NbWRKY40 Positively Regulates the Response of Nicotiana benthamiana to Tomato Mosaic Virus via Salicylic Acid Signaling

Expression and antiviral application of exogenous lectin (griffithsin) in sweetpotatoes

Griffithsin (GRFT) is a highly effective, broad-spectrum, safe, and stable viral inhibitor used to suppress a variety of viruses. However, little information is available on whether GRFT can prevent plant viral diseases. In this study, we constructed a GRFT overexpression vector containing the sweetpotato storage cell signal peptide and generated exogenous GRFT overexpression lines through genetic transformation. The transgenic plants showed notable resistance to sweetpotato virus disease in the virus nursery. To verify the antiplant virus function of GRFT, transient expression in tobacco leaves showed that GRFT inhibited the sweetpotato leaf curl virus (SPLCV). The replication of SPLCV was entirely inhibited when the concentration of GRFT reached a certain level. The results of pulldown and BIFC assays showed that GRFT did not interact with the six components of SPLCV. In addition, the mutated GRFTD/A without the binding ability of carbohydrate and anticoronavirus function, in which three aspartate residues at carbohydrate binding sites were all mutated to alanine, also inhibited SPLCV. Quantitative reverse-transcription PCR analyses showed that the tobacco antiviral-related genes HIN1, ICS1, WRKY40, and PR10 were overexpressed after GRFT/GRFTD/A injection. Furthermore, HIN1, ICS1, and PR10 were more highly expressed in the leaves injected with GRFTD/A. The results suggest that sweetpotato is able to express GRFT exogenously as a bioreactor. Moreover, exogenous GRFT expression inhibits plant viruses by promoting the expression of plant antiviral genes.

TaWRKY50-TaSARK7 module-mediated cysteine-rich protein phosphorylation suppresses the programmed cell death response to Chinese wheat mosaic virus infection

WRKY transcription factors are widely involved in plant responses to biotic and abiotic stresses. However, there is currently a limited understanding of the regulation of viral infection by WRKY transcription factors in wheat (Triticum aestivum). The WRKY transcription factor TaWRKY50 in group IIb wheat exhibited a significant response to Chinese wheat mosaic virus infection. TaWRKY50 is localized in the nucleus and is an activating transcription factor. Interestingly, we found that silencing TaWRKY50 induces cell death following inoculation with CWMV. The protein kinase TaSAPK7 is specific to plants, whereas NbSRK is a closely related kinase with high homology to TaSAPK7. The transcriptional activities of both TaSAPK7 and NbSRK can be enhanced by TaWRKY50 binding to their promoters. CRP is an RNA silencing suppressor. Furthermore, TaWRKY50 may regulate CWMV infection by regulating the expression of TaSAPK7 and NbSRK to increase CRP phosphorylation and reduce the amount of programmed cell death (PCD).

JrPHL8-JrWRKY4-JrSTH2L module regulates resistance to Colletotrichum gloeosporioides in walnut

Walnut anthracnose (Colletotrichum gloeosporioides) reduces walnut yield and quality and seriously threatens the healthy development of the walnut industry. WRKY transcription factors (TFs) are crucial regulatory factors involved in plant-pathogen interactions. Our previous transcriptome analysis results indicate that JrWRKY4 responds to infection by C. gloeosporioides, but its specific regulatory network and disease resistance mechanism are still unclear. Herein, the characteristics of JrWRKY4 as a transcription activator located in the nucleus were first identified. Gain-of-function and loss-of-function analyses showed that JrWRKY4 could enhance walnut resistance against C. gloeosporioides. A series of molecular experiments showed that JrWRKY4 directly interacted with the promoter region of JrSTH2L and positively regulated its expression. In addition, JrWRKY4 interacted with JrVQ4 to form the protein complex, which inhibited JrWRKY4 for the activation of JrSTH2L. Notably, a MYB TF JrPHL8 interacting with the JrWRKY4 promoter has also been identified, which directly bound to the MBS element in the promoter of JrWRKY4 and induced its activity. Our study elucidated a novel mechanism of the JrPHL8-JrWRKY4-JrSTH2L in regulating walnut resistance to anthracnose. This mechanism improves our understanding of the molecular mechanism of WRKY TF mediated resistance to anthracnose in walnut, which provides new insights for molecular breeding of disease-resistant walnuts in the future.

