Investigation and Computational Analysis of the Sulfotransferase (SOT) Gene Family in Potato (Solanum tuberosum): Insights into Sulfur Adjustment for Proper Development and Stimuli Responses

Catalysts for sulfur: understanding the intricacies of enzymes orchestrating plant sulfur anabolism

MAIN CONCLUSION

This review highlights the sulfur transporters, key enzymes and their encoding genes involved in plant sulfur anabolism, focusing on their occurrence, chemistry, location, function, and regulation within sulfur assimilation pathways. Sulfur, a vital element for plant life, plays diverse roles in metabolism and stress response. This review provides a comprehensive overview of the sulfur assimilation pathway in plants, highlighting the intricate network of enzymes and their regulatory mechanisms. The primary focus is on the key enzymes involved: ATP sulfurylase (ATPS), APS reductase (APR), sulfite reductase (SiR), serine acetyltransferase (SAT), and O-acetylserine(thiol)lyase (OAS-TL). ATPS initiates the process by activating sulfate to form APS, which is then reduced to sulfite by APR. SiR further reduces sulfite to sulfide, a crucial step that requires significant energy. The cysteine synthase complex (CSC), formed by SAT and OAS-TL, facilitates the synthesis of cysteine, thereby integrating serine metabolism with sulfur assimilation. The alternative sulfation pathway, catalyzed by APS kinase and sulfotransferases, is explored for its role in synthesizing essential secondary metabolites. This review also delves into the regulatory mechanism of these enzymes such as environmental stresses, sulfate availability, phytohormones, as well as translational and post-translational regulations. Understanding the key transporters and enzymes in sulfur assimilation pathways and their corresponding regulation mechanisms can help researchers grasp the importance of sulfur anabolism for the life cycle of plants, clarify how these enzymes and their regulatory processes are integrated to balance plant life systems in response to changes in both external conditions and intrinsic signals.

Identification and characterization of sulphotransferase (SOT) genes for tolerance against drought and heat in wheat and six related species

BACKGROUND

Sulphotransferase (SOT) enzyme (encoded by a conserved family of SOT genes) is involved in sulphonation of a variety of compounds, through transfer of a sulphuryl moiety from 3'phosphoadenosine- 5'phosphosulphate (PAPS) to a variety of secondary metabolites. The PAPS itself is derived from 3'adenosine-5'phosphosulphate (APS) that is formed after uptake of sulphate ions from the soil. The process provides tolerance against abiotic stresses like drought and heat in plants. Therefore, a knowledge of SOT genes in any crop may help in designing molecular breeding methods for improvement of tolerance for drought and heat.

METHODS

Sequences of rice SOT genes and SOT domain (PF00685) of corresponding proteins were both used for identification of SOT genes in wheat and six related species (T. urartu, Ae. tauschii, T. turgidum, Z. mays, B. distachyon and Hordeum vulgare), although detailed analysis was conducted only in wheat. The wheat genes were mapped on individual chromosomes and also subjected to synteny and collinearity analysis. The proteins encoded by these genes were examined for the presence of a complete SOT domain using 'Conserved Domain Database' (CDD) search tool at NCBI.

RESULTS

In wheat, 107 TaSOT genes, ranging in length from 969 bp to 7636 bp, were identified and mapped onto individual chromosomes. SSRs (simple sequence repeats), microRNAs, long non-coding RNAs (lncRNAs) and their target sites were also identified in wheat SOT genes. SOT proteins were also studied in detail. An expression assay of TaSOT genes via wheat RNA-seq data suggested engagement of these genes in growth, development and responses to various hormones and biotic/abiotic stresses.

CONCLUSIONS

The results of the present study should help in further functional characterization of SOT genes in wheat and other related crops.

Genome-wide analysis of the Tritipyrum NAC gene family and the response of TtNAC477 in salt tolerance

NAC transcription factors are widely distributed in the plant kingdom and play an important role in the response to various abiotic stresses in plant species. Tritipyrum, an octoploid derived from hybridization of Triticum aestivum (AABBDD) and Thinopyrum elongatum (EE), is an important genetic resource for integrating the desirable traits of Th. elongatum into wheat. In this study, we investigated the tissue distribution and expression of Tritipyrum NAC genes in the whole genomes of T. aestivum and Th. elongatum after obtaining their complete genome sequences. Based on phylogenetic relationships, conserved motifs, gene synthesis, evolutionary analysis, and expression patterns, we identified and characterized 732 Tritipyrum NAC genes. These genes were divided into six main groups (A, B, C, D, E, and G) based on phylogenetic relationships and evolutionary studies, with members of these groups sharing the same motif composition. The 732 TtNAC genes are widely distributed across 28 chromosomes and include 110 duplicated genes. Gene synthesis analysis indicated that the NAC gene family may have a common ancestor. Transcriptome data and quantitative polymerase chain reaction (qPCR) expression profiles showed 68 TtNAC genes to be highly expressed in response to various salt stress and recovery treatments. Tel3E01T644900 (TtNAC477) was particularly sensitive to salt stress and belongs to the same clade as the salt tolerance genes ANAC019 and ANAC055 in Arabidopsis. Pearson correlation analysis identified 751 genes that correlated positively with expression of TtNAC477, and these genes are enriched in metabolic activities, cellular processes, stimulus responses, and biological regulation. TtNAC477 was found to be highly expressed in roots, stems, and leaves in response to salt stress, as confirmed by real-time PCR. These findings suggest that TtNAC477 is associated with salt tolerance in plants and might serve as a valuable exogenous gene for enhancing salt tolerance in wheat.

