Roles In Plant Defense Responses Research Articles

GhWRKY75 positively regulates GhPR6-5b via binding to a W-box TTGAC (C/T) to orchestrate cotton resistance to Verticillium dahliae

Verticillium dahliae is an important fungal pathogen affecting cotton yield and quality. Therefore, the mining of V. dahlia-resistance genes has important implications and is urgently required. Protease and protease inhibitors play crucial roles in plant defense responses. However, little is known regarding the functions and regulatory mechanisms of the protease inhibitor PR6 gene family. This study conducted a comprehensive analysis of the PR6 gene family within the cotton genome. We performed genome-wide identification and functional characterization of the cotton GhPR6 gene family, which belongs to the potato protease inhibitor I family of inhibitors. Thirty-nine PR6s were identified in Gossypium arboreum, G. raimondii, G. barbadense, and G. hirsutum and were clustered into four groups. Based on the analysis of pathogen-induced and Ghlmm transcriptome data, the key gene for V. dahliae resistance, GhPR6-5b, was identified. Virus-induced gene silencing experiments revealed that cotton was more sensitive to V. dahliae V991 after PR6-5b silencing. The present study established that GhWRKY75 plays an important role in resistance to cotton Verticillium wilt by positively regulating GhPR6-5b expression by directly binding to W-box TTGAC(T/C). Our findings established that GhWRKY75 is a potential candidate for improving cotton resistance to V. dahliae, providing primary information for further investigations and the development of specific strategies to bolster the defense mechanisms of cotton against V. dahliae.

Genome-Wide Identification of Calmodulin-Binding Protein 60 Gene Family and the Function of GhCBP60B in Cotton Growth and Development and Abiotic Stress Response.

The calmodulin-binding protein 60 (CBP60) family is a gene family unique to plants, and its members play a crucial role in plant defense responses to pathogens and growth and development. Considering that cotton is the primary source of natural cotton textile fiber, the functional study of its CBP60 gene family members is critical. In this research, we successfully identified 162 CBP60 members from the genomes of 21 species. Of these, 72 members were found in four cotton species, divided into four clades. To understand the function of GhCBP60B in cotton in depth, we conducted a detailed analysis of its sequence, structure, cis-acting elements, and expression patterns. Research results show that GhCBP60B is located in the nucleus and plays a crucial role in cotton growth and development and response to salt and drought stress. After using VIGS (virus-induced gene silencing) technology to conduct gene silencing experiments, we found that the plants silenced by GhCBP60B showed dwarf plants and shortened stem nodes, and the expression of related immune genes also changed. In further abiotic stress treatment experiments, we found that GhCBP60B-silenced plants were more sensitive to drought and salt stress, and their POD (peroxidase) activity was also significantly reduced. These results imply the vital role of GhCBP60B in cotton, especially in regulating plant responses to drought and salt stress. This study systematically analyzed CBP60 gene family members through bioinformatics methods and explored in depth the biological function of GhCBP60B in cotton. These research results lay a solid foundation for the future use of the GhCBP60B gene to improve cotton plant type and its drought and salt resistance.

Combining association with linkage mapping to dissect the phenolamides metabolism of the maize kernel.

Phenolamides are important secondary metabolites in plant species. They play important roles in plant defense responses against pathogens and insect herbivores, protection against UV irradiation and floral induction and development. However, the accumulation and variation in phenolamides content in diverse maize lines and the genes responsible for their biosynthesis remain largely unknown. Here, we combined genetic mapping, protein regulatory network and bioinformatics analysis to further enhance the understanding of maize phenolamides biosynthesis. Sixteen phenolamides were identified in multiple populations, and they were all significantly correlated with one or several of 19 phenotypic traits. By linkage mapping, 58, 58, 39 and 67 QTLs, with an average of 3.9, 3.6, 3.6 and 4.2 QTLs for each trait were mapped in BBE1, BBE2, ZYE1 and ZYE2, explaining 9.47%, 10.78%, 9.51% and 11.40% phenotypic variation for each QTL on average, respectively. By GWAS, 39 and 36 significant loci were detected in two different environments, 3.3 and 2.8 loci for each trait, explaining 10.00% and 9.97% phenotypic variation for each locus on average, respectively. Totally, 58 unique candidate genes were identified, 31% of them encoding enzymes involved in amine and derivative metabolic processes. Gene Ontology term analysis of the 358 protein-protein interrelated genes revealed significant enrichment in terms relating to cellular nitrogen metabolism, amine metabolism. GRMZM2G066142, GRMZM2G066049, GRMZM2G165390 and GRMZM2G159587 were further validated involvement in phenolamides biosynthesis. Our results provide insights into the genetic basis of phenolamides biosynthesis in maize kernels, understanding phenolamides biosynthesis and its nutritional content and ability to withstand biotic and abiotic stress.

