A New Ethylene-Responsive Factor CaPTI1 Gene of Pepper (Capsicum annuum L.) Involved in the Regulation of Defense Response to Phytophthora capsici

Ethylene-MPK8-ERF.C1-PR module confers resistance against Botrytis cinerea in tomato fruit without compromising ripening

The plant hormone ethylene plays a critical role in fruit defense against Botrytis cinerea attack, but the underlying mechanisms remain poorly understood. Here, we showed that ethylene response factor SlERF.C1 acts as a key regulator to trigger the ethylene-mediated defense against B. cinerea in tomato fruits without compromising ripening. Knockout of SlERF.C1 increased fruit susceptibility to B. cinerea with no effect on ripening process, while overexpression enhanced resistance. RNA-Seq, transactivation assays, EMSA and ChIP-qPCR results indicated that SlERF.C1 activated the transcription of PR genes by binding to their promoters. Moreover, SlERF.C1 interacted with the mitogen-activated protein kinase SlMPK8 which allowed SlMPK8 to phosphorylate SlERF.C1 at the Ser174 residue and increases its transcriptional activity. Knocking out of SlMPK8 increased fruit susceptibility to B. cinerea, whereas overexpression enhanced resistance without affecting ripening. Furthermore, genetic crosses between SlMPK8-KO and SlERF.C1-OE lines reduced the resistance to B. cinerea attack in SlERF.C1-OE fruits. In addition, B. cinerea infection induced ethylene production which in turn triggered SlMPK8 transcription and enhanced the phosphorylation of SlERF.C1. Overall, our findings reveal the regulatory mechanism of the 'Ethylene-MPK8-ERF.C1-PR' module in resistance against B. cinerea and provide new insight into the manipulation of gray mold disease in fruits.

Unveiling molecular mechanisms of pepper resistance to Phytophthora capsici through grafting using iTRAQ-based proteomic analysis

Phytophthora blight severely threatens global pepper production. Grafting bolsters plant disease resistance, but the underlying molecular mechanisms remain unclear. In this study, we used P. capsici-resistant strain 'ZCM334' and susceptible strain 'Early Calwonder' for grafting. Compared to self-rooted 'Early Calwonder' plants, 'ZCM334' grafts exhibited delayed disease onset, elevated resistance, and reduced leaf cell damage, showcasing the potential of grafting in enhancing pepper resistance to P. capsici. Proteomic analysis via the iTRAQ technology unveiled 478 and 349 differentially expressed proteins (DEPs) in the leaves and roots, respectively, between the grafts and self-rooted plants. These DEPs were linked to metabolism and cellular processes, stimulus responses, and catalytic activity and were significantly enriched in the biosynthesis of secondary metabolites, carbon fixation in photosynthetic organizations, and pyruvate metabolism pathways. Twelve DEPs exhibiting consistent expression trends in both leaves and roots, including seven related to P. capsici resistance, were screened. qRT-PCR analysis confirmed a significant correlation between the protein and transcript levels of DEPs after P. capsici inoculation. This study highlights the molecular mechanisms whereby grafting enhances pepper resistance to Phytophthora blight. Identification of key genes provides a foundation for studying the regulatory network governing the resistance of pepper to P. capsici.

Transcriptome and metabolome analyses revealed the response mechanism of pepper roots to Phytophthora capsici infection

BACKGROUND

Phytophthora root rot caused by the oomycete Phytophthora capsici is the most devastating disease in pepper production worldwide, and current management strategies have not been effective in preventing this disease. Therefore, the use of resistant varieties was regarded as an important part of disease management of P. capsici. However, our knowledge of the molecular mechanisms underlying the defense response of pepper roots to P. capsici infection is limited.

METHODS

A comprehensive transcriptome and metabolome approaches were used to dissect the molecular response of pepper to P. capsici infection in the resistant genotype A204 and the susceptible genotype A198 at 0, 24 and 48 hours post-inoculation (hpi).

RESULTS

More genes and metabolites were induced at 24 hpi in A204 than A198, suggesting the prompt activation of defense responses in the resistant genotype, which can attribute two proteases, subtilisin-like protease and xylem cysteine proteinase 1, involved in pathogen recognition and signal transduction in A204. Further analysis indicated that the resistant genotype responded to P. capsici with fine regulation by the Ca2+- and salicylic acid-mediated signaling pathways, and then activation of downstream defense responses, including cell wall reinforcement and defense-related genes expression and metabolites accumulation. Among them, differentially expressed genes and differentially accumulated metabolites involved in the flavonoid biosynthesis pathways were uniquely activated in the resistant genotype A204 at 24 hpi, indicating a significant role of the flavonoid biosynthesis pathways in pepper resistance to P. capsici.

CONCLUSION

The candidate transcripts may provide genetic resources that may be useful in the improvement of Phytophthora root rot-resistant characters of pepper. In addition, the model proposed in this study provides new insight into the defense response against P. capsici in pepper, and enhance our current understanding of the interaction of pepper-P. capsici.

Phytophthora capsici: Recent Progress on Fundamental Biology and Disease Management 100 Years After Its Description

Phytophthora capsici is a destructive oomycete pathogen of vegetable, ornamental, and tropical crops. First described by L.H. Leonian in 1922 as a pathogen of pepper in New Mexico, USA, P. capsici is now widespread in temperate and tropical countries alike. Phytophthora capsici is notorious for its capability to evade disease management strategies. High genetic diversity allows P. capsici populations to overcome fungicides and host resistance, the formation of oospores results in long-term persistence in soils, zoospore differentiation in the presence of water increases epidemic potential, and a broad host range maximizes economic losses and limits the effectiveness of crop rotation. The severity of disease caused by P. capsici and management challenges have led to numerous research efforts in the past 100 years. Here, we discuss recent findings regarding the biology, genetic diversity, disease management, fungicide resistance, host resistance, genomics, and effector biology of P. capsici.

Proteomics analysis of a tobacco variety resistant to brown spot disease and functional characterization of NbMLP423 in Nicotiana benthamiana

BACKGROUND

Tobacco brown spot disease is an important disease caused by Alternaria alternata that affects tobacco production and quality worldwide. Planting resistant varieties is the most economical and effective way to control this disease. However, the lack of understanding of the mechanism of tobacco resistance to tobacco brown spot has hindered progress in the breeding of resistant varieties.

