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The abscisic acid (ABA) receptor PYR/PYL/RCAR, located upstream of the ABA signaling pathway, recognizes ABA signals and initiates the primary process of signal transduction. In our previous study, we found that the PYL4 gene in tomato plants was significantly upregulated after exogenous treatment with the hormone ABA. The present study used virus-induced gene silencing (VIGS) to further elucidate the role of the PYL4 gene in response to drought in tomato (Solanum lycopersicum) plants. Under the drought treatment, the SlPYL4-silenced plants wilted faster than the control plants did. Physiological indicators showed that the total reactive oxygen species (ROS) content and superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities of the SlPYL4-silenced plants were lower than those of the control plants after 3 and 6 h of drought stress treatment. After 3 h of drought treatment, hydrogen peroxide (H2O2) and superoxide anion (O2−.) accumulated much more in the leaves of the SlPYL4-silenced plants than in the leaves of the control plants. These results indicated that PYL4 plays a positive role in drought tolerance in tomato plants. Our results also suggest that SlPYL4 is located upstream of the ABA pathway to regulate the expression of PP2C, SnRK, and AREB/ABF genes.

BRI1-EMS-SUPPRESSOR 1 (BES1) transcription factor is closely associated with the brassinosteroid (BR) signaling pathway and plays an important role in plant growth and development. SLB3 is a member of BES1 transcription factor family and its expression was previously shown to increase significantly in tomato seedlings under drought stress. In the present study, we used virus-induced gene silencing (VIGS) technology to downregulate SLB3 expression to reveal the function of the SLB3 gene under drought stress further. The downregulated expression of SLB3 weakened the drought tolerance of the plants appeared earlier wilting and higher accumulation of H2O2 and O2−·, decreased superoxide dismutase (SOD) activity, and increased proline (PRO) and malondialdehyde (MDA) contents and peroxidase (POD) activity. Quantitative real-time PCR (qRT-PCR) analysis of BR-related genes revealed that the expression of SlCPD, SlDWARF and BIN2-related genes was significantly upregulated in SLB3-silenced seedlings under drought stress, but that the expression of TCH4-related genes was downregulated. These results showed that silencing the SLB3 gene reduced the drought resistance of tomato plants and had an impact on the BR signaling transduction which may be probably responsible for the variation in drought resistance of the tomato plants.

Background: Tomato gray leaf spot caused by Stemphylium lycopersici (S. lycopersici) is a serious disease that can severely hinder tomato production. To date, only Sm has been reported to provide resistance against this disease, and the molecular mechanism underlying resistance to this disease in tomato remains unclear. To better understand the mechanism of tomato resistance to S. lycopersici, real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR)-based analysis, physiological indexes, microscopy observations and transgenic technology were used in this study.Results: Our results showed that the expression of SlERF01 was strongly induced by S. lycopersici and by exogenous applications of the hormones salicylic acid (SA) and jasmonic acid (JA). Furthermore, overexpression of SlERF01 enhanced the hypersensitive response (HR) to S. lycopersici and elevated the expression of defense genes in tomato. Furthermore, the accumulation of lignin, callose and hydrogen peroxide (H2O2) increased in the transgenic lines after inoculation with S. lycopersici. Taken together, our results showed that SlERF01 played an indispensable role in multiple SA, JA and reactive oxygen species (ROS) signaling pathways to provide resistance to S. lycopersici invasion. Our findings also indicated that SlERF01 could activate the expression of the PR1 gene and enhance resistance to S. lycopersici.Conclusions: We identified the SlERF01 gene, which encodes a novel tomato AP2/ERF transcription factor (TF). Functional analysis revealed that SlERF01 positively regulates tomato resistance to S. lycopersici. Our findings indicate that SlERF01 plays a key role in multiple SA, JA and ROS signaling pathways to provide resistance to invasion by S. lycopersici. The findings of this study not only help to better understand the mechanisms of response to pathogens but also enable targeted breeding strategies for tomato resistance to S. lycopersici.

