Genome-wide identification and expression profiling of DREB genes in Saccharum spontaneum

H3K27 demethylase SsJMJ4 negatively regulates drought-stress responses in sugarcane

Sugarcane (Saccharum spp.), a leading sugar and energy crop, is seriously impacted by drought stress. However, the molecular mechanisms underlying sugarcane drought resistance, especially the functions of epigenetic regulators, remain elusive. Here, we show that a S. spontaneum KDM4/JHDM3 group JmjC protein, SsJMJ4, negatively regulates drought-stress responses through its H3K27me3 demethylase activity. Ectopic overexpression of SsJMJ4 in Arabidopsis reduced drought resistance possibly by promoting expression of AtWRKY54 and AtWRKY70, encoding two negative regulators of drought stress. SsJMJ4 directly bound to AtWRKY54 and AtWRKY70, and reduced H3K27me3 levels at these loci to ensure their proper transcription under normal conditions. Drought stress down-regulated both transcription and protein abundance of SsJMJ4, which was correlated with the reduced occupancy of SsJMJ4 at AtWRKY54 and AtWRKY70 chromatin, increased H3K27me3 levels at these loci, as well as reduced transcription levels of these genes. In S. spontaneum, drought stress-repressed transcription of SsWRKY122, an ortholog of AtWRKY54 and AtWRKY70, was associated with increased H3K27me3 levels at these loci. Transient overexpression of SsJMJ4 in S. spontaneum protoplasts raised transcription of SsWRKY122, paralleled with reduced H3K27me3 levels at its loci. These results suggest that the SsJMJ4-mediated dynamic deposition of H3K27me3 is required for an appropriate response to drought stress.

Identification and characterization of the Remorin gene family in Saccharum and the involvement of ScREM1.5e-1/-2 in SCMV infection on sugarcane

Introduction

Remorins (REMs) are plant-specific membrane-associated proteins that play important roles in plant-pathogen interactions and environmental adaptations. Group I REMs are extensively involved in virus infection. However, little is known about the REM gene family in sugarcane (Saccharum spp. hyrid), the most important sugar and energy crop around world.

Methods

Comparative genomics were employed to analyze the REM gene family in Saccharum spontaneum. Transcriptomics or RT-qPCR were used to analyze their expression files in different development stages or tissues under different treatments. Yeast two hybrid, bimolecular fluorescence complementation and co-immunoprecipitation assays were applied to investigate the protein interaction.

Results

In this study, 65 REMs were identified from Saccharum spontaneum genome and classified into six groups based on phylogenetic tree analysis. These REMs contain multiple cis-elements associated with growth, development, hormone and stress response. Expression profiling revealed that among different SsREMs with variable expression levels in different developmental stages or different tissues. A pair of alleles, ScREM1.5e-1/-2, were isolated from the sugarcane cultivar ROC22. ScREM1.5e-1/-2 were highly expressed in leaves, with the former expressed at significantly higher levels than the latter. Their expression was induced by treatment with H2O2, ABA, ethylene, brassinosteroid, SA or MeJA, and varied upon Sugarcane mosaic virus (SCMV) infection. ScREM1.5e-1 was localized to the plasma membrane (PM), while ScREM1.5e-2 was localized to the cytoplasm or nucleus. ScREM1.5e-1/-2 can self-interact and interact with each other, and interact with VPgs from SCMV, Sorghum mosaic virus, or Sugarcane streak mosaic virus. The interactions with VPgs relocated ScREM1.5e-1 from the PM to the cytoplasm.

Discussion

These results reveal the origin, distribution and evolution of the REM gene family in sugarcane and may shed light on engineering sugarcane resistance against sugarcane mosaic pathogens.

Genomic investigation of duplication, functional conservation, and divergence in the LRR-RLK Family of Saccharum

BACKGROUND

Sugarcane (Saccharum spp.) holds exceptional global significance as a vital crop, serving as a primary source of sucrose, bioenergy, and various by-products. The optimization of sugarcane breeding by fine-tuning essential traits has become crucial for enhancing crop productivity and stress resilience. Leucine-rich repeat receptor-like kinases (LRR-RLK) genes present promising targets for this purpose, as they are involved in various aspects of plant development and defense processes.

