Genome-Wide Analysis of the NAC Domain Transcription Factor Gene Family in Theobroma cacao

Network pharmacology and molecular docking: combined computational approaches to explore the antihypertensive potential of Fabaceae species

Hypertension is a major global public health issue, affecting quarter of adults worldwide. Numerous synthetic drugs are available for treating hypertension; however, they often come with a higher risk of side effects and long-term therapy. Modern formulations with active phytoconstituents are gaining popularity, addressing some of these issues. This study aims to discover novel antihypertensive compounds in Cassia fistula, Senna alexandrina, and Cassia occidentalis from family Fabaceae and understand their interaction mechanism with hypertension targeted genes, using network pharmacology and molecular docking. Total 414 compounds were identified; initial screening was conducted based on their pharmacokinetic and ADMET properties, with a particular emphasis on adherence to Lipinski's rules. 6 compounds, namely Germichrysone, Benzeneacetic acid, Flavan-3-ol, 5,7,3',4'-Tetrahydroxy-6, 8-dimethoxyflavon, Dihydrokaempferol, and Epiafzelechin, were identified as effective agents. Most of the compounds found non-toxic against various indicators with greater bioactivity score. 161 common targets were obtained against these compounds and hypertension followed by compound-target network construction and protein-protein interaction, which showed their role in diverse biological system. Top hub genes identified were TLR4, MMP9, MAPK14, AKT1, VEGFA and HSP90AA1 with their respective associates. Higher binding affinities was found with three compounds Dihydrokaempferol, Flavan-3-ol and Germichrysone, -7.1, -9.0 and -8.0 kcal/mol, respectively. The MD simulation results validate the structural flexibility of two complexes Flavan-MMP9 and Germich-TLR4 based on no. of hydrogen bonds, root mean square deviations and interaction energies. This study concluded that C. fistula (Dihydrokaempferol, Flavan-3-ol) and C. occidentalis (Germichrysone) have potential therapeutic active constituents to treat hypertension and in future novel drug formulation.

Genome-Wide Identification of NAC Family Genes in Oat and Functional Characterization of AsNAC109 in Abiotic Stress Tolerance

The plant-specific NAC gene family is one of the largest transcription factor families, participating in plant growth regulation and stress response. Despite extensive characterization in various plants, our knowledge of the NAC family in oat is lacking. Herein, we identified 333 NAC genes from the latest release of the common oat genome. We provide a comprehensive overview of the oat NAC gene family, covering gene structure, chromosomal localization, phylogenetic characteristics, conserved motif compositions, and gene duplications. AsNAC gene expression in different tissues and the response to various abiotic stresses were characterized using RT-qPCR. The main driver of oat NAC gene family expansion was identified as segmental duplication using collinearity analysis. In addition, the functions of AsNAC109 in regulating abiotic stress tolerance in Arabidopsis were clarified. This is the first genome-wide investigation of the NAC gene family in cultivated oat, which provided a unique resource for subsequent research to elucidate the mechanisms responsible for oat stress tolerance and provides valuable clues for the improvement of stress resistance in cultivated oat.

Comprehensive Analysis of NAC Transcription Factors Reveals Their Evolution in Malvales and Functional Characterization of AsNAC019 and AsNAC098 in Aquilaria sinensis

NAC is a class of plant-specific transcription factors that are widely involved in the growth, development and (a)biotic stress response of plants. However, their molecular evolution has not been extensively studied in Malvales, especially in Aquilaria sinensis, a commercial and horticultural crop that produces an aromatic resin named agarwood. In this study, 1502 members of the NAC gene family were identified from the genomes of nine species from Malvales and three model plants. The macroevolutionary analysis revealed that whole genome duplication (WGD) and dispersed duplication (DSD) have shaped the current architectural structure of NAC gene families in Malvales plants. Then, 111 NAC genes were systemically characterized in A. sinensis. The phylogenetic analysis suggests that NAC genes in A. sinensis can be classified into 16 known clusters and four new subfamilies, with each subfamily presenting similar gene structures and conserved motifs. RNA-seq analysis showed that AsNACs presents a broad transcriptional response to the agarwood inducer. The expression patterns of 15 AsNACs in A. sinensis after injury treatment indicated that AsNAC019 and AsNAC098 were positively correlated with the expression patterns of four polyketide synthase (PKS) genes. Additionally, AsNAC019 and AsNAC098 were also found to bind with the AsPKS07 promoter and activate its transcription. This comprehensive analysis provides valuable insights into the molecular evolution of the NAC gene family in Malvales plants and highlights the potential mechanisms of AsNACs for regulating secondary metabolite biosynthesis in A. sinensis, especially for the biosynthesis of 2-(2-phenyl) chromones in agarwood.

Genome-Wide Analysis of WRKY and NAC Transcription Factors in Carica papaya L. and Their Possible Role in the Loss of Drought Tolerance by Recent Cultivars through the Domestication of Their Wild Ancestors

A genome-wide analysis for two families of key transcription factors (TF; WRKY and NAC) involved in drought response revealed 46 WRKY and 66 NAC members of the Carica papaya genome. A phylogenetic analysis grouped the CpWRKY proteins into three groups (I, II a, b, c, d, e and III), while the CpNAC proteins were clustered into 15 groups. The conserved domains, chromosomal localization and promoter cis-acting elements were also analyzed. In addition, from a previous transcriptome study of two contrasting genotypes in response to 14 days of water deficit stress (WDS), we found that 29 of the 46 CpWRKYs genes and 25 of the 66 CpNACs genes were differentially expressed in response to the WDS. In the present paper, the native wild genotype (WG) (collected in its center of origin) consistently showed a higher expression (transcripts per million; TPM and fold change; FC) than the commercial genotype (CG) in almost all the members of the CpWRKY and CpNAC gene families. To corroborate this, we selected CpWRKY50 and CpNAC83.1 for further evaluation by RT-qPCR. Consistently, the WG showed higher relative expression levels (REL) after 14 days of WDS than the CG, in both the leaves and roots. The results suggest that the CpWRKY and CpNAC TF families are important for drought tolerance in this species. The results may also suggest that, during the domestication process, the ability of the native (wild) C. papaya genotypes to respond to drought (including the overexpression of the CpWRKY and CpNAC genes) was somehow reduced in the current commercial genotypes.