Superior haplotypes towards the development of blast and bacterial blight-resistant rice.

Rice blast and bacterial leaf blight, are major disease, significantly threatens rice yield in all rice growing regions under favorable conditions and identification of resistance genes and their superior haplotypes is a potential strategy for effectively managing and controlling this devastating disease. In this study, we conducted a genome-wide association study (GWAS) using a diverse set of 147 rice accessions for blast and bacterial blight diseases in replications. Results revealed 23 (9 for blast and 14 for BLB) significant marker-trait associations (MTAs) that corresponded to 107 and 210 candidate genes for blast and BLB, respectively. The haplo-pheno analysis of the candidate genes led to the identification of eight superior haplotypes for blast, with an average SES score ranging from 0.00 to 1.33, and five superior haplotypes for BLB, with scores ranging from 1.52cm to 4.86cm superior haplotypes. Among these, superior haplotypes LOC_OS12G39700-H4 and LOC_Os06g30440-H33 were identified with the lowest average blast scores of 0.00-0.67, and superior haplotype LOC_Os02g12660-H39 exhibited the lowest average lesion length (1.88 - 2.06cm) for BLB. A total of ten accessions for blast and eight accessions for BLB were identified carrying superior haplotypes were identified. These haplotypes belong to aus and indx subpopulations of five countries (Bangladesh, Brazil, India, Myanmar, and Pakistan). For BLB resistance, eight accessions from six countries (Bangladesh, China, India, Myanmar, Pakistan, and Sri Lanka) and four subpopulations (aus, ind1A, ind2, and ind3) were identified carrying superior haplotypes. Interestingly, four candidate genes, LOC_Os06g21040, LOC_Os04g23960, LOC_Os12g39700, and LOC_Os01g24640 encoding transposon and retrotransposon proteins were among those with superior haplotypes known to play a crucial role in plant defense responses. These identified superior haplotypes have the potential to be combined into a single genetic background through haplotype-based breeding for a broader resistance spectrum against blast and bacterial blight diseases.

Quantitative proteomics analysis identified new interacting proteins of JAL30 in Arabidopsis

Jacalin-related lectins (JALs) are a unique group of plant lectins derived from the jacalin protein family, which play important roles in plant defense responses. JAL30/PBP1 (PYK10 binding protein 1) interacts with inactive PYK10, exerting negative regulatory control over the size of the PYK10 complex, which is formed and activated upon insect or pathogen invasion. However, the precise interplay between JAL30 and other components remains elusive. In this study, we found JAL30 as a nucleocytoplasmic protein, but no obvious phenotype was observed in jal30–1 single mutant. Through immunoprecipitation (IP) enrichment combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS), dozens of new JAL30 interacting proteins were found in addition to several reported ones. Gene Ontology (GO) analysis revealed that these interacting proteins were highly related to the wounding and bacterial stimuli, suggesting their potential involvement in the jasmonate (JA) response. Importantly, the expression of JAL30 was induced by MeJA treatment, further highlighting its relevance in plant defense mechanisms. A novel JAL30 interacting protein, ESM1, was identified and its interaction with JAL30 was confirmed by Co-immunoprecipitation. Moreover, ESM1 was found as an O-GlcNAcylated protein, suggesting that JAL30 may possess glycosylated protein binding ability, particularly in O-GlcNAcylated protein and peptide recognition. Overall, our study provides valuable insights into the interacting protein network and biological function of JAL30, demonstrates the interaction between JAL30 and ESM1, and uncovers the potential significance of JAL30 in plant defense system, potentially through its association with PYK10 complex or JA response. SignificanceThe biological functions of lectin proteins, including defense responses, immunity responses, signal transduction, have been well studied. Lectin proteins were also utilized to enrich glycosylated proteins for their specific carbohydrates binding capability. Jacalin-related lectins (JALs) were found to involve in plant defense mechanism. However, it is not yet clear whether JALs could use for enrichment of glycosylated proteins. In this study, we used label-free quantification method to identify interacting proteins of JAL30. A novel interacting protein, ESM1, as an O-GlcNAcylated protein was found. ESM1 has been reported to take part in defense against insect herbivory. Therefore, our findings provided experimental evidence to confirm that JALs have potential to be developed as the bio-tools to enrich glycosylated proteins. Finally, our data not only illustrated the vital biological role of JALs in plants, but also verified unique function of JAL30 in recognizing O-GlcNAcylated proteins.