RESULTS

Here, we present a detailed overview of phylogeny and expression of 288 (495 alleles) and 312 (1365 alleles) LRR-RLK genes from two founding Saccharum species, respectively. Phylogenetic analysis categorized these genes into 15 subfamilies, revealing considerable expansion or reduction in certain LRR-type subfamilies. Compared to other plant species, both Saccharum species had more significant LRR-RLK genes. Examination of cis-acting elements demonstrated that SsLRR-RLK and SoLRR-RLK genes exhibited no significant difference in the types of elements included, primarily involved in four physiological processes. This suggests a broad conservation of LRR-RLK gene function during Saccharum evolution. Synteny analysis indicated that all LRR-RLK genes in both Saccharum species underwent gene duplication, primarily through whole-genome duplication (WGD) or segmental duplication. We identified 28 LRR-RLK genes exhibiting novel expression patterns in response to different tissues, gradient development leaves, and circadian rhythm in the two Saccharum species. Additionally, SoLRR-RLK104, SoLRR-RLK7, SoLRR-RLK113, and SsLRR-RLK134 were identified as candidate genes for sugarcane disease defense response regulators through transcriptome data analysis of two disease stresses. This suggests LRR-RLK genes of sugarcane involvement in regulating various biological processes, including leaf development, plant morphology, photosynthesis, maintenance of circadian rhythm stability, and defense against sugarcane diseases.

CONCLUSIONS

This investigation into gene duplication, functional conservation, and divergence of LRR-RLK genes in two founding Saccharum species lays the groundwork for a comprehensive genomic analysis of the entire LRR-RLK gene family in Saccharum. The results reveal LRR-RLK gene played a critical role in Saccharum adaptation to diverse conditions, offering valuable insights for targeted breeding and precise phenotypic adjustments.

Drought and salinity stresses induced physio-biochemical changes in sugarcane: an overview of tolerance mechanism and mitigating approaches

Sugarcane productivity is being hampered globally under changing environmental scenarios like drought and salinity. The highly complex nature of the plant responses against these stresses is determined by a variety of factors such as genotype, developmental phase of the plant, progression rate and stress, intensity, and duration. These factors influence plant responses and can determine whether mitigation approaches associated with acclimation are implemented. In this review, we attempt to summarize the effects of drought and salinity on sugarcane growth, specifically on the plant's responses at various levels, viz., physiological, biochemical, and metabolic responses, to these stresses. Furthermore, mitigation strategies for dealing with these stresses have been discussed. Despite sugarcane's complex genomes, conventional breeding approaches can be utilized in conjunction with molecular breeding and omics technologies to develop drought- and salinity-tolerant cultivars. The significant role of plant growth-promoting bacteria in sustaining sugarcane productivity under drought and salinity cannot be overlooked.

DREB1 and DREB2 Genes in Garlic (Allium sativum L.): Genome-Wide Identification, Characterization, and Stress Response

Dehydration-responsive element-binding (DREB) transcription factors (TFs) of the A1 and A2 subfamilies involved in plant stress responses have not yet been reported in Allium species. In this study, we used bioinformatics and comparative transcriptomics to identify and characterize DREB A1 and A2 genes redundant in garlic (Allium sativum L.) and analyze their expression in A. sativum cultivars differing in the sensitivity to cold and Fusarium infection. Eight A1 (AsaDREB1.1-1.8) and eight A2 (AsaDREB2.1-2.8) genes were identified. AsaDREB1.1-1.8 genes located in tandem on chromosome 1 had similar expression patterns, suggesting functional redundancy. AsaDREB2.1-2.8 were scattered on different chromosomes and had organ- and genotype-specific expressions. AsaDREB1 and AsaDREB2 promoters contained 7 and 9 hormone- and stress-responsive cis-regulatory elements, respectively, and 13 sites associated with TF binding and plant development. In both Fusarium-resistant and -sensitive cultivars, fungal infection upregulated the AsaDREB1.1-1.5, 1.8, 2.2, 2.6, and 2.8 genes and downregulated AsaDREB2.5, but the magnitude of response depended on the infection susceptibility of the cultivar. Cold exposure strongly upregulated the AsaDREB1 genes, but downregulated most AsaDREB2 genes. Our results provide the foundation for further functional analysis of the DREB TFs in Allium crops and could contribute to the breeding of stress-tolerant varieties.