Genome-Wide Identification, Evolution and Expression Profile Analysis of NAC Transcription Factor in Simmondsia chinensis

NAC transcription factors (TFs) are one of the largest plant-specific gene families and play important roles in plant growth, development, and the biotic and abiotic stress response. Although the sequencing of Jojoba (Simmondsia chinensis) has been completed, the genome-wide identification and analysis of its NAC TFs has not been reported. In this study, a total of 57 genes were identified in Jojoba, which were divided into eight groups based on phylogenetic analysis. The genes clustered in the same groups have a similar gene structure and motif distribution. Based on the analysis of cis-elements in NAC TFs, nine cis-acting elements were identified in the promoter region that involved in light response, hormonal response, and stress response. Synteny analysis showed a greater collinearity between Jojoba and V. vinifera than Arabidopsis thaliana. The 24 genes in the Jojoba NAC TFs are derived from fragment replication, which may be the main source of NAC amplification. Gene expression analysis identified seven genes that were highly expressed in seeds. The differential expression analysis of NAC TFs in cotyledon and embryonic axis tissues showed that the expression of 10 genes was up-regulated and 1 gene was down-regulated. This study provides more information on the classification, gene structure, conserved motif, and evolution of NAC TFs in Jojoba, facilitating further exploration of their specific functional analysis in Jojoba seed development.

ClNAC100 Is a NAC Transcription Factor of Chinese Fir in Response to Phosphate Starvation

Phosphate (Pi) deficiency is one of the most limiting factors for Chinese fir growth and production. Moreover, continuous cultivation of Chinese fir for multiple generations led to the reduction of soil nutrients, which hindered the yield of Chinese fir in southern China. Although NAC (NAM, ATAF, and CUC) transcription factors (TFs) play critical roles in plant development and abiotic stress resistance, it is still unclear how they regulate the response of Chinese fir to phosphate (Pi) starvation. Based on Pi-deficient transcriptome data of Chinses fir root, we identified a NAC transcription factor with increased expression under Pi deficiency, which was obtained by PCR and named ClNAC100. RT-qPCR confirmed that the expression of ClNAC100 in the root of Chinese fir was induced by phosphate deficiency and showed a dynamic change with time. It was positively regulated by ABA and negatively regulated by JA, and ClNAC100 was highly expressed in the roots and leaves of Chinese fir. Transcriptional activation assay confirmed that ClNAC100 was a transcriptional activator. The promoter of ClNAC100 was obtained by genome walking, which was predicted to contain a large number of stress, hormone, and growth-related cis-elements. Tobacco infection was used to verify the activity of the promoter, and the core promoter was located between -1519 bp and -589 bp. We identified 18 proteins bound to the ClNAC100 promoter and 5 ClNAC100 interacting proteins by yeast one-hybrid and yeast two-hybrid, respectively. We speculated that AHL and TIFY family transcription factors, calmodulin, and E3 ubiquitin ligase in these proteins might be important phosphorus-related proteins. These results provide a basis for the further study of the regulatory mechanism and pathways of ClNAC100 under Pi starvation.

Genome-Wide Identification and Analysis of the GRAS Transcription Factor Gene Family in Theobroma cacao

GRAS genes exist widely and play vital roles in various physiological processes in plants. In this study, to identify Theobroma cacao (T. cacao) GRAS genes involved in environmental stress and phytohormones, we conducted a genome-wide analysis of the GRAS gene family in T. cacao. A total of 46 GRAS genes of T. cacao were identified. Chromosomal distribution analysis showed that all the TcGRAS genes were evenly distributed on ten chromosomes. Phylogenetic relationships revealed that GRAS proteins could be divided into twelve subfamilies (HAM: 6, LISCL: 10, LAS: 1, SCL4/7: 1, SCR: 4, DLT: 1, SCL3: 3, DELLA: 4, SHR: 5, PAT1: 6, UN1: 1, UN2: 4). Of the T. cacao GRAS genes, all contained the GRAS domain or GRAS superfamily domain. Subcellular localization analysis predicted that TcGRAS proteins were located in the nucleus, chloroplast, and endomembrane system. Gene duplication analysis showed that there were two pairs of tandem repeats and six pairs of fragment duplications, which may account for the rapid expansion in T. cacao. In addition, we also predicted the physicochemical properties and cis-acting elements. The analysis of GO annotation predicted that the TcGRAS genes were involved in many biological processes. This study highlights the evolution, diversity, and characterization of the GRAS genes in T. cacao and provides the first comprehensive analysis of this gene family in the cacao genome.

Comprehensive analysis of the NAC transcription factor gene family in Kandelia obovata reveals potential members related to chilling tolerance

BACKGROUND

Kandelia obovata is an important mangrove species extensively distributed in Eastern Asia that is susceptible to low-temperature stress. NAC (NAM, ATAF1/2 and CUC2) domain proteins are transcription factors (TFs) that play various roles in plant growth and development and in the plant response to environmental stresses. Nevertheless, genome-wide analyses of K. obovata NAC genes (KoNACs) and their responses to chilling stress have rarely been studied.