Genome-wide association study for charcoal rot resistance in soybean harvested in Kazakhstan.

Charcoal rot (CR) caused by the fungal pathogen Macrophomina phaseolina is a devastating disease affecting soybean (Glycine max (L.) Merrill.) worldwide. Identifying the genetic factors associated with resistance to charcoal rot is crucial for developing disease-resistant soybean cultivars. In this research, we conducted a genome-wide association study (GWAS) using different models and genotypic data to unravel the genetic determinants underlying soybean resistance to сharcoal rot. The study relied on a panel of 252 soybean accessions, comprising commercial cultivars and breeding lines, to capture genetic variations associated with resistance. The phenotypic evaluation was performed under natural conditions during the 2021-2022 period. Disease severity and survival rates were recorded to quantify the resistance levels in the accessions. Genotypic data consisted of two sets: the results of genotyping using the Illumina iSelect 6K SNP (single-nucleotide polymorphism) array and the results of whole-genome resequencing. The GWAS was conducted using four different models (MLM, MLMM, FarmCPU, and BLINK) based on the GAPIT platform. As a result, SNP markers of 11 quantitative trait loci associated with CR resistance were identified. Candidate genes within the identified genomic regions were explored for their functional annotations and potential roles in plant defense responses. The findings from this study may further contribute to the development of molecular breeding strategies for enhancing CR resistance in soybean cultivars. Marker-assisted selection can be efficiently employed to accelerate the breeding process, enabling the development of cultivars with improved resistance to сharcoal rot. Ultimately, deploying resistant cultivars may significantly reduce yield losses and enhance the sustainability of soybean production, benefiting farmers and ensuring a stable supply of this valuable crop.

Panax notoginseng transcription factor WRKY15 modulates resistance to Fusarium solani by up-regulating osmotin-like protein expression and inducing JA/SA signaling pathways

BackgroundPanax notoginseng (Burk) F. H. Chen is a valuable traditional Chinese medicinal plant, but its commercial production is seriously affected by root rot caused by some pathogenic fungi, including Fusarium solani. Nevertheless, the genetic breeding for disease resistance of P. notoginseng remains limited. The WRKY transcription factors have been revealed to play important roles in plant defense responses, which might provide an inspiration for resistance improvement in P. notoginseng.ResultsIn this study, the regulatory mechanism of transcription factor PnWRKY15 on P. notoginseng resistance to F. solani infection was revealed. The suppressed expression of PnWRKY15 via RNA interference increased the sensitivity of P. notoginseng to F. solani and decreased the expression levels of some defense-related genes, including PnOLP1, which encodes an osmotin-like protein that confers resistance to F. solani. Ectopic expression of PnWRKY15 in the model plant tobacco significantly enhanced the resistance to F. solani. Moreover, the transcriptome sequencing analysis discovered that some pathogenesis-related genes were expressed at higher levels in the PnWRKY15-overexpressing tobacco than that in the wild-type tobacco. In addition, the jasmonic acid (JA) and salicylic acid (SA) signaling pathways were evidently induced by PnWRKY15-overexpression, that was evidenced by that the JA and SA contents were significantly higher in the PnWRKY15-overexpressing tobacco than that in the wild-type. Furthermore, PnWRKY15, which was localized in the nucleus, can trans-activate and up-regulate PnOLP1 expression according to the EMSA, yeast one-hybrid and co-expression assays.ConclusionsPnWRKY15 contributes to P. notoginseng resistance to F. solani by up-regulating the expression of resistance-related gene PnOLP1 and activating JA/SA signaling pathways. These findings will help to further elucidate the transcriptional regulatory mechanism associated with the P. notoginseng defense response to F. solani.

A comprehensive investigation of lipid-transfer proteins from Cicer arietinum disentangles their role in plant defense against Helicoverpa armigera-infestation.