FlbZIP12 gene enhances drought tolerance via modulating flavonoid biosynthesis in Fagopyrum leptopodum

Karst lands provide a poor substrate to support plant growth, as they are low in nutrients and water content. Common buckwheat (Fagopyrum esculentum) is becoming a popular crop for its gluten-free grains and their high levels of phenolic compounds, but buckwheat yields are affected by high water requirements during grain filling. Here, we describe a wild population of drought-tolerant Fagopyrum leptopodum and its potential for enhancing drought tolerance in cultivated buckwheat. We determined that the expression of a gene encoding a Basic leucine zipper (bZIP) transcription factor, FlbZIP12, from F. leptopodum is induced by abiotic stresses, including treatment with the phytohormone abscisic acid, salt, and polyethylene glycol. In addition, we show that overexpressing FlbZIP12 in Tartary buckwheat (Fagopyrum tataricum) root hairs promoted drought tolerance by increasing the activities of the enzymes superoxide dismutase and catalase, decreasing malondialdehyde content, and upregulating the expression of stress-related genes. Notably, FlbZIP12 overexpression induced the expression of key genes involved in flavonoid biosynthesis. We also determined that FlbZIP12 interacts with protein kinases from the FlSnRK2 family in vitro and in vivo. Taken together, our results provide a theoretical basis for improving drought tolerance in buckwheat via modulating the expression of FlbZIP12 and flavonoid contents.

Genome-wide analysis of the AP2/ERF gene family in Tritipyrum and the response of TtERF_B2-50 in salt-tolerance

The AP2/ERF transcription factor is widely distributed across the plant kingdom and plays a crucial role in various abiotic stress responses in plants. Tritipyrum, an octoploid resulting from an intergeneric cross between Triticum aestivum (AABBDD) and Thinopyrum elongatum (EE), is a valuable source of germplasm for incorporating superior traits of Th. elongatum into T. aestivum. With the recent availability of whole -genome sequences for T. aestivum and Th. elongatum, we explored the organization and expression profiling of Tritipyrum AP2/ERF genes across the entire genome. Our investigation identified 543 Tritipyrum AP2/ERF genes, which evolutionary analysis categorized into four major groups (AP2, DREB, ERF, and RAV), whose members share a conserved motif composition. These 543 TtAP2/ERF genes were distributed throughout 28 chromosomes, with 132 duplications. Synteny analysis suggests that the AP2/ERF gene family may have a common ancestor. Transcriptome data and Real-Time PCR expression profiles revealed 43 TtAP2/ERF genes with high expression levels in response to various salt stressors and recovery regimens. Tel2E01T236300 (TtERF_B2-50) was particularly salt stress-sensitive and evolutionarily related to the salt-tolerant gene AtERF7 in A. thaliana. Pearson correlation analysis identified 689 genes positively correlated (R > 0.9) with TtERF_B2-50 expression, enriched in metabolic activities, cellular processes, stimulus response, and biological regulation. Real-time PCR showed that TtERF_B2-50 was highly expressed in roots, stems, and leaves under salt stress. These findings suggest that TtERF_B2-50 may be associated with salt stress tolerance and may serve as a valuable foreign gene for enhancing salt tolerance in wheat.

Genome-wide identification and characterization of SRLK gene family reveal their roles in self-incompatibility of Erigeron breviscapus

Self-incompatibility (SI) is a reproductive protection mechanism that plants acquired during evolution to prevent self-recession. As the female determinant of SI specificity, SRK has been shown to be the only recognized gene on the stigma and plays important roles in SI response. Asteraceae is the largest family of dicotyledonous plants, many of which exhibit self-incompatibility. However, systematic studies on SRK gene family in Asteraceae are still limited due to lack of high-quality genomic data. In this study, we performed the first systematic genome-wide identification of S-locus receptor like kinases (SRLKs) in the self-incompatible Asteraceae species, Erigeron breviscapus, which is also a widely used perennial medicinal plant endemic to China.52 SRLK genes were identified in the E. breviscapus genome. Structural analysis revealed that the EbSRLK proteins in E. breviscapus are conserved. SRLK proteins from E. breviscapus and other SI plants are clustered into 7 clades, and the majority of the EbSRLK proteins are distributed in Clade I. Chromosomal and duplication analyses indicate that 65% of the EbSRLK genes belong to tandem repeats and could be divided into six tandem gene clusters. Gene expression patterns obtained in E. breviscapus multiple-tissue RNA-Seq data revealed differential temporal and spatial features of EbSRLK genes. Among these, two EbSRLK genes having high expression levels in tongue flowers were cloned. Subcellular localization assay demonstrated that both of their fused proteins are localized on the plasma membrane. All these results indicated that EbSRLK genes possibly involved in SI response in E. breviscapus. This comprehensive genome-wide study of the SRLK gene family in E. breviscapus provides valuable information for understanding the mechanism of SSI in Asteraceae.

Genome-wide analysis of the GLP gene family and overexpression of GLP1-5-1 to promote lignin accumulation during early somatic embryo development in Dimocarpus longan

Longan (Dimocarpus longan Lour.) is an economically important subtropical fruit tree. Its fruit quality and yield are affected by embryo development. As a plant seed germination marker gene, the germin-like protein (GLP) gene plays an important role in embryo development. However, the mechanism underlying the role of the GLP gene in somatic embryos is still unclear. Therefore, we conducted genome-wide identification of the longan GLP (DlGLP) gene and preliminarily verified the function of DlGLP1-5-1. Thirty-five genes were identified as longan GLP genes and divided into 8 subfamilies. Based on transcriptome data and qRT‒PCR results, DlGLP genes exhibited the highest expression levels in the root, and the expression of most DlGLPs was upregulated during the early somatic embryogenesis (SE) in longan and responded to high temperature stress and 2,4-D treatment; eight DlGLP genes were upregulated under MeJA treatment, and four of them were downregulated under ABA treatment. Subcellular localization showed that DlGLP5-8-2 and DlGLP1-5-1 were located in the cytoplasm and extracellular stroma/chloroplast, respectively. Overexpression of DIGLP1-5-1 in the globular embryos (GEs) of longan promoted the accumulation of lignin and decreased the H₂O₂ content by regulating the activities of ROS-related enzymes. The results provide a reference for the functional analysis of DlGLPs and related research on improving lignin accumulation in the agricultural industry through genetic engineering.