METHODS AND RESULTS

In this study, differentially expressed proteins (DEPs), including 12 up-regulated and 11 down-regulated proteins, were screened using isobaric tags for relative and absolute quantification (iTRAQ) by comparing resistant and susceptible pools and analyzing the associated functions and metabolic pathways. Significantly up-regulated expression of the major latex-like protein gene 423 (MLP 423) was detected in both the resistant parent and the population pool. Bioinformatics analysis showed that the NbMLP423 cloned in Nicotiana benthamiana had a similar structure to the NtMLP423 in Nicotiana tabacum, and that expression of both genes respond rapidly to Alternaria alternata infection. NbMLP423 was then used to study the subcellular localization and expression in different tissues, followed by both silencing and the construction of an overexpression system for NbMLP423. The silenced plants demonstrated inhibited TBS resistance, while the overexpressed plants exhibited significantly enhanced resistance. Exogenous applications of plant hormones, such as salicylic acid, had a significant inducing effect on NbMLP423 expression.

CONCLUSIONS

Taken together, our results provide insights into the role of NbMLP423 in plants against tobacco brown spot infection and provide a foundation for obtaining resistant tobacco varieties through the construction of new candidate genes of the MLP subfamily.

Transcriptome, proteome and functional characterization reveals salt stress tolerance mechanisms in upland cotton (Gossypium hirsutum L.)

Uncovering the underlying mechanism of salt tolerance is important to breed cotton varieties with improved salt tolerance. In this study, transcriptome and proteome sequencing were performed on upland cotton (Gossypium hirsutum L.) variety under salt stress, and integrated analysis was carried out to exploit salt-tolerance genes in cotton. Enrichment analysis using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) was performed on differentially expressed genes (DEGs) obtained from transcriptome and proteome sequencing. GO enrichment was carried out mainly in the cell membrane, organelle, cellular process, metabolic process, and stress response. The expression of 23,981 genes was changed in physiological and biochemical processes such as cell metabolism. The metabolic pathways obtained by KEGG enrichment included glycerolipid metabolism, sesquiterpene and triterpenoid biosynthesis, flavonoid production, and plant hormone signal transduction. Combined transcriptome and proteome analysis to screen and annotate DEGs yielded 24 candidate genes with significant differential expression. The quantitative real-time polymerase chain reaction (qRT-PCR) validation of the candidate genes showed that two genes (Gh_D11G0978 and Gh_D10G0907) responded significantly to the induction of NaCl, and these two genes were further selected as target genes for gene cloning and functional validation through virus-induced gene silencing (VIGS). The silenced plants exhibited early wilting with a greater degree of salt damage under salt treatment. Moreover, they showed higher levels of reactive oxygen species (ROS) than the control. Therefore, we can infer that these two genes have a pivotal role in the response to salt stress in upland cotton. The findings in this research will facilitate the breeding of salt tolerance cotton varieties that can be grown on saline alkaline lands.

Enantioselective Synthesis of Pyrazolo[3,4-b]pyridone Derivatives with Antifungal Activities against Phytophthora capsici and Colletotrichum fructicola

A chiral NHC-catalyzed [3 + 3] cycloaddition reaction is developed for the efficient synthesis of pyrazolo[3,4-b]pyridones in generally excellent yields and optical purities. The R, S, and racemic forms of these molecules are systematically studied via in vitro tests that detect antifungal activity against Phytophthora capsici and Colletotrichum fructicola. Chiral compounds (R)-3i, (R)-3j, and (R)-3p are identified to have excellent inhibitory effects against P. capsici and C. fructicola.

Transcriptomic Analysis of the CM-334/P. capsici/N. aberrans Pathosystem to Identify Components in Plant Resistance and Resistance-Breaking Responses

Phytophthora capsici is an important pathogen worldwide because its spread affects pepper production globally. The “Criollo de Morelos” pepper 334 (CM-334) is resistant to P. capsici strains, regardless of the aggressiveness of the strain or the environmental conditions. However, when the nematode Nacobbus aberrans infects peppers, they lose this resistance by a process defined as “Resistance-breaking”. Breakdown of resistance results from a transcriptomic reconfiguration of the pepper that induces some defense genes, such as WRKY-a, POX, and EAS. The interest in identifying and describing the resistance process to P. capsici, and the breakdown that occurs by N. aberrans, has allowed us to establish a model in which we can analyze the modulation process in both scenarios and identify this transcriptomic modulation. The objective of the present work is to carry out a transcriptomic analysis that demonstrates the modulation of resistance and resistance-breaking processes. It would allow us to identify relevant genes in the early (12 h) and late (24 h) stages in these processes of the CM-334 pepper. Our findings demonstrate that modulation of resistance and resistance-breaking are independent processes that depend on the presence of both pathogens (P. capsici and N. aberrans) and that their timing modulation is dynamic.

Mecanismos de defensa en plantas de Capsicum contra Phytophthora capsici

Phytophthora capsici es un oomiceto causante de la pudrición de raíz, tallo, frutos y tizón foliar en varias especies vegetales de importancia agrícola, principalmente en Solanáceas del género Capsicum como ají y pimiento. Este fitopatógeno cosmopolita posee mecanismos de ataque que favorecen la rápida infección, colonización y reproducción en huéspedes susceptibles. Contrariamente, estos procesos son retrasados o evitados fuertemente por genotipos resistentes, debido principalmente a sus mecanismos de defensa. En esas interacciones incompatibles, las plantas resistentes de Capsicum reconocen el oomiceto y rápidamente expresan múltiples genes que posteriormente señalizan moléculas, que permiten la acumulación de compuestos fenólicos, fitoalexinas y especies reactivas de oxígeno, la actividad de diferentes enzimas, que pueden permitir incluso la formación de barreras físicas. Esta revisión aborda, expone y discute los avances y el progreso de las investigaciones a lo largo de los ultimos veinte años, referente a los mecanismos de defensa estructurales, bioquimicos y moleculares que utilizan las plantas resistentes de Capsicum para defenderse de P. capsici. Palabras claves. ají, pimiento, pudrición de raíz y corona, tizón foliar, resistencia vegetal

Jasmonate resistant 1 and ethylene responsive factor 11 are involved in chilling sensitivity in pepper fruit (Capsicum annuum L.)

