Stemphylium Lycopersici Research Articles

Secondary Metabolites from the Endophytic Fungus Stemphylium lycopersici and Their Antibacterial Activities

Secondary Metabolites from the Endophytic Fungus Stemphylium lycopersici and Their Antibacterial Activities

Functional analysis of the SlERF01 gene in disease resistance to S. lycopersici

BackgroundTomato 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.ResultsOur 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.ConclusionsWe 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.

Virus-induced gene silencing of SlPKY1 attenuates defense responses against gray leaf spot in tomato

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.

First Report of Leaf and Stem Spot on Common Bean Caused by Stemphylium lycopersici in China

Common bean (Phaseolus vulgaris L.) is one of the most economically important vegetable crops in China. In October 2018, leaf and stem spot symptoms were observed on P. vulgaris in Pozhuang County, Anqiu City, Shandong Province, China. The disease incidence ranged from 15 to 20%, causing large economic losses to growers. Lesions were initially small (1 to 2 mm in diameter), scattered, reddish-brown spots on leaves and stems. As the disease progressed, lesions expanded and merged, resulting in withering of the whole leaves and gradually drying of the whole plant. To isolate the pathogen, diseased tissue (5 × 5 mm) was cut from the margins of lesions and surface disinfected with 70% ethanol for 15 s followed by 0.1% mercuric dichloride for 2 min and then rinsed four to five times with sterile distilled water. The specimens were then transferred to potato dextrose agar plates and incubated at 28°C for 5 or 7 days. Nineteen fungal isolates with similar morphological characteristics were obtained. The colony of G9RS, a representative isolate, was white to brownish in obverse and deep red in reverse with a vivid red mycelial pigmentation that diffused into the culture medium. The conidia produced on potato carrot agar (PCA) as the standard medium were solitary, oblong, constricted at the main transverse septum, and measured 36.4 ± 7.3 × 16.5 ± 2.6 μm (n = 50). For molecular characterization, genomic DNA was extracted by CTAB (Niu et al. 2010), and sequences of the internal transcribed spacer (ITS) regions (White et al. 1990) and glyceraldehyde-3-phosphate dehydrogenase (GPD) genes were amplified from isolates using the primer pairs ITS1/ITS4 and gpdf/gpdr (Câmara et al. 2002), respectively. The ITS and GPD sequences of isolate G9RS were submitted to GenBank (MN386223 and MN393479, respectively). BLASTn analysis of the sequences showed 99% identity with Stemphylium lycopersici (KX858848 and KR911809). Phylogenetic analysis (MEGA 7) using the neighbor-joining algorithm showed that the current isolate was clustered with S. lycopersici isolates (NO 425 and EGS46-001). Based on morphological and molecular characteristics, the isolate G9RS was identified as S. lycopersici. A pathogenicity test was conducted on intact plants according to Koch’s postulates. Conidia were collected from 21-day-old PCA cultures grown at 28°C under black light blue irradiation (365 nm) with a 12-h light/dark cycle, suspended in sterilized distilled water at 1.0 × 10⁵ conidia/ml, and the conidial suspension applied to ten 50-day-old bean plants (3 ml/plant). Ten plants inoculated with sterile distilled water served as controls. All samples were incubated in a growth chamber at 28°C. After 8 to 10 days, inoculated plants developed symptoms similar to original diseased plants in the field, whereas control plants remained symptomless. The same fungus was successfully reisolated from inoculated leaves and reidentified based on morphology and molecular evidence. The assay was conducted twice. Although S. lycopersici has been reported to cause leaf spot symptoms on other hosts, such as lettuce (Liu et al. 2019), potato (Yang et al. 2018), eggplant (Yang et al. 2017), Sansevieria (Kee et al. 2018), and pepino (Nasehi et al. 2016), to our knowledge, this is the first report of leaf and stem spot on common bean in China. Because the common bean is one of the most intensively planted crops in Shandong, this pathogen could have serious economic impact and may warrant development of integrated management strategies.