Genome-wide identification, bioinformatics and expression analysis of HD-Zip gene family in peach

BACKGROUND

HD-Zips (Homeodomain-Leucine Zippers) are a class of plant-specific transcription factors that play multiple roles in plant growth and development. Although some functions of HD-Zip transcription factor have been reported in several plants, it has not been comprehensively studied in peach, especially during adventitious root formation of peach cuttings.

RESULTS

In this study, 23 HD-Zip genes distributed on 6 chromosomes were identified from the peach (Prunus persica) genome, and named PpHDZ01-23 according to their positions on the chromosomes. These 23 PpHDZ transcription factors all contained a homeomorphism box domain and a leucine zipper domain, were divided into 4 subfamilies(I-IV) according to the evolutionary analysis, and their promoters contained many different cis-acting elements. Spatio-temporal expression pattern showed that these genes were expressed in many tissues with different levels, and they had distinct expression pattern during adventitious root formation and development.

CONCLUSION

Our results showed the roles of PpHDZs on root formation, which is helpful to better understand the classification and function of peach HD-Zip genes.

Genome-wide analysis of the laccase (LAC) gene family in Aeluropus littoralis: A focus on identification, evolution and expression patterns in response to abiotic stresses and ABA treatment

Laccases are plant enzymes with essential functions during growth and development. These monophenoloxidases are involved in lignin polymerization, and their expression respond to environmental stress. However, studies of laccases in some plants and fungi have highlighted that many structural and functional aspects of these genes are still unknown. Here, the laccase gene family in Aeluropus littoralis (AlLAC) is described based on sequence structure and expression patterns under abiotic stresses and ABA treatment. Fifteen non-redundant AlLACs were identified from the A. littoralis genome, which showed differences in physicochemical characteristics and gene structure. Based on phylogenetic analysis, AlLACs and their orthologues were classified into five groups. A close evolutionary relationship was observed between LAC gene family members in rice and A. littoralis. According to the interaction network, AlLACs interact more with proteins involved in biological processes such as iron incorporation into the metallo-sulfur cluster, lignin catabolism, regulation of the symbiotic process and plant-type primary cell wall biogenesis. Gene expression analysis of selected AlLACs using real-time RT (reverse transcription)-PCR revealed that AlLACs are induced in response to abiotic stresses such as cold, salt, and osmotic stress, as well as ABA treatment. Moreover, AlLACs showed differential expression patterns in shoot and root tissues. Our findings indicate that AlLACs are preferentially involved in the late response of A. littoralis to abiotic stress.

Genome-wide identification, characterization, and expression pattern of the late embryogenesis abundant (LEA) gene family in Juglans regia and its wild relatives J. mandshurica

BACKGROUND

Late Embryogenesis Abundant (LEA) proteins are a class of proteins associated with plant stress resistance. Two Juglans species, Juglans regia and J. mandshurica, are both diploid (2n = 32), monoecious perennial economic tree species with high edible, pharmaceutical, and timber value. The identification, characterization, and expression patterns of LEA proteins in J. regia and its wild relative, J. mandshurica, would not only provide the genetic basis of this gene family, but it would also supply clues for further studies of the evolution and regulating mechanisms of LEA proteins in other tree species.

RESULTS

In this study, we identified 25 and 20 members of the LEA gene family in Juglans regia and its wild relative, Juglans mandshurica, respectively. The results of phylogenetic analysis showed that the LEA members were divided into eight main subgroups. Predictions of their physicochemical properties showed the variable characteristics of LEA proteins, and the subcellular localization analysis indicated that most LEA proteins are localized in the nucleus. Chromosomal localization analysis and gene replication pattern prediction indicated that WGD is the predominant duplication mode of LEA genes. The results of the comparative analysis indicated a high level of collinearity between the two Juglans species. Analysis of cis-acting elements indicated that LEA genes had a relatively wide range of responses to abiotic stresses and phytohormonal processes, particularly in two phytohormones, methyl jasmonate and abscisic acid. Transcriptome profiling and qRT-PCR experiments showed that JrLEAs are commonly expressed in leaves, green husks, and male and female flowers, and most JmLEAs are more highly expressed in male flowers. We also hypothesized that JrLEAs are involved in the process of anthracnose resistance. Anthracnose-resistant varieties of JrLEAs presented relatively high expression levels at later stages.

CONCLUSION

In this study, we provide a theoretical basis for the functional study of LEA genes in J. regia and J. mandshurica. Analysis of cis-acting elements and gene expression indicated that JrLEAs and JmLEAs play important roles in resistance to biotic stresses in these species.

Genome-Wide Characterization of the Sulfate Transporter Gene Family in Oilseed Crops: Camelina sativa and Brassica napus

Sulfate transporters (SULTRs) are responsible for the uptake of sulfate (SO₄^2-) ions in the rhizosphere by roots and their distribution to plant organs. In this study, SULTR family members in the genomes of two oilseed crops (Camelina sativa and Brassica napus) were identified and characterized based on their sequence structures, duplication events, phylogenetic relationships, phosphorylation sites, and expression levels. In total, 36 and 45 putative SULTR genes were recognized in the genomes of C. sativa and B. napus, respectively. SULTR proteins were predicted to be basophilic proteins with low hydrophilicity in both studied species. According to the observed phylogenetic relationships, we divided the SULTRs into five groups, out of which the SULTR 3 group showed the highest variation. Additionally, several duplication events were observed between the SULTRs. The first duplication event occurred approximately five million years ago between three SULTR 3.1 genes in C. sativa. Furthermore, two subunits were identified in the 3D structures of the SULTRs, which demonstrated that the active binding sites differed between C. sativa and B. napus. According to the available RNA-seq data, the SULTRs showed diverse expression levels in tissues and diverse responses to stimuli. SULTR 3 was expressed in all tissues. SULTR 3.1 was more upregulated in response to abiotic stresses in C. sativa, while SULTR 3.3 and SULTR 2.1 were upregulated in B. napus. Furthermore, SULTR 3 and SULTR 4.1 were upregulated in response to biotic stresses in B. napus. Additionally, the qPCR data showed that the SULTRs in C. sativa were involved in the plant's response to salinity. Based on the distribution of cis-regulatory elements in the promoter region, we speculated that SULTRs might be controlled by phytohormones, such as ABA and MeJA. Therefore, it seems likely that SULTR genes in C. sativa have been more heavily influenced by evolutionary processes and have acquired further diversity. The results reveal new insights of the structures and functions of SULTRs in oilseed crops. However, further analyses, related to functional studies, are needed to uncover the role of SULTRs in the plants' development and growth processes, as well as in their response to stimuli.