The DREB transcription factor, a biomacromolecule, responds to abiotic stress by regulating the expression of stress-related genes

Abiotic stress is a crucial factor that affects plant survival and growth and even leads to plant death in severe cases. Transcription factors can enhance the ability of plants to fight against various stresses by controlling the expression of downstream genes. The dehydration response element binding protein (DREB) is the most extensive subfamily of AP2/ERF transcription factors involved in abiotic stress. However, insufficient research on the signal network of DREB transcription factors has limited plant growth and reproduction. Furthermore, field planting of DREB transcription factors and their roles under multiple stress also require extensive research. Previous reports on DREB transcription factors have focused on the regulation of DREB expression and its roles in plant abiotic stress. In recent years, there has been new progress in DREB transcription factors. Here, the structure and classification, evolution and regulation, role in abiotic stress, and application in crops of DREB transcription factors were reviewed. And this paper highlighted the evolution of DREB1/CBF, as well as the regulation of DREB transcription factors under the participation of plant hormone signals and the roles of subgroups in abiotic stress. In the future, it will lay a solid foundation for further study of DREB transcription factors and pave the way for the cultivation of resistant plants.

In vitro and in vivo screening for the identification of salt-tolerant sugarcane (Saccharum officinarum L.) clones: molecular, biochemical, and physiological responses to salt stress

Sugarcane is a glycophyte whose growth and yield can be negatively affected by salt stress. As the arable lands with potential saline soils expand annually, the increase of salt-tolerance in sugarcane cultivars is highly desired. We, herein, employed in vitro and in vivo conditions in order to screen sugarcane plants for salt tolerance at the cellular and at the whole plant levels. Calli of sugarcane cv. Khon Kaen 3 (KK3) were selected after culturing in selective media containing various NaCl concentrations, and regenerated plants were then reselected after culturing in selective media containing higher NaCl concentrations. The surviving plants were finally selected after an exposure to 254 mM NaCl under greenhouse conditions. A total of 11 sugarcane plants survived the selection process. Four plants that exhibited tolerance to the four different salt concentrations applied during the aforementioned screening process were then selected for the undertaking of further molecular, biochemical, and physiological studies. The construction of a dendrogram has revealed that the most salt-tolerant plant was characterized by the lowest genetic similarity to the original cultivar. The relative expression levels of six genes (i.e., SoDREB, SoNHX1, SoSOS1, SoHKT, SoBADH, and SoMIPS) were found to be significantly higher in the salt-tolerance clones than those measured in the original plant. The measured proline levels, the glycine betaine content, the relative water content, the SPAD unit, the contents of chlorophyll a and b, as well as the K⁺/Na⁺ ratios of the salt-tolerant clones were also found to be significantly higher than those of the original plant.When the salt-tolerant clones were grown in a low saline soil, they exhibited a higher Brix percentage than that of the original cultivar.

Genome-Wide Identification, Evolution, and Expression Analyses of AP2/ERF Family Transcription Factors in Erianthus fulvus

The AP2/ERF transcription factor family is one of the most important gene families in plants and plays a vital role in plant abiotic stress responses. Although Erianthus fulvus is very important in the genetic improvement of sugarcane, there are few studies concerning AP2/ERF genes in E. fulvus. Here, we identified 145 AP2/ERF genes in the E. fulvus genome. Phylogenetic analysis classified them into five subfamilies. Evolutionary analysis showed that tandem and segmental duplication contributed to the expansion of the EfAP2/ERF family. Protein interaction analysis showed that twenty-eight EfAP2/ERF proteins and five other proteins had potential interaction relationships. Multiple cis-acting elements present in the EfAP2/ERF promoter were related to abiotic stress response, suggesting that EfAP2/ERF may contribute to adaptation to environmental changes. Transcriptomic and RT-qPCR analyses revealed that EfDREB10, EfDREB11, EfDREB39, EfDREB42, EfDREB44, EfERF43, and EfAP2-13 responded to cold stress, EfDREB5 and EfDREB42 responded to drought stress, and EfDREB5, EfDREB11, EfDREB39, EfERF43, and EfAP2-13 responded to ABA treatment. These results will be helpful for better understanding the molecular features and biological role of the E. fulvus AP2/ERF genes and lay a foundation for further research on the function of EfAP2/ERF genes and the regulatory mechanism of the abiotic stress response.

