscisic acid (ABA), cold, heat, drought and salt stresses of these Dof genes were comprehensively analyzed. The Dof genes family in alfalfa could be classified into eight classes. Gene ontology (GO) and tissue-specific analysis indicated that most MsDof genes may be involved in biological functions during plant growth. Moreover, the expression profiles and quantitative real-time PCR analysis indicated that eight candidate abiotic tolerance genes were induced in response to four abiotic stresses. This study identified the possibility of abiotic tolerance candidate genes playing various roles in stress resistance at the whole genome level, which would provide new information on the Dof family in alfalfa.

CDF transcription factors: plant regulators to deal with extreme environmental conditions

In terrestrial environments, water and nutrient availabilities and temperature conditions are highly variable, and especially in extreme environments limit survival, growth, and reproduction of plants. To sustain growth and maintain cell integrity under unfavourable environmental conditions, plants have developed a variety of biochemical and physiological mechanisms, orchestrated by a large set of stress-responsive genes and a complex network of transcription factors. Recently, cycling DOF factors (CDFs), a group of plant-specific transcription factors (TFs), were identified as components of the transcriptional regulatory networks involved in the control of abiotic stress responses. The majority of the members of this TF family are activated in response to a wide range of adverse environmental conditions in different plant species. CDFs regulate different aspects of plant growth and development such as photoperiodic flowering-time control and root and shoot growth. While most of the functional characterization of CDFs has been reported in Arabidopsis, recent data suggest that their diverse roles extend to other plant species. In this review, we integrate information related to structure and functions of CDFs in plants, with special emphasis on their role in plant responses to adverse environmental conditions.

Genome-wide analysis of wheat DNA-binding with one finger (Dof) transcription factor genes: evolutionary characteristics and diverse abiotic stress responses

Background

DNA binding with one finger (Dof) transcription factors play important roles in plant growth and abiotic stress responses. Although genome-wide identification and analysis of the DOF transcription factor family has been reported in other species, no relevant studies have emerged in wheat. The aim of this study was to investigate the evolutionary and functional characteristics associated with plant growth and abiotic stress responses by genome-wide analysis of the wheat Dof transcription factor gene family.

Results

Using the recently released wheat genome database (IWGSC RefSeq v1.0), we identified 96 wheat Dof gene family members, which were phylogenetically clustered into five distinct subfamilies. Gene duplication analysis revealed a broad and heterogeneous distribution of TaDofs on the chromosome groups 1 to 7, and obvious tandem duplication genes were present on chromosomes 2 and 3.Members of the same gene subfamily had similar exon-intron structures, while members of different subfamilies had obvious differences. Functional divergence analysis indicated that type-II functional divergence played a major role in the differentiation of the TaDof gene family. Positive selection analysis revealed that the Dof gene family experienced different degrees of positive selection pressure during the process of evolution, and five significant positive selection sites (30A, 31 T, 33A, 102G and 104S) were identified. Additionally, nine groups of coevolving amino acid sites, which may play a key role in maintaining the structural and functional stability of Dof proteins, were identified. The results from the RNA-seq data and qRT-PCR analysis revealed that TaDof genes exhibited obvious expression preference or specificity in different organs and developmental stages, as well as in diverse abiotic stress responses. Most TaDof genes were significantly upregulated by heat, PEG and heavy metal stresses.

Conclusions

The genome-wide analysis and identification of wheat DOF transcription factor family and the discovery of important amino acid sites are expected to provide new insights into the structure, evolution and function of the plant Dof gene family.

Genome-Wide Identification, Structure Characterization, and Expression Profiling of Dof Transcription Factor Gene Family in Wheat (Triticum aestivum L.)

