Genome-Wide Identification of Tomato Golden 2-Like Transcription Factors and Abiotic Stress Related Members Screening

Background: Golden 2-Like (G2-like) transcription factors play an important role in plant development. However, the roles of these G2-like regulatory genes in response to abiotic stresses in tomato are not well understood.Results: In this study, we identified 66 putative G2-like genes in tomato (Solanum lycopersicum) and classified them into 5 groups (I to V) according to gene structure, motif composition and phylogenetic analysis. The G2-like genes were unevenly distributed across all 12 chromosomes. There were nine pairs of duplicated gene segments and four tandem duplicated SlGlk genes. Analysis of the cis-regulatory elements (CREs) showed that the promoter regions of SlGlks contain many kinds of stress- and hormone-related CREs. Based on RNA-seq, SlGlks were expressed in response to three abiotic stresses. Thirty-six differentially expressed SlGlks were identified; these genes have multiple functions according to Gene Ontology (GO) analysis and are enriched mainly in the zeatin biosynthesis pathway. Further studies exhibited that silencing SlGlk16 in tomato would reduce drought stress tolerance by earlier wilted, lower superoxide dismutase (SOD), peroxidase (POD) activities, less Pro contents and more MDA contents. Conclusion: Overall, the results of this study provide comprehensive information on G2-like transcription factors and G2-like genes that may be expressed in response to abiotic stresses.

Genome-Wide Identification and Characterization of Hsf and Hsp Gene Families and Gene Expression Analysis under Heat Stress in Eggplant (Solanum melongema L.)

Under high temperature stress, a large number of proteins in plant cells will be denatured and inactivated. Meanwhile Hsfs and Hsps will be quickly induced to remove denatured proteins, so as to avoid programmed cell death, thus enhancing the thermotolerance of plants. Here, a comprehensive identification and analysis of the Hsf and Hsp gene families in eggplant under heat stress was performed. A total of 24 Hsf-like genes and 117 Hsp-like genes were identified from the eggplant genome using the interolog from Arabidopsis. The gene structure and motif composition of Hsf and Hsp genes were relatively conserved in each subfamily in eggplant. RNA-seq data and qRT-PCR analysis showed that the expressions of most eggplant Hsf and Hsp genes were increased upon exposure to heat stress, especially in thermotolerant line. The comprehensive analysis indicated that different sets of SmHsps genes were involved downstream of particular SmHsfs genes. These results provided a basis for revealing the roles of SmHsps and SmHsp for thermotolerance in eggplant, which may potentially be useful for understanding the thermotolerance mechanism involving SmHsps and SmHsp in eggplant.

Genome-Wide Identification and Expression Analyses of AnSnRK2 Gene Family under Osmotic Stress in Ammopiptanthus nanus

Sucrose non-fermenting-1 (SNF1)-related protein kinase 2’s (SnRK2s) are plant-specific serine/threonine protein kinases and play crucial roles in the abscisic acid signaling pathway and abiotic stress response. Ammopiptanthus nanus is a relict xerophyte shrub and extremely tolerant of abiotic stresses. Therefore, we performed genome-wide identification of the AnSnRK2 genes and analyzed their expression profiles under osmotic stresses including drought and salinity. A total of 11 AnSnRK2 genes (AnSnRK2.1-AnSnRK2.11) were identified in the A. nanus genome and were divided into three groups according to the phylogenetic tree. The AnSnRK2.6 has seven introns and others have eight introns. All of the AnSnRK2 proteins are highly conserved at the N-terminus and contain similar motif composition. The result of cis-acting element analysis showed that there were abundant hormone- and stress-related cis-elements in the promoter regions of AnSnRK2s. Moreover, the results of quantitative real-time PCR exhibited that the expression of most AnSnRK2s was induced by NaCl and PEG-6000 treatments, but the expression of AnSnRK2.3 and AnSnRK2.6 was inhibited, suggesting that the AnSnRK2s might play key roles in stress tolerance. The study provides insights into understanding the function of AnSnRK2s.