Background Leaf mold disease caused by Cladosporium fulvum is a serious threat affecting the global production of tomato. Cf genes are associated with leaf mold resistance, including Cf-16, which confers effective resistance to leaf mold in tomato. However, the molecular mechanism of the Cf-16-mediated resistance response is largely unknown. Results We performed a comparative transcriptome analysis of C. fulvum-resistant (cv. Ontario7816) and C. fulvum-susceptible (cv. Moneymaker) tomato cultivars to identify differentially expressed genes (DEGs) at 4 and 8 days post inoculation (dpi) with C. fulvum. In total, 1588 and 939 more DEGs were found in Cf-16 tomato than in Moneymaker at 4 and 8 dpi, respectively. Additionally, 1350 DEGs were shared between the 4- and 8-dpi Cf-16 groups, suggesting the existence of common core DEGs in response to C. fulvum infection. The up-regulated DEGs in Cf-16 tomato were primarily associated with defense processes and phytohormone signaling, including salicylic acid (SA) and jasmonic acid (JA). Moreover, SA and JA levels were significantly increased in Cf-16 tomato at the early stages of C. fulvum infection. Contrary to the previous study, the number of up-regulated genes in Cf-16 compared to Cf-10 and Cf-12 tomatoes was significantly higher at the early stages of C. fulvum infection. Conclusion Our results provide new insight into the Cf-mediated mechanism of resistance to C. fulvum, especially the unique characteristics of Cf-16 tomato in response to this fungus.

Background Leaves, which are the most important organs of plants, can not only fix carbon sources through photosynthesis, but also absorb nutrients through transpiration. Leaf development directly determines the growth, flowering and fruiting of plants. There are many factors that affect leaf development, such as the growth environment, gene expression, and hormone synthesis. In this study, tomatoes were used to study the role of the transcription factor Solanum lycopersicum salt-related MYB1-like (SlSRM1-like) in the development of tomato leaves. Results Loss-of-function of the SlSRM1-like gene mediated by clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR-associated 9 (Cas9) resulted in abnormal tomato leaf morphology, including thinner leaves, wrinkled edges, raised veins, disordered edge veins, and left and right asymmetry. An analysis of the transcription levels of genes related to leaf development revealed that the expression of these genes was significantly altered in the SlSRM1-like mutants (SlSRM1-like-Ms). Moreover, the SlSRM1-like gene was expressed at higher transcription levels in young tissues than in old tissues, and its expression was also induced in response to auxin. In addition, the transcription levels of genes related to the auxin pathway, which regulates tomato growth and development, were severely affected in the SlSRM1-like-Ms. Therefore, it is hypothesized that the SlSRM1-like gene functions in the regulation of tomato leaf development through the auxin-related pathway. Conclusions In this study, we successfully knocked out the SlSRM1-like gene in the tomato variety Ailsa Craig using CRISPR technology and found that knockout of the SlSRM1-like gene resulted in abnormal development of tomato leaves. Further research indicated that SlSRM1-like regulated tomato leaf development through auxin-related pathways. The results provide an important reference for the functional study of other SRM1-like genes in plants and provide new insights into the regulation of leaf development in tomato and other plants.

Flowering is a morphogenetic process in which angiosperms shift from vegetative growth to reproductive growth. Flowering time has a strong influence on fruit growth, which is closely related to productivity. Therefore, research on crop flowering time is particularly important. To better understand the flowering period of the tomato, we performed transcriptome sequencing of early flower buds and flowers during the extension period in the later-flowering “Moneymaker” material and the earlier-flowering “20965” homozygous inbred line, and we analyzed the obtained data. At least 43.92 million clean reads were obtained from 12 datasets, and the similarity with the tomato internal reference genome was 92.86–94.57%. Based on gene expression and background annotations, 49 candidate genes related to flowering time and flower development were initially screened, among which the greatest number belong to the photoperiod pathway. According to the expression pattern of candidate genes, the cause of early flowering of “20965” is predicted. The modes of action of the differentially expressed genes were classified, and the results show that they are closely related to hormone regulation and participated in a variety of life activities in crops. The candidate genes we screened and the analysis of their expression patterns provide a basis for future functional verification, helping to explore the molecular mechanism of tomato flowering time more comprehensively.