DNA binding with one finger (Dof) proteins are plant-specific transcription factors with crucial roles in plant growth and stress response. Even so, little is known about them in wheat. In this study, 108 wheat Dof (TaDof) genes across 21 chromosomes were detected. Although variable in sequence length, molecular weight, and isoelectric point, all TaDof proteins contained conserved zinc-finger structures and were phylogenetically divided into 7 sub-groups. Exon/intron and motif analyses suggested that TaDof structures and conserved motifs were similar within sub-groups but diverse among sub-groups. Many segmental duplications were identified and Ka/Ks and inter-species synthetic analyses indicated that polyploidization was main reason for increased number of TaDofs. Prediction and experimental confirmation revealed that TaDofs functioned as transcription factors in the nucleus. Expression pattern profiling showed that TaDofs specifically affected growth and development, and biotic and abiotic stress responses. Wheat miRNAs and cis-regulator were predicted as essential players in molding TaDofs expression patterns. qRT-PCR analysis revealed that TaDofs were induced by salt and drought stresses. Customized annotation revealed that TaDofs were widely involved in phytohormone response, defense, growth and development, and metabolism. Our study provided a comprehensive understanding to wheat TaDofs.

Genome-wide characterization and expression analysis of the Dof gene family related to abiotic stress in watermelon

The plant DNA-binding with one finger (Dof) gene family is a class of plant-specific transcription factors that play vital roles in many biological processes and stress responses. In the present study, a total of 36 ClDof genes were identified in the watermelon genome, which were unevenly distributed on 10 chromosomes. Phylogenetic analysis showed that the ClDof proteins could be divided into nine groups, and the members in a particular group had similar motif arrangement and exon-intron structure. Synteny analysis indicated the presence of a large number of syntenic relationship events between watermelon and cucumber. In promoter analysis, five kinds of stress-related and nine kinds of hormone-related cis-elements were identified in the promoter regions of ClDof genes. We then analyzed the expression patterns of nine selected ClDof genes in eight specific tissues by qRT-PCR, and the results showed that they have tissue-specific expression patterns. We also evaluated the expression levels of 12 selected ClDof genes under salt stress and ABA treatments using qRT-PCR. As a result, they showed differential expression under these treatments, suggesting their important roles in stress response. Taken together, our results provide a basis for future research on the biological functions of Dof genes in watermelon.

Allele specific expression of Dof genes responding to hormones and abiotic stresses in sugarcane

Dof transcription factors plant-specific and associates with growth and development in plants. We conducted comprehensive and systematic analyses of Dof transcription factors in sugarcane, and identified 29 SsDof transcription factors in sugarcane genome. Those SsDof genes were divided into five groups, with similar gene structures and conserved motifs within the same groups. Segmental duplications are predominant in the evolution of Dof in sugarcane. Cis-element analysis suggested that the functions of SsDofs were involved in growth and development, hormones and abiotic stresses responses in sugarcane. Expression patterns indicated that SsDof7, SsDof23 and SsDof24 had a comparatively high expression in all detected tissues, indicating these genes are crucial in sugarcane growth and development. Moreover, we examined the transcription levels of SsDofs under four plant hormone treatments, SsDof7-3 and SsDof7-4 were down-regulated after ABA treatment, while SsDof7-1 and SsDof7-2 were induced after the same treatment, indicating different alleles may play different roles in response to plant hormones. We also analyzed SsDofs' expression profiling under four abiotic stresses, SsDof5 and SsDof28 significantly responded to these four stresses, indicating they are associate with abiotic stresses responses. Collectively, our results yielded allele specific expression of Dof genes responding to hormones and abiotic stresses in sugarcane, and their cis-elements could be crucial for sugarcane improvement.

The Role of Major Transcription Factors in Solanaceous Food Crops under Different Stress Conditions: Current and Future Perspectives

Plant growth, development, and productivity are adversely affected by environmental stresses such as drought (osmotic stress), soil salinity, cold, oxidative stress, irradiation, and diverse diseases. These impacts are of increasing concern in light of climate change. Noticeably, plants have developed their adaptive mechanism to respond to environmental stresses by transcriptional activation of stress-responsive genes. Among the known transcription factors, DoF, WRKY, MYB, NAC, bZIP, ERF, ARF and HSF are those widely associated with abiotic and biotic stress response in plants. Genome-wide identification and characterization analyses of these transcription factors have been almost completed in major solanaceous food crops, emphasizing these transcription factor families which have much potential for the improvement of yield, stress tolerance, reducing marginal land and increase the water use efficiency of solanaceous crops in arid and semi-arid areas where plant demand more water. Most importantly, transcription factors are proteins that play a key role in improving crop yield under water-deficient areas and a place where the severity of pathogen is very high to withstand the ongoing climate change. Therefore, this review highlights the role of major transcription factors in solanaceous crops, current and future perspectives in improving the crop traits towards abiotic and biotic stress tolerance and beyond. We have tried to accentuate the importance of using genome editing molecular technologies like CRISPR/Cas9, Virus-induced gene silencing and some other methods to improve the plant potential in giving yield under unfavorable environmental conditions.