METHODS

The KoNAC gene family was identified and characterized using bioinformatic analysis, the subcellular location of some NAC proteins was confirmed using confocal microscopy analysis, and the KoNACs that responded to chilling stress were screened using RNA-seq and qRT-PCR analysis.

RESULTS

A total of 79 KoNACs were identified, and they were unequally distributed across all 18 chromosomes of K. obovata. The KoNAC proteins could be divided into 16 subgroups according to the phylogenetic tree based on NAC family members of Arabidopsis thaliana. The KoNACs exhibited greater synteny with A. thaliana sequences than with Oryza sativa sequences, indicating that KoNACs underwent extensive evolution after the divergence of dicotyledons and monocotyledons. Segmental duplication was the main driving force of the expansions of KoNAC genes. Confocal microscopy analysis verified that the four randomly selected KoNACs localized to the nucleus, indicating the accuracy of the bioinformatic predictions. Tissue expression pattern analysis demonstrated that some KoNAC genes showed tissue-specific expression, suggesting that these KoNACs might be important for plant development and growth. Additionally, the expression levels of 19 KoNACs were significantly (15 positively and 4 negatively) induced by cold treatment, demonstrating that these KoNACs might play important roles during cold stress responses and might be candidate genes for the genetic engineering of K. obovata with enhanced chilling stress tolerance. Coexpression network analysis revealed that 381 coexpressed pairs (between 13 KoNACs and 284 other genes) were significantly correlated.

CONCLUSIONS

Seventy-nine KoNACs were identified in K. obovata, nineteen of which displayed chilling-induced expression patterns. These genes may serve as candidates for functional analyses of KoNACs engaged in chilling stress. Our results lay the foundation for evolutionary analyses of KoNACs and their molecular mechanisms in response to environmental stress.

Identification of the NAC Transcription Factors and Their Function in ABA and Salinity Response in Nelumbo nucifera

Nelumbo nucifera Gaertn. is an important perennial aquatic herb that has high ornamental, edible, medicinal, and economic value, being widely distributed and used in China. The NAC superfamily (NAM, ATAF1/2, CUC2) plays critical roles in plant growth, development, and response to abiotic and biotic stresses. Though there have been a few reports about NAC genes in lotus, systematic analysis is still relatively lacking. The present study aimed to characterize all the NAC genes in the lotus and obtain better insights on the NnNACs in response to salt stress by depending on ABA signaling. Here, 97 NAC genes were identified by searching the whole lotus genome based on the raw HMM models of the conserved NAM domain and NAC domain. They were characterized by bioinformatics analysis and divided into 18 subgroups based on the phylogenetic tree. Cis-element analysis demonstrated that NAC genes are responsive to biotic and abiotic stresses, light, low temperature, and plant hormones. Meanwhile, NAC genes had tissue expression specificity. qRT-PCR analysis indicated that NAC genes could be upregulated or downregulated by NaCl treatment, ABA, and fluoridone. In addition, NAC016, NAC025, and NAC070, whose encoding genes were significantly induced by NaCl and ABA, were located in the nucleus. Further analysis showed the three NAC proteins had transcriptional activation capabilities. The co-expression network analysis reflected that NAC proteins may form complexes with other proteins to play a role together. Our study provides a theoretical basis for further research to be conducted on the regulatory mechanisms of salinity resistance in the lotus.

Receptor-like Kinases (LRR-RLKs) in Response of Plants to Biotic and Abiotic Stresses

Plants live under different biotic and abiotic stress conditions, and, to cope with the adversity and severity, plants have well-developed resistance mechanisms. The mechanism starts with perception of the stimuli followed by molecular, biochemical, and physiological adaptive measures. The family of LRR-RLKs (leucine-rich repeat receptor-like kinases) is one such group that perceives biotic and abiotic stimuli and also plays important roles in different biological processes of development. This has been mostly studied in the model plant, Arabidopsis thaliana, and to some extent in other plants, such as Solanum lycopersicum, Nicotiana benthamiana, Brassica napus, Oryza sativa, Triticum aestivum, Hordeum vulgare, Brachypodium distachyon, Medicago truncatula, Gossypium barbadense, Phaseolus vulgaris, Solanum tuberosum, and Malus robusta. Most LRR-RLKs tend to form different combinations of LRR-RLKs-complexes (dimer, trimer, and tetramers), and some of them were observed as important receptors in immune responses, cell death, and plant development processes. However, less is known about the function(s) of LRR-RLKs in response to abiotic and biotic stresses. Here, we give recent updates about LRR-RLK receptors, specifically focusing on their involvement in biotic and abiotic stresses in the model plant, A. thaliana. Furthermore, the recent studies on LRR-RLKs that are homologous in other plants is also reviewed in relation to their role in triggering stress response processes against biotic and abiotic stimuli and/or in exploring their additional function(s). Furthermore, we present the interactions and combinations among LRR-RLK receptors that have been confirmed through experiments. Moreover, based on GENEINVESTIGATOR microarray database analysis, we predict some potential LRR-RLK genes involved in certain biotic and abiotic stresses whose function and mechanism may be explored.