Flowering is a morphogenetic process in which angiosperms shift from vegetative growth to reproductive growth. Flowering time has a strong influence on fruit growth, which is closely related to productivity. Therefore, research on crop flowering time is particularly important. To better understand the flowering period of the tomato, we performed transcriptome sequencing of early flower buds and flowers during the extension period in the later-flowering “Moneymaker” material and the earlier-flowering “20965” homozygous inbred line, and we analyzed the obtained data. At least 43.92 million clean reads were obtained from 12 datasets, and the similarity with the tomato internal reference genome was 92.86–94.57%. Based on gene expression and background annotations, 49 candidate genes related to flowering time and flower development were initially screened, among which the greatest number belong to the photoperiod pathway. According to the expression pattern of candidate genes, the cause of early flowering of “20965” is predicted. The modes of action of the differentially expressed genes were classified, and the results show that they are closely related to hormone regulation and participated in a variety of life activities in crops. The candidate genes we screened and the analysis of their expression patterns provide a basis for future functional verification, helping to explore the molecular mechanism of tomato flowering time more comprehensively.

Zinc finger-homeodomain proteins (ZF-HDs) are transcription factors that regulate plant growth, development, and abiotic stress tolerance. The SL-ZH13 gene was found to be significantly upregulated under drought stress treatment in tomato ( Solanum lycopersicum ) leaves in our previous study. In this study, to further understand the role that the SL-ZH13 gene plays in the response of tomato plants to drought stress, the virus-induced gene silencing (VIGS) method was applied to downregulate SL-ZH13 expression in tomato plants, and these plants were treated with drought stress to analyze the changes in drought tolerance. The SL-ZH13 silencing efficiency was confirmed by quantitative real-time PCR (qRT-PCR) analysis. In SL-ZH13 -silenced plants, the stems wilted faster, leaf shrinkage was more severe than in control plants under the same drought stress treatment conditions, and the mean stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analyses showed that the activity of superoxide dismutase (SOD) and peroxidase (POD) and the content of proline (Pro) in SL-ZH13 -silenced plants were lower than those in control plants after 1.5 and 3 h of drought stress treatment. The malondialdehyde (MDA) content in SL-ZH13 -silenced plants was higher than that in control plants after 1.5 and 3 h of drought stress treatment, and H 2 O 2 and O 2 – · accumulated much more in the leaves of SL-ZH13- silenced plants than in the leaves of control plants. These results suggested that silencing the SL-ZH13 gene affected the response of tomato plants to drought stress and decreased the drought tolerance of tomato plants.

GATA transcription factors (TFs) are widely distributed in eukaryotes. Some GATA TFs have been shown to be related to photosynthesis, germination, circadian rhythm, and other functions in plants. Our previous study found that some members of this family have obvious responses when tomato plants are subjected to drought stress, in which the SlGATA17 gene is significantly upregulated. To further verify the function of this gene under drought stress, we constructed tomato lines with this gene overexpressed. Phenotypic and physiological indicators indicated that the SlGATA17-overexpressing plants were more drought tolerant than the wild-type plants. Transcriptomic sequencing results showed that the overexpression of the SlGATA17 gene improved the activity of the phenylpropanoid biosynthesis pathway. The PAL enzyme activity assay results confirmed that the initial activity of this pathway was enhanced in transgenic plants, especially in the initial response stage, indicating that the SlGATA17 gene regulates the drought resistance of tomato plants by regulating the activity of the phenylpropanoid biosynthesis pathway.

The SlZF-31 gene is a member of the tomato C2H2 transcription factor family. Previous studies have shown that SlZF-31 gene expression is upregulated under drought stress and salt stress, but the specific function of this gene in tomato plants in response to these two kinds of stress is still unclear. To further explore the function of the SlZF-31 gene in tomato under drought stress and salt stress, we employed the virus-induced gene silencing (VIGS) method to reduce the expression of the SlZF-31 gene in tomato. The results showed that TRV2-SlZF-31 plants had higher levels of wilt and stem bending than CK and CK-TRV2 plants under drought and salt stress. The ABA content of TRV2-SlZF-31 plants were lower than those of CK and CK-TRV2 plants. The analysis of physiological indexes showed that the SOD and POD activity and the PRO content of TRV2-SlZF-31 plants were lower than those of CK and CK-TRV2 plants, while the MDA content of TRV2-SLlZF-31 plants was higher than those of CK and CK-TRV2 plants. The accumulation of H2O2 and O2- in TRV2-SlZF-31 plants was greater than those in CK and CK-TRV2 plants. The values of the chlorophyll fluorescence parameters (ΦII and qL) of TRV2-SlZF-31 plants were significantly lower than those of CK and CK-TRV2 plants. These results showed that the silencing of the SlZF-31 gene reduces the drought resistance and salt tolerance of tomato.