Grape (Vitis vinifera) VvDOF3 functions as a transcription activator and enhances powdery mildew resistance

DOF proteins are plant-specific transcription factors that play vital roles in plant development and defense responses. However, DOFs have primarily been investigated in model plants, and fairly limited research has been performed on grape (Vitis vinifera). In this study, we isolated and characterized a C₂-C₂ zinc finger structural DOF gene, VvDOF3, from the grape cultivar Jingxiu. The VvDOF3 protein showed nuclear localization and transcriptional activation ability, indicating that it functions as a transcription factor. The VvDOF3 gene was rapidly induced by exogenous salicylic acid (SA), jasmonic acid (JA), and powdery mildew infection. Overexpression of VvDOF3 in Arabidopsis thaliana enhanced resistance to Golovinomyces cichoracearum. Expression of the SA-responsive defense-related gene PR1 and the concentration of SA were up-regulated in transgenic Arabidopsis plants overexpressing VvDOF3. Together, these data suggest that VvDOF3 functions as a transcription factor in grape and enhances powdery mildew resistance through the SA signaling pathway.

Genome-wide analysis of the Dof gene family in durian reveals fruit ripening-associated and cultivar-dependent Dof transcription factors

DNA binding with one finger (Dof) proteins constitute a ubiquitous plant-specific transcription factor (TF) family associated with diverse biological processes, including ripening. We conducted a genome-wide analysis of durian (Durio zibethinus Murr.) and identified 24 durian Dofs (DzDofs), 15 of which were expressed in fruit pulp. Gene expression analysis revealed differential expression of DzDofs during ripening in two commercial durian cultivars from Thailand, Monthong and Chanee. Comparing the expression levels of fruit pulp-expressed DzDofs between cultivars revealed ten potential cultivar-dependent Dofs, among which DzDof2.2 showed a significantly greater fold increase at every ripening stage in Chanee than in Monthong. The prediction of DzDof2.2's function based on its orthologue in Arabidopsis revealed its possible role in regulating auxin biosynthesis. We observed significantly higher auxin levels during ripening of Chanee than Monthong which concurred with the greater expression of auxin biosynthetic genes. Transient expression of DzDof2.2 in Nicotiana benthamiana significantly upregulated the expression levels of auxin biosynthetic genes. Higher expression levels of DzDof2.2 in Chanee would enhance auxin levels through transcriptional regulation of auxin biosynthetic genes. Higher auxin levels in Chanee could activate auxin-mediated transcription, contributing to its faster ripening compared to Monthong through earlier initiation of the ethylene response (auxin-ethylene crosstalk).

Genome-Wide Identification and Characterization of the AREB/ABF/ABI5 Subfamily Members from Solanum tuberosum

Abscisic acid (ABA) plays crucial roles in plant development and adaption to environmental stresses. The ABA-responsive element binding protein/ABRE-binding factor and ABA INSENSITIVE 5 (AREB/ABF/ABI5) gene subfamily members, which belong to the basic domain/leucine zipper (bZIP) transcription factors family, participate in the ABA-mediated signaling pathway by regulating the expression of their target genes. However, information about potato (Solanum tuberosum) AREB/ABF/ABI5 subfamily members remains scarce. Here, seven putative AREB/ABF/ABI5 members were identified in the potato genome. Sequences alignment revealed that these members shared high protein sequence similarity, especially in the bZIP region, indicating that they might possess overlapping roles in regulating gene expression. Subcellular localization analysis illustrated that all seven AREB/ABF/ABI5 members were localized in the nucleus. Transactivation activity assays in yeast demonstrated that these AREB/ABF/ABI5 members possessed distinct transcriptional activity. Electrophoretic mobility shift assays (EMSA) confirmed that all of these AREB/ABF/ABI5 members could have an affinity to ABRE in vitro. The expression patterns of these AREB/ABF/ABI5 genes showed that they were in response to ABA or osmotic stresses in varying degrees. Moreover, most AREB/ABF/ABI5 genes were induced during stolon swelling. Overall, these results provide the first comprehensive identification of the potato AREB/ABF/ABI5 subfamily and would facilitate further functional characterization of these subfamily members in future work.