Pepper fruit (Capsicum annuum L.) is sensitive to chilling stress with chilling injuries occurring below 7 °C; however, chilling injuries occur at different temperatures depending on the genotype. The present study aimed to identify the factors that affect chilling sensitivity in pepper fruits. A total of 112 F₂ pepper fruits crossed between chilling-insensitive 'UZB-GJG-1999–51' and chilling-sensitive 'C00562' pepper were grouped according to the seed browning rate, which is a typical chilling symptom of pepper fruit under chilling conditions. Physiological traits, amino acids, fatty acids, as well as ethylene responsive factor (ERF) and jasmonate resistant 1 (JAR1) expression levels were analyzed, and their correlations with the seed browning rate were confirmed. The expression level of JAR1 showed a strong negative correlation with the seed browning rate (r =  − 0.7996). The expression level of ERF11 and content of hydrogen peroxide showed strong positive correlation with the seed browning rate (r = 0.7622 and 0.6607, respectively). From these results, we inferred that JAR1 and ERF11 are important factors influencing the chilling sensitivity of pepper fruit.

Dynamic Transcriptome Profiling of Mungbean Genotypes Unveil the Genes Respond to the Infection of Mungbean Yellow Mosaic Virus

Yellow mosaic disease (YMD), incited by mungbean yellow mosaic virus (MYMV), is a primary viral disease that reduces mungbean production in South Asia, especially in India. There is no detailed knowledge regarding the genes and molecular mechanisms conferring resistance of mungbean to MYMV. Therefore, disclosing the genetic and molecular bases related to MYMV resistance helps to develop the mungbean genotypes with MYMV resistance. In this study, transcriptomes of mungbean genotypes, VGGRU-1 (resistant) and VRM (Gg) 1 (susceptible) infected with MYMV were compared to those of uninfected controls. The number of differentially expressed genes (DEGs) in the resistant and susceptible genotypes was 896 and 506, respectively. Among them, 275 DEGs were common between the resistant and susceptible genotypes. Functional annotation of DEGs revealed that the DEGs belonged to the following categories defense and pathogenesis, receptor-like kinases; serine/threonine protein kinases, hormone signaling, transcription factors, and chaperons, and secondary metabolites. Further, we have confirmed the expression pattern of several DEGs by quantitative real-time PCR (qRT-PCR) analysis. Collectively, the information obtained in this study unveils the new insights into characterizing the MYMV resistance and paved the way for breeding MYMV resistant mungbean in the future.

Integrative RNA-Seq analysis of Capsicum annuum L.-Phytophthora capsici L. pathosystem reveals molecular cross-talk and activation of host defence response

Chili pepper (Capsicum annuum L.) is economically one of the most important spice. But, it's productivity is highly affected by the pathogen, Phytophthora capsici L. Our current understanding of the molecular mechanisms associated with the defence response in C. annuum-P. capsici pathosystem is limited. The current study used RNA-seq technology to dissect the genes associated with defence response against P. capsici infection in two contrasting landraces, i.e. GojamMecha_9086 (Resistant) and Dabat_80045 (Susceptible) exposed to P. capsici infection. The transcriptomes from four leaf samples (RC, RI, SC and SI) of chili pepper resulted in a total of 118,879 assembled transcripts along with 52,384 pooled unigenes. The enrichment analysis of the transcripts indicated 23 different KEGG pathways under five main categories. Out of 774 and 484 differentially expressed genes (DEGs) of two landraces (under study), respectively, 57 and 29 DEGs were observed as associated with defence responses against P. capsici infection in RC vs. RI and SC vs. SI leaf samples, respectively. qRT-PCR analysis of six randomly selected genes validated the results of Illumina NextSeq500 sequencing. A total of 58 transcription factor families (bHLH most abundant) and 2095 protein families (Protein kinase most abundant) were observed across all the samples with maximum hits in RI and SI samples. Expression analysis revealed differential regulation of genes associated with defence and signalling response with shared coordination of molecular function, cellular component and biological processing. The results presented here would enhance our present understanding of the defence response in chili pepper against P. capsici infection, which the molecular breeders could utilize to develop resistant chili genotypes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01122-y.

Cinnamaldehyde inhibits the growth of Phytophthora capsici through disturbing metabolic homoeostasis

Background

Phytophthora capsici Leonian (P. capsici) can cause wilting and roots rotting on pepper and other cash crops. The new fungicide cinnamaldehyde (CA) has high activity against this pathogen. However, its potential mechanism is still unknown.

Methods

In order to gain insights into the mechanism, isobaric tags for relative and absolute quantification (iTRAQ)-based quantitative proteomics was used to analyze P. capsici treated with CA. The iTRAQ results were evaluated by parallel reaction monitoring (PRM) analysis and quantitative real-time PCR (qRT-PCR) analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was used to speculate the biochemical pathways that the agent may act on.

Results

The results showed that 1502 differentially expressed proteins were identified, annotated and classified into 209 different terms (like metabolic process, cellular process, single-organism process) based on Gene Ontology (GO) functional enrichment analysis and nine different pathways (glyoxylate and dicarboxylate metabolism, fatty acid metabolism and so on) based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. This study suggested that CA disordered fatty acid metabolism, polysaccharide metabolism and leucine metabolism. Based on PRM analysis, five proteins including CAMK/CAMK1 protein kinase, glucan 1,3-beta-glucosidase, 1,3-beta-glucanosyltransferase, methylcrotonoyl-CoA carboxylase subunit alpha and isovaleryl-CoA dehydrogenase were down-regulated in P. capsici treated with CA. Furthermore, the qRT-PCR analysis showed that the gene expression level of the interested proteins was consistent with the protein expression level, except for CAMK/CAMK1 protein kinase, acetyl-CoA carboxylase and fatty acid synthase subunit alpha.

Conclusions

CA destroyed the metabolic homoeostasisof P. capsici, which led to cell death. This is the first proteomic analysis of P. capsici treated with CA, which may provide an important information for exploring the mechanism of the fungicide CA against P. capsici.

CaSBP11 Participates in the Defense Response of Pepper to Phytophthora capsici through Regulating the Expression of Defense-Related Genes

Squamosa promoter binding protein (SBP)-box genes are plant-specific transcription factors involved in plant growth and development, morphogenesis and biotic and abiotic stress responses. However, these genes have been understudied in pepper, especially with respect to defense responses to Phytophthora capsici infection. CaSBP11 is a SBP-box family gene in pepper that was identified in our previous research. Silencing CaSBP11 enhanced the defense response of pepper plants to Phytophthora capsici. Without treatment, the expression of defense-related genes (CaBPR1, CaPO1, CaSAR8.2 and CaDEF1) increased in CaSBP11-silenced plants. However, the expression levels of these genes were inhibited under transient CaSBP11 expression. CaSBP11 overexpression in transgenic Nicotiana benthamiana decreased defense responses, while in Arabidopsis, it induced or inhibited the expression of genes in the salicylic acid and jasmonic acid signaling pathways. CaSBP11 overexpression in sid2-2 mutants induced AtNPR1, AtNPR3, AtNPR4, AtPAD4, AtEDS1, AtEDS5, AtMPK4 and AtNDR1 expression, while AtSARD1 and AtTGA6 expression was inhibited. CaSBP11 overexpression in coi1-21 and coi1-22 mutants, respectively, inhibited AtPDF1.2 expression and induced AtPR1 expression. These results indicate CaSBP11 has a negative regulatory effect on defense responses to Phytophthora capsici. Moreover, it may participate in the defense response of pepper to Phytophthora capsici by regulating defense-related genes and the salicylic and jasmonic acid-mediated disease resistance signaling pathways.