Genome-wide identification of the CER1 gene family in apple and response of MdCER1-1 to drought stress

Plant cuticular wax was a major consideration affecting the growth and quality of plants through protecting the plant from drought and other diseases. According to existing studies, CER1, as the core enzyme encoding the synthesis of alkanes, the main component of wax, can directly affect the response of plants to stress. However, there were few studies on the related functions of CER1 in apple. In this study, three MdCER1 genes in Malus domestica were identified and named MdCER1-1, MdCER1-2, and MdCER1-3 according to their distribution on chromosomes. Then, their physicochemical properties, sequence characteristics, and expression patterns were analyzed. MdCER1-1, with the highest expression level among the three members, was screened for cloning and functional verification. Real-time fluorescence quantitative PCR (qRT-PCR) analysis also showed that drought stress could increase the expression level of MdCER1-1. The experiment of water loss showed that overexpression of MdCER1-1 could effectively prevent water loss in apple calli, and the effect was more significant under drought stress. Meanwhile, MdYPB5, MdCER3, and MdKCS1 were significantly up-regulated, which would be bound up with waxy metabolism. Gas chromatography-mass spectrometer assay of wax fraction makes known that overexpression of MdCER1-1 apparently scaled up capacity of alkanes. The enzyme activities (SOD, POD) of overexpressed apple calli increased significantly, while the contents of proline increased compared with wild-type calli. In conclusion, MdCER1-1 can resist drought stress by reducing water loss in apple calli epidermis, increasing alkanes component content, stimulating the expression of waxy related genes (MdYPB5, MdCER3, and MdKCS1), and increasing antioxidant enzyme activity, which also provided a theoretical basis for exploring the role of waxy in other stresses.

Genome-wide analysis of the Tritipyrum WRKY gene family and the response of TtWRKY256 in salt-tolerance

INTRODUCTION

The transcription factor WRKY is widespread in the plant kingdom and plays a crucial role in diverse abiotic stress responses in plant species. Tritipyrum, an octoploid derived from an intergeneric cross between Triticum aestivum (AABBDD) and Thinopyrum elongatum (EE), is a valuable germplasm resource for introducing superior traits of Th. elongatum into T. aestivum. The recent release of the complete genome sequences of T. aestivum and Th. elongatum enabled us to investigate the organization and expression profiling of Tritipyrum WRKY genes across the entire genome.

RESULTS

In this study, 346 WRKY genes, from TtWRKY1 to TtWRKY346, were identified in Tritipyrum. The phylogenetic analysis grouped these genes into three subfamilies (I-III), and members of the same subfamilies shared a conserved motif composition. The 346 TtWRKY genes were dispersed unevenly across 28 chromosomes, with 218 duplicates. Analysis of synteny suggests that the WRKY gene family may have a common ancestor. Expression profiles derived from transcriptome data and qPCR demonstrated that 54 TtWRKY genes exhibited relatively high levels of expression across various salt stresses and recovery treatments. Tel1E01T143800 (TtWRKY256) is extremely sensitive to salt stress and is on the same evolutionary branch as the salt-tolerant A. thaliana genes AtWRKY25 and AtWRKY33. From 'Y1805', the novel AtWRKY25 was cloned. The Pearson correlation analysis identified 181 genes that were positively correlated (R>0.9) with the expression of TtWRKY256, and these genes were mainly enriched in metabolic processes, cellular processes, response to stimulus, biological regulation, and regulation of biological. Subcellular localization and qRT-PCR analysis revealed that TtWRKY256 was located in the nucleus and was highly expressed in roots, stems, and leaves under salt stress.

DISCUSSION

The above results suggest that TtWRKY256 may be associated with salt stress tolerance in plants and may be a valuable alien gene for improving salt tolerance in wheat.

Genome-Wide Identification and Expression Profiling of Aconitase Gene Family Members Reveals Their Roles in Plant Development and Adaptation to Diverse Stress in Triticum aestivum L

Global warming is a serious threat to food security and severely affects plant growth, developmental processes, and, eventually, crop productivity. Respiratory metabolism plays a critical role in the adaptation of diverse stress in plants. Aconitase (ACO) is the main enzyme, which catalyzes the revocable isomerization of citrate to isocitrate in the Krebs cycle. The function of ACO gene family members has been extensively studied in model plants, for instance Arabidopsis. However, their role in plant developmental processes and various stress conditions largely remained unknown in other plant species. Thus, we identified 15 ACO genes in wheat to elucidate their function in plant developmental processes and different stress environments. The phylogenetic tree revealed that TaACO genes were classified into six groups. Further, gene structure analysis of TaACOs has shown a distinctive evolutionary path. Synteny analysis showed the 84 orthologous gene pairs in Brachypodium distachyon, Aegilops tauschii, Triticum dicoccoides, Oryza sativa, and Arabidopsis thaliana. Furthermore, Ka/Ks ratio revealed that most TaACO genes experienced strong purifying selection during evolution. Numerous cis-acting regulatory elements were detected in the TaACO promoters, which play a crucial role in plant development processes, phytohormone signaling, and are related to defense and stress. To understand the function of TaACO genes, the expression profiling of TaACO genes were investigated in different tissues, developmental stages, and stress conditions. The transcript per million values of TaACOs genes were retrieved from the Wheat Expression Browser Database. We noticed the differential expression of the TaACO genes in different tissues and various stress conditions. Moreover, gene ontology analysis has shown enrichment in the tricarboxylic acid metabolic process (GO:0072350), citrate metabolic process (GO:0006101), isocitrate metabolic process GO:0006102, carbohydrate metabolic (GO:0005975), and glyoxylate metabolic process (GO:0046487). Therefore, this study provided valuable insight into the ACO gene family in wheat and contributed to the further functional characterization of TaACO during different plant development processes and various stress conditions.