Identification of Dof transcription factors in ramie (Boehmeria nivea L. Gaud) and their expression in response to different nitrogen treatments

19 DNA binding with one finger (Dof) transcription factor genes were identified from genome and transcriptome data of ramie (Boehmeria nivea L. Gaud). Chemical character, subnuclear localization, motif analysis, phylogenetic analysis, and tissue-specific analysis were performed. To select BnDof genes participating in nitrogen metabolism, we analyzed the expression patterns of BnDof genes in different nitrogen conditions (N0, N4, N8, and N12) in different tissues. As a result, eight BnDof genes were identified. BnDof07 (stem) and BnDof14 (root) had higher expression levels in N0 and N4, and BnDof15 (stem and leaves) and BnDof18 (stem) both exhibited the highest expression level in N0, suggesting that these four genes may take part in nitrogen stress. In the leaves, BnDof01, BnDof06, BnDof09, and BnDof19 expression levels were higher in N8 and N12 but lower in N0 and N4. The present findings provide insights into nitrogen metabolism in ramie highlighting the need to investigate this aspect in further detail in future studies.

Expression and function analysis of a rice OsHSP40 gene under salt stress

Heat shock proteins (HSPs) play essential roles in both plant growth and abiotic stress tolerance. In rice, OsHSP40 was recently reported to regulate programmed cell death (PCD) of suspension cells under high temperature. However, the expression and functions of OsHSP40 under normal growth or other abiotic stress conditions is still unknown. We reported the expression and function of a rice OsHSP40 gene under salt stress. Homologous proteins of OsHSP40 were collected from the NCBI database and constructed the neighbor-joining (NJ) phylogenetic tree. The expression pattern of OsHSP40 was detected by qRT-PCR under NaCl (150 mM) treatment. Then, identified a rice T-DNA insertion mutant oshsp40. At last, we compared and analyzed the phenotypes of oshsp40 and wild type under salt stress. OsHSP40 was a constitutively expressed small HSP (sHSP) gene and was close related to other plant sHSPs. Moreover, the expression of OsHSP40 was regulated by salt, varying across time points and tissues. Furthermore, the growth of T-DNA insertion mutant of OsHSP40 (designated as oshsp40) was suppressed by NaCl (150 mM) compared with that of the WT at seedling stage. Detailed measurement showed root and shoot length of the oshsp40 seedlings were significantly shorter than those of the WT seedlings under NaCl stress. In addition, the pot experiment results revealed that seedlings of oshsp40 withered more seriously compared with those of WT after NaCl treatment and recovery, and that survival rate and fresh weight of oshsp40 seedlings were significantly reduced. Taken together, these data suggested that OsHSP40 had multiple functions in rice normal growth and abiotic stress tolerance.

Genome-Wide Screening and Characterization of the Dof Gene Family in Physic Nut (Jatropha curcas L.)

Physic nut (Jatropha curcas L.) is a species of flowering plant with great potential for biofuel production and as an emerging model organism for functional genomic analysis, particularly in the Euphorbiaceae family. DNA binding with one finger (Dof) transcription factors play critical roles in numerous biological processes in plants. Nevertheless, the knowledge about members, and the evolutionary and functional characteristics of the Dof gene family in physic nut is insufficient. Therefore, we performed a genome-wide screening and characterization of the Dof gene family within the physic nut draft genome. In total, 24 JcDof genes (encoding 33 JcDof proteins) were identified. All the JcDof genes were divided into three major groups based on phylogenetic inference, which was further validated by the subsequent gene structure and motif analysis. Genome comparison revealed that segmental duplication may have played crucial roles in the expansion of the JcDof gene family, and gene expansion was mainly subjected to positive selection. The expression profile demonstrated the broad involvement of JcDof genes in response to various abiotic stresses, hormonal treatments and functional divergence. This study provides valuable information for better understanding the evolution of JcDof genes, and lays a foundation for future functional exploration of JcDof genes.