First Report of Leaf Spot Caused by Stemphylium lycopersici on Zinnia elegans in China

Zinnia elegans originated from Mexico and has been widely cultivated as an ornamental plant in China. In August 2018, leaf spots were observed on Z. elegans in Tai’an, Shandong province, China. The symptoms appeared on the edge of the leaves as small brown spots. In serious cases, the leaves were withered, which affected the ornamental value of the plants. Diseased leaf samples were cut into small segments, put onto moist filter papers within Petri dishes, and incubated at 25°C. Spores resembling Stemphylium developed from the tissues after 1 day and were singly picked up and transferred to potato dextrose agar (PDA). Morphologically, all the colonies were identical to each other, and the strain YZU 181216 was selected for further study. A pure culture of YZU 181216 was deposited in the Fungi Herbarium of Yangtze University, Jingzhou, Hubei, China. To determine the colony morphology of the species, mycelial plugs (6 mm in diameter) were transferred to fresh PDA and incubated at 23°C in darkness. After 7 days, the colony was vinaceous buff, reverse cinnamon to buff, 52 to 53 mm in size. To examine its conidial morphology, the mycelium was transferred onto potato carrot agar (PCA) and incubated at 23°C under an 8-h photoperiod for 7 days. On PCA, conidiophores were straight or curved, 88 to 179 × 3.5 to 6 µm in size; conidia were solitary, oblong, three to five transverse septa, 24 to 59 × 11.5 to 20.5 µm in size, with a conical apex and bluntly rounded base. Based on morphology, the fungus was identified as Stemphylium lycopersici (21 to 60 × 12 to 24 µm) described by Yamamoto (1960). To corroborate morphological identification, genomic DNA of the strain was extracted from 3-day-old mycelia grown on PDA. Three gene fragments, including the internal transcribed spacer rDNA region (ITS), glyceraldehydes-3-phosphate dehydrogenase (gapdh), and calmodulin (cmdA), were amplified with primer pairs ITS5/ITS4, gpd1/gpd2, and CALDF1/CALDR2, respectively (Woudenberg et al. 2017). Sequences of the strain were deposited in the GenBank with accession numbers MK895975 (ITS), MK895977 (gapdh), and MK895976 (cmdA). Relevant gene sequences of Stemphylium spp. were derived from GenBank, and the three gene sequences were combined after alignment. Maximum likelihood analysis based on the combined three gene sequences was conducted with an evolutionary model of GTR+I+G under 1,000 bootstrap replicates. The phylogenetic tree showed that the strain YZU 181216 clustered with S. lycopersici (CBS 124980 and CBS 124981) and was supported by a bootstrap value of 100%. To confirm its pathogenicity, mycelial plugs (6 mm in diameter) were inoculated on living leaves of Z. elegans. Control groups were inoculated with fresh PDA plugs. The plants were covered with plastic bags and incubated in a greenhouse at 25°C. Brown spots were observed on the leaves after 2 days. Infected tissues withered after 5 days, similar to the original symptoms that occurred in the field. No symptoms were observed on control groups. The fungus reisolated from infected leaves was identical to S. lycopersici based on conidial morphology and gapdh gene sequence. To our knowledge, this is the first report of Z. elegans leaf spot caused by S. lycopersici in China.

In Vitro Mutagenesis followed by Polymorphism Detection Using Start Codon Targeted Markers to Engineer Brown Spot Resistance in Kalanchoe