Genome-wide identification and expression analysis of DREB family genes in cotton

BACKGROUND

Dehydration responsive element-binding (DREB) transcription factors are widely present in plants, and involve in signalling transduction, plant growth and development, and stress response. DREB genes have been characterized in multiple species. However, only a few DREB genes have been studied in cotton, one of the most important fibre crops. Herein, the genome‑wide identification, phylogeny, and expression analysis of DREB family genes are performed in diploid and tetraploid cotton species.

RESULTS

In total, 193, 183, 80, and 79 putative genes containing the AP2 domain were identified using bioinformatics approaches in G. barbadense, G. hirsutum, G. arboretum, and G. raimondii, respectively. Phylogenetic analysis showed that based on the categorization of Arabidopsis DREB genes, 535 DREB genes were divided into six subgroups (A1-A6) by using MEGA 7.0. The identified DREB genes were distributed unevenly across 13/26 chromosomes of A and/or D genomes. Synteny and collinearity analysis confirmed that during the evolution, the whole genome duplications, segmental duplications, and/or tandem duplications occurred in cotton DREB genes, and then DREB gene family was further expanded. Further, the evolutionary trees with conserved motifs, cis-acting elements, and gene structure of cotton DREB gene family were predicted, and these results suggested that DREB genes might be involved in the hormone and abiotic stresses responses. The subcellular localization showed that in four cotton species, DREB proteins were predominantly located in the nucleus. Further, the analysis of DREB gene expression was carried out by real-time quantitative PCR, confirming that the identified DREB genes of cotton were involved in response to early salinity and osmotic stress.

CONCLUSIONS

Collectively, our results presented a comprehensive and systematic understanding in the evolution of cotton DREB genes, and demonstrated the potential roles of DREB family genes in stress and hormone response.

Global Responses of Autopolyploid Sugarcane Badila (Saccharum officinarum L.) to Drought Stress Based on Comparative Transcriptome and Metabolome Profiling

Sugarcane (Saccharum spp. hybrid) is frequently affected by seasonal drought, which causes substantial declines in quality and yield. To understand the drought resistance mechanisms of S. officinarum, the main species of modern sugarcane, at a molecular level, we carried out a comparative analysis of transcriptome and metabolome profiling of the sugarcane variety Badila under drought stress (DS). Compared with control group (CG) plants, plants exposed to DS had 13,744 (6663 up-regulated and 7081 down-regulated) differentially expressed genes (DEGs). GO and KEGG analysis showed that the DEGs were enriched in photosynthesis-related pathways and most DEGs had down-regulated expression. Moreover, the chlorophyll content, photosynthesis (Photo), stomatal conductance (Cond), intercellular carbon dioxide concentration (Ci) and transpiration rate (Trmmol) were sharply decreased under DS. These results indicate that DS has a significant negative influence on photosynthesis in sugarcane. Metabolome analysis identified 166 (37 down-regulated and 129 up-regulated) significantly regulated metabolites (SRMs). Over 50% of SRMs were alkaloids, amino acids and their derivatives, and lipids. The five most significantly enriched KEGG pathways among SRMs were Aminoacyl-tRNA biosynthesis, 2-Oxocarboxylic acid metabolism, Biosynthesis of amino acids, Phenylalanine metabolism, and Arginine and proline metabolism (p < 0.05). Comparing CG with DS for transcriptome and metabolome profiling (T_CG/DS and M_CG/DS, respectively), we found three of the same KEGG-enriched pathways, namely Biosynthesis of amino acids, Phenylalanine metabolism and Arginine and proline metabolism. The potential importance of Phenylalanine metabolism and Arginine and proline metabolism was further analyzed for response to DS in sugarcane. Seven SRMs (five up-regulated and two down-regulated) and 60 DEGs (17 up-regulated and 43 down-regulated) were enriched in Phenylalanine metabolism under DS, of which novel.31261, Sspon.04G0008060-1A, Sspon.04G0008060-2B and Sspon.04G0008060-3C were significantly correlated with 7 SRMs. In Arginine and proline metabolism, eight SRMs (seven up-regulated and one down-regulated) and 63 DEGs (32 up-regulated and 31 down-regulated) were enriched, of which Sspon.01G0026110-1A (OAT) and Sspon.03G0002750-3D (P5CS) were strongly associated with proline (r > 0.99). These findings present the dynamic changes and possible molecular mechanisms of Phenylalanine metabolism as well as Arginine and proline metabolism under DS and provide a foundation for future research and sugarcane improvement.