Background APETALA2/ethylene responsive factor (AP2/ERF) transcription factors are a plant-specific family of transcription factors and one of the largest families of transcription factors. Ethylene response factors (ERF) regulate plant growth, development, and responses to biotic and abiotic stress. In a previous study, the ERF2 gene was significantly upregulated in both resistant and susceptible tomato cultivars in response to Stemphylium lycopersici. The main purpose of this study was to systematically analyze the ERF family and to explore the mechanism of ERF2 in tomato plants resisting pathogen infection by the Virus-induced Gene Silencing technique. Results In this experiment, 134 ERF genes were explored and subjected to bioinformatic analysis and divided into twelve groups. The spatiotemporal expression characteristics of ERF transcription factor gene family in tomato were diverse. Combined with RNA-seq, we found that the expression of 18 ERF transcription factors increased after inoculation with S. lycopersici. In ERF2-silenced plants, the susceptible phenotype was observed after inoculation with S. lycopersici. The hypersensitive response and ROS production were decreased in the ERF2-silenced plants. Physiological analyses showed that the superoxide dismutase, peroxidase and catalase activities were lower in ERF2-silenced plants than in control plants, and the SA and JA contents were lower in ERF2-silenced plants than in control plants after inoculation with S. lycopersici. Furthermore, the results indicated that ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance. Conclusions In this study, we identified and analyzed members of the tomato ERF family by bioinformatics methods and classified, described and analyzed these genes. Subsequently, we used VIGS technology to significantly reduce the expression of ERF2 in tomatoes. The results showed that ERF2 had a positive effect on tomato resistance to S. lycopersici. Interestingly, ERF2 played a key role in multiple SA, JA and ROS signaling pathways to confer resistance to invasion by S. lycopersici. In addition, ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance to S. lycopersici. In summary, this study provides gene resources for breeding for disease resistance in tomato.

Background APETALA2/ethylene responsive factor (AP2/ERF) transcription factors are a plant-specific family of transcription factors and one of the largest families of transcription factors. Ethylene response factors (ERFs) regulate plant growth, development, and responses to biotic and abiotic stress. In a previous study, the ERF2 gene was significantly upregulated in both resistant and susceptible tomato cultivars in response to Stemphylium lycopersici. The main purpose of this study is to systematically analyze the ERF family and to explore the mechanism of ERF2 in tomato plants resisting pathogen infection by Virus-induced Gene Silencing (VIGS) technique. Results In this experiment, 134 ERF genes were excavated and subjected to bioinformatic analysis. This experiment divided 134 ERF members into twelve groups based on the conserved domain of the genes. Specific expression of the tomato ERF transcription factor family genes in different organs. Combined with RNA-seq, we found that the expression of 18 ERF transcription factor increased after inoculation with S. lycopersici. In ERF2-silenced plants, the susceptible phenotype was observed after inoculation with S. lycopersici. The hypersensitive response and ROS production were decreased in the silenced ERF2 plants. Physiological analyses showed that the superoxide dismutase, peroxidase and catalase activities were lower in ERF2-silenced plants than in control plants, and the SA and JA contents were lower in ERF2-silenced plants than in control plants after inoculation with S. lycopersici. Furthermore, the results indicated that ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance. Conclusions In this study, we identified and analyzed the members of tomato ERF family by bioinformatics methods, and classified, described and analyzed these genes. we found that ERF2 was positively regulated tomato resistance to S. lycopersici by VIGS. Interestingly, ERF2 played a key role in multiple SA, JA and ROS signaling pathways to confer resistance to invasion by S. lycopersici. In addition, ERF2may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance to S. lycopersici. In summary, this study provides gene resources for breeding for disease resistance in tomato.