Genome-Wide Identification and Analysis of the R2R3-MYB Gene Family in Theobroma cacao

The MYB gene family is involved in the regulation of plant growth, development and stress responses. In this paper, to identify Theobroma cacao R2R3-MYB (TcMYB) genes involved in environmental stress and phytohormones, we conducted a genome-wide analysis of the R2R3-MYB gene family in Theobroma cacao (cacao). A total of 116 TcMYB genes were identified, and they were divided into 23 subgroups according to the phylogenetic analysis. Meanwhile, the conserved motifs, gene structures and cis-acting elements of promoters were analyzed. Moreover, these TcMYB genes were distributed on 10 chromosomes. We conducted a synteny analysis to understand the evolution of the cacao R2R3-MYB gene family. A total of 37 gene pairs of TcMYB genes were identified through tandem or segmental duplication events. Additionally, we also predicted the subcellular localization and physicochemical properties. All the studies showed that TcMYB genes have multiple functions, including responding to environmental stresses. The results provide an understanding of R2R3-MYB in Theobroma cacao and lay the foundation for a further functional analysis of TcMYB genes in the growth of cacao.

Genome-wide identification and comprehensive analyses of NAC transcription factor gene family and expression analysis under Fusarium kyushuense and drought stress conditions in Passiflora edulis

The NAC gene family is one of the largest plant transcription factors (TFs) families and plays important roles in plant growth, development, metabolism, and biotic and abiotic stresses. However, NAC gene family has not been reported in passion fruit (Passiflora edulis). In this study, a total of 105 NAC genes were identified in the passion fruit genome and were unevenly distributed across all nine-passion fruit chromomere, with a maximum of 48 PeNAC genes on chromosome one. The physicochemical features of all 105 PeNAC genes varied including 120 to 3,052 amino acids, 3 to 8 conserved motifs, and 1 to 3 introns. The PeNAC genes were named (PeNAC001-PeNAC105) according to their chromosomal locations and phylogenetically grouped into 15 clades (NAC-a to NAC-o). Most PeNAC proteins were predicted to be localized in the nucleus. The cis-element analysis indicated the possible roles of PeNAC genes in plant growth, development, light, hormones, and stress responsiveness. Moreover, the PeNAC gene duplications including tandem (11 gene pairs) and segmental (12 gene pairs) were identified and subjected to purifying selection. All PeNAC proteins exhibited similar 3D structures, and a protein-protein interaction network analysis with known Arabidopsis proteins was predicted. Furthermore, 17 putative ped-miRNAs were identified to target 25 PeNAC genes. Potential TFs including ERF, BBR-BPC, Dof, and bZIP were identified in promoter region of all 105 PeNAC genes and visualized in a TF regulatory network. GO and KEGG annotation analysis exposed that PeNAC genes were related to different biological, molecular, and cellular terms. The qRT-PCR expression analysis discovered that most of the PeNAC genes including PeNAC001, PeNAC003, PeNAC008, PeNAC028, PeNAC033, PeNAC058, PeNAC063, and PeNAC077 were significantly upregulated under Fusarium kyushuense and drought stress conditions compared to controls. In conclusion, these findings lay the foundation for further functional studies of PeNAC genes to facilitate the genetic improvement of plants to stress resistance.

Genome-wide analyses of the mung bean NAC gene family reveals orthologs, co-expression networking and expression profiling under abiotic and biotic stresses

BACKGROUND

Mung bean is a short-duration and essential food crop owing to its cash prominence in Asia. Mung bean seeds are rich in protein, fiber, antioxidants, and phytonutrients. The NAC transcription factors (TFs) family is a large plant-specific family, participating in tissue development regulation and abiotic and biotic stresses.

RESULTS

In this study, we perform genome-wide comparisons of VrNAC with their homologs from Arabidopsis. We identified 81 NAC transcription factors (TFs) in mung bean genome and named as per their chromosome location. A phylogenetic analysis revealed that VrNACs are broadly distributed in nine groups. Moreover, we identified 20 conserved motifs across the VrNACs highlighting their roles in different biological process. Based on the gene structure of the putative VrNAC and segmental duplication events might be playing a vital role in the expansion of mung bean genome. A comparative phylogenetic analysis of mung bean NAC together with homologs from Arabidopsis allowed us to classify NAC genes into 13 groups, each containing several orthologs and paralogs. Gene ontology (GO) analysis categorized the VrNACs into biological process, cellular components and molecular functions, explaining the functions in different plant physiology processes. A gene co-expression network analysis identified 173 genes involved in the transcriptional network of putative VrNAC genes. We also investigated how miRNAs potentially target VrNACs and shape their interactions with proteins. VrNAC1.4 (Vradi01g03390.1) was targeted by the Vra-miR165 family, including 9 miRNAs. Vra-miR165 contributes to leaf development and drought tolerance. We also performed qRT-PCR on 22 randomly selected VrNAC genes to assess their expression patterns in the NM-98 genotype, widely known for being tolerant to drought and bacterial leaf spot disease.

CONCLUSIONS

This genome-wide investigation of VrNACs provides a unique resource for further detailed investigations aimed at predicting orthologs functions and what role the play under abiotic and biotic stress, with the ultimate aim to improve mung bean production under diverse environmental conditions.