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.

Identification of peach growth regulating-factors and their expression under UVB

Background: Growth-regulating factors (GRFs) are one of the most important plant-specific transcription factors with vital roles in multiple biological processes. GRFs have been identified in a variety of plant species, but a handful of research has addressed GRF genes in peach (Prunus persica).Results: Here, we report 46 members of the GRF family in four Rosaceae, divided into six subfamilies according to phylogeny, gene structure, and motif composition. We detected three collinear gene pairs generated from peach by whole-genome duplication or segmental duplication, but no tandem repeats were detected. Expression pattern analysis found that most PpGRFs were preferentially expressed in young tissues, At the sametime, multiple types cis-elements were observed in PpGRF promoters, and PpGRFs could positively respond to ultraviolet B-rays (UVB) and gibberellin (GA)treatments at the transcriptional level. Also, the content of GA3 and indole-3-acetic acid (IAA) changed significantly after UVB irradiation, indicating that GRFs might be involved in new shoot development in peach.Conclusions: This study identified 10 GRF genes in the peach genome and systematically analyzed their properties, thereby providing a foundation for researchers to have a better understanding of this gene family in peach. PpGRF 3, 4, 5, 6, 7, 9, and 10 positive responses to UVB and GA3 signals indicate that they can serve as candidate functional genes to further study how tree potential is regulated in peach.

Haplotype Diversity and Sequence Heterogeneity of Human Telomeres

Telomeres are regions of repetitive nucleotide sequences capping the ends of eukaryotic chromosomes that protect against deterioration, whose lengths can be correlated with age and disease risk factors. Given their length and repetitive nature, telomeric regions are not easily reconstructed from short read sequencing, making telomere sequence resolution a very costly and generally intractable problem. Recently, long-read sequencing, with read lengths measuring in hundreds of Kbp, has made it possible to routinely read into telomeric regions and inspect their structure. Here, we describe a framework for extracting telomeric reads from single-molecule sequencing experiments, describing their sequence variation and motifs, and for haplotype inference. We find that long telomeric stretches can be accurately captured with long-read sequencing, observe extensive sequence heterogeneity of human telomeres, discover and localize non-canonical motifs (both previously reported as well as novel), and report the first motif composition maps of human telomeric diplotypes on a multi-Kbp scale.

Characterization and Functional Divergence of a Novel DUF668 Gene Family in Rice Based on Comprehensive Expression Patterns

The domain of unknown function (DUF) superfamily encodes proteins of unknown functions in plants. Among them, DUF668 family members in plants possess a 29 amino-acid conserved domain, and this family has not been described previously. Here, we report this plant-specific novel DUF668 gene family containing 12 OsDUF668 genes in rice (Oryza sativa) and 91 DUF668s for the other seven plant species. In our study, DUF668 genes were present in both dicot and monocot plants, indicating that DUF668 is a conserved gene family that originated by predating the dicot–monocot divergence. Based on the gene structure and motif composition, the DUF668 family consists of two distinct clades, I and II in the phylogenetic tree. Remarkably, OsDUF668 genes clustered on the chromosomes merely show close phylogenetic relationships, suggesting that gene duplications or collinearity seldom happened. Cis-elements prediction display that over 80% of DUF668s contain phytohormone and light responsiveness factors. Further comprehensive experimental analyses of the OsDUF668 family are implemented in 22 different tissues, five hormone treatments, seven environmental factor stresses, and two pathogen-defense related stresses. The OsDUF668 genes express ubiquitously in analyzed rice tissues, and seven genes show tissue-specific high expression profiles. All OsDUF668s respond to drought, and some of Avr9/Cf-9 rapidly elicited genes resist to salt, wound, and rice blast with rapidly altered expression patterns. These findings imply that OsDUF668 is essential for drought-enduring and plant defense. Together, our results bring the important role of the DUF668 gene family in rice development and fitness to the fore.