Background: Tomato gray leaf spot caused by Stemphylium lycopersici (S. lycopersici) is a serious disease that can severely hinder tomato production. To date, only Sm has been reported to provide resistance against this disease, and the molecular mechanism underlying resistance to this disease in tomato remains unclear. To better understand the mechanism of tomato resistance to S. lycopersici, real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR)-based analysis, physiological indexes, microscopy observations and transgenic technology were used in this study.Results: Our results showed that the expression of SlERF01 was strongly induced by S. lycopersici and by exogenous applications of the hormones salicylic acid (SA) and jasmonic acid (JA). Furthermore, overexpression of SlERF01 enhanced the hypersensitive response (HR) to S. lycopersici and elevated the expression of defense genes in tomato. Furthermore, the accumulation of lignin, callose and hydrogen peroxide (H2O2) increased in the transgenic lines after inoculation with S. lycopersici. Taken together, our results showed that SlERF01 played an indispensable role in multiple SA, JA and reactive oxygen species (ROS) signaling pathways to provide resistance to S. lycopersici invasion. Our findings also indicated that SlERF01 could activate the expression of the PR1 gene and enhance resistance to S. lycopersici.Conclusions: We identified the SlERF01 gene, which encodes a novel tomato AP2/ERF transcription factor (TF). Functional analysis revealed that SlERF01 positively regulates tomato resistance to S. lycopersici. Our findings indicate that SlERF01 plays a key role in multiple SA, JA and ROS signaling pathways to provide resistance to invasion by S. lycopersici. The findings of this study not only help to better understand the mechanisms of response to pathogens but also enable targeted breeding strategies for tomato resistance to S. lycopersici.

In a previous study, when resistant tomato plants (cv. Motelle) carrying the Sm gene were challenged with S. lycopersici, the SLNLC1 gene was significantly upregulated. In this study, to verify the function of the SLNLC1 gene response to disease resistance against S. lycopersici, virus-induced gene silencing (VIGS) was used to downregulate the expression level of the SLNLC1 gene in resistant tomato plants inoculated with S. lycopersici. After inoculation with S. lycopersici, a susceptible phenotype was observed in the silenced SLNLC1-resistant plants. Through microscopy, impaired hypersensitive response (HR) and decreased ROS accumulation were also observed in the silenced SLNLC1 plants. In addition, the production of lignin and callose were decreased in the silenced SLNLC1 plants. Taken together, these results indicated that silencing the SLNLC1 gene attenuated the resistance of tomato plants resistant to S. lycopersici.

S-adenosylmethionine decarboxylase (SAMDC) is a key enzyme in polyamine (PA) biosynthesis, and overexpression of SAMDC in plants can increase the PA level and enhance tolerance to multiple abiotic and biotic stresses. In our previous study, this gene was significantly up-regulated during Cladosporium fulvum resistance gene ( Cf )/ Avirulence ( Avr ) interaction in tomato. In this study, to further understand the role that the SAMDC gene plays in Cf / Avr interaction, the virus-induced gene silencing (VIGS) method was applied to down-regulate SAMDC expression in CGN18423, a line carrying the Cf-19 gene for resistance to C. fulvum . Then, these plants were infected with C. fulvum to analyze changes in resistance. The silencing of SAMDC was confirmed by quantitative real-time PCR (qRT-PCR) analysis and PA quantification. The resistance levels of SAMDC -silenced plants were lower than those of untreated CGN18423 plants. No visible signs of infection were observed on the leaves of untreated CGN18423 plants, while some small chlorotic spots were observed on parts of the leaf margins of SAMDC -silenced plants, and hyphae inside the chlorotic spots were observed late in the hypersensitive response (HR) process. These changes suggested that silencing of the SAMDC gene affected the process of Cf/Avr interaction and decreased the resistance of CGN18423 to C. fulvum .

The plant disease resistance system involves a very complex regulatory network in which jasmonates play a key role in response to external biotic or abiotic stresses. As inhibitors of the jasmonic acid (JA) signaling pathway, JASMONATE ZIM domain (JAZ) proteins have been identified in many plant species, and their functions are gradually being clarified. In this study, 26 JAZ genes were identified in tomato. The physical and chemical properties, predicted subcellular localization, gene structure, cis-acting elements, and interspecies collinearity of 26 SlJAZ genes were subsequently analyzed. RNA-seq data combined with qRT-PCR analysis data showed that the expression of most SlJAZ genes were induced in response to Stemphylium lycopersici, methyl jasmonate (MeJA) and salicylic acid (SA). Tobacco rattle virus RNA2-based VIGS vector (TRV2)-SlJAZ25 plants were more resistant to tomato gray leaf spots than TRV2-00 plants. Therefore, we speculated that SlJAZ25 played a negative regulatory role in tomato resistance to gray leaf spots. Based on combining the results of previous studies and those of our experiments, we speculated that SlJAZ25 might be closely related to JA and SA hormone regulation. SlJAZ25 interacted with SlJAR1, SlCOI1, SlMYC2, and other resistance-related genes to form a regulatory network, and these genes played an important role in the regulation of tomato gray leaf spots. The subcellular localization results showed that the SlJAZ25 gene was located in the nucleus. Overall, this study is the first to identify and analyze JAZ family genes in tomato via bioinformatics approaches, clarifying the regulatory role of SlJAZ25 genes in tomato resistance to gray leaf spots and providing new ideas for improving plant disease resistance.

