PR Genes Research Articles

Jasmonic Acid and Salicylic Acid improved resistance against Spodoptera frugiperda Infestation in maize by modulating growth and regulating redox homeostasis

Exploring host plant resistance and elevating plant defense mechanisms through the application of exogenous elicitors stands as a promising strategy for integrated pest management. The fall armyworm, a pernicious menace to grain crops in tropical and subtropical regions, stands as a formidable threat due to its capacity for devastation and a wide-ranging spectrum of host plants. There is no literature regarding artificially induced resistance in maize against fall armyworm (Spodoptera frugiperda) by exogenous application