Comparative transcriptome analysis revealed resistance differences of Cavendish bananas to Fusarium oxysporum f.sp. cubense race1 and race4

Background

Banana Fusarium wilt is a devastating disease of bananas caused by Fusarium oxysporum f. sp. cubense (Foc) and is a serious threat to the global banana industry. Knowledge of the pathogenic molecular mechanism and interaction between the host and Foc is limited.

Results

In this study, we confirmed the changes of gene expression and pathways in the Cavendish banana variety ‘Brazilian’ during early infection with Foc1 and Foc4 by comparative transcriptomics analysis. 1862 and 226 differentially expressed genes (DEGs) were identified in ‘Brazilian’ roots at 48 h after inoculation with Foc1 and Foc4, respectively. After Foc1 infection, lignin and flavonoid synthesis pathways were enriched. Glucosinolates, alkaloid-like compounds and terpenoids were accumulated. Numerous hormonal- and receptor-like kinase (RLK) related genes were differentially expressed. However, after Foc4 infection, the changes in these pathways and gene expression were almost unaffected or weakly affected. Furthermore, the DEGs involved in biological stress-related pathways also significantly differed after infection within two Foc races. The DEGs participating in phenylpropanoid metabolism and cell wall modification were also differentially expressed. By measuring the expression patterns of genes associated with disease defense, we found that five genes that can cause hypersensitive cell death were up-regulated after Foc1 infection. Therefore, the immune responses of the plant may occur at this stage of infection.

Conclusion

Results of this study contribute to the elucidation of the interaction between banana plants and Foc and to the development of measures to prevent banana Fusarium wilt.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12863-020-00926-3.

Molecular Characterization of a Pathogen-Inducible Bidirectional Promoter from Hot Pepper (Capsicum annuum)

In hot pepper, the sesquiterpene phytoalexin capsidiol is catalyzed by the two final-step enzymes, a sesquiterpene cyclase (EAS) and a hydroxylase (EAH), which are genetically linked and present as head-to-head orientation in the genome. Transcriptomic analysis revealed that a subset of EAS and EAH is highly induced following pathogen infection, suggesting the coregulation of EAS and EAH by a potential bidirectional activity of the promoter (pCaD). A series of the nested deletions of pCaD in both directions verified the bidirectional promoter activity of the pCaD. Promoter deletion analysis revealed that the 226 bp of the adjacent promoter region of EAS and GCC-box in EAH orientation were determined as critical regulatory elements for the induction of each gene. Based on promoter analyses, we generated a set of synthetic promoters to maximize reporter gene expression within the minimal length of the promoter in both directions. We found that the reporter gene expression was remarkably induced upon infection with Phytophthora capsici, Phytophthora infestans, and bacterial pathogen Pseudomonas syringae pv. tomato DC3000 but not with necrotrophic fungi Botrytis cinerea. Our results confirmed the bidirectional activity of the pCaD located between the head-to-head oriented phytoalexin biosynthetic genes in hot pepper. Furthermore, the synthetic promoter modified in pCaD could be a potential tool for pathogen-inducible expression of target genes for developing disease-resistant crops.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Transcriptional Changes of Plant Defense-Related Genes in Response to Clavibacter Infection in Pepper and Tomato

Pepper and tomato plants infected with two Clavibacter species, C. capsici and C. michiganensis have shown different patterns of disease development depending on their virulence. Here, we investigated how pepper and tomato plants respond to infection by the high-virulent or low-virulent Clavibacter strains. For this, we chose two strains of each Clavibacter species to show different virulence level in the host plants. Although low-virulent strains showed less disease symptoms, they grew almost the same level as the high-virulent strains in both plants. To further examine the response of host plants to Clavibacter infection, we analyzed the expression patterns of plant defense-related genes in the leaves inoculated with different strains of C. capsici and C. michiganensis. Pepper plants infected with high-virulent C. capsici strain highly induced the expression of CaPR1, CaDEF, CaPR4b, CaPR10, and CaLOX1 at 5 days after inoculation (dai), but their expression was much less in low-virulent Clavibacter infection. Expression of CaSAR8.2 was induced at 2 dai, regardless of virulence level. Expression of GluA, Pin2, and PR2 in tomato plants infected with high-virulent C. michiganensis were much higher at 5 dai, compared with mock or low-virulent strain. Expression of PR1a, Osmotin-like, Chitinase, and Chitinase class 2 was increased, regardless of virulence level. Expression of LoxA gene was not affected by Clavibacter inoculation. These results suggested that Clavibacter infection promotes induction of certain defense-related genes in host plants and that differential expression of those genes by low-virulent Clavibacter infection might be affected by their endophytic lifestyle in plants.

Systematic analysis of the Capsicum ERF transcription factor family: identification of regulatory factors involved in the regulation of species-specific metabolites

BACKGROUND

ERF transcription factors (TFs) belong to the Apetala2/Ethylene responsive Factor (AP2/ERF) TF family and play a vital role in plant growth and development processes. Capsorubin and capsaicinoids have relatively high economic and nutritional value, and they are specifically found in Capsicum. However, there is little understanding of how ERFs participate in the regulatory networks of capsorubin and capsaicinoids biosynthesis.