Kalanchoe (Kalanchoe blossfeldiana) is a common potted flower that is popular throughout the world. Brown spot (caused by Stemphylium lycopersici) is one of the common foliage diseases in kalanchoe. This disease tends to infect leaves of kalanchoe plants in hot and humid environments, reducing their aesthetic value. The current investigation aimed to generate mutations resistant to brown spot in ‘Mary’ kalanchoe through chemical mutagenesis followed by molecular marker identification. Putative mutants were developed by treating embryogenic calluses with ethyl methanesulfonate (EMS) at median lethal doses (LD50)–either a 0.8% concentration for 2 hours or a 1.0% concentration for 0.5 hours. Brown spot crude toxin solution was used as the selection agent to identify disease-resistant calluses during tissue culture. The optimal crude concentration (60%) was determined by soaking calluses with different concentrations of crude pathogen: 0%, 20%, 40%, 60%, and 80% (v/v). A total of 32 anti-brown spot lines were regenerated and tested for disease resistance with detached leaves. Three regenerated EMS mutant lines showed no obvious brown spot lesions on their leaves after the disease resistance assay and were subjected to polymorphism identification by start codon targeted (SCoT) molecular markers. Three (SCoT40, SCoT71, and SCoT72) of 45 selected primers were chosen to identify the mutants. This work may lay the foundation for further development of new disease-resistant cultivars of kalanchoe.

Anthraquinone derivatives from a coral associated fungus Stemphylium lycopersici

Two new anthraquinone derivatives, alterporriol Y (1) and macrosporin 2-O-α-D-glucopyranoside (2), together with five known analogues (3-7) were isolated from the fungus Stemphylium lycopersici associated with the gorgonian coral Dichotella gemmacea collected from the South China Sea. Their structures were determined on the basis of detailed spectroscopic analysis and comparison with reported data. The absolute configurations were determined by the ECD method. In an in vitro cytotoxic assay, compound 3 and 4 showed potent effects against HCT-116 and MCF-7 cell lines. Compound 4 also exhibited cytotoxicity toward Huh7 stem cell-like cells.

Potential of Novel Sequence Type of Burkholderia cenocepacia for Biological Control of Root Rot of Maize (Zea mays L.) Caused by Fusarium temperatum.

In this study, two Burkholderia strains, strain KNU17BI2 and strain KNU17BI3, were isolated from maize rhizospheric soil, South Korea. The 16S rRNA gene and multilocus sequence analysis and typing (MLSA-MLST) were used for the identification of the studied strains. Strain KNU17BI2, which belonged to Burkholderia cenocepacia, was of a novel sequence type (ST) designated ST-1538, while strain KNU17BI3 had a similar allelic profile with the seven loci of Burkholderia contaminans strain LMG 23361. The strains were evaluated in vitro for their specific plant growth promoting (PGP) traits, such as zinc solubilization, phosphate solubilization, ammonia production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole acetic acid (IAA) production, siderophore, and hydrolytic enzyme activity. Interestingly, the strains exhibited a positive effect on all of the tested parameters. The strains also showed broad-spectrum antifungal activity against economically important phytopathogens in the dual culture assay. Furthermore, the strains were evaluated under greenhouse conditions for their in vivo effect to promote plant growth and to suppress the root rot of maize that is caused by Fusarium temperatum on four Korean maize cultivars. The results of the greenhouse study revealed that both of the strains were promising to significantly suppress fusarium root rot and enhance plant growth promotion on the four maize cultivars. This study, for the first time, reported in vitro antifungal potential of B. cenocepacia of novel ST against economically important plant pathogens viz., F. temperatum, Fusarium graminearum, Fusarium moniliforme, Fusarium oxysporum f.sp. melonis, Fusarium subglutinans, Phytophthora drechsleri, and Stemphylium lycopersici. This is also the first report of zinc solubilization by B. cenocepacia. Moreover, the present research work reports, for the first time, about the potential of B. cenocepacia and B. contaminans to control the root rot of maize that is caused by F. temperatum. Therefore, we recommend further studies to precisely identify the bioactive chemical compounds behind such activities that would be novel sources of natural products for biological control and plant growth promotion of different crops.

First report of Stemphylium lycopersici causing leaf spot on hot pepper in China

Hot pepper is an exceedingly popular vegetable crop in China and is cultivated on 737 hectares in Beijing. A severe leaf disease with typical symptoms of spots with grey centres and dark brown borders was observed on hot pepper plants in Beijing in the winter of 2016. More than 50% of all plants in the region were infected. Fungal cultures were isolated from naturally infected leaf tissue, and identified as Stemphylium lycopersici based on morphological features, cultural characteristics and molecular identification by sequencing the ITS, gpd and cmdA genes. Pathogenicity was determined by inoculating healthy pepper plants with hyphal suspensions, and the fungus was re-isolated from developing lesions on the inoculated plants, thus fulfilling Koch’s postulates. This is the first report of natural infection by S. lycopersici causing leaf spot on hot pepper in China.