Identification and Characterization of High-Molecular-Weight Proteins Secreted by Plasmodiophora brassicae That Suppress Plant Immunity

Plasmodiophora brassicae is an obligate intracellular parasitic protist that causes clubroot disease on cruciferous plants. So far, some low-molecular-weight secreted proteins from P. brassicae have been reported to play an important role in plant immunity regulation, but there are few reports on its high-molecular-weight secreted proteins. In this study, 35 putative high-molecular-weight secreted proteins (>300 amino acids) of P. brassicae (PbHMWSP) genes that are highly expressed during the infection stage were identified using transcriptome analysis and bioinformatics prediction. Then, the secretory activity of 30 putative PbHMWSPs was confirmed using the yeast signal sequence trap system. Furthermore, the genes encoding 24 PbHMWSPs were successfully cloned and their functions in plant immunity were studied. The results showed that ten PbHMWSPs could inhibit flg22-induced reactive oxygen burst, and ten PbHMWSPs significantly inhibited the expression of the SA signaling pathway marker gene PR1a. In addition, nine PbHMWSPs could inhibit the expression of a marker gene of the JA signaling pathway. Therefore, a total of 19 of the 24 tested PbHMWSPs played roles in suppressing the immune response of plants. Of these, it is worth noting that PbHMWSP34 can inhibit the expression of JA, ET, and several SA signaling pathway marker genes. The present study is the first to report the function of the high-molecular-weight secreted proteins of P. brassicae in plant immunity, which will enrich the theory of interaction mechanisms between the pathogens and plants.

A comprehensive analysis of the WRKY family in soybean and functional analysis of GmWRKY164-GmGSL7c in resistance to soybean mosaic virus

BACKGROUND

Soybean mosaic disease caused by soybean mosaic virus (SMV) is one of the most devastating and widespread diseases in soybean producing areas worldwide. The WRKY transcription factors (TFs) are widely involved in plant development and stress responses. However, the roles of the GmWRKY TFs in resistance to SMV are largely unclear.

RESULTS

Here, 185 GmWRKYs were characterized in soybean (Glycine max), among which 60 GmWRKY genes were differentially expressed during SMV infection according to the transcriptome data. The transcriptome data and RT-qPCR results showed that the expression of GmWRKY164 decreased after imidazole treatment and had higher expression levels in the incompatible combination between soybean cultivar variety Jidou 7 and SMV strain N3. Remarkably, the silencing of GmWRKY164 reduced callose deposition and enhanced virus spread during SMV infection. In addition, the transcript levels of the GmGSL7c were dramatically lower upon the silencing of GmWRKY164. Furthermore, EMSA and ChIP-qPCR revealed that GmWRKY164 can directly bind to the promoter of GmGSL7c, which contains the W-box element.

CONCLUSION

Our findings suggest that GmWRKY164 plays a positive role in resistance to SMV infection by regulating the expression of GmGSL7c, resulting in the deposition of callose and the inhibition of viral movement, which provides guidance for future studies in understanding virus-resistance mechanisms in soybean.

Transcription factor WRKY75 maintains auxin homeostasis to promote tomato defense against Pseudomonas syringae