RESULTS

In this study, a total of 142 ERFs were identified in the Capsicum annuum genome. Subsequent phylogenetic analysis allowed us to divide ERFs into DREB (dehydration responsive element binding proteins) and ERF subfamilies, and further classify them into 11 groups with several subgroups. Expression analysis of biosynthetic pathway genes and CaERFs facilitated the identification of candidate genes related to the regulation of capsorubin and capsaicinoids biosynthesis; the candidates were focused in cluster C9 and cluster C10, as well as cluster L3 and cluster L4, respectively. The expression patterns of CaERF82, CaERF97, CaERF66, CaERF107 and CaERF101, which were found in cluster C9 and cluster C10, were consistent with those of accumulating of carotenoids (β-carotene, zeaxanthin and capsorubin) in the pericarp. In cluster L3 and cluster L4, the expression patterns of CaERF102, CaERF53, CaERF111 and CaERF92 were similar to those of the accumulating capsaicinoids. Furthermore, CaERF92, CaERF102 and CaERF111 were found to be potentially involved in temperature-mediated capsaicinoids biosynthesis.

CONCLUSION

This study will provide an extremely useful foundation for the study of candidate ERFs in the regulation of carotenoids and capsaicinoids biosynthesis in peppers.

Tissue-specific synergistic bio-priming of pepper by two Streptomyces species against Phytophthora capsici

Among several studied strains, Streptomyces rochei IT20 and S. vinaceusdrappus SS14 showed a high level of inhibitory effect against Phytophthora capsici, the causal agent of pepper blight. The effect of two mentioned superior antagonists, as single or combination treatments, on suppression of stem and fruit blight diseases and reproductive growth promotion was investigated in pepper. To explore the induced plant defense reactions, ROS generation and transcriptional changes of selected genes in leaf and fruit tissues of the plant were evaluated. The plants exposed to the combination of two species responded differently in terms of H₂O₂ accumulation and expression ratio of GST gene compared to single treatments upon pathogen inoculation. Besides, the increment of shoot length, flowering, and fruit weight were observed in healthy plants compared to control. Likely, these changes depended on the coordinated relationships between PR1, ACCO genes and transcription factors WRKY40 enhanced after pathogen challenge. Our findings indicate that appropriate tissue of the host plant is required for inducing Streptomyces-based priming and relied on the up-regulation of SUS and differential regulation of ethylene-dependent genes.

The CaChiVI2 Gene of Capsicum annuum L. Confers Resistance Against Heat Stress and Infection of Phytophthora capsici

Extreme environmental conditions seriously affect crop growth and development, resulting in substantial reduction in yield and quality. However, chitin-binding proteins (CBP) family member CaChiVI2 plays a crucial role in eliminating the impact of adverse environmental conditions, such as cold and salt stress. Here, for the first time it was discovered that CaChiVI2 (Capana08g001237) gene of pepper (Capsicum annuum L.) had a role in resistance to heat stress and physiological processes. The full-length open-reading frame (ORF) of CaChiVI2 (606-bp, encoding 201-amino acids), was cloned into TRV2:CaChiVI2 vector for silencing. The CaChiVI2 gene carries heat shock elements (HSE, AAAAAATTTC) in the upstream region, and thereby shows sensitivity to heat stress at the transcriptional level. The silencing effect of CaChiVI2 in pepper resulted in increased susceptibility to heat and Phytophthora capsici infection. This was evident from the severe symptoms on leaves, the increase in superoxide (O2 -) and hydrogen peroxide (H2O2) accumulation, higher malondialdehyde (MDA), relative electrolyte leakage (REL) and lower proline contents compared with control plants. Furthermore, the transcript level of other resistance responsive genes was also altered. In addition, the CaChiIV2-overexpression in Arabidopsis thaliana showed mild heat and drought stress symptoms and increased transcript level of a defense-related gene (AtHSA32), indicating its role in the co-regulation network of the plant. The CaChiVI2-overexpressed plants also showed a decrease in MDA contents and an increase in antioxidant enzyme activity and proline accumulation. In conclusion, the results suggest that CaChiVI2 gene plays a decisive role in heat and drought stress tolerance, as well as, provides resistance against P. capsici by reducing the accumulation of reactive oxygen species (ROS) and modulating the expression of defense-related genes. The outcomes obtained here suggest that further studies should be conducted on plants adaptation mechanisms in variable environments.

Identification of Pepper CaSBP08 Gene in Defense Response Against Phytophthora capsici Infection

Little information is available on the role of Squamosa promoter binding protein (SBP)-box genes in pepper plants. This family of genes is known to have transcription characteristics specific to plants and to regulate plant growth, development, stress responses, and signal transduction. To investigate their specific effects in pepper (Capsicum annuum), we screened pepper SBP-box family genes (CaSBP genes) for Phytophthora capsici (P. capsici) resistance genes using virus-induced gene silencing. CaSBP08, CaSBP11, CaSBP12, and CaSBP13, which are associated with plant defense responses against P. capsici, were obtained from among fifteen identified CaSBP genes. The function of CaSBP08 was identified in pepper defense response against P. capsici infection in particular. CaSBP08 protein was localized to the nucleus. Silencing of CaSBP08 enhanced resistance to P. capsici infection. Following P. capsici inoculation, the malondialdehyde content, peroxidase activity, and disease index percentage of the CaSBP08-silenced plants decreased compared to the control. Additionally, the expression levels of other defense-related genes, especially those of CaBPR1 and CaSAR8.2, were more strongly induced in CaSBP08-silenced plants than in the control. However, CaSBP08 overexpression in Nicotiana benthamiana enhanced susceptibility to P. capsici infection. This work provides a foundation for the further research on the role of CaSBP genes in plant defense responses against P. capsici infection.

Apple ethylene response factor MdERF11 confers resistance to fungal pathogen Botryosphaeria dothidea

Ethylene response factor (ERF) is a plant-specific transcription factor involved in many biological processes including root formation, hypocotyl elongation, fruit ripening, organ senescence and stress responses, as well as fruit quality formation. However, its underlying mechanism in plant pathogen defense against Botryosphaeria dothidea (B. dothidea) remains poorly understood. Here, we isolate MdERF11, an apple nucleus-localized ERF transcription factor, from apple cultivar 'Royal Gala'. qRT-PCR assays show that the expression of MdERF11 is significantly induced in apple fruits after B. dothidea infection. Overexpression of MdERF11 gene in apple calli significantly increases the resistance to B.dothidea infection, while silencing MdERF11 in apple calli results in reduced resistance. Ectopic expression of MdERF11 in Arabidopsis also exhibits enhanced resistance to B. dothidea infection compared to that of wild type. Infections in apple calli and Arabidopsis leaves by B. dothidea respectively cause an increase in endogenous levels of salicylic acid (SA) followed by induction of SA synthesis-related and signaling-related gene expression. Taken together, these findings illustrate a potential mechanism by which MdERF11 elevates plant pathogen defense against B. dothidea by regulating SA synthesis pathway.