Genome-wide identification of BBX gene family and their expression patterns under salt stress in soybean

BACKGROUND

BBX genes are key players in the regulation of various developmental processes and stress responses, which have been identified and functionally characterized in many plant species. However, our understanding of BBX family was greatly limited in soybean.

RESULTS

In this study, 59 BBX genes were identified and characterized in soybean, which can be phylogenetically classified into 5 groups. GmBBXs showed diverse gene structures and motif compositions among the groups and similar within each group. Noticeably, synteny analysis suggested that segmental duplication contributed to the expansion of GmBBX family. Moreover, our RNA-Seq data indicated that 59 GmBBXs showed different transcript profiling under salt stress, and qRT-PCR analysis confirmed their expression patterns. Among them, 22 GmBBXs were transcriptionally altered with more than two-fold changes by salt stress, supporting that GmBBXs play important roles in soybean tolerance to salt stress. Additionally, Computational assay suggested that GmBBXs might potentially interact with GmGI3, GmTOE1b, GmCOP1, GmCHI and GmCRY, while eight types of transcription factors showed potentials to bind the promoter regions of GmBBX genes.

CONCLUSIONS

Fifty-nine BBX genes were identified and characterized in soybean, and their expression patterns under salt stress and computational assays suggested their functional roles in response to salt stress. These findings will contribute to future research in regard to functions and regulatory mechanisms of soybean BBX genes in response to salt stress.

Genome-wide identification, molecular evolution and expression analysis of the non-specific lipid transfer protein (nsLTP) family in Setaria italica

BACKGROUND

Foxtail millet (Setaria italica L.) is a millet species with high tolerance to stressful environments. Plant non-specific lipid transfer proteins (nsLTPs) are a kind of small, basic proteins involved in many biological processes. So far, the genome of S. italica has been fully sequenced, and a comprehensive understanding of the evolution and expression of the nsLTP family is still lacking in foxtail millet.

RESULTS

Forty-five nsLTP genes were identified in S. italica and clustered into 5 subfamilies except three single genes (SinsLTP38, SinsLTP7, and SinsLTP44). The proportion of SinsLTPs was different in each subfamily, and members within the same subgroup shared conserved exon-intron structures. Besides, 5 SinsLTP duplication events were investigated. Both tandem and segmental duplication contributed to nsLTP expansion in S. italica, and the duplicated SinsLTPs had mainly undergone purifying selection pressure, which suggested that the function of the duplicated SinsLTPs might not diverge much. Moreover, we identified the nsLTP members in 5 other monocots, and 41, 13, 10, 4, and 1 orthologous gene pairs were identified between S. italica and S. viridis, S. bicolor, Z. mays, O. sativa, and B. distachyon, respectively. The functional divergence within the nsLTP orthologous genes might be limited. In addition, the tissue-specific expression patterns of the SinsLTPs were investigated, and the expression profiles of the SinsLTPs in response to abiotic stress were analyzed, all the 10 selected SinsLTPs were responsive to drought, salt, and cold stress. Among the selected SinsLTPs, 2 paired duplicated genes shared almost equivalent expression profiles, suggesting that these duplicated genes might retain some essential functions during subsequent evolution.

CONCLUSIONS

The present study provided the first systematic analysis for the phylogenetic classification, conserved domain and gene structure, expansion pattern, and expression profile of the nsLTP family in S. italica. These findings could pave a way for further comparative genomic and evolution analysis of nsLTP family in foxtail millet and related monocots, and lay the foundation for the functional analysis of the nsLTPs in S. italica.

Genome-Wide Identification of ATG Gene Family Members in Fagopyrum tataricum and Their Expression during Stress Responses

Abiotic stresses such as drought and salinity are major environmental factors limiting plant productivity. Autophagy-related genes are extensively involved in plant growth, development, and adverse stress responses, which have not yet been characterized in Tartary buckwheat (Fagopyrum tataricum, TB). In this study, we verified that drought stress could induce autophagy in TB roots. Next, 49 FtATGs in the whole genome of TB were identified. All FtATGs were randomly distributed in 8 known chromosomes, while 11 FtATGs were predictably segmental repeats. As the core component of autophagy, there were 8 FtATG8s with similar gene structures in TB, while FtATG8s showed high expression at the transcription level under drought and salt stresses. The cis-acting element analysis identified that all FtATG8 promoters contain light-responsive and MYB-binding elements. FtATG8s showed a cell-wide protein interaction network and strongly correlated with distinct stress-associated transcription factors. Furthermore, overexpression of FtATG8a and FtATG8f enhanced the antioxidant enzyme activities of TB under adverse stresses. Remarkably, FtATG8a and FtATG8f may be vital candidates functioning in stress resistance in TB. This study prominently aids in understanding the biological role of FtATG genes in TB.

Pangenome-wide analysis of cyclic nucleotide-gated channel (CNGC) gene family in citrus Spp. Revealed their intraspecies diversity and potential roles in abiotic stress tolerance