The hemibiotrophic bacterial pathogen Pseudomonas syringae infects a range of plant species and causes enormous economic losses. Auxin and WRKY transcription factors play crucial roles in plant responses to P. syringae, but their functional relationship in plant immunity remains unclear. Here, we characterized tomato (Solanum lycopersicum) SlWRKY75, which promotes defenses against P. syringae pv. tomato (Pst) DC3000 by regulating plant auxin homeostasis. Overexpressing SlWRKY75 resulted in low free indole-3-acetic acid (IAA) levels, leading to attenuated auxin signaling, decreased expansin transcript levels, upregulated expression of PATHOGENESIS-RELATED GENES (PRs) and NONEXPRESSOR OF PATHOGENESIS-RELATED GENE 1 (NPR1), and enhanced tomato defenses against Pst DC3000. RNA interference-mediated repression of SlWRKY75 increased tomato susceptibility to Pst DC3000. Yeast one-hybrid, electrophoretic mobility shift assays, and luciferase activity assays suggested that SlWRKY75 directly activates the expression of GRETCHEN HAGEN 3.3 (SlGH3.3), which encodes an IAA-amido synthetase. SlGH3.3 enhanced tomato defense against Pst DC3000 by converting free IAA to the aspartic acid (Asp)-conjugated form IAA-Asp. In addition, SlWRKY75 interacted with a tomato valine-glutamine (VQ) motif-containing protein 16 (SlVQ16) in vivo and in vitro. SlVQ16 enhanced SlWRKY75-mediated transcriptional activation of SlGH3.3 and promoted tomato defense responses to Pst DC3000. Our findings illuminate a mechanism in which the SlVQ16-SlWRKY75 complex participates in tomato pathogen defense by positively regulating SlGH3.3-mediated auxin homeostasis.

Defense signaling pathways in resistance to plant viruses: Crosstalk and finger pointing

Resistance to infection by plant viruses involves proteins encoded by plant resistance (R) genes, viz., nucleotide-binding leucine-rich repeats (NLRs), immune receptors. These sensor NLRs are activated either directly or indirectly by viral protein effectors, in effector-triggered immunity, leading to induction of defense signaling pathways, resulting in the synthesis of numerous downstream plant effector molecules that inhibit different stages of the infection cycle, as well as the induction of cell death responses mediated by helper NLRs. Early events in this process involve recognition of the activation of the R gene response by various chaperones and the transport of these complexes to the sites of subsequent events. These events include activation of several kinase cascade pathways, and the syntheses of two master transcriptional regulators, EDS1 and NPR1, as well as the phytohormones salicylic acid, jasmonic acid, and ethylene. The phytohormones, which transit from a primed, resting states to active states, regulate the remainder of the defense signaling pathways, both directly and by crosstalk with each other. This regulation results in the turnover of various suppressors of downstream events and the synthesis of various transcription factors that cooperate and/or compete to induce or suppress transcription of either other regulatory proteins, or plant effector molecules. This network of interactions results in the production of defense effectors acting alone or together with cell death in the infected region, with or without the further activation of non-specific, long-distance resistance. Here, we review the current state of knowledge regarding these processes and the components of the local responses, their interactions, regulation, and crosstalk.

Comparative Transcriptomics Analysis Reveals the Differences in Transcription between Resistant and Susceptible Pepper (Capsicum annuum L.) Varieties in Response to Anthracnose

Pepper (Capsicum annuum L.) is a herbaceous plant species in the family Solanaceae. Capsicum anthracnose is caused by the genus Colletotrichum. spp., which decreases pepper production by about 50% each year due to anthracnose. In this study, we evaluated the resistance of red ripe fruits from 17 pepper varieties against anthracnose fungus Colletotrichum capsici. We assessed the size of the lesion diameter and conducted significance analysis to identify the resistant variety of B158 and susceptible variety of B161. We selected a resistant cultivar B158 and a susceptible cultivar B161 of pepper and used a transcription to investigate the molecular mechanisms underlying the plant's resistance to C. capsici, of which little is known. The inoculated fruit from these two varieties were used for the comparative transcription analysis, which revealed the anthracnose-induced differential transcription in the resistant and susceptible pepper samples. In the environment of an anthrax infection, we found that there were more differentially expressed genes in resistant varieties compared to susceptible varieties. Moreover, the response to stimulus and stress ability was stronger in the KANG. The transcription analysis revealed the activation of plant hormone signaling pathways, phenylpropanoid synthesis, and metabolic processes in the defense response of peppers against anthracnose. In addition, ARR-B, AP2-EREBP, bHLH, WRKY, and NAC are associated with disease resistance to anthracnose. Notably, WRKY and NAC were found to have a potentially positive regulatory role in the defense response against anthracnose. These findings contribute to a more comprehensive understanding of the resistance mechanisms of red pepper fruit to anthracnose infection, providing valuable molecular insights for further research on the resistance mechanisms and genetic regulations during this developmental stage of pepper.