Identification of MdDof genes in apple and analysis of their response to biotic or abiotic stress

As a classic plant-specific transcription factor family - the Dof domain proteins - are involved in a variety of biological processes in organisms ranging from unicellular Chlamydomonas to higher plants. However, there are limited reports of MdDof (Malus domestica Borkh. DNA-binding One Zinc Finger) domain proteins in fruit trees, especially in apple. In this study we identified 54 putative Dof transcription factors in the apple genome. We analysed the gene structures, protein motifs, and chromosome locations of each of the MdDof genes. Next, we characterised all 54 MdDofs their expression patterns under different abiotic and biotic stress conditions. It was found that MdDof6,26 not only played an important role in the biotic/abiotic stress but may also be involved in many molecular functions. Further, both in flower development and pollen tube growth it was found that the relative expression of MdDof24 increased rapidly, also with gene ontology analysis it was indicated that MdDof24 was involved in the chemical reaction and flower development pathways. Taken together, our results provide useful clues as to the function of MdDof genes in apple and serve as a reference for studies of Dof zinc finger genes in other plants.

Genome-wide identification and characterization of Dof transcription factors in eggplant (Solanum melongena L.)

Eggplant (Solanum melongena L.) is an important vegetable cultivated in Asia, Africa and southern Europe and, following tomato and pepper, ranks as the third most important solanaceous vegetable crop. The Dof (DNA-binding with one finger) family is a group of plant-specific transcription factors that play important roles in plant growth, development, and response to biotic and abiotic stresses. The genes in the Dof family have been identified and analysed in many plant species, but the information remains lacking for eggplant. In the present study, we identified 29 SmeDof members from the eggplant genome database, which were classifed into nine subgroups. The phylogeny, gene structure, conserved motifs and homologous genes of SmeDof genes were comprehensively investigated. Subsequently, we analysed the expression patterns of SmeDof genes in six different eggplant subspecies. The results provide novel insights into the family of SmeDof genes and will promote the understanding of the structure and function of Dof genes in eggplant, and the role of Dof expression during stress.

Characterization of moso bamboo (Phyllostachys edulis) Dof transcription factors in floral development and abiotic stress responses

The Dof transcription factor (TF) family belongs to a class of plant-specific TFs and is involved in plant growth, development, and response to abiotic stresses. However, there are only very limited reports on the characterization of Dof TFs in moso bamboo (Phyllostachys edulis). In the present research, PheDof TFs showed specific expression profiles based on RNA-seq data analyses. The co-expression network indicated that PheDof12, PheDof14, and PheDof16 might play vital roles during flower development. Cis-regulatory element analysis of these PheDof genes suggested diverse functions. Expression patterns of 12 selected genes from seven different classes under three abiotic stresses (cold, salt, and drought) are further investigated by quantitative real-time PCR. This work will provide useful information for functional analysis and regulation mechanisms of Dof TFs in moso bamboo.

Expression, purification and DNA-binding properties of zinc finger domains of DOF proteins from Arabidopsis thaliana