Identification of CBL and CIPK gene families and functional characterization of CaCIPK1 under Phytophthora capsici in pepper (Capsicum annuum L.)

Background

Calcineurin B-like proteins (CBLs) are major Ca²⁺ sensors that interact with CBL-interacting protein kinases (CIPKs) to regulate growth and development in plants. The CBL-CIPK network is involved in stress response, yet little is understood on how CBL-CIPK function in pepper (Capsicum annuum L.), a staple vegetable crop that is threatened by biotic and abiotic stressors.

Results

In the present study, nine CaCBL and 26 CaCIPK genes were identified in pepper and the genes were named based on their chromosomal order. Phylogenetic and structural analysis revealed that CaCBL and CaCIPK genes clustered in four and five groups, respectively. Quantitative real-time PCR (qRT-PCR) assays showed that CaCBL and CaCIPK genes were constitutively expressed in different tissues, and their expression patterns were altered when the plant was exposed to Phytophthora capsici, salt and osmotic stress. CaCIPK1 expression changed in response to stress, including exposure to P. capsici, NaCl, mannitol, salicylic acid (SA), methyl jasmonate (MeJA), abscisic acid (ABA), ethylene (ETH), cold and heat stress. Knocking down CaCIPK1 expression increased the susceptibility of pepper to P. capsici, reduced root activity, and altered the expression of defense related genes. Transient overexpression of CaCIPK1 enhanced H₂O₂ accumulation, cell death, and expression of genes involved in defense.

Conclusions

Nine CaCBL and 26 CaCIPK genes were identified in the pepper genome, and the expression of most CaCBL and CaCIPK genes were altered when the plant was exposed to stress. In particular, we found that CaCIPK1 is mediates the pepper plant’s defense against P. capsici. These results provide the groundwork for further functional characterization of CaCBL and CaCIPK genes in pepper.

Knockdown of the chitin-binding protein family gene CaChiIV1 increased sensitivity to Phytophthora capsici and drought stress in pepper plants

Phytophthora capsici has been the most destructive pathogen of pepper plants (Capsicum annuum L.), possessing the ability to quickly overcome the host defense system. In this context, the chitin-binding protein (CBP) family member CaChiIV1 regulates the response to P. capsici and abiotic stresses. The relevance of functional characterization and regulation of CaChiIV1 has not been explored in horticultural crops, especially pepper plants. The target gene (CaChiIV1) was isolated from pepper plants and cloned; the encoded protein carries a chitin-binding domain (CBD) that is rich in cysteine residues and has a hinge region with an abundance of proline and glycine residues. Additionally, the conserved regions in the promoter have a remarkable motif, "TTGACC". The expression of CaChiIV1 was markedly regulated by methyl-jasmonate (MeJA), hydrogen peroxide (H₂O₂), melatonin, mannitol and P. capsici (PC and HX-9) infection. Knockdown of CaChiIV1 in pepper plants increased sensitivity to P. capsici (PC strain). Higher malondialdehyde (MDA) content and relative electrolyte leakage (REL) but lower antioxidant enzyme activities, chlorophyll content, root activity, and proline content were observed in CaChiIV1-silenced plants than in control plants. In conclusion, CaChiIV1-silenced pepper plants displayed increased susceptibility to P. capsici infection due to changes in expression of defense-related genes, thus showing its coregulation affect in particular conditions. Furthermore, antioxidant enzymes and proline content were largely diminished in CaChiIV1-silenced plants. Therefore, this evidence suggests that the CaChiIV1 gene plays a prominent role in the defense mechanism of pepper plants against P. capsici infection. In the future, the potential role of the CaChiIV1 gene in defense regulatory pathways and its coregulation with other pathogen-related genes should be identified.

The CaAP2/ERF064 Regulates Dual Functions in Pepper: Plant Cell Death and Resistance to Phytophthora capsici

Phytophthora blight is one of the most destructive diseases of pepper (Capsicum annuum L.) globally. The APETALA2/Ethylene Responsive Factors (AP2/ERF) genes play a crucial role in plant response to biotic stresses but, to date, have not been studied in the context of Phytophthora resistance in pepper. Here, we documented potential roles for the pepper CaAP2/ERF064 gene in inducing cell death and conferring resistance to Phytophthora capsici (P. capsici) infection. Results revealed that the N-terminal, AP2 domain, and C-terminal of CaAP2/ERF064 protein is responsible for triggering cell death in Nicotiana benthamiana (N. benthamiana). Moreover, the transcription of CaAP2/ERF064 in plant is synergistically regulated by the Methyl-Jasmonate (MeJA) and ethephon (ET) signaling pathway. CaAP2/ERF064 was found to regulate the expression of CaBPR1, which is a pathogenesis-related (PR) gene of pepper. Furthermore, the silencing of CaAP2/ERF064 compromised the pepper plant resistance to P.capsici by reducing the transcript level of defense-related genes CaBPR1, CaPO2, and CaSAR82, while the ectopic expression of CaAP2/ERF064 in N. benthamiana plant elevated the expression level of NbPR1b and enhanced resistance to P.capsici. These results suggest that CaAP2/ERF064 could positively regulate the defense response against P. capsici by modulating the transcription of PR genes in the plant.

Knockdown of the chitin-binding protein family gene CaChiIV1 increased sensitivity to Phytophthora capsici and drought stress in pepper plants

Phytophthora capsici has been the most destructive pathogen of pepper plants (Capsicum annuum L.), possessing the ability to quickly overcome the host defense system. In this context, the chitin-binding protein (CBP) family member CaChiIV1 regulates the response to P. capsici and abiotic stresses. The relevance of functional characterization and regulation of CaChiIV1 has not been explored in horticultural crops, especially pepper plants. The target gene (CaChiIV1) was isolated from pepper plants and cloned; the encoded protein carries a chitin-binding domain (CBD) that is rich in cysteine residues and has a hinge region with an abundance of proline and glycine residues. Additionally, the conserved regions in the promoter have a remarkable motif, "TTGACC". The expression of CaChiIV1 was markedly regulated by methyl-jasmonate (MeJA), hydrogen peroxide (H₂O₂), melatonin, mannitol and P. capsici (PC and HX-9) infection. Knockdown of CaChiIV1 in pepper plants increased sensitivity to P. capsici (PC strain). Higher malondialdehyde (MDA) content and relative electrolyte leakage (REL) but lower antioxidant enzyme activities, chlorophyll content, root activity, and proline content were observed in CaChiIV1-silenced plants than in control plants. In conclusion, CaChiIV1-silenced pepper plants displayed increased susceptibility to P. capsici infection due to changes in expression of defense-related genes, thus showing its coregulation affect in particular conditions. Furthermore, antioxidant enzymes and proline content were largely diminished in CaChiIV1-silenced plants. Therefore, this evidence suggests that the CaChiIV1 gene plays a prominent role in the defense mechanism of pepper plants against P. capsici infection. In the future, the potential role of the CaChiIV1 gene in defense regulatory pathways and its coregulation with other pathogen-related genes should be identified.