Transcriptomic characterization of Trichoderma harzianum T34 primed tomato plants: assessment of biocontrol agent induced host specific gene expression and plant growth promotion

In this study, we investigated the intricate interplay between Trichoderma and the tomato genome, focusing on the transcriptional and metabolic changes triggered during the late colonization event. Microarray probe set (GSE76332) was utilized to analyze the gene expression profiles changes of the un-inoculated control (tomato) and Trichoderma-tomato interactions for identification of the differentially expressed significant genes. Based on principal component analysis and R-based correlation, we observed a positive correlation between the two cross-comaparable groups, corroborating the existence of transcriptional responses in the host triggered by Trichoderma priming. The statistically significant genes based on different p-value cut-off scores [(padj-values or q-value); padj-value < 0.05], [(pcal-values); pcal-value < 0.05; pcal < 0.01; pcal < 0.001)] were cross compared. Through cross-comparison, we identified 156 common genes that were consistently significant across all probability thresholds, and showing a strong positive corelation between p-value and q-value in the selected probe sets. We reported TD2, CPT1, pectin synthase, EXT-3 (extensin-3), Lox C, and pyruvate kinase (PK), which exhibited upregulated expression, and Glb1 and nitrate reductase (nii), which demonstrated downregulated expression during Trichoderma-tomato interaction. In addition, microbial priming with Trichoderma resulted into differential expression of transcription factors related to systemic defense and flowering including MYB13, MYB78, ERF2, ERF3, ERF5, ERF-1B, NAC, MADS box, ZF3, ZAT10, A20/AN1, polyol sugar transporter like zinc finger proteins, and a novel plant defensin protein. The potential bottleneck and hub genes involved in this dynamic response were also identified. The protein-protein interaction (PPI) network analysis based on 25 topmost DEGS (pcal-value < 0.05) and the Weighted Correlation Gene Network Analysis (WGCNA) of the 1786 significant DEGs (pcal-value < 0.05) we reported the hits associated with carbohydrate metabolism, secondary metabolite biosynthesis, and the nitrogen metabolism. We conclude that the Trichoderma-induced microbial priming re-programmed the host genome for transcriptional response during the late colonization event and were characterized by metabolic shifting and biochemical changes specific to plant growth and development. The work also highlights the relevance of statistical parameters in understanding the gene regulatory dynamics and complex regulatory networks based on differential expression, co-expression, and protein interaction networks orchestrating the host responses to beneficial microbial interactions.

CaWRKY50 Acts as a Negative Regulator in Response to Colletotrichum scovillei Infection in Pepper

Chili anthracnose is one of the most common and destructive fungal pathogens that affects the yield and quality of pepper. Although WRKY proteins play crucial roles in pepper resistance to a variety of pathogens, the mechanism of their resistance to anthracnose is still unknown. In this study, we found that CaWRKY50 expression was obviously induced by Colletotrichum scovillei infection and salicylic acid (SA) treatments. CaWRKY50-silencing enhanced pepper resistance to C. scovillei, while transient overexpression of CaWRKY50 in pepper increased susceptibility to C. scovillei. We further found that overexpression of CaWRKY50 in tomatoes significantly decreased resistance to C. scovillei by SA and reactive oxygen species (ROS) signaling pathways. Moreover, CaWRKY50 suppressed the expression of two SA-related genes, CaEDS1 (enhanced disease susceptibility 1) and CaSAMT1 (salicylate carboxymethyltransferase 1), by directly binding to the W-box motif in their promoters. Additionally, we demonstrated that CaWRKY50 interacts with CaWRKY42 and CaMIEL1 in the nucleus. Thus, our findings revealed that CaWRKY50 plays a negative role in pepper resistance to C. scovillei through the SA-mediated signaling pathway and the antioxidant defense system. These results provide a theoretical foundation for molecular breeding of pepper varieties resistant to anthracnose.