Genome-wide identification, comprehensive characterization of transcription factors, cis-regulatory elements, protein homology, and protein interaction network of DREB gene family in Solanum lycopersicum

Tomato is a drought-sensitive crop which has high susceptibility to adverse climatic changes. Dehydration-responsive element-binding (DREB) are significant plant transcription factors that have a vital role in regulating plant abiotic stress tolerance by networking with DRE/CRT cis-regulatory elements in response to stresses. In this study, bioinformatics analysis was performed to conduct the genome-wide identification and characterization of DREB genes and promoter elements in Solanum lycopersicum. In genome-wide coverage, 58 SlDREB genes were discovered on 12 chromosomes that justified the criteria of the presence of AP2 domain as conserved motifs. Intron-exon organization and motif analysis showed consistency with phylogenetic analysis and confirmed the absence of the A3 class, thus dividing the SlDREB genes into five categories. Gene expansion was observed through tandem duplication and segmental duplication gene events in SlDREB genes. Ka/Ks values were calculated in ortholog pairs that indicated divergence time and occurrence of purification selection during the evolutionary period. Synteny analysis demonstrated that 32 out of 58 and 47 out of 58 SlDREB genes were orthologs to Arabidopsis and Solanum tuberosum, respectively. Subcellular localization predicted that SlDREB genes were present in the nucleus and performed primary functions in DNA binding to regulate the transcriptional processes according to gene ontology. Cis-acting regulatory element analysis revealed the presence of 103 motifs in 2.5-kbp upstream promoter sequences of 58 SlDREB genes. Five representative SlDREB proteins were selected from the resultant DREB subgroups for 3D protein modeling through the Phyre2 server. All models confirmed about 90% residues in the favorable region through Ramachandran plot analysis. Moreover, active catalytic sites and occurrence in disorder regions indicated the structural and functional flexibility of SlDREB proteins. Protein association networks through STRING software suggested the potential interactors that belong to different gene families and are involved in regulating similar functional and biological processes. Transcriptome data analysis has revealed that the SlDREB gene family is engaged in defense response against drought and heat stress conditions in tomato. Overall, this comprehensive research reveals the identification and characterization of SlDREB genes that provide potential knowledge for improving abiotic stress tolerance in tomato.

Genome-wide analysis of the DREB family genes and functional identification of the involvement of BrDREB2B in abiotic stress in wucai (Brassica campestris L.)

Dehydration responsive element binding protein (DREB) is a significant transcription factor class known to be implicated in abiotic stresses. In this study, we systematically conducted a genome-wide identification and expression analysis of the DREB gene family, including gene structures, evolutionary relationships, chromosome distribution, conserved domains, and expression patterns. A total of 65 DREB family gene members were identified in Chinese cabbage (Brassica rapa L.) and were classified into five subgroups based on phylogenetic analysis. Through analysis of the conserved domains of BrDREB family genes, only one exon existed in the gene structure. Through the analysis of cis-acting elements, these genes were mainly involved in hormone regulation and adversity stress. In order to identify the function of BrDREB2B, overexpressed transgenic Arabidopsis was constructed. After different stress treatments, the germination rate, root growth, survival rate, and various plant physiological indicators were measured. The results showed that transgenic Arabidopsis thaliana plants overexpressing BrDREB2B exhibited enhanced tolerance to salt, heat and drought stresses. Taken together, our results are the first to report the BrDREB2B gene response to drought and heat stresses in Chinese cabbage and provide a basis for further studies to determine the function of BrDREBs in response to abiotic stresses.