Lipid Transfer Proteins (LTPs) play a crucial role in synthesizing lipid barrier polymers and are involved in defense signaling during pest and pathogen attacks. Although LTPs are conserved with multifaceted roles in plants, these are not yet identified and characterized in Cicer arietinum. In this study, a genome-wide analysis of LTPs was executed and their physiochemical properties, biochemical function, gene structure analysis, chromosomal localization, promoter analysis, gene duplication, and evolutionary analysis were performed using in silico tools. Furthermore, tissue-specific expression analysis and gene expression analysis during pest attack was also conducted for the LTPs. A total of 48 LTPs were identified and named as CaLTPs. They were predicted to be small unstable proteins with "Glycolipid transfer protein" and "Alpha-Amylase Inhibitors, Lipid Transfer and Seed Storage" domains, that are translocated to the extracellular region. CaLTPs were predicted to possess 3-4 introns and were located on all the eight chromosomes of chickpea with half of the CaLTPs being localized on chromosomes 4, 5, and 6, and found to be closely related to LTPs of Arabidopsis thaliana and Medicago trancatula. Gene duplication and synteny analysis revealed that most of the CaLTPs have evolved due to tandem or segmental gene duplication and were subjected to purifying selection during evolution. The promoters of CaLTPs had development-related, phytohormone-responsive, and abiotic and biotic stress-related cis-acting elements. A few CaLTP transcripts exhibited differential expression in diverse tissue types, while others showed no/very low expression. Out of 20 jasmonate-regulated CaLTPs, 14 exhibited differential expression patterns during Helicoverpa armigera-infestation, indicating their role in plant defense response. This study identified and characterized CaLTPs from an important legume, C. arietinum, and indicated their involvement in plant defense against H. armigera-infestation, which can be further utilized to explore lipid signaling during plant-pest interaction and pest management.

The wheat lipid transfer protein (TdLTP2) mitigates biotic and abiotic stress damages in transgenic Arabidopsis thaliana plants

Lipid transfer proteins (LTPs) are members of the pathogenesis-related protein family 14 (PR-14), believed to play a role in plant defense responses. This study reports the overexpression of TdLTP2, a family 2 LTP from durum wheat, in Arabidopsis thaliana. Transgenic Arabidopsis plants with increased TdLTP2 expression unveiled greater tolerance to salt, abscisic acid (ABA), and salicylic acid (SA) stresses, as well as higher tolerance to oxidative stress when compared to wild type (Wt) plants. The transgenic plants also exhibited significant increases in the accumulation of antioxidant enzymes, including catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), along with decreased levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2). RT-qPCR analysis of the antioxidant enzymes confirm the role played by TdLTP2 in regulating oxidative stress under salt (100 mM NaCl) and oxidative (3 mM H2O2) stresses. Moreover, detached leaves from transgenic Arabidopsis lines expressing the TdLTP2 gene displayed enhanced resistance against fungal pathogens such as Aspergillus niger, Fusarium graminarium, Botrytis cinerea, and Alternaria solani. Finally, RT-qPCR results for biotic stress-related genes (PR1, PDF1.2, LOX3, and VSP2) showed differential expression in transgenic TdLTP2 lines when plants were treated with jasmonic acid (JA). Collectively, these findings provide evidence for the involvement of TdLTP2 gene in enhancing tolerance to both abiotic and biotic stresses in crop plants.

Over-Expression of Soybean GmSAUL1 Enhances Disease Resistance in Nicotiana tabacum

E3 ubiquitin ligases play essential roles in plant defense responses. However, their roles in other plant species have not been investigated extensively. Here, we used a gain-of-function approach to interrogate the function of GmSAUL1 (Senescence-Associated E3 Ubiquitin Ligase 1) homologs in soybeans. Ectopic over-expression of GmSAUL1a in Nicotiana tabacum resulted in autoimmune responses that could be suppressed by high temperature, which is a hallmark of NLR (nucleotide-binding leucine-rich repeat protein)-mediated resistance. Interestingly, an elevated activation of NtMPK6, but reduced activation of NtMPK4, responding to flg22 treatment, was observed in these GmSAUL1a-over-expressing tobacco lines, suggesting that over-expressing GmSAUL1a activates immune signaling through activating NtMPK6, but suppressing NtMPK4 kinase activity. Collectively, these results demonstrated that GmSAUL1 plays a positive and pivotal role in soybean immunity that is likely governed by NLR proteins.