Cyclic nucleotide-gated channels (CNGC) gene family has been found to be involved in physiological processes including signaling pathways, environmental stresses, plant growth, and development. This gene family of non-selective cation channels is known to regulate the uptake of calcium and is reported in several plant species. The pangenome-wide studies enable researchers to understand the genetic diversity comprehensively; as a comparative analysis of multiple plant species or member of a species at once helps to better understand the evolutionary relationships and diversity present among them. In the current study, pangenome-wide analysis of the CNGC gene family has been performed on five Citrus species. As a result, a total of 32 genes in Citrus sinensis, 27 genes in Citrus recticulata, 30 genes in Citrus grandis, 31 genes in Atalantia buxfolia, and 30 genes in Poncirus trifoliata were identified. In addition, two unique genes CNGC13 and CNGC14 were identified, which may have potential roles. All the identified CNGC genes were unevenly distributed on 9 chromosomes except P. trifoliata had genes distributed on 7 chromosomes and were classified into four major groups and two sub-groups namely I, II, III, IV-A, and IV-B. Cyclic nucleotide binding (CNB) motif, calmodulin-binding motif (CaMB), and motif for IQ-domain were conserved in Citrus Spp. Intron exon structures of citrus species were not exactly as same as the gene structures of Arabidopsis. The majority of cis-regulatory elements (CREs) were light responsive and others include growth, development, and stress-related indicating potential roles of the CNGC gene family in these functions. Both segmental and tandem duplication were involved in the expansion of the CNGC gene family in Citrus Spp. The miRNAs are involved in the response of CsCNGC genes towards drought stress along with having regulatory association in the expression of these genes. Protein- Protein interaction (PPI) analysis also showed the interaction of CNGC proteins with other CNGCs which suggested their potential role in pathways regulating different biological processes. GO enrichment revealed that CNGC genes were involved in the transport of ions across membranes. Furthermore, tissue-specific expression patterns of leaves sample of C. sinensis were studied under drought stress. Out of 32 genes of C. sinensis 3 genes i.e., CsCNGC1.4, CsCNGC2.1, and CsCNGC4.2 were highly up-regulated, and only CsCNGC4.6 was highly down-regulated. The qRT-PCR analysis also showed that CNGC genes were highly expressed after treatment with drought stress, while gene expression was lower under controlled conditions. This work includes findings based on multiple genomes instead of one, therefore, this will provide more genomic information rather than single genome-based studies. These findings will serve as a basis for further functional insights into the CNGC gene family.

Genome-wide identification of Cymbidium sinense WRKY gene family and the importance of its Group III members in response to abiotic stress

Transcription factors (TFs) of the WRKY family play pivotal roles in defense responses and secondary metabolism of plants. Although WRKY TFs are well documented in numerous plant species, no study has performed a genome-wide investigation of the WRKY gene family in Cymbidium sinense. In the present work, we found 64 C. sinense WRKY (CsWRKY) TFs, and they were further divided into eight subgroups. Chromosomal distribution of CsWRKYs revealed that the majority of these genes were localized on 16 chromosomes, especially on Chromosome 2. Syntenic analysis implied that 13 (20.31%) genes were derived from segmental duplication events, and 17 orthologous gene pairs were identified between Arabidopsis thaliana WRKY (AtWRKY) and CsWRKY genes. Moreover, 55 of the 64 CsWRKYs were detectable in different plant tissues in response to exposure to plant hormones. Among them, Group III members were strongly induced in response to various hormone treatments, indicating their potential essential roles in hormone signaling. We subsequently analyzed the function of CsWRKY18 in Group III. The CsWRKY18 was localized in the nucleus. The constitutive expression of CsWRKY18 in Arabidopsis led to enhanced sensitivity to ABA-mediated seed germination and root growth and elevated plant tolerance to abiotic stress within the ABA-dependent pathway. Overall, our study represented the first genome-wide characterization and functional analysis of WRKY TFs in C. sinense, which could provide useful clues about the evolution and functional description of CsWRKY genes.

Genome-wide identification and expression analysis reveals spinach brassinosteroid-signaling kinase (BSK) gene family functions in temperature stress response

Background

Brassinosteroid (BR)- signaling kinase (BSK) is a critical family of receptor-like cytoplasmic kinase for BR signal transduction, which plays important roles in plant development, immunity, and abiotic stress responses. Spinach (Spinacia oleracea) is cold- tolerant but heat- sensitive green leafy vegetable. A study on BSK family members and BSKs- mediated metabolic processes in spinach has not been performed.

Results

We identified and cloned seven SoBSKs in spinach. Phylogenetic and collinearity analyses suggested that SoBSKs had close relationship with dicotyledonous sugar beet (Beta vulgaris) rather than monocotyledons. The analyses of gene structure and conserved protein domain/ motif indicated that most SoBSKs were relative conserved, while SoBSK6 could be a truncated member. The prediction of post-translation modification (PTM) sites in SoBSKs implied their possible roles in signal transduction, redox regulation, and protein turnover of SoBSKs, especially the N-terminal myristoylation site was critical for BSK localization to cell periphery. Cis-acting elements for their responses to light, drought, temperature (heat and cold), and hormone distributed widely in the promoters of SoBSKs, implying the pivotal roles of SoBSKs in response to diverse abiotic stresses and phytohormone stimuli. Most SoBSKs were highly expressed in leaves, except for SoBSK7 in roots. Many SoBSKs were differentially regulated in spinach heat- sensitive variety Sp73 and heat- tolerant variety Sp75 under the treatments of heat, cold, as well as exogenous brassinolide (BL) and abscisic acid (ABA). The bsk134678 mutant Arabidopsis seedlings exhibited more heat tolerance than wild- type and SoBSK1- overexpressed seedlings.

Conclusions

A comprehensive genome- wide analysis of the BSK gene family in spinach presented a global identification and functional prediction of SoBSKs. Seven SoBSKs had relatively- conserved gene structure and protein function domains. Except for SoBSK6, all the other SoBSKs had similar motifs and conserved PTM sites. Most SoBSKs participated in the responses to heat, cold, BR, and ABA. These findings paved the way for further functional analysis on BSK- mediated regulatory mechanisms in spinach development and stress response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08684-5.