Initial Description of the Genome of Aeluropus littoralis, a Halophile Grass

The use of wild plant species or their halophytic relatives has been considered in plant breeding programs to improve salt and drought tolerance in crop plants. Aeluropus littoralis serves as halophyte model for identification and isolation of novel stress adaptation genes. A. littoralis, a perennial monocot grass, grows in damp or arid areas, often salt-impregnated places and wasteland in cultivated areas, can survive periodically high water salinity, and tolerate high salt concentrations in the soil up to 1,100 mM sodium chloride. Therefore, it serves as valuable genetic resource to understand molecular mechanisms of stress-responses in monocots. The knowledge can potentially be used for improving tolerance to abiotic stresses in economically important crops. Several morphological, anatomical, ecological, and physiological traits of A. littoralis have been investigated so far. After watering with salt water the grass is able to excrete salt via its salt glands. Meanwhile, a number of ESTs (expressed sequence tag), genes and promoters induced by the salt and drought stresses were isolated, sequenced and annotated at a molecular level. Transfer of stress related genes to other species resulted in enhanced stress resistance. Here we describe the genome sequence and structure of A. littoralis analyzed by whole genome sequencing and histological analysis. The chromosome number was determined to be 20 (2n = 2x = 20). The genome size was calculated to be 354 Mb. This genomic information provided here, will support the functional investigation and application of novel genes improving salt stress resistance in crop plants. The utility of the sequence information is exemplified by the analysis of the DREB-transcription factor family.

Genome-wide identification and expression analysis of ethylene responsive factor family transcription factors in Juglans regia

Background

Walnut is an important economic tree species with prominent economic value and ecological functions. However, in recent years, walnuts have become susceptible to drought stress, resulting in a decline in comprehensive benefits. Therefore, it is necessary to identify the regulatory molecular mechanism associated with walnut response to drought. In many plants, ethylene responsive factor (ERF) gene family plays important roles in response to biotic and abiotic stress, especial drought. Therefore, the identification and characterisation of walnut ERF genes will benefit walnut with regard to the clarification of drought response mechanism as well as the management, production, and quality of plantations.

Methods

‘ERF’ was compared against the walnut transcriptome, and the JrERFs with a complete open reading frame (ORF) were identified by ORF Finder. The molecular weights, amino acid residues, and theoretical isoelectric point (pI) were predicted by ExPASy. The distribution of JrERFs in chromosome locations was determined based on walnut genome data from NCBI. The intron-exon structures and conserved domains were analysed using Gene Structure Display Server 2.0 and CD-Search, accordingly. Multi-sequence alignment and a phylogenetic tree were constructed by ClustalX2.1 and MEGA7, respectively. The conserved motifs were acquired using MEME. Total RNA was isolated using the cetyltrimethylammonium ammonium bromide (CTAB) method (Yang et al., 2018). Gene expression was determined by using real-time quantitative polymerase chain reaction (qRT-PCR) analysis and calculated according to the 2^−ΔΔCT method (Livak & Schmittgen, 2001).

Results

A total of 44 JrERFs were identified from the walnut transcriptome, whose ORFs were 450–1,239 bp in length. The molecular weights of the JrERF proteins (consisting 149–412 amino acids) were 16.81–43.71 kDa, with pI ranging from 4.8 (JrERF11) to 9.89 (JrERF03). The JrERFs can be divided into six groups (B1–B6), and among the groups, B6 contained the most number of members. Each JrERF contained 1–6 motifs and each motif comprised 9–50 amino acids. Among the motifs, motif1, motif2, and motif3 were the most abundant. More than 40% of JrERFs were up-regulated continuously when subjected to ethephon (ETH), PEG₆₀₀₀, and PEG₆₀₀₀+ETH treatments. Of all the JrERFs, JrERF11 showed the highest expression. Therefore, we conclude that walnut ERF genes are highly conserved and involved in the regulation of drought response in the presence of ETH. JrERFs are possibly important candidate genes for molecular breeding; hence, the findings of this study provides the theoretical basis for further investigation of ERF genes in walnut and other species.