Identification of endophytic fungi from the medicinal plants of Biligirirangana hill, Karnataka

Four plants with medicinal properties Carica papaya, Phyllanthus amarus, Tinospora cordifolia and Azadiracta indica were selected as a host plant for the isolation of endophytic fungi collected from Biligirirangana Hill, ranges from 11° 40’ to 12° 09’ North and 77° 05’ to 77° 01’ East, the southern part of Eastern Ghats Chamarajanagar District, Karnataka. The leaves of these plants revealed two, four, six and three isolates of endophytic fungi which belonged to the family Hypomycetes, Ascomycetes, Dothideomycetes, Coleomycetes respectively. One of the unidentified strain from each of the above four medicinal plant isolate was subjected to molecular analysis followed by 18SrRNA sequence, internal transcribed spacer regions and phylogenetic analysis. Based on the gene sequencing and phylogenetic tree the clusters species of the fungal isolate was found to be Stemphylium lycopersici, Epicoccum nigrum, Leptosphaerulina arachidicola and Phomopsis azadirachtae reported in this paper.

Prediction of pathogenesis-related secreted proteins from Stemphylium lycopersici

BackgroundGray leaf spot is a devastating disease caused by Stemphylium lycopersici that threatens tomato-growing areas worldwide. Typically, many pathogenesis-related and unrelated secreted proteins can be predicted in genomes using bioinformatics and computer-based prediction algorithms, which help to elucidate the molecular mechanisms of pathogen-plant interactions.ResultsS. lycopersici-secreted proteins were predicted from 8997 proteins using a set of internet-based programs, including SignalP v4.1 TMHMM v2.0, big-PI Fungal Predictor, ProtComp V9.0 and TargetP v1.1. Analysis showed that 511 proteins are predicted to be secreted. These proteins vary from 51 to 600 residues in length, with signal peptides ranging from 14 to 30 residues in length. Functional analysis of differentially expressed proteins was performed using Blast2GO. Gene ontology analysis of 305 proteins classified them into 8 groups in biological process (BP), 6 groups in molecular function (MF), and 10 groups in cellular component (CC). Pathogen-host interaction (PHI) partners were predicted by performing BLASTp analysis of the predicted secreted proteins against the PHI database. In total, 159 secreted proteins in S. lycopersici might be involved in pathogenicity and virulence pathways. Scanning S. lycopersici-secreted proteins for the presence of carbohydrate-active enzyme (CAZyme)-coding gene homologs resulted in the prediction of 259 proteins. In addition, 12 of the 511 proteins predicted to be secreted are small cysteine-rich proteins (SCRPs).ConclusionsS. lycopersici secretory proteins have not yet been studied. The study of S. lycopersici genes predicted to encode secreted proteins is highly significant for research aimed at understanding the hypothesized roles of these proteins in host penetration, tissue necrosis, immune subversion and the identification of new targets for fungicides.

Crystal Structure of a Novel 1,2,4- Triazolo[4,3-a]Pyridine Compound with Antifungal Activity

The title compound 8-chloro-3-((4-cyanobenzyl)thio)-[1,2,4]triazolo[4,3-a]pyridine is prepared from 1- cyano-4-(chloromethyl)benzene and 8-chloro-[1,2,4]triazolo[4,3-a]pyridine-3(2H)-thione in the presence of NaOH, and its structure is determined by the X-ray diffraction analysis. The crystals are monoclinic, space group P2(1)/n, with a = 14.018(8) A, b = 4.096(2) A, c = 22.974(12) A, β = 99.759(9)°, V = 1300.1(12) A3, and Z = 4, the final R = 0.0343 and wR = 0.0788 for 2505 observed reflections with I > 2σ(I). The preliminary biological test shows that the title compound has activities against Stemphylium lycopersici (Enjoji) Yamamoto, Fusarium oxysporum. sp. cucumebrium, and Botrytis cinerea with inhibitory to be 51.19%, 62.02%, 15.56% respectively.