The Role of Plant Transcription Factors in the Fight against Plant Viruses

Plants are vulnerable to the challenges of unstable environments and pathogen infections due to their immobility. Among various stress conditions, viral infection is a major threat that causes significant crop loss. In response to viral infection, plants undergo complex molecular and physiological changes, which trigger defense and morphogenic pathways. Transcription factors (TFs), and their interactions with cofactors and cis-regulatory genomic elements, are essential for plant defense mechanisms. The transcriptional regulation by TFs is crucial in establishing plant defense and associated activities during viral infections. Therefore, identifying and characterizing the critical genes involved in the responses of plants against virus stress is essential for the development of transgenic plants that exhibit enhanced tolerance or resistance. This article reviews the current understanding of the transcriptional control of plant defenses, with a special focus on NAC, MYB, WRKY, bZIP, and AP2/ERF TFs. The review provides an update on the latest advances in understanding how plant TFs regulate defense genes expression during viral infection.

The 'Candidatus Phytoplasma tritici' effector SWP12 degrades the transcription factor TaWRKY74 to suppress wheat resistance

'Candidatus Phytoplasma tritici' ('Ca. P. tritici') is an insect-borne obligate pathogen that infects wheat (Triticum aestivum) causing wheat blue dwarf disease, and leads to yield losses. SWP12 is a potential effector secreted by 'Ca. P. tritici' that manipulates host processes to create an environment conducive to phytoplasma colonization, but the detailed mechanism of action remains to be investigated. In this study, the expression of SWP12 weakened the basal immunity of Nicotiana benthamiana and promoted leaf colonization by Phytophthora parasitica, Sclerotinia sclerotiorum, and tobacco mild green mosaic virus. Moreover, the expression of SWP12 in wheat plants promoted phytoplasma colonization. Triticum aestivum WRKY74 and N. benthamiana WRKY17 were identified as host targets of SWP12. The expression of TaWRKY74 triggered reactive oxygen species bursts, upregulated defense-related genes, and decreased TaCRR6 transcription, leading to reductions in NADH dehydrogenase complex (NDH) activity. Expression of TaWRKY74 in wheat increased plant resistance to 'Ca. P. tritici', and silencing of TaWRKY74 enhanced plant susceptibility, which indicates that TaWRKY74 is a positive regulator of wheat resistance to 'Ca. P. tritici'. We showed that SWP12 weakens plant resistance and promotes 'Ca. P. tritici' colonization by destabilizing TaWRKY74.

Integrated next-generation sequencing and comparative transcriptomic analysis of leaves provides novel insights into the ethylene pathway of Chrysanthemum morifolium in response to a Chinese isolate of chrysanthemum virus B

Background

Chrysanthemum virus B (CVB), a key member of the genus Carlavirus, family Betaflexiviridae, causes severe viral diseases in chrysanthemum (Chrysanthemum morifolium) plants worldwide. However, information on the mechanisms underlying the response of chrysanthemum plants to CVB is scant.

Methods

Here, an integrated next-generation sequencing and comparative transcriptomic analysis of chrysanthemum leaves was conducted to explore the molecular response mechanisms of plants to a Chinese isolate of CVB (CVB-CN) at the molecular level.

Results

In total, 4934 significant differentially expressed genes (SDEGs) were identified to respond to CVB-CN, of which 4097 were upregulated and 837 were downregulated. Gene ontology and functional classification showed that the majority of upregulated SDEGs were categorized into gene cohorts involved in plant hormone signal transduction, phenylpropanoid and flavonoid biosynthesis, and ribosome metabolism. Enrichment analysis demonstrated that ethylene pathway-related genes were significantly upregulated following CVB-CN infection, indicating a strong promotion of ethylene biosynthesis and signaling. Furthermore, disruption of the ethylene pathway in Nicotiana benthamiana, a model plant, using virus-induced gene silencing technology rendered them more susceptible to cysteine-rich protein of CVB-CN induced hypersensitive response, suggesting a crucial role of this pathway in response to CVB-CN infection.

Conclusion

This study provides evidence that ethylene pathway has an essential role of plant in response to CVB and offers valuable insights into the defense mechanisms of chrysanthemum against Carlavirus.