Ingeniería genética contra estrés abiótico en cultivos neotropicales: osmolitos, factores de transcripción y CRISPR/Cas9

El neotrópico es sitio de origen de gran variedad de plantas que actualmente son cultivadas con éxito en diferentes regiones del mundo. Sin embargo, condiciones climáticas adversas, que se pueden ver acrecentadas por efectos del cambio climático antropogénico, pueden afectar su rendimiento y productividad debido a las situaciones de estrés abiótico que se pueden generar. Como alternativa para contrarrestar estos efectos, se ha experimentado con modificaciones genéticas, particularmente en genes relacionados con la producción de osmolitos y factores de transcripción que han llevado a que estas plantas, a nivel experimental, tengan mayor tolerancia a estrés oxidativo, altas y bajas temperaturas y fotoinhibición, sequía y salinidad, mediante la acumulación de osmoprotectores, la regulación en la expresión de genes y cambios en el fenotipo. En este trabajo se presentan y describen las estrategias metodológicas planteadas con estos fines y se complementan con ejemplos de trabajos realizados en cultivos de origen neotropical de importancia económica, como maíz, algodón, papa y tomate. Además, y debido a la novedad y potencial que ofrece la edición génica por medio del sistema CRISPR/Cas9, también se mencionan trabajos realizados en plantas con origen neotropical, enfocados en comprender e implementar mecanismos de tolerancia a sequía. Las metodologías aquí descritas podrían constituirse en opciones prácticas para mejorar la seguridad alimentaria con miras a contrarrestar las consecuencias negativas del cambio climático antropogénico.

Genome-Wide Identification and Analysis of the MADS-Box Gene Family in Theobroma cacao

The MADS-box family gene is a class of transcription factors that have been extensively studied and involved in several plant growth and development processes, especially in floral organ specificity, flowering time and initiation and fruit development. In this study, we identified 69 candidate MADS-box genes and clustered these genes into five subgroups (Mα: 11; Mβ: 2; Mγ: 14; Mδ: 9; MIKC: 32) based on their phylogenetical relationships with Arabidopsis. Most TcMADS genes within the same subgroup showed a similar gene structure and highly conserved motifs. Chromosomal distribution analysis revealed that all the TcMADS genes were evenly distributed in 10 chromosomes. Additionally, the cis-acting elements of promoter, physicochemical properties and subcellular localization were also analyzed. This study provides a comprehensive analysis of MADS-box genes in Theobroma cacao and lays the foundation for further functional research.

The BAHD Gene Family in Cacao (Theobroma cacao, Malvaceae): Genome-Wide Identification and Expression Analysis

The benzyl alcohol O-acetyl transferase, anthocyanin O-hydroxycinnamoyl transferase, N-hydroxycinnamoyl anthranilate benzoyl transferase, and deacetylvindoline 4-O-acetyltransferase (BAHD) enzymes play a critical role in regulating plant metabolites and affecting cell stability. In the present study, members of the BAHD gene family were recognized in the genome of Theobroma cacao and characterized using various bioinformatics tools. We found 27 non-redundant putative tcBAHD genes in cacao for the first time. Our findings indicate that tcBAHD genes are diverse based on sequence structure, physiochemical properties, and function. When analyzed with BAHDs of Gossypium raimondii and Corchorus capsularis clustered into four main groups. According to phylogenetic analysis, BAHD genes probably evolved drastically after their divergence. The divergence time of duplication events with purifying selection pressure was predicted to range from 1.82 to 15.50 MYA. Pocket analysis revealed that serine amino acid is more common in the binding site than other residuals, reflecting its key role in regulating the activity of tcBAHDs. Furthermore, cis-acting elements related to the responsiveness of stress and hormone, particularly ABA and MeJA, were frequently observed in the promoter region of tcBAHD genes. RNA-seq analysis further illustrated that tcBAHD13 and tcBAHD26 are involved in response to Phytophthora megakarya fungi. In conclusion, it is likely that evolutionary processes, such as duplication events, have caused high diversity in the structure and function of tcBAHD genes.

Characterization of NAC family genes in Salvia miltiorrhiza and NAC2 potentially involved in the biosynthesis of tanshinones

The NAC (NAM, ATAF, and CUC) family members are specific transcription factors in plants. The large family is involved in many plant growth and developmental processes, as well as in abiotic/biotic stress responses. It has been well studied in the genomes of various plants, including Arabidopsis thaliana, tomato, and quinoa. However, identification and functional studies of NAC family members in medicinal Salvia miltiorrhiza are limited. Here, we systematically identified 84 NAC genes and named them according to their gene IDs in the recently sequenced genome. The phylogeny of NAC family protein sequences was analyzed using bioinformatics methods, which divided them into nine subfamilies. Then, their chromosomal locations, gene structures and conserved domains were analyzed comprehensively. To further investigate the regulatory functions of NACs in S. miltiorrhiza, we analyzed the response of 10 selected NAC genes to methyl jasmonate and used NAC2 for transgenic experiments. The overexpression of Sm-NAC2 decreased the tanshinone I and IIA contents by 56% and 62%, respectively. However, Sm-NAC2-RNAi promoted the accumulation of four tanshinones, tanshinone I, tanshinone IIA, cryptotanshinone, and dihydrotanshinone I, which increased 3.68-, 4.1-, 3.13- and 5.9- fold, respectively, compared with wild type. In the tanshinone biosynthetic pathways, the overexpression of Sm-NAC2 down-regulated CYP76AH1, and the silencing of Sm-NAC2 up-regulated the expression levels of HMGR1, DXS2, KSL2, and CYP76AH1. This study provides information on the evolution of Sm-NAC genes and their possible functions, and it lays a foundation for further research into the NAC family-associated regulation of tanshinone biosynthesis.