Introduction: DOF proteins are a family of plant-specific transcription factors with a conserved zinc finger (ZF) DNA-binding domain. Although several studies have demonstrated their specific DNA binding, quantitative affinity data is not available for the binding of DOF domains to their binding sites. Methods: ZF domains of DOF2.1, DOF3.4, and DOF5.8 from Arabidopsis thaliana were expressed and purified. Their DNA binding affinities were assessed using gel retardation assays and microscale thermophoresis with two different oligonucleotide probes containing one and two copies of recognition sequence AAAG. Results: DOF zinc finger domains (DOF-ZFs) were shown to form independently folded structures. Assessments using microscale thermophoresis demonstrated that DOF-ZFs interact more tightly (~ 100 fold) with double-motif probe than the single-motif probe. The overall Kd values for the DOF3.4-ZF and DOF5.8-ZF to the double-motif probe were ~2.3±1 and 2.5±1 µM, respectively. Conclusion: Studied DOF-ZF domains formed stable complexes with the double-motif probe. Although DOF3.4-ZF and DOF5.8-ZF do not dimerize with an appreciable affinity in the absence of DNA (judging from size-exclusion and multiangle laser light scattering data), it is possible that these ZFs form protein-protein contacts when bound to this oligonucleotide, consistent with previous reports that DOF proteins can homo- and hetero-dimerize.

Evolution analysis of Dof transcription factor family and their expression in response to multiple abiotic stresses in Malus domestica

As a family of transcription factors, DNA binding with one figure (Dof) proteins play important roles in various biological processes in plants. Here, a total of 60 putative apple (Malus domestica) Dof genes (MdDof) were identified and mapped to different chromosomes. Chromosomal distribution and synteny analysis indicated that the expansion of the MdDof genes came primarily from segmental and duplication events, and from whole genome duplication, which lead to more Dof members in apples than in other plants. All 60 MdDof genes were classified into thirteen groups, according to multiple sequence alignment and the phylogenetic tree constructed of Dof genes from apple, peach (Prunus persica), Arabidopsis and rice. Within each group, the members shared a similar exon/intron and motif compositions, although the sizes of the MdDof genes and encoding proteins were quite different. Several Dof genes from the apple and peach were identified to be homologues based on their close synteny relationship, which suggested that these genes bear similar functions. Half of the MdDof genes were randomly selected to determine their responses to different stresses. The majority of MdDof genes were quite sensitive to PEG, NaCl, cold and exogenous ABA treatment. Our results suggested that MdDof family members may play important roles in plant tolerance to abiotic stress.

Genome-Wide Analysis of the Biosynthesis and Deactivation of Gibberellin-Dioxygenases Gene Family in Camellia sinensis (L.) O. Kuntze

Gibberellins (GAs), a class of diterpenoid phytohormones, play a key role in regulating diverse processes throughout the life cycle of plants. Bioactive GA levels are rapidly regulated by Gibberellin-dioxygenases (GAox), which are involved in the biosynthesis and deactivation of gibberellin. In this manuscript, a comprehensive genome-wide analysis was carried out to find all GAox in Camellia sinensis. For the first time in a tea plant, 14 CsGAox genes, containing two domains, DIOX_N (PF14226) and 2OG-FeII_Oxy, were identified (PF03171). These genes all belong to 2-oxoglutarate-dependent dioxygenases (2-ODD), including four CsGA20ox (EC: 1.14.11.12), three CsGA3ox (EC: 1.14.11.15), and seven CsGA2ox (EC: 1.14.11.13). According to the phylogenetic classification as in Arabidopsis, the CsGAox genes spanned five subgroups. Each CsGAox shows tissue-specific expression patterns, although these vary greatly. Some candidate genes, which may play an important role in response to external abiotic stresses, have been identified with regards to patterns, such as CsGA20ox2, CsGA3ox2, CsGA3ox3, CsGA2ox1, CsGA2ox2, and CsGA2ox4. The bioactive GA levels may be closely related to the GA20ox, GA3ox and GA2ox genes. In addition, the candidate genes could be used as marker genes for abiotic stress resistance breeding in tea plants.