Genome-wide analysis of the C2H2 zinc finger protein gene family and its response to salt stress in ginseng, Panax ginseng Meyer

The C2H2 zinc finger protein (C2H2-ZFP) gene family plays important roles in response to environmental stresses and several other biological processes in plants. Ginseng is a precious medicinal herb cultivated in Asia and North America. However, little is known about the C2H2-ZFP gene family and its functions in ginseng. Here, we identified 115 C2H2-ZFP genes from ginseng, defined as the PgZFP gene family. It was clustered into five groups and featured with eight conserved motifs, with each gene containing one to six of them. The family genes are categorized into 17 gene ontology subcategories and have numerous regulatory elements responsive to a variety of biological process, suggesting their functional differentiation. The 115 PgZFP genes were spliced into 228 transcripts at seed setting stage and varied dramatically in expression across tissues, developmental stages, and genotypes, but they form a co-expression network, suggesting their functional correlation. Furthermore, four genes, PgZFP31, PgZFP78-01, PgZFP38, and PgZFP39-01, were identified from the gene family that were actively involved in plant response to salt stress. These results provide new knowledge on origin, differentiation, evolution, and function of the PgZFP gene family and new gene resources for C2H2-ZFP gene research and application in ginseng and other plant species.

Identification and expression analysis of the CqSnRK2 gene family and a functional study of the CqSnRK2.12 gene in quinoa (Chenopodium quinoa Willd.)

Background

Sucrose non-fermenting 1 (SNF1)-associated protein kinase 2 (SnRK2) proteins belong to a relatively small family of plant-specific serine/threonine (Ser/Thr) protein kinases. SnRK2s participate in the abscisic acid (ABA) signaling pathway and play important roles in many biotic and abiotic stresses. At present, no SnRK2 gene has been reported in quinoa, and the recently published genome for this species provides an opportunity to identify and characterize the SnRK2 gene family.

Results

We identified 13 SnRK2 genes in the C. quinoa genome by bioinformatics analysis. Based on their phylogenetic relationships, these genes were divided into three subfamilies, similar to the situation in other plant species. Gene duplication analysis showed that there were seven pairs of homologous genes in the CqSnRK2 family, and that purifying selection played an important role in the evolution of SnRK2 genes. Gene structure analysis showed that the first exon in the SnRK2 family genes has the same length as the last exon, and that CqSnRK2 genes in the same subfamily have similar gene structures. Sequence analysis showed that the N-terminal region contains three highly conserved motifs. In addition, many kinds of cis-elements were identified in the promoter region of CqSnRK2, including those for hormone responses, stress responses, and tissue-specific expression. Transcription data analysis and qRT-PCR results showed that CqSnRK2 has different expression patterns in roots, stems, and leaves, and responded to biotic and abiotic stresses such as low temperature, salt, drought, and abscisic acid (ABA). In addition, we found that the protein encoded by CqSnRK2.12 was localized to the cytoplasm and nucleus, and there was no self-activation. The results of CqSnRK2.12 overexpression showed that transgenic Arabidopsis thaliana lines had increased drought tolerance compared to the controls.

Conclusion

The results of our study provide references for further studies on the evolution, function, and expression of the SnRK2 gene family in quinoa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08626-1.

FAR1/FHY3 Transcription Factors Positively Regulate the Salt and Temperature Stress Responses in Eucalyptus grandis

FAR-RED ELONGATED HYPOCOTYLS3 (FHY3) and its homolog FAR-RED IMPAIRED RESPONSE1 (FAR1), which play pivotal roles in plant growth and development, are essential for the photo-induced phyA nuclear accumulation and subsequent photoreaction. The FAR1/FHY3 family has been systematically characterized in some plants, but not in Eucalyptus grandis. In this study, genome-wide identification of FAR1/FHY3 genes in E. grandis was performed using bioinformatic methods. The gene structures, chromosomal locations, the encoded protein characteristics, 3D models, phylogenetic relationships, and promoter cis-elements were analyzed with this gene family. A total of 33 FAR1/FHY3 genes were identified in E. grandis, which were divided into three groups based on their phylogenetic relationships. A total of 21 pairs of duplicated repeats were identified by homology analysis. Gene expression analysis showed that most FAR1/FHY3 genes were differentially expressed in a spatial-specific manner. Gene expression analysis also showed that FAR1/FHY3 genes responded to salt and temperature stresses. These results and observation will enhance our understanding of the evolution and function of the FAR1/FHY3 genes in E. grandis and facilitate further studies on the molecular mechanism of the FAR1/FHY3 gene family in growth and development regulations, especially in response to salt and temperature.

Genome-wide identification and expression profiling analysis of sucrose synthase (SUS) and sucrose phosphate synthase (SPS) genes family in Actinidia chinensis and A. eriantha

Sucrose synthase (SUS) is a common sugar-base transfer enzyme in plants, and sucrose phosphate synthase (SPS) is one of the major enzymes in higher plants that regulates sucrose synthesis. However, information of the SPS and SUS gene families in Actinidia, as well as their evolutionary and functional properties, is limited. According to the SPS and SUS proteins conserved domain of Arabidopsis thaliana, we found 6 SPS genes and 6 SUS genes from A. chinensis (cultivar: 'Hongyang'), and 3 SPS genes and 6 SUS genes from A. eriantha (cultivar: 'White'). The novel CDC50 conserved domains were discovered on AcSUS2, and all members of the gene family contain similar distinctive conserved domains. The majority of SUS and SPS proteins were hydrophilic, lipid-soluble enzymes that were expected to be found in the cytoplasm. The tertiary structure of SPS and SUS protein indicated that there were many tertiary structures in SPS, and there were windmill-type and spider-type tertiary structures in SUS. The phylogenetic tree was created using the neighbor-joining method, and members of the SPS and SUS gene families are grouped into three subgroups. Genes with comparable intron counts, conserved motifs, and phosphorylation sites were clustered together first. SPS and SUS were formed through replication among their own family members. AcSPS1, AcSPS2, AcSPS4, AcSPS5, AcSUS5, AcSUS6, AeSPS3, AeSUS3 and AeSUS4 were the important genes in regulating the synthesis and accumulation of sucrose for Actinidia during the fruit growth stages.