A Novel Transcription Factor CaSBP12 Gene Negatively Regulates the Defense Response against Phytophthora capsici in Pepper (Capsicum annuum L.)

SBP-box (Squamosa-promoter binding protein) genes are a type of plant-specific transcription factor and play important roles in plant growth, signal transduction and stress response. However, little is known about the SBP-box genes in pepper (CaSBP), especially in the process of Phytophthora capsici infection. In this study, a novel gene (CaSBP12) was selected from the CaSBP gene family, which was isolated from the pepper genome database in our previous study. The CaSBP12 gene was located in the nucleus of the cell and its silencing in the pepper plant enhanced the defense response against Phytophthora capsici infection. After inoculation with Phytophthora capsici, the root activity of the CaSBP12-silenced plants is compared to control plants, while malondialdehyde (MDA) content is compared viceversa. Additionally, the expression of defense related genes (CaPO1, CaSAR8.2, CaBPR1, and CaDEF1) in the silenced plants were induced to different degrees and the peak of CaSAR8.2 and CaBPR1 were higher than that of CaDEF1. The CaSBP12 over-expressed Nicotiana benthamiana plants were more susceptible to Phytophthora capsici infection with higher EC (electrical conductivity) and MDA contents as compared to the wild-type. The relative expression of defense related genes (NbDEF, NbNPR1, NbPR1a, and NbPR1b) in transgenic and wild-type Nicotiana benthamiana plants were induced, especially the NbPR1a and NbPR1b. In conclusion, these results indicate that CaSBP12 gene negative regulates the defense response against Phytophthora capsici infection which suggests their potentially significant role in plant defense. To our knowledge, this is the first report on CaSBP gene which negative regulate defense response.

Genome-wide identification of the AP2/ERF transcription factor family in pepper (Capsicum annuum L.)

The AP2/ERF family is one of the largest transcription factor families in the plant kingdom. AP2/ERF genes contributing to various processes including plant growth, development, and response to various stresses have been identified. In this study, 175 putative AP2/ERF genes were identified in the latest pepper genome database and classified into AP2, RAV, ERF, and Soloist subfamilies. Their chromosomal localization, gene structure, conserved motif, cis-acting elements within the promoter region, and subcellular locations were analyzed. Transient expression of CaAP2/ERF proteins in tobacco revealed that CaAP2/ERF064, CaAP2/ERF109, and CaAP2/ERF127 were located in the nucleus, while CaAP2/ERF171 was located in the nucleus and cytoplasm. Most of the CaAP2/ERF genes contained cis-elements within their promoter regions that responded to various stresses (HSE, LTR, MBS, Box-W1/W-box, and TC-rich repeats) and phytohormones (ABRE, CGTCA-motif, and TCA-element). Furthermore, RNA-seq analysis revealed that CaAP2/ERF genes showed differential expression profiles in various tissues as well as under biotic stresses. Moreover, qRT-PCR analysis of eight selected CaAP2/ERF genes also showed differential expression patterns in response to infection with Phytophthora capsici (HX-9) and in response to phytohormones (SA, MeJA, and ETH). This study will provide basic insights for further studies of the CaAP2/ERF genes involved in the interaction between pepper and P. capsici.

Genome-wide identification of the auxin/indole-3-acetic acid (Aux/IAA) gene family in pepper, its characterisation, and comprehensive expression profiling under environmental and phytohormones stress

Auxin is an essential phytohormone that plays a crucial role in the growth and development of plants in stressful environments. Here, we analysed the auxin/indole-3-acetic acid (Aux/IAA) gene family, which produces auxin in pepper, and succeeded in identifying 27 putative members containing four conserved domains (I. II. III and IV) in their protein sequences. Sequence analysis, chromosomal mapping and motif prediction of all identified CaAux/IAA genes were performed. It was observed that these genes contained four conserved motifs divided into nine different groups and distributed across nine chromosomes in pepper plants. RNA-seq analysis revealed the organ specific expression of many CaAux/IAA genes. However, the majority of genes were expressed with high expression levels in the early stages of fruit development. However, the maximum expression level of the CA03g34540 gene was observed in the breaker stage. Moreover, thirteen CaAux/IAA genes were labelled as early responsive genes to various phytohormone and abiotic stresses. Furthermore, RNA-seq analysis in response to pathogen inoculation (PepMoV, TMV strains P0/P1, and Phytophthora capsici) showed distinct expression profiles of all identified genes, suggesting the diverse expression nature of genes under these stress conditions. Overall, this study provides insight into the dynamic response of CaAux/IAA genes under environmental and phytohormones stress conditions, providing bases to further explore the importance of these genes through mutant/transgenic analysis in pepper.

Classification and Genome-Wide Analysis of Chitin-Binding Proteins Gene Family in Pepper (Capsicum annuum L.) and Transcriptional Regulation to Phytophthora capsici, Abiotic Stresses and Hormonal Applications

Chitin-binding proteins are pathogenesis-related gene family, which play a key role in the defense response of plants. However, thus far, little is known about the chitin-binding family genes in pepper (Capsicum annuum L.). In current study, 16 putative chitin genes (CaChi) were retrieved from the latest pepper genome database, and were classified into four distinct classes (I, III, IV and VI) based on their sequence structure and domain architectures. Furthermore, the structure of gene, genome location, gene duplication and phylogenetic relationship were examined to clarify a comprehensive background of the CaChi genes in pepper. The tissue-specific expression analysis of the CaChi showed the highest transcript levels in seed followed by stem, flower, leaf and root, whereas the lowest transcript levels were noted in red-fruit. Phytophthora capsici post inoculation, most of the CaChi (CaChiI3, CaChiIII1, CaChiIII2, CaChiIII4, CaChiIII6, CaChiIII7, CaChiIV1, CaChiVI1 and CaChiVI2) were induced by both strains (PC and HX-9). Under abiotic and exogenous hormonal treatments, the CaChiIII2, CaChiIII7, CaChiVI1 and CaChiVI2 were upregulated by abiotic stress, while CaChiI1, CaChiIII7, CaChiIV1 and CaChiIV2 responded to hormonal treatments. Furthermore, CaChiIV1-silenced plants display weakened defense by reducing (60%) root activity and increase susceptibility to NaCl stress. Gene ontology (GO) enrichment analysis revealed that CaChi genes primarily contribute in response to biotic, abiotic stresses and metabolic/catabolic process within the biological process category. These results exposed that CaChi genes are involved in defense response and signal transduction, suggesting their vital roles in growth regulation as well as response to stresses in pepper plant. In conclusion, these finding provide basic insights for functional validation of the CaChi genes in different biotic and abiotic stresses.