A Group I WRKY Gene, TaWRKY133, Negatively Regulates Drought Resistance in Transgenic Plants

WRKYs are one of the largest transcription factor (TF) families and play an important role in plant resistance to various stresses. TaWRKY133, a group I WRKY protein, responds to a variety of abiotic stresses, including PEG treatment. The TaWRKY133 protein is located in the nucleus of tobacco epidermal cells, and both its N-terminal and C-terminal domains exhibit transcriptional activation activity. Overexpression of TaWRKY133 reduced drought tolerance in Arabidopsis thaliana, as reflected by a lower germination rate, shorter roots, higher stomatal aperture, poorer growth and lower antioxidant enzyme activities under drought treatment. Moreover, expression levels of stress-related genes (DREB2A, RD29A, RD29B, ABF1, ABA2, ABI1, SOD (Cu/Zn), POD1 and CAT1) were downregulated in transgenic Arabidopsis under drought stress. Gene silencing of TaWRKY133 enhanced the drought tolerance of wheat, as reflected in better growth, higher antioxidant enzyme activities, and higher expression levels of stress-related genes including DREB1, DREB3, ABF, ERF3, SOD (Fe), POD, CAT and P5CS. In conclusion, these results suggest that TaWRKY133 might reduce drought tolerance in plants by regulating the expression of stress-related genes.

JrWRKY21 interacts with JrPTI5L to activate the expression of JrPR5L for resistance to Colletotrichum gloeosporioides in walnut

Walnut (Juglans regia L.) anthracnose, induced by Colletotrichum gloeosporioides, is a catastrophic disease impacting the walnut industry in China. Although WRKY transcription factors play a key role in plant immunity, the function of the WRKY gene family in walnut resistance to C. gloeosporioides is not clear. Here, through transcriptome sequencing and quantitative real-time polymerase chain reaction (qRT-PCR), we identified a differentially expressed gene, JrWRKY21, that was significantly upregulated upon C. gloeosporioides infection in walnut. JrWRKY21 positively regulated walnut resistance to C. gloeosporioides, as demonstrated by virus-induced gene silencing and transient gene overexpression. Additionally, JrWRKY21 directly interacted with the transcriptional activator of the pathogenesis-related (PR) gene JrPTI5L in vitro and in vivo, and could bind to the W-box in the JrPTI5L promoter for transcriptional activation. Moreover, JrPTI5L could induce the expression of the PR gene JrPR5L through binding to the GCCGAC motif in the promoter. Our data support that JrWRKY21 can indirectly activate the expression of the JrPR5L gene via the WRKY21-PTI5L protein complex to promote resistance against C. gloeosporioides in walnut. The results will enhance our understanding of the mechanism behind walnut disease resistance and facilitate the genetic improvement of walnut by molecular breeding for anthracnose-resistant varieties.

A WRKY Protein, MfWRKY40, of Resurrection Plant Myrothamnus flabellifolia Plays a Positive Role in Regulating Tolerance to Drought and Salinity Stresses of Arabidopsis

WRKY transcription factors (TFs), one of the largest transcription factor families in plants, play an important role in abiotic stress responses. The resurrection plant, Myrothamnus flabellifolia, has a strong tolerance to dehydration, but only a few WRKY proteins related to abiotic stress response have been identified and functionally characterized in M. flabellifolia. In this study, we identified an early dehydration-induced gene, MfWRKY40, of M. flabellifolia. The deduced MfWRKY40 protein has a conserved WRKY motif but lacks a typical zinc finger motif in the WRKY domain and is localized in the nucleus. To investigate its potential roles in abiotic stresses, we overexpressed MfWRKY40 in Arabidopsis and found that transgenic lines exhibited better tolerance to both drought and salt stresses. Further detailed analysis indicated that MfWRKY40 promoted primary root length elongation and reduced water loss rate and stomata aperture (width/length) under stress, which may provide Arabidopsis the better water uptake and retention abilities. MfWRKY40 also facilitated osmotic adjustment under drought and salt stresses by accumulating more osmolytes, such as proline, soluble sugar, and soluble protein. Additionally, the antioxidation ability of transgenic lines was also significantly enhanced, represented by higher chlorophyll content, less malondialdehyde and reactive oxygen species accumulations, as well as higher antioxidation enzyme activities. All these results indicated that MfWRKY40 might positively regulate tolerance to drought and salinity stresses. Further investigation on the relationship of the missing zinc finger motif of MfWRKY40 and its regulatory role is necessary to obtain a better understanding of the mechanism underlying the excellent drought tolerance of M. flabellifolia.