Sugar is an important component affecting fruit quality and taste and has been studied in many plants. Tomatoes are consumed in very large amounts worldwide, but to date, few reports on the quantitative trait loci (QTLs) for the sugar content in tomato fruits have been published. In this study, we analyzed the genetic model of the soluble sugar content in ripe tomato fruits and the reasons for the differences. We determined that the inheritance of the soluble sugar content in tomato fruits followed a negative dominance pattern, with a predominantly polygenic effect. Moreover, we identified two chromosomal regions by bulked-segregant analysis (BSA) sequencing analysis and initially screened 47 genes that may affect the soluble sugar content of tomato fruits.

Tomato gray leaf spot caused by Stemphylium lycopersici is a recent epidemic disease. In a previous study, SlPKY1 was obviously upregulated after infection with S. lycopersici in resistant (cv. Motelle) tomato plants. Our study aimed to identify the function of SlPKY1 in response to tomato gray leaf spot. In addition, the expression of SlPKY1 was significantly upregulated in tomato plants sprayed with salicylic acid (SA) and jasmonic acid (JA). Virus-induced gene silencing (VIGS) was used to confirm the function of SlPKY1 in resistant plants. The results showed that SlPKY1-silenced plants were susceptible at 3 days post inoculation (dpi) with increased accumulation of reactive oxygen species and showed changed activities of disease-resistance enzymes. Lactophenol trypan blue staining was used to identify the hypersensitive response (HR) mediated by the resistance protein Sm at key time points after inoculation with S. lycopersici. qRT-PCR was used to explore the possible relationships between SlPKY1 and related defense genes. We found that the silencing of SlPKY1 resulted in attenuated expression of related defense genes after infection with S. lycopersici in tomato plants. Overall, our results indicated that SlPKY1 may be a positive regulator of response to tomato gray leaf spot.

Tomato yellow leaf curl virus (TYLCV) is one of the most devastating viruses of cultivated tomato in both tropical and subtropical regions. Five major genes (Ty-1, Ty-2, Ty-3, Ty-4 and Ty-5) from wild tomato species have been associated with resistance to TYLCV. Researchers have recently attempted to determine the functions of these resistance genes, but molecular mechanisms underlying the observed resistance remain unclear. Here, resistant (cv. CLN3212A-23, carrying Ty-5) and susceptible (cv. Moneymaker) plants were either left untreated (R and S, respectively) or artificially inoculated with TYLCV via Agrobacterium-mediated transformation (RT and ST, respectively). The transcriptomes of the plants in the four groups were then analyzed by RNA-Seq, and the results identified 8,639 differentially expressed genes (DEGs) between the R and RT groups, 2,818 DEGs between the RT and ST groups, 8,899 DEGs between the S and ST groups, and 707 DEGs between the R and S groups. The gene expression profiles in both the resistant and susceptible tomato cultivars appeared to undergo notable changes after viral inoculation, and functional classification revealed that most DEGs were associated with 18 GO terms. Moreover, the functional classification of the response of Ty-5-carrying tomato plants to TYLCV infection identified the importance of the GO term “response to stimulus” in the BP category, which is related to disease resistance. In addition, 28 genes were significantly enriched in the “Plant hormone signal transduction”, “Carbon metabolism”, “ Carbon fixation in photosynthetic organisms ” and “ Glutathione metabolism ” pathways. The differential expression levels of 12 select genes were confirmed by quantitative real-time PCR. The present study indicates that the Ty-5 gene activates the expression of multiple genes involved in the resistance process and will aid a more in-depth understanding of the effects of the Ty-5 gene on resistance based on its molecular mechanism with the aim of improving TYLCV disease management in tomato.