Regulation of BcMYB44 on Anthocyanin Synthesis and Drought Tolerance in Non-Heading Chinese Cabbage (Brassica campestris ssp. chinensis Makino)

The purpose of this study was to explore the regulation of BcMYB44 on anthocyanin synthesis and drought tolerance of non-heading Chinese cabbage. The BcMYB44 gene was cloned from the purple inbred line ‘NJZX1-3’ and its green mutant ‘NJZX1-0’. Sequence analysis confirmed that BcMYB44 belongs to the R2R3-MYB family and has the highest homology with BnMYB44. Subcellular localization revealed that BcMYB44 is a nuclear protein. Yeast two-hybrid (Y2H) and Bimolecular Fluorescent Complimentary (BiFC) experiments showed that BcMYB44 interacts with BcPAP1 and BcEGL3. Pigment detection of BcPAP1 and BcMYB44 protein activity in N. benthamiana indicates that BcMYB44 plays a negative regulatory role by inhibiting the expression of key structural genes (F3H, DFR, etc.) in anthocyanin synthesis. Virus-induced gene silencing (VIGS) further confirmed this inhibition. Analysis of drought tolerance of non-heading Chinese cabbage based on VIGS showed that pTY-S plants are more resistant to drought than pTY-BcMYB44 plants. The results indicate that BcMYB44 has a positive regulatory role in drought stress, which most likely is achieved by inhibiting anthocyanin accumulation, regulating stomatal movement, and improving osmotic regulation and homeostasis of reactive oxygen species (ROS).

Genome-Wide Identification of Cotton (Gossypium spp.) Trehalose-6-Phosphate Phosphatase (TPP) Gene Family Members and the Role of GhTPP22 in the Response to Drought Stress

Trehalose-6-phosphate phosphatase (TPP) is a key enzyme involved in trehalose synthesis in higher plants. Previous studies have shown that TPP family genes increase yields without affecting plant growth under drought conditions, but their functions in cotton have not been reported. In this study, 17, 12, 26 and 24 TPP family genes were identified in Gossypium arboreum, Gossypium raimondii, Gossypium barbadense and Gossypium hirsutum, respectively. The 79 TPP family genes were divided into three subgroups by phylogenetic analysis. Virus-induced gene silencing (VIGS) of GhTPP22 produced TRV::GhTPP22 plants that were more sensitive to drought stress than the control plants, and the relative expression of GhTPP22 was decreased, as shown by qRT–PCR. Moreover, we analysed the gene structure, targeted small RNAs, and gene expression patterns of TPP family members and the physicochemical properties of their encoded proteins. Overall, members of the TPP gene family in cotton were systematically identified, and the function of GhTPP22 under drought stress conditions was preliminarily verified. These findings provide new information for improving drought resistance for cotton breeding in the future.

Genome-Wide Identification and Functional Characterization of the Chloride Channel TaCLC Gene Family in Wheat (Triticum aestivum L.)

In plants, chloride channels (CLC) are involved in a series of specific functions, such as regulation of nutrient transport and stress tolerance. Members of the wheat Triticum aestivum L. CLC (TaCLC) gene family have been proposed to encode anion channels/transporters that may be related to nitrogen transportation. To better understand their roles, TaCLC family was screened and 23 TaCLC gene sequences were identified using a Hidden Markov Model in conjunction with wheat genome database. Gene structure, chromosome location, conserved motif, and expression pattern of the resulting family members were then analyzed. Phylogenetic analysis showed that the TaCLC family can be divided into two subclasses (I and II) and seven clusters (-a, -c1, -c2, -e, -f1, -f2, and -g2). Using a wheat RNA-seq database, the expression pattern of TaCLC family members was determined to be an inducible expression type. In addition, seven genes from seven different clusters were selected for quantitative real-time PCR (qRT-PCR) analysis under low nitrogen stress or salt stress conditions, respectively. The results indicated that the gene expression levels of this family were up-regulated under low nitrogen stress and salt stress, except the genes of TaCLC-c2 cluster which were from subfamily -c. The yeast complementary experiments illustrated that TaCLC-a-6AS-1, TaCLC-c1-3AS, and TaCLC-e-3AL all had anion transport functions for NO₃⁻ or Cl⁻, and compensated the hypersensitivity of yeast GEF1 mutant strain YJR040w (Δgef1) in restoring anion-sensitive phenotype. This study establishes a theoretical foundation for further functional characterization of TaCLC genes and provides an initial reference for better understanding nitrate nitrogen transportation in wheat.

Identification and Characterization of Csa-miR395s Reveal Their Involvements in Fruit Expansion and Abiotic Stresses in Cucumber

The miR395 plays an indispensable role in biochemical processes by regulating their target genes. However, little is known about the roles of miR395 in cucumber fruit expansion and response to abiotic stresses. Here, 4 Csa-miR395s and 8 corresponding target genes were identified in the cucumber genome. Csa-miR395s were all located on the same chromosome (Chr 5). Csa-miR395a/b/c and Csa-miR395d were distributed in different branches without a closer genetic relationship. Massive cis-acting elements, including light, phytohormone, and stress response elements, were detected in the promoter regions of Csa-MIR395s, indicating that Csa-miR395s might be involved in complex regulatory networks to control cucumber growth and development and stress response. In addition, Csa-miR395a/b/c shared the same target genes, and Csa-miR395d had its specific target genes. Tissue-specific expression analysis showed that Csa-miR395a/b/c were all expressed in the leaf, root, ovary, and expanded fruit of cucumber and highly expressed in the expanded fruits compared to the ovary, while Csa2G215520 and Csa1G502860 (target genes of Csa-miR395a/b/c) presented a downregulated trend in the expanded fruit compared to the ovary. Meanwhile, the protein co-expression network revealed that these target genes had interactions in sulfur metabolism. These results suggested that Csa-miR395a/b/c targeting Csa2G215520 and Csa1G502860 might promote cucumber fruit expansion by affecting sulfur metabolism. Additionally, Quantitative Real-time PCR analysis validated that Csa-miR395s could be regulated by NaCl stress, and Csa-miR395a/b/c could respond to PEG stress, which further confirmed the reliability of cis-acting elements data. Taken together, our results could be helpful for further exploration of the functions of miR395s in cucumber fruit expansion and response to abiotic stresses.