Stilbenoids as Promising Natural Product-Based Solutions in a Race against Mycotoxigenic Fungi: A Comprehensive Review.

Exposure to mycotoxins can pose a variety of adverse health effects to mammals. Despite dozens of mycotoxin decontamination strategies applied from pre- to postharvest stages, it is always challenging to guarantee a safe level of these natural toxic compounds in food and feedstuffs. In the context of the increased occurrence of drug-resistance strains of mycotoxin-producing fungi driven by the overuse of fungicides, the search for new natural-product-based solutions is a top priority. This review aims to shed a light on the promising potential of stilbenoids extracted from renewable agricultural wastes (e.g., grape canes and forestry byproducts) as antimycotoxin agents. Deeper insights into the mode of actions underlying the bioactivity of stilbenoid molecules against fungal pathogens, together with their roles in plant defense responses, are provided. Safety aspects of these natural compounds on humans and ecology are discussed. Perspectives on the development of stilbenoid-based formulations using encapsulation technology, which allows the bypassing of the limitations related to stilbenoids, particularly low aqueous solubility, are addressed. Optimistically, the knowledge gathered in the present review supports the use of currently underrated agricultural byproducts to produce stilbenoid-abundant extracts with a high efficiency in the mitigation of mycotoxins in food and feedstuffs.

Expression of genes related to hydrogen peroxide generation and phytohormones in Ganoderma-inoculated oil palm seedlings pretreated with phytohormones and their inhibitors

Hydrogen peroxide, salicylic acid (SA) and jasmonic acid (JA) are reported to play important role in plant defense responses against pathogens. In this study, we analyzed the transcript abundance of oil palm respiratory burst oxidase B (EgRbohB1) and H (EgRbohH), Coronatine Insensitive 1 (EgCOI1), OPR5 (EgOPR5), hypersensitive induced response 1 (EgHIR1) and Nonexpressor of pathogenesis-related (EgNPR1) in Ganoderma boninense-inoculated oil palm roots that were pretreated with SA, JA and their inhibitors, paclobutrazol (PAC) and diethyldithiocarbamate (DIECA), respectively. We showed that EgNPR1 was down-regulated by G. boninense infection in SA-pretreated oil palm roots while EgHIR1 was up-regulated by G. boninense in PAC-pretreated oil palm roots. G. boninense inoculation did not change the gene expression levels of EgOPR5 in JA- and DIECA-treated oil palm roots significantly, compared to the uninoculated oil palms roots that were treated similarly. EgCOI1 was up-regulated by G. boninense in JA- and DIECA-pretreated oil palm roots, respectively. G. boninense up-regulated EgRbohB1 in SA-pretreated oil palm roots but down-regulated it in PAC-pretreated oil palm roots. EgRbohH was also down-regulated by G. boninense in PAC-pretreated oil palm roots. These findings facilitate the understanding of phytohormone effects on oil palm-Ganoderma interaction.

Vloga malih RNK pri odzivu rastlin na okužbo s patogenimi organizmi

Rastline imajo razvite raznolike in kompleksne mehanizme za regulacijo izražanja genov. Nedavno je bil odkrit nov mehanizem, imenovan RNK interferenca (RNKi). Osrednjo vlogo v RNKi imajo male nekodirajoče RNK (sRNK) dolge od 21-24 nukleotidov, ki z vezavo na komplementarna mesta v transkriptih preprečijo njihovo prevajanje v proteine. Ker sRNK definira izvor, strukturne lastnosti prekurzorjev ter sekvenčne lastnosti, jih delimo v več različnih razredov. mikroRNK (miRNK) ter sekundarne male interferenčne RNK (siRNK), med katere prištevamo tasiRNK in phasiRNK imajo pomembno vlogo v regulaciji izražanja genov v številnih bioloških procesih ter odzivu rastlin na biotske ali abiotske dejavnike stresa. Kljub številnim ohranjenim sRNK med rastlinskimi vrstami ter karakterizaciji njihovega delovanja, do danes še ni celovitega razumevanja njihove vloge v obrambnem odzivu rastlin pred fitopatogeni. Ta pregled povzema trenutno razumevanje patogeneze verticilijske uvelosti, obrambnega mehanizma rastlin pred fitopatogeni in biogeneze ter vloge miRNK, tasiRNK ter phasiRNK v obrambnem odzivu rastlin pred glivnimi patogeni. Nadaljnje raziskave rastlinskih sRNK in njihovo izražanje v odzivu rastlin na različne fitopatogene organizme so potrebne za jasno določitev njihove vloge. Novi pristopi sekvenciranja ter bioinformacijske analize in napovedovanja vloge miRNK tarč v času okužb nam lahko pri nemodelnih organizmih omogočijo razvoj novih načinov varstva rastlin.