Variations in the Structure and Evolution of Rice WRKY Genes in Indica and Japonica Genotypes and their Co-expression Network in Mediating Disease Resistance

WRKY transcription factor (TF) family regulates many functions in plant growth and development and also during biotic and abiotic stress. In this study, 101 WRKY TF gene models in indica and japonica rice were used to conduct evolutionary analysis, gene structure analysis, and motif composition. Co-expression analysis was carried out first by selecting the differentially expressing genes that showed a significant change in response to the pathogens from Rice Oligonucleotide Array Database (ROAD). About 82 genes showed responses to infection by Magnaporthe oryzae or Xanthomonas oryzae pv. oryzae. Co-expression gene network was constructed using direct neighborhood and context associated inbuilt mode in RiceNetv2 tool. Only 41 genes showed interaction with 2299 non- WRKY genes. Variations exist in the structure and evolution of WRKY genes among indica and japonica genotypes which have important implications in their differential roles including disease resistance. WRKY genes mediate a complex networking and co-express along with other WRKY and non- WRKY genes to mediate resistance against fungal and bacterial pathogens in rice.

Genome-wide characterization and expression analysis of GRAS gene family in pepper (Capsicum annuum L.)

Plant-specific GRAS transcription factors diversely participate in the regulation of multiple biological processes including growth and development, signal cross-talking and biotic/abiotic responses. However, this gene family was not characterized detailed in pepper ( Capsicum annuum L.), an economically important vegetable crop. Here, a total of 50 Ca GRAS members were identified in the pepper genome and renamed by their respective chromosomal distribution. Genomic organization revealed that most CaGRAS genes (84%) have no intron. A phylogenetic analysis was carried out using Arabidopsis thaliana to classify pepper GARS genes into at least ten subfamilies. Multiple sequence alignment showed GRAS-typical domains present in those proteins, with the members from the same phylogenetic subfamily exhibiting the similar motif composition. The presence of highly divergent N-terminus may be associated with functional specificity of each CaGRAS protein. Expression of 12 CaGRAS genes was not detected in all tissues tested, suggesting that their functions may be lost during evolution. By contrast, the rest 38 CaGRAS genes were expressed largely in several organs, showing their important roles in pepper life activities. Moreover, 21 CaGRAS genes were differentially expressed under cold, drought, salt and GA treatments, indicating that they play vital roles in response to abiotic stress in pepper. The first comprehensive analysis of GRAS gene family in the pepper genome in this study provide insights into understanding the CRAS-mediated regulation network, benefiting the genetic improvements in pepper and some other relative plants.

Genome-wide characterization and expression analysis of GRAS gene family in pepper (Capsicum annuum L.)

Plant-specific GRAS transcription factors diversely participate in the regulation of multiple biological processes including growth and development, signal cross-talking and biotic/abiotic responses. However, this gene family was not characterized detailed in pepper ( Capsicum annuum L.), an economically important vegetable crop. Here, a total of 50 Ca GRAS members were identified in the pepper genome and renamed by their respective chromosomal distribution. Genomic organization revealed that most CaGRAS genes (84%) have no intron. A phylogenetic analysis was carried out using Arabidopsis thaliana to classify pepper GARS genes into at least ten subfamilies. Multiple sequence alignment showed GRAS-typical domains present in those proteins, with the members from the same phylogenetic subfamily exhibiting the similar motif composition. The presence of highly divergent N-terminus may be associated with functional specificity of each CaGRAS protein. Expression of 12 CaGRAS genes was not detected in all tissues tested, suggesting that their functions may be lost during evolution. By contrast, the rest 38 CaGRAS genes were expressed largely in several organs, showing their important roles in pepper life activities. Moreover, 21 CaGRAS genes were differentially expressed under cold, drought, salt and GA treatments, indicating that they play vital roles in response to abiotic stress in pepper. The first comprehensive analysis of GRAS gene family in the pepper genome in this study provide insights into understanding the CRAS-mediated regulation network, benefiting the genetic improvements in pepper and some other relative plants.