A maize triacylglycerol lipase inhibits sugarcane mosaic virus infection

Triacylglycerol lipase (TGL) plays critical roles in providing energy for seed germination and plant development. However, the role of TGL in regulating plant virus infection is largely unknown. In this study, we adopted affinity purification coupled with mass spectrometry and identified that a maize (Zea mays) pathogenesis-related lipase protein Z. mays TGL (ZmTGL) interacted with helper component-proteinase (HC-Pro) of sugarcane mosaic virus (SCMV). Yeast two-hybrid, luciferase complementation imaging, and bimolecular fluorescence complementation assays confirmed that ZmTGL directly interacted with SCMV HC-Pro in vitro and in vivo. The 101-460 residues of SCMV HC-Pro were important for its interaction with ZmTGL. ZmTGL and SCMV HC-Pro co-localized at the mitochondria. Silencing of ZmTGL facilitated SCMV infection, and over-expression of ZmTGL reduced the RNA silencing suppression activity, most likely through reducing HC-Pro accumulation. Our results provided evidence that the lipase hydrolase activity of ZmTGL was associated with reducing HC-Pro accumulation, activation of salicylic acid (SA)-mediated defense response, and inhibition of SCMV infection. We show that ZmTGL inhibits SCMV infection by reducing HC-Pro accumulation and activating the SA pathway.

Identification and Characterization of WRKY41, a Gene Conferring Resistance to Powdery Mildew in Wild Tomato (Solanum habrochaites) LA1777

WRKYs, a large family of transcription factors, are involved in plant response to biotic and abiotic stresses, but the role of them in tomato resistance to Oidium neolycopersici is still unclear. In this study, we evaluate the role of WRKYs in powdery mildew-resistant wild tomato (Solanum habrochaites) LA1777 defense against O. neolycopersici strain lz (On-lz) using a combination of omics, classical plant pathology- and cell biology-based approaches. A total of 27 WRKYs, belonging to group I, II, and III, were identified as differentially expressed genes in LA1777 against On-lz. It was found that expression of ShWRKY41 was increased after Pseudomonas syringae pv. tomato (Pst) DC3000, On-lz and Botrytiscinerea B05 inoculation or ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) treatment. GUS staining of ShWRKY41 promoter indicated that the expression of ShWRKY41 could be induced by SA and ethylene. Furthermore, ShWRKY41 gene silencing reduced the resistance to On-lz infection by decreasing the generation of H₂O₂ and HR in LA1777 seedlings. Overall, our research suggests that ShWRKY41 plays a positive role in defense activation and host resistance to O. neolycopersici in wild tomato (S. habrochaites) LA1777.

The small GTPase NtRHO1 negatively regulates tobacco defense response to tobacco mosaic virus by interacting with NtWRKY50

Small GTPases play critical roles in the regulation of plant growth and development. However, the mechanism of action of small GTPases in plant response to virus infection remains largely unknown. Here, the gene encoding a Rho-type GTPase, NtRHO1, was identified as one of the genes up-regulated after tobacco mosaic virus (TMV) infection. Subcellular localization of NtRHO1 showed that it was located in the cytoplasm, plasma membrane, and nucleus. Transient overexpression of NtRHO1 in Nicotiana benthamiana accelerated TMV reproduction and led to the production of reactive oxygen species. By contrast, silencing of NtRHO1 reduced the sensitivity of N. benthamiana to TMV-GFP. Further exploration revealed a direct interaction between NtRHO1 and NtWRKY50, a positive regulator of the N. benthamiana response to virus infection. Yeast one-hybrid and electrophoretic mobility shift assays showed that this regulation was related to the capacity of NtWRKY50 to bind to the WK-box of the PR1 promoter, which was weakened by the interaction between NtRHO1 and NtWRKY50. Thus, our results indicate that the small GTPase NtRHO1 plays a negative role in tobacco response to TMV infection by interacting with transcription factor NtWRKY50, resulting in reduced plant immunity.