First Report of Stemphylium lycopersici Causing Gray Leaf Spot on Potato in China.

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.

Draft Genome Sequences of Sporulating (CIDEFI-213) and Nonsporulating (CIDEFI-212) Strains of Stemphylium lycopersici.

Stemphylium lycopersici (Pleosporales) is a pathogenic fungus found on a broad range of plant hosts. It is one of the causal agents of gray leaf spot disease in tomato that causes severe yield reductions and economic losses worldwide. Here, we present the draft genome sequences and the gene annotations of two strains of S. lycopersici, nonsporulating strain CIDEFI-212 and sporulating strain CIDEFI-213.

Effectiveness of multi-trait Burkholderia contaminans KNU17BI1 in growth promotion and management of banded leaf and sheath blight in maize seedling

Plant growth promoting (PGP) bacteria enhance plant growth and are a green alternative to chemical fertilizers. In our study, an effective plant growth promoting rhizobacteria (PGPR) strain, KNU17BI1, was isolated from rhizospheric soil of maize, South Korea. The strain was tested in vitro for specific PGP and antifungal traits, such as phosphate solubilization, zinc solubilization, indole acetic acid (IAA) production, ammonia production, nitrogen fixation, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, siderophore hydrogen cyanide production (HCN) and hydrolytic enzyme activity. Furthermore, in viro antifungal activity was done in a laboratory and in vivo effect of KNU17BI1 on banded leaf and sheath blight intensity as well as plant growth promotion on maize seedling were conducted under greenhouse conditions. The strain was found to be highly effective toward all the parameters except HCN production. The strain KNU17BI1 was identified on the basis of 16S RNA and multilocus sequence analysis (MLSA) and confirmed as Burkholderia contaminans. This study for the first time demonstrated potent in vitro antifungal activity of B. contaminans against Rhizoctonia solani AG-1(IA), Pythium graminicola, Fusarium moniliforme, Alternaria alternata, Alternaria solani, Fusarium graminearum, Stemphylium botryosum Wallr, Colletotrichum dematium, Stemphylium lycopersici and Fusarium oxysporum f.sp. melonis. Furthermore, in this study, for the first time, the potential of B. contaminans stain KNU17BI1 in controlling banded leaf and sheath blight of maize caused by R. solani AG-1(IA) was reported. Therefore, further studies are warranted on the structural identification of actual compounds behind such activities that would be exploited further for biocontrol as well as plant growth promotion.

Enantioselective biotransformation of sterically hindered amine substrates by the fungus Stemphylium lycopersici.

To screen 20 micro-organisms for ω-transaminase (ω-TA) activity by the kinetic resolution of rac-1-phenylethylamine, followed by testing rac-amines of pharmaceutical interest with bulky substituents and to conduct the asymmetric synthesis of a chiral amine. Stemphylium lycopersici was selected as the best biocatalyst. By the central composite rotatable design (CCRD), it was found that, at lower pH (5·5 and 6·5), the lyophilized micro-organism biocatalysed the kinetic resolution of rac-1-phenylethylamine with 99% enantiomeric excess (e.e.) ((R)-enantiomer) with acetophenone conversions ranged from 41 to 45%. Interestingly, the lyophilized crude enzymatic extract lead to better results at pH from 7·0 to 9·0, with conversions up to 47% and about 99% e.e. We also attested that as much as higher is the pyruvate (amino acceptor) concentration, higher is the acetophenone conversion, corroborating the presence of ω-TA-type enzymes. Among different sterically hindered racemic amines tested, rac-1,2,3,4-tetrahydro-1-naphthylamine and rac-phenylbutylamine were satisfactorily kinetically resolved in up to 91% e.e. (R). The results for the asymmetric synthesis showed excellent conversion (>85%) for the S-1-phenylethylamine, indicating (S)-stereopreference. Stemphylium lycopersici showed to be an important tool for broader substrate scope transaminases and a relevant player on the development of new biocatalysts with ability in asymmetric synthesis reactions. Here in, we contribute to the improvement of the biocatalytic toolbox for chiral amines synthesis. Interestingly, we have found that the crude enzymatic extract of the endophytic fungus S. lycopersici could accept bulky substrates with reasonable activity, compared to the wild-type transaminase already published over literature, and with high enantioselectivity.