Comprehensive Analyses of NAC Transcription Factor Family in Almond (Prunus dulcis) and Their Differential Gene Expression during Fruit Development

As plant specific transcription factors, NAC (NAM, ATAF1/2, CUC2) domain is involved in the plant development and stress responses. Due to the vitality of NAC gene family, BLASTp was performed to identify NAC genes in almond (Prunus dulcis). Further, phylogenetic and syntenic analyses were performed to determine the homology and evolutionary relationship. Gene duplication, gene structure, motif, subcellular localization, and cis-regulatory analyses were performed to assess the function of PdNAC. Whereas RNA-seq analysis was performed to determine the differential expression of PdNAC in fruits at various developmental stages. We identified 106 NAC genes in P. dulcis genome and were renamed according to their chromosomal distribution. Phylogenetic analysis in both P. dulcis and Arabidopsis thaliana revealed the presence of 14 subfamilies. Motif and gene structure followed a pattern according to the PdNAC position in phylogenetic subfamilies. Majority of NAC are localized in the nucleus and have ABA-responsive elements in the upstream region of PdNAC. Differential gene expression analyses revealed one and six PdNAC that were up and down-regulated, respectively, at all development stages. This study provides insights into the structure and function of PdNAC along with their role in the fruit development to enhance an understanding of NAC in P. dulcis.

The GASA Gene Family in Cacao (Theobroma cacao, Malvaceae): Genome Wide Identification and Expression Analysis

The gibberellic acid-stimulated Arabidopsis (GASA/GAST) gene family is widely distributed in plants and involved in various physiological and biological processes. These genes also provide resistance to abiotic and biotic stresses, including antimicrobial, antiviral, and antifungal. We are interested in characterizing the GASA gene family and determining its role in various physiological and biological process in Theobroma cacao. Here, we report 17 tcGASA genes distributed on six chromosomes in T. cacao. The gene structure, promoter region, protein structure and biochemical properties, expression, and phylogenetics of all tcGASAs were analyzed. Phylogenetic analyses divided tcGASA proteins into five groups. Among 17 tcGASA genes, nine segmentally duplicating genes were identified which formed four pairs and cluster together in phylogenetic tree. Differential expression analyses revealed that most of the tcGASA genes showed elevated expression in the seeds (cacao food), implying their role in seed development. The differential expression of tcGASAs was recorded between the tolerant and susceptible cultivars of cacao, which indicating their possible role as fungal resistant. Our findings provide new insight into the function, evolution, and regulatory system of the GASA family genes in T.cacao and may suggest new target genes for development of fungi-resistant cacao varieties in breeding programs.

Genome-wide identification and characterization of NAC genes in Brassica juncea var. tumida

Background

NAC (NAM, ATAF1/2, and CUC2) transcription factors play an important role in plant growth and development. However, in tumorous stem mustard (Brassica juncea var. tumida), one of the economically important crops cultivated in southwest China and some southeast Asian countries, reports on the identification of NAC family genes are lacking. In this study, we conducted a genome-wide investigation of the NAC family genes in B. juncea var. tumida, based on its recently published genome sequence data.

Methods

The NAC genes were identified in B. juncea var. tumida using the bioinformatics approach on the whole genome level. Additionally, the expression of BjuNAC genes was analyzed under high- and low-temperature stresses by quantitative real-time PCR (qRT-PCR).

Results

A total of 300 BjuNAC genes were identified, of which 278 were mapped to specific chromosomes. Phylogenetic analysis of B. juncea var. tumida, Brassica rapa, Brassica nigra, rice and Arabidopsis thaliana NAC proteins revealed that all NAC genes were divided into 18 subgroups. Furthermore, gene structure analysis showed that most of the NAC genes contained two or three exons. Conserved motif analysis revealed that BjuNAC genes contain a conserved NAM domain. Additionally, qRT-PCR data indicated that thirteen BjuNAC genes with a varying degree of up-regulation during high-temperature stress. Conversely, four BjuNAC genes (BjuNAC006, BjuNAC083, BjuNAC170 and BjuNAC223) were up-regulated and two BjuNAC genes (BjuNAC074 and BjuNAC295) down-regulated under low temperature, respectively. Together, the results of this study provide a strong foundation for future investigation of the biological function of NAC genes in B. juncea var. tumida.

Genome-wide identification of sucrose nonfermenting-1-related protein kinase (SnRK) genes in barley and RNA-seq analyses of their expression in response to abscisic acid treatment

Background

Sucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs) play important roles in regulating metabolism and stress responses in plants, providing a conduit for crosstalk between metabolic and stress signalling, in some cases involving the stress hormone, abscisic acid (ABA). The burgeoning and divergence of the plant gene family has led to the evolution of three subfamilies, SnRK1, SnRK2 and SnRK3, of which SnRK2 and SnRK3 are unique to plants. Therefore, the study of SnRKs in crops may lead to the development of strategies for breeding crop varieties that are more resilient under stress conditions. In the present study, we describe the SnRK gene family of barley (Hordeum vulgare), the widespread cultivation of which can be attributed to its good adaptation to different environments.

Results

The barley HvSnRK gene family was elucidated in its entirety from publicly-available genome data and found to comprise 50 genes. Phylogenetic analyses assigned six of the genes to the HvSnRK1 subfamily, 10 to HvSnRK2 and 34 to HvSnRK3. The search was validated by applying it to Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) genome data, identifying 50 SnRK genes in rice (four OsSnRK1, 11 OsSnRK2 and 35 OsSnRK3) and 39 in Arabidopsis (three AtSnRK1, 10 AtSnRK2 and 26 AtSnRK3). Specific motifs were identified in the encoded barley proteins, and multiple putative regulatory elements were found in the gene promoters, with light-regulated elements (LRE), ABA response elements (ABRE) and methyl jasmonate response elements (MeJa) the most common. RNA-seq analysis showed that many of the HvSnRK genes responded to ABA, some positively, some negatively and some with complex time-dependent responses.

Conclusions

The barley HvSnRK gene family is large, comprising 50 members, subdivided into HvSnRK1 (6 members), HvSnRK2 (10 members) and HvSnRK3 (34 members), showing differential positive and negative responses to ABA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07601-6.