The AP2/ERF transcription factor ORA59 regulates ethylene-induced phytoalexin synthesis through modulation of an acyltransferase gene expression.

The gaseous ethylene (ET) and the oxylipin-derived jasmonic acid (JA) in plants jointly regulate an arsenal of pathogen responsive genes involved in defending against necrotrophic pathogens. The APETALA2 (AP2)/ETHYLENE RESPONSE FACTOR (ERF) transcription factor ORA59 is a major positive regulator of the ET/JA-mediated defense pathway in Arabidopsis thaliana. The Arabidopsis agmatine coumaroyltransferase (AtACT) catalyzes the formation of hydroxycinnamic acid amides (HCAAs) which are effective toxic antimicrobial substances known as phytoalexins and play an important role in plant defense response. However, induction and regulation of AtACT gene expression and HCAAs synthesis in plants remain less understood. Through gene coexpression network analysis, we identified a list of GCC-box cis-element containing genes that were coexpressed with ORA59 under diverse biotic stress conditions and might be potential downstream targets of this AP2/ERF-domain transcription factor. Particularly, ORA59 directly binds to AtACT gene promoter via the GCC-boxes and activates AtACT gene expression. The ET precursor 1-aminocyclopropane-1-carboxylic acid (ACC)-treatment significantly induces AtACT gene expression. Both ORA59 and members of the class II TGA transcription factors are indispensable for ACC-induced AtACT expression. Interestingly, the expression of AtACT is also subject to the signaling crosstalk of the salicylic acid- and ET/JA-mediated defense response pathways. In addition, we found that genes of the phenylpropanoid metabolism pathway were specifically induced by Botrytis cinerea. Taking together, these evidence suggest that the ET/JA signaling pathway activate the expression of AtACT to increase antimicrobial HCAAs production through the transcription factor ORA59 in response to the infection of necrotrophic plant pathogens.

ZmRop1 participates in maize defense response to the damage of Spodoptera frugiperda larvae through mediating ROS and soluble phenol production.

As plant-specific molecular switches, Rho-like GTPases (Rops) are vital for plant survival in response to biotic and abiotic stresses. However, their roles in plant defense response to phytophagous insect's damage are largely unknown. In this study, the expression levels of nine maize RAC family genes were analyzed after fall armyworm (FAW) larvae infestation. Among the analyzed genes, ZmRop1 was specifically and highly expressed, and its role in maize response to FAW larvae damage was studied. The results showed that upon FAW larvae infestation, salicylic acid and methyl jasmonate treatment ZmRop1 gene transcripts were all down-regulated. However, upon mechanical injury, the expression level of ZmRop1 was up-regulated. Overexpression of ZmRop1 gene in maize plants could improve maize plant resistance to FAW larvae damage. Conversely, silencing of ZmRop1 increased maize plant susceptibility to FAW larvae damage. The analysis of the potential anti-herbivore metabolites, showed that ZmRop1 promoted the enzyme activities of catalase, peroxidase and the expression levels of ZmCAT, ZmPOD, ZmRBOHA and ZmRBOHB, thereby enhancing the reactive oxygen species (ROS) production, including the content of O2- and H2O2. In addition, overexpression or silencing of ZmRop1 could have influence on the content of the total soluble phenol through mediating the activity of polyphenol oxidase. In summary, the results illuminated our understanding of how ZmRop1 participate in maize defense response to FAW larvae damage as a positive regulator through mediating ROS production and can be used as a reference for the green prevention and control of FAW larvae.

A R2R3 MYB Transcription Factor, TaMYB391, Is Positively Involved in Wheat Resistance to Puccinia striiformis f. sp. tritici.