The 5' untranslated region of potato SBgLR gene contributes to pollen-specific expression

MAIN CONCLUSION

The 5'UTR of SBgLR enhances gene expression by regulating both its transcription and translation. SBgLR (Solanum tuberosum genomic lysine rich) is a pollen-specific gene in Solanum tuberosum that encodes a microtubule-associated protein. The region from -85 to +180 (transcription start site at +1) was determined to be critical for specific expression in pollen grains. Transient and stable expression assays showed that the 5'UTR (from +1 to +184) enhanced gene expression in all detected tissues of transgenic tobacco. Deletion analysis demonstrated that the secondary structure of the 5'UTR had no effect on pollen-specific SBgLR expression, while the region from +31 to +60 was crucial. Further investigation indicated that mRNA expression was slightly decreased when the +31 to +60 region was deleted, but the mRNA decay rate remained unchanged. Mutation analysis also confirmed that the pollen-specific element TTTCT, located at +37, played an important role in pollen-specific expression. Using yeast one-hybrid screening, we isolated a DNA-binding with one finger (Dof) protein gene (StDof23) and an AT-hook motif nuclear-localized (AHL) protein gene (StAHL) from potato pollen. Further investigation indicated that StDof23 interacted with and positively regulated the +31 to +60 region; moreover, StAHL interacted with and negatively regulated the -49 to +60 region. These results demonstrate that the 5'UTR not only enhanced gene expression but also altered the tissue-specific expression pattern by regulating both transcription and translation.

The fruit-specific transcription factor FaDOF2 regulates the production of eugenol in ripe fruit receptacles

Only a few transcription factors have been described in the regulation of the strawberry (Fragaria x ananassa) fruit ripening process. Using a transcriptomic approach, we identified and functionally characterized FaDOF2, a DOF-type ripening-related transcription factor, which is hormonally regulated and specific to the receptacle, though high expression levels were also found in petals. The expression pattern of FaDOF2 correlated with eugenol content, a phenylpropanoid volatile, in both fruit receptacles and petals. When FaDOF2 expression was silenced in ripe strawberry receptacles, the expression of FaEOBII and FaEGS2, two key genes involved in eugenol production, were down-regulated. These fruits showed a concomitant decrease in eugenol content, which confirmed that FaDOF2 is a transcription factor that is involved in eugenol production in ripe fruit receptacles. By using the yeast two-hybrid system and bimolecular fluorescence complementation, we demonstrated that FaDOF2 interacts with FaEOBII, a previously reported regulator of eugenol production, which determines fine-tuning of the expression of key genes that are involved in eugenol production. These results provide evidence that FaDOF2 plays a subsidiary regulatory role with FaEOBII in the expression of genes encoding enzymes that control eugenol production. Taken together, our results provide new insights into the regulation of the volatile phenylpropanoid pathway in ripe strawberry receptacles.

Overexpression of Grain Amaranth (Amaranthus hypochondriacus) AhERF or AhDOF Transcription Factors in Arabidopsis thaliana Increases Water Deficit- and Salt-Stress Tolerance, Respectively, via Contrasting Stress-Amelioration Mechanisms

Two grain amaranth transcription factor (TF) genes were overexpressed in Arabidopsis plants. The first, coding for a group VII ethylene response factor TF (i.e., AhERF-VII) conferred tolerance to water-deficit stress (WS) in transgenic Arabidopsis without affecting vegetative or reproductive growth. A significantly lower water-loss rate in detached leaves coupled to a reduced stomatal opening in leaves of plants subjected to WS was associated with this trait. WS tolerance was also associated with an increased antioxidant enzyme activity and the accumulation of putative stress-related secondary metabolites. However, microarray and GO data did not indicate an obvious correlation between WS tolerance, stomatal closure, and abscisic acid (ABA)-related signaling. This scenario suggested that stomatal closure during WS in these plants involved ABA-independent mechanisms, possibly involving reactive oxygen species (ROS). WS tolerance may have also involved other protective processes, such as those employed for methyl glyoxal detoxification. The second, coding for a class A and cluster I DNA binding with one finger TF (i.e., AhDof-AI) provided salt-stress (SS) tolerance with no evident fitness penalties. The lack of an obvious development-related phenotype contrasted with microarray and GO data showing an enrichment of categories and genes related to developmental processes, particularly flowering. SS tolerance also correlated with increased superoxide dismutase activity but not with augmented stomatal closure. Additionally, microarray and GO data indicated that, contrary to AhERF-VII, SS tolerance conferred by AhDof-AI in Arabidopsis involved ABA-dependent and ABA-independent stress amelioration mechanisms.