Transcriptome-wide and expression analysis of the NAC gene family in pepino (Solanum muricatum) during drought stress

Solanum muricatum (Pepino) is an increasingly popular solanaceous crop and is tolerant of drought conditions. In this study, 71 NAC transcription factor family genes of S. muricatum were selected to provide a theoretical basis for subsequent in-depth study of their regulatory roles in the response to biological and abiotic stresses, and were subjected to whole-genome analysis. The NAC sequences obtained by transcriptome sequencing were subjected to bioinformatics prediction and analysis. Three concentration gradient drought stresses were applied to the plants, and the target gene sequences were analyzed by qPCR to determine their expression under drought stress. The results showed that the S. muricatum NAC family contains 71 genes, 47 of which have conserved domains. The protein sequence length, molecular weight, hydrophilicity, aliphatic index and isoelectric point of these transcription factors were predicted and analyzed. Phylogenetic analysis showed that the S. muricatum NAC gene family is divided into seven subfamilies. Some NAC genes of S. muricatum are closely related to the NAC genes of Solanaceae crops such as tomato, pepper and potato. The seedlings of S. muricatum were grown under different gradients of drought stress conditions and qPCR was used to analyze the NAC expression in roots, stems, leaves and flowers. The results showed that 13 genes did not respond to drought stress while 58 NAC genes of S. muricatum that responded to drought stress had obvious tissue expression specificity. The overall expression levels in the root were found to be high. The number of genes at extremely significant expression levels was very large, with significant polarization. Seven NAC genes with significant responses were selected to analyze their expression trend in the different drought stress gradients. It was found that genes with the same expression trend also had the same or part of the same conserved domain. Seven SmNACs that may play an important role in drought stress were selected for NAC amino acid sequence alignment of Solanaceae crops. Four had strong similarity to other Solanaceae NAC amino acid sequences, and SmNAC has high homology with the Solanum pennellii. The NAC transcription factor family genes of S. muricatum showed strong structural conservation. Under drought stress, the expression of NAC transcription factor family genes of S. muricatum changed significantly, which actively responded to and participated in the regulation process of drought stress, thereby laying foundations for subsequent in-depth research of the specific functions of NAC transcription factor family genes of S. muricatum.

Functional Characterization of PsnNAC036 under Salinity and High Temperature Stresses

Plant growth and development are challenged by biotic and abiotic stresses including salinity and heat stresses. For Populus simonii × P. nigra as an important greening and economic tree species in China, increasing soil salinization and global warming have become major environmental challenges. We aim to unravel the molecular mechanisms underlying tree tolerance to salt stress and high temprerature (HT) stress conditions. Transcriptomics revealed that a PsnNAC036 transcription factor (TF) was significantly induced by salt stress in P. simonii × P. nigra. This study focuses on addressing the biological functions of PsnNAC036. The gene was cloned, and its temporal and spatial expression was analyzed under different stresses. PsnNAC036 was significantly upregulated under 150 mM NaCl and 37 °C for 12 h. The result is consistent with the presence of stress responsive cis-elements in the PsnNAC036 promoter. Subcellular localization analysis showed that PsnNAC036 was targeted to the nucleus. Additionally, PsnNAC036 was highly expressed in the leaves and roots. To investigate the core activation region of PsnNAC036 protein and its potential regulatory factors and targets, we conducted trans-activation analysis and the result indicates that the C-terminal region of 191-343 amino acids of the PsnNAC036 was a potent activation domain. Furthermore, overexpression of PsnNAC036 stimulated plant growth and enhanced salinity and HT tolerance. Moreover, 14 stress-related genes upregulated in the transgenic plants under high salt and HT conditions may be potential targets of the PsnNAC036. All the results demonstrate that PsnNAC036 plays an important role in salt and HT stress tolerance.

Evolutionary Divergence and Biased Expression of NAC Transcription Factors in Hexaploid Bread Wheat (Triticum aestivum L.)

The NAC genes, a large plant-specific family of transcription factors, regulate a wide range of pathways involved in development and response to biotic and abiotic stress. In this study, the NAC transcription factors were identified in 27 green plants, and the results showed that NAC transcription factors in plants undergo an appearance stage from water to land and a number expansion stage from gymnosperm to angiosperm. Investigating the evolutionary process of the NAC transcription factors from diploid species to hexaploid wheat revealed that tandem replications during the polyploidization process is an important event for increasing the number of NAC transcription factors in wheat. Then, the molecular characteristics, phylogenetic relationships, and expression patterns of 462 NAC transcription factors of hexaploid wheat (TaNACs) were analyzed. The protein structure results showed that TaNAC was relatively conservative at the N-terminal that contains five subdomains. All these TaNACs were divided into Group I and Group II by phylogenetic analysis, and the TaNACs in Group I should undergo strong artificial selection based on single nucleotide polymorphism (SNP) analysis. Through genome synteny and phylogenetic analysis, these TaNACs were classified into 88 groups and 9 clusters. The biased expression results of these TaNACs showed that there are 24 groups and 67 groups of neofunctionalization genes under biotic and abiotic stress, respectively, and 16 groups and 59 groups of subfunctionalization genes. This shows that neofunctionalization plays an important role in coping with different stresses. Our study provides new insights into the evolution of NAC transcription factors in hexaploid wheat.