A biotrophic fungus, Puccinia striiformis f.sp. tritici (Pst), which causes stripe rust disease in wheat is the most yield-limiting factor in wheat production. Plants have complex defense mechanisms against invading pathogens. Hypersensitive response (HR), a kind of programmed cell death (PCD) at the infection site, is among these defense mechanisms. Transcription factors (TFs) play a crucial role in plant defense response against invading pathogens. Myeloblastosis (MYB) TFs are among the largest TFs families that are involved in response to both biotic and abiotic stresses. However, little is known about the mechanisms of MYB TFs during the interaction between wheat and the stripe rust fungus. Here, we identified an R2R3 MYB TF from wheat, designated as TaMYB391, and characterized its functional role during wheat-Pst interaction. Our data indicated that TaMYB391 is induced by Pst infection and exogenous application of salicylic acid (SA) and abscisic acid (ABA). TaMYB391 is localized in the nucleus of both wheat and Nicotiana benthamiana. Transient overexpression of TaMYB391 in N. benthamiana triggered HR-related PCD accompanied by increased electrolyte leakage, high accumulation of reactive oxygen species (ROS), and transcriptional accumulation of SA defense-related genes and HR-specific marker genes. Overexpression of TaMYB391 in wheat significantly enhanced wheat resistance to stripe rust fungus through the induction of pathogenesis-related (PR) genes, ROS accumulation and hypersensitive cell death. On the other hand, RNAi-mediated silencing of TaMYB391 decreased the resistance of wheat to Pst accompanied by enhanced growth of the pathogen. Together our findings demonstrate that TaMYB391 acts as a positive regulator of HR-associated cell death and positively contributes to the resistance of wheat to the stripe rust fungus by regulating certain PR genes, possibly through SA signaling pathways.

The Banana MaWRKY18, MaWRKY45, MaWRKY60 and MaWRKY70 Genes Encode Functional Transcription Factors and Display Differential Expression in Response to Defense Phytohormones.

WRKY transcription factors (TFs) play key roles in plant defense responses through phytohormone signaling pathways. However, their functions in tropical fruit crops, especially in banana, remain largely unknown. Several WRKY genes from the model plants rice (OsWRKY45) and Arabidopsis (AtWRKY18, AtWRKY60, AtWRKY70) have shown to be attractive TFs for engineering disease resistance. In this study, we isolated four banana cDNAs (MaWRKY18, MaWRKY45, MaWRKY60, and MaWRKY70) with homology to these rice and Arabidopsis WRKY genes. The MaWRKY cDNAs were isolated from the wild banana Musa acuminata ssp. malaccensis, which is resistant to several diseases of this crop and is a progenitor of most banana cultivars. The deduced amino acid sequences of the four MaWRKY cDNAs revealed the presence of the conserved WRKY domain of ~60 amino acids and a zinc-finger motif at the N-terminus. Based on the number of WRKY repeats and the structure of the zinc-finger motif, MaWRKY18 and MaWRKY60 belong to group II of WRKY TFs, while MaWRKY45 and MaWRKY70 are members of group III. Their corresponding proteins were located in the nuclei of onion epidermal cells and were shown to be functional TFs in yeast cells. Moreover, expression analyses revealed that the majority of these MaWRKY genes were upregulated by salicylic acid (SA) or methyl jasmonate (MeJA) phytohormones, although the expression levels were relatively higher with MeJA treatment. The fact that most of these banana WRKY genes were upregulated by SA or MeJA, which are involved in systemic acquired resistance (SAR) or induced systemic resistance (ISR), respectively, make them interesting candidates for bioengineering broad-spectrum resistance in this crop.

OsVTC1-1 Gene Silencing Promotes a Defense Response in Rice and Enhances Resistance to Magnaporthe oryzae

Rice blast disease is a serious disease in rice caused by Magnaporthe oryzae (M. oryzae). Ascorbic acid (AsA), or vitamin C, is a strong antioxidant that prevents oxidative damage to cellular components and plays an essential role in plant defense response. GDP-D-mannose pyrophosphorylase (GMP or VTC1) is an enzyme that generates GDP-D-mannose for AsA, cell wall, and glycoprotein synthesis. The OsVTC1 gene has three homologs in the rice genome: OsVTC1-1, OsVTC1-3, and OsVTC1-8. Using OsVTC1-1 RNAi lines, this study investigated the role of the OsVTC1-1 gene during rice blast fungus inoculation. The OsVTC1-1 RNAi inoculated with rice blast fungus induced changes to cell wall monosaccharides, photosynthetic efficiency, reactive oxygen species (ROS) accumulation, and malondialdehyde (MDA) content. Additionally, the OsVTC1-1 RNAi lines were shown to be more resistant to rice blast fungus than the wild type. Genes and proteins related to defense response, plant hormone synthesis, and signaling pathways, especially salicylic acid and jasmonic acid, were up-regulated in the OsVTC1-1 RNAi lines after rice blast inoculation. These results suggest that the OsVTC1-1 gene regulates rice blast resistance through several defense mechanisms, including hormone synthesis and signaling pathways.