Gray leaf spot disease caused by Stemphylium lycopersici is a major disease in cultivated tomato plants and threatens tomato-growing areas worldwide. Sm is a single dominant gene that confers resistance to tomato gray leaf spot disease agent. However, the underlying molecular mechanism remains unclear. Here, resistant (cv. Motelle, containing the Sm gene) and susceptible (cv. Moneymaker) plants were inoculated with virulent Stemphylium lycopersici isolate at a time point at which both cultivars showed a strong response to S. lycopersici infection. Transcriptome analyses were performed in both cultivars using RNA-seq. The number of differentially expressed genes (DEGs) was higher in Motelle than Moneymaker. Functional classification revealed that most DEGs were involved in plant–pathogen interactions, plant hormone signal transduction, regulation of autophagy, glycerophospholipid metabolism, and α-linolenic acid metabolism. Moreover, the genes that were significantly up-regulated in Sm tomatoes were involved in plant–pathogen interaction pathways. A total of 26 genes were selected for confirmation of differentially expressed levels by quantitative real-time PCR. This knowledge will yield new insights into the molecular mechanism of Sm responses to S. lycopersici infection.

Gray leaf spot disease caused by Stemphylium lycopersici is a major disease in cultivated tomato plants and threatens tomato-growing areas worldwide. Sm is a single dominant gene that confers resistance to tomato gray leaf spot disease agent. However, the underlying molecular mechanism remains unclear. Here, resistant (cv. Motelle, containing the Sm gene) and susceptible (cv. Moneymaker) plants were inoculated with virulent Stemphylium lycopersici isolate at a time point at which both cultivars showed a strong response to S. lycopersici infection. Transcriptome analyses were performed in both cultivars using RNA-seq. The number of differentially expressed genes (DEGs) was higher in Motelle than Moneymaker. Functional classification revealed that most DEGs were involved in plant–pathogen interactions, plant hormone signal transduction, regulation of autophagy, glycerophospholipid metabolism, and α-linolenic acid metabolism. Moreover, the genes that were significantly up-regulated in Sm tomatoes were involved in plant–pathogen interaction pathways. A total of 26 genes were selected for confirmation of differentially expressed levels by quantitative real-time PCR. This knowledge will yield new insights into the molecular mechanism of Sm responses to S. lycopersici infection.

During the summer growing season in 2016 and 2017, a disease of potato (Solanum tuberosum) was observed in the suburbs of Harbin City, Heilongjiang Province, China. The disease was prevalent in nine greenhouses, and in over half the greenhouses the disease was observed on more than 75% of the plants. Symptoms in the early stages appeared as brownish-black specks with chlorotic, yellowish haloes. Subsequently, the specks developed into grayish lesions (2 to 10 mm in diameter). Occasionally, the middle part of a lesion became necrotic and fell off, forming a hole. Rapid wilting of the foliage also occurred with disease development. Small pieces of infected leaves were surface sterilized in 75% ethanol followed by 0.1% mercuric chloride solution, rinsed twice with sterile distilled water, and plated on potato dextrose agar in Petri dishes incubated at 28°C for 5 to 10 days with a 12-h photoperiod. A fungus producing oblong conidia with a conical apex and a bluntly rounded base, that measured 51 to 76 μm long and 16 to 25 μm wide, were constricted at three major transverse septa, and that were pale to mid brown in color were consistently isolated from symptomatic tissue. Based on these morphological characteristics the fungus was identified as Stemphylium lycopersici (Woudenberg et al. 2017). Genomic DNA was extracted, and the internal transcribed spacer (ITS) regions were amplified and sequenced with primers ITS1 and ITS4. All sequences were submitted to GenBank (accession nos. MF480547, MF480548, and MF480549). BLAST search results showed that all sequences showed 99% identity with S. lycopersici (KR911814) (Hong et al. 2012). The isolates were also identified as S. lycopersici based on the glyceraldehyde-3-phosphate dehydrogenase, and all sequences were submitted to GenBank (accession nos. MH135281 and MH135282) and showed 100% identity with S. lycopersici isolate from tomato (KT957743.1) (Sun et al. 2016). To complete Koch’s postulates, leaves of five potato plants were sprayed with a conidial suspension (1 × 10⁵ spores/ml) of one of the above isolates. Control plants were sprayed with sterilized water. Plants were maintained in a greenhouse at 25 ± 2°C with relative humidity >80%. After 5 to 8 days, inoculated plants developed symptoms similar to original diseased plants in the field, whereas control plants remained symptomless. The fungus was reisolated from leaf lesions, thus confirming Koch’s postulates. Following reports of the fungus causing disease on eggplant (Yang et al. 2017) and tomato (Sun et al. 2016) in the new geographic location of China, to our knowledge this is the first report of S. lycopersici causing gray leaf spot of potato.