Mapping and screening of the tomato Stemphylium lycopersici resistance gene, Sm, based on bulked segregant analysis in combination with genome resequencing

BackgroundTomato gray leaf spot disease caused by Stemphylium lycopersici (S. lycopersici) is considered one of the major diseases of cultivated tomatoes. The only S. lycopersici resistance gene, Sm, was derived from the wild tomato species S. pimpinellifolium. Sm has been identified as an effective source of gray leaf spot resistance in tomatoes and has been mapped to tomato chromosome 11. In this study, the first bulked segregant analysis (BSA) combined with genome resequencing for the mapping and screening of the Sm candidate gene was performed.ResultsBased on the resequencing results, we identified 50,968 Diff-markers, most of which were distributed on chromosome 11. A total of 37 genes were located in the interval of 0.26-Mb. The gene loci of resistant and susceptible lines were sequenced successfully using PCR products. The relative expression levels of candidate genes in resistant and susceptible lines were confirmed via qRT-PCR, Solyc11g011870.1.1 and Solyc11g011880.1.1 were identified through qRT-PCR. A marker, D5, which was cosegregated with the resistant locus, was identified according to the mutation of the Solyc11g011880.1.1 trait in the resistant line.ConclusionsThe Sm gene was mapped to the short arm of chromosome 11. The candidate genes Solyc11g011870.1.1 and Solyc11g011880.1.1 displayed expression patterns related to the resistance response. This study will be valuable for Sm cloning and Sm gene breeding in tomato.

The mitochondrial genome of the plant-pathogenic fungus Stemphylium lycopersici uncovers a dynamic structure due to repetitive and mobile elements.

Stemphylium lycopersici (Pleosporales) is a plant-pathogenic fungus that has been associated with a broad range of plant-hosts worldwide. It is one of the causative agents of gray leaf spot disease in tomato and pepper. The aim of this work was to characterize the mitochondrial genome of S. lycopersici CIDEFI-216, to use it to trace taxonomic relationships with other fungal taxa and to get insights into the evolutionary history of this phytopathogen. The complete mitochondrial genome was assembled into a circular double-stranded DNA molecule of 75,911 bp that harbors a set of 37 protein-coding genes, 2 rRNA genes (rns and rnl) and 28 tRNA genes, which are transcribed from both sense and antisense strands. Remarkably, its gene repertoire lacks both atp8 and atp9, contains a free-standing gene for the ribosomal protein S3 (rps3) and includes 13 genes with homing endonuclease domains that are mostly located within its 15 group I introns. Strikingly, subunits 1 and 2 of cytochrome oxidase are encoded by a single continuous open reading frame (ORF). A comparative mitogenomic analysis revealed the large extent of structural rearrangements among representatives of Pleosporales, showing the plasticity of their mitochondrial genomes. Finally, an exhaustive phylogenetic analysis of the subphylum Pezizomycotina based on mitochondrial data reconstructed their relationships in concordance with several studies based on nuclear data. This is the first report of a mitochondrial genome belonging to a representative of the family Pleosporaceae.

Corynespora cassiicola and Stemphylium lycopersici infection and disease development on tomatoes in Argentina

Two pathogens were isolated from tomatoes with severe chlorosis and necrosis in northwestern Argentina. Monosporic cultures were morphologically characterised and molecularly identified as Stemphylium lycopersici and Corynespora cassiicola. This is the first report of C. cassiicola infecting tomato in Argentina.

Transcriptome Analysis of the Sm-Mediated Hypersensitive Response to Stemphylium lycopersici 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.