TaPR1 Interacts With TaTLP1 via the αIV Helix to Be Involved in Wheat Defense to Puccinia triticina Through the CAPE1 Motif.

Pathogenesis-related (PR) proteins play important roles in plant defense response and systemic acquired resistance (SAR). PR1 has antifungal activity against many plant pathogens. In our previous study, RNA sequencing (RNA-seq) was conducted on resistant wheat line TcLr19 and sensitive wheat cultivar Chinese Spring inoculated with Puccinia triticina (Pt) race PHNT. In this study, seven salicylic acid (SA)-induced TaPR1 genes involved in plant disease resistance were found in the RNA-seq library. Quantitative PCR (qPCR) results showed that TaPR1-4 was most induced by Pt among these seven TaPR1 genes in the incompatible interaction. Yeast two-hybrid (Y2H) results showed that TaPR1-4 interacted with TaTLP1 via the αIV helix. Protein-mediated phenotyping assays in vivo and antifungal activity in vitro demonstrated that wheat leaves infiltrated with pure TaPR1-4 protein developed significantly less disease compared to control leaves. This effect was correlated with a strong increase in defense gene expression, and resistance activity was dependent on the CAPE1 motif located in the C-terminal region of TaPR1-4. These findings increase current knowledge regarding the interaction of TaPR1 and TaTLP1 and provide new insights on the role of TaPR1 protein in the resistance of wheat to Pt.

In vivo Antiphytoviral Activity of Essential Oils and Hydrosols From Origanum vulgare, Thymus vulgaris, and Rosmarinus officinalis to Control Zucchini Yellow Mosaic Virus and Tomato Leaf Curl New Delhi Virus in Cucurbita pepo L.

In the last decades, the interest in biological activity of natural compounds has been growing. In plant protection, essential oils have been reported to exhibit antiviral, antimycotic, and antiparasitic activities, and are regarded as promising for the formulation of safe antimicrobial agents. Attention has also been focused on hydrosols, the by-products of hydro-distillation of essential oils. Their production is easy, fast, and cheap, and they seem to arise less concern for human health than essential oils. Plant viruses represent a major concern for agricultural crops since no treatment compound is available for virus control. This work was aimed at evaluating the antiphytoviral effectiveness of treatments with three essential oils and corresponding hydrosols extracted from Origanum vulgare, Thymus vulgaris, and Rosmarinus officinalis on Cucurbita pepo plants infected by zucchini yellow mosaic virus or tomato leaf curl New Delhi virus. Treatments were applied either concurrently or after virus inoculation to ascertain an inhibition or curative activity, respectively. Symptoms were observed and samplings were performed weekly. Virus titer and expression levels of phenylalanine ammonia lyase gene (PAL) were measured on treated and untreated infected plants by real-time PCR. PAL gene plays an important role in plant defense response as it is involved in tolerance/resistance to phytopathogens. Results indicated that treatments were effective against tomato leaf curl New Delhi virus whether applied simultaneously with the inoculation or after. A major inhibition was observed with O. vulgare essential oil and hydrosol, resulting in 10–4-fold decrease of virus titer 3 weeks after treatment. Curative activity gave maximum results with all three essential oils and T. vulgaris and R. officinalis hydrosols, recording from 10–2-fold decrease to virus not detected 4 weeks after treatment. An induction of PAL gene expression was recorded at 12 d.p.i. and then was restored to the levels of untreated control. This allows to hypothesize an early plant defense response to virus infection, possibly boosted by treatments. Plant extracts’ composition was characterized by gas chromatography-mass spectrometry. Phenols were largely main components of O. vulgare and T. vulgaris extracts (carvacrol and thymol, respectively), while extracts from R. officinalis were based on monoterpene hydrocarbons (essential oil) and oxygenated monoterpenes (hydrosol).