Challenges and Strategies for Breeding Resistance in Capsicum annuum to the Multifarious Pathogen, Phytophthora capsici

Phytophthora capsici is the most devastating pathogen for chile pepper production worldwide and current management strategies are not effective. The population structure of the pathogen is highly variable and few sources of widely applicable host resistance have been identified. Recent genomic advancements in the host and the pathogen provide important insights into the difficulties reported by epidemiological and physiological studies published over the past century. This review highlights important challenges unique to this complex pathosystem and suggests strategies for resistance breeding to help limit losses associated with P. capsici.

Genome-wide analysis of dirigent gene family in pepper (Capsicum annuum L.) and characterization of CaDIR7 in biotic and abiotic stresses

The dirigent (DIR and DIR-like) proteins involved in lignification, play a pivotal role against biotic and abiotic stresses in plants. However, no information is available about DIR gene family in pepper (Capsicum annuum L.). In this study, 24 putative dirigent genes (CaDIRs) were identified, their gene structure, genome location, gene duplication and phylogenetic relationship were elucidated. Tissue-specific expression analysis displayed the highest transcription levels in flower, stem and leaf. Some CaDIRs were up-regulated by virulent (CaDIR2, 3, 6, 7, 11, 14, 16, 22 and 23) and avirulent (CaDIR3, 5, 7, 16, 20, 22, 23 and 24) Phytophthora capsici strains, as well as by Methyl jasmonate, salicylic acid, NaCl and mannitol stresses. Acid-soluble lignin content increased (103.21%) after P. capsici inoculation (48-hour). Silencing of CaDIR7 weakened plant defense by reducing (~50%) root activity and made plants more susceptible (35.7%) to P. capsici and NaCl (300 mM). Leaf discs of the CaDIR7:silenced plants exposed to NaCl and mannitol (300 mM each), exhibited a significant decrease (56.25% and 48% respectively) in the chlorophyll content. These results suggested that CaDIR7 is involved in pepper defense response against pathogen and abiotic stresses and the study will provide basic insights for future research regarding CaDIRs.

Comparative Digital Gene Expression Analysis of Tissue-Cultured Plantlets of Highly Resistant and Susceptible Banana Cultivarsin Response to Fusarium oxysporum

Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is one of the most destructive soil-borne diseases. In this study, young tissue-cultured plantlets of banana (Musa spp. AAA) cultivars differing in Foc susceptibility were used to reveal their differential responses to this pathogen using digital gene expression (DGE). Data were evaluated by various bioinformatic tools (Venn diagrams, gene ontology (GO) annotation and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses) and immunofluorescence labelling method to support the identification of gene candidates determining the resistance of banana against Foc. Interestingly, we have identified MaWRKY50 as an important gene involved in both constitutive and induced resistance. We also identified new genes involved in the resistance of banana to Foc, including several other transcription factors (TFs), pathogenesis-related (PR) genes and some genes related to the plant cell wall biosynthesis or degradation (e.g., pectinesterases, β-glucosidases, xyloglucan endotransglucosylase/hydrolase and endoglucanase). The resistant banana cultivar shows activation of PR-3 and PR-4 genes as well as formation of different constitutive cell barriers to restrict spreading of the pathogen. These data suggest new mechanisms of banana resistance to Foc.

Virus-Induced Gene Silencing (VIGS) in Aegilops tauschii and Its Use in Functional Analysis of AetDREB2

Among the available reverse genetic approaches for studying gene function, virus-induced gene silencing (VIGS) has several advantages. It allows rapid characterization of gene function independent of stable transformation, which is basically difficult to achieve in monocots, and offers the potential to silence individual or multiple genes of a gene family. In order to establish a VIGS system in Aegilops tauschii, modified vectors derived from Barley stripe mosaic virus (BSMV) were used for silencing a phytoene desaturase gene that provides a convenient visual reporter for silencing. The results demonstrated a high efficiency of BSMV-VIGS in A. tauschii. Moreover, the BSMV-VIGS system was used to target a 354 bp specific region of the Dehydration-responsive element-binding (AetDreb2) gene, resulting in successful silencing of the gene in A. tauschii plants, as verified by real-time qRT-PCR. Indeed, in comparison with plants that were inoculated with an empty vector (BSMV:00), a faster rate of wilting and a lower relative water content were observed in plants inoculated with BSMV:AetDreb2 when they were exposed to drought stress. Therefore, BSMV-VIGS can be efficiently employed as a novel tool for reverse genetics in A. tauschii. It can also be used to study the effects of polyploidization on the gene function by a comparative analysis between bread wheat and its diploid progenitor.

A novel Gossypium barbadense ERF transcription factor, GbERFb, regulation host response and resistance to Verticillium dahliae in tobacco

Ethylene-responsive factors (ERFs) are commonly considered to play an important role in pathogen defense responses. However, only few of ERF members have been characterized in Sea island cotton (Gossypium barbadense). Here, we reported a novel AP2/ERF transcription factors gene, named GbERFb which was cloned and identified from Sea island cotton by RACE. The expression of GbERFb was significantly induced by treatments with ethylene, Methyl jasmonate, salicylic acid, wounding, H₂O₂ and Verticillium dahliae (V. dahliae) infection. Bioinformatics analysis showed that GbERFb protein containing a conserved ERF DNA binding domain and a nuclear localization signal sequence, belonged to IXb subgroup of the ERF family. Further experiments demonstrated that GbERFb could bind the GCC box cis-acting element and interact with GbMAPKb (MAP kinase) directly in yeast. Over-expression of GbERFb in tobacco could increase the disease resistance to V. dahliae. The results suggest that the GbERFb, a new AP2/ERF transcription factor, could enhance the resistance to V. dahliae and be useful in improvement of crop resistance to pathogenes.