The GASA Gene Family in Theobroma cacao: Genome wide Identification and Expression Analysis.. [DOI: 10.1101/2021.01.27.425041]

The gibberellic acid-stimulated Arabidopsis (GASA/GAST) gene family is widely distributed in plants. The role of the GASA gene family has been reported previously in various physiological and biological processes, such as cell division, root and seed development, stem growth, and fruit ripening. These genes also provide resistance to abiotic and biotic stresses including antimicrobial, antiviral, and antifungal. Here, we report 17 tcGASA genes in Theobroma cacao L. distributed on six chromosomes. The gene structure, promoter-region sequences, protein structure, and biochemical properties, expression, and phylogenetics of all tcGASAs were analyzed. Phylogenetic analyses divided tcGASA proteins into five groups. The nine segmentally duplicating genes form four pairs and cluster together in phylogenetic tree. Purifying selection pressure was recorded on tcGASA, including duplicated genes. Several stress/hormone-responsive cis-regulatory elements were also recognized in the promoter region of tcGASAs. Differential expression analyses revealed that most of the tcGASA genes showed elevated expression in the seeds (cacao food), implying their role in seed development. The black rod disease of genus Phytophthora caused up to 20–25% loss (700,000 metric tons) in world cacao production. The role of tcGASA genes in conferring fungal resistance was also explored based on RNAseq data against Phytophthora megakarya. The differential expression of tcGASA genes was recorded between the tolerant and susceptible cultivars of cacao plants, which were inoculated with the fungus for 24h and 72h. This differential expression indicating possible role of tcGASA genes to fungal resistant in cacao. Our findings provide new insight into the function, evolution, and regulatory system of the GASA family genes in T. cacao and provide new target genes for development of fungi-resistant cacao varieties in breeding programs.

Exploring the biochemical properties of three polyphenol oxidases from blueberry (Vaccinium corymbosum L.)

Purification of blueberry polyphenol oxidase (PPO) has not been substantially progressed for a long time, which leads to little further study. We purified three PPOs from blueberries for the first time by modified Native-Page. The PPO-2 consists of two subunits (68 and 36 kDa), whereas PPO-3 and PPO-4 contain only one subunit (36 kDa). The optimum pH and temperature of PPO-2, PPO-3, and PPO-4 were 5.8-6.2 and 40 °C-45 °C with catechol as a substrate. The optimal substrates for them were all catechol (K_m = 14.91, 7.19, and 11.20, respectively). High-pressure processing (HPP) had a limited inhibitory effect on the three PPOs. The activities of PPO-2, PPO-3, and PPO-4 were significantly reduced with increased SDS concentration. The binding of substrate to catalytic cavity is related to the residues His76, His209, His213, Gly228, and Phe230. The carbonyl group of residue Gly228 is one of the key sites for screening substrates.

Comprehensive genomic characterization of NAC transcription factor family and their response to salt and drought stress in peanut

BACKGROUND

Peanut is one of the most important oil crop species worldwide. NAC transcription factor (TF) genes play important roles in the salt and drought stress responses of plants by activating or repressing target gene expression. However, little is known about NAC genes in peanut.

RESULTS

We performed a genome-wide characterization of NAC genes from the diploid wild peanut species Arachis duranensis and Arachis ipaensis, which included analyses of chromosomal locations, gene structures, conserved motifs, expression patterns, and cis-acting elements within their promoter regions. In total, 81 and 79 NAC genes were identified from A. duranensis and A. ipaensis genomes. Phylogenetic analysis of peanut NACs along with their Arabidopsis and rice counterparts categorized these proteins into 18 distinct subgroups. Fifty-one orthologous gene pairs were identified, and 46 orthologues were found to be highly syntenic on the chromosomes of both A. duranensis and A. ipaensis. Comparative RNA sequencing (RNA-seq)-based analysis revealed that the expression of 43 NAC genes was up- or downregulated under salt stress and under drought stress. Among these genes, the expression of 17 genes in cultivated peanut (Arachis hypogaea) was up- or downregulated under both stresses. Moreover, quantitative reverse transcription PCR (RT-qPCR)-based analysis revealed that the expression of most of the randomly selected NAC genes tended to be consistent with the comparative RNA-seq results.

CONCLUSION

Our results facilitated the functional characterization of peanut NAC genes, and the genes involved in salt and drought stress responses identified in this study could be potential genes for peanut improvement.

Genome-Wide Analysis of the Shi-Related Sequence Family and Functional Identification of GmSRS18 Involving in Drought and Salt Stresses in Soybean

The plant-special SHI-RELATED SEQUENCE (SRS) family plays vital roles in various biological processes. However, the genome-wide analysis and abiotic stress-related functions of this family were less reported in soybean. In this work, 21 members of soybean SRS family were identified, which were divided into three groups (Group I, II, and III). The chromosome location and gene structure were analyzed, which indicated that the members in the same group may have similar functions. The analysis of stress-related cis-elements showed that the SRS family may be involved in abiotic stress signaling pathway. The analysis of expression patterns in various tissues demonstrated that SRS family may play crucial roles in special tissue-dependent regulatory networks. The data based on soybean RNA sequencing (RNA-seq) and quantitative Real-Time PCR (qRT-PCR) proved that SRS genes were induced by drought, NaCl, and exogenous abscisic acid (ABA). GmSRS18 significantly induced by drought and NaCl was selected for further functional verification. GmSRS18, encoding a cell nuclear protein, could negatively regulate drought and salt resistance in transgenic Arabidopsis. It can affect stress-related physiological index, including chlorophyll, proline, and relative electrolyte leakage. Additionally, it inhibited the expression levels of stress-related marker genes. Taken together, these results provide valuable information for understanding the classification of soybean SRS transcription factors and indicates that SRS plays important roles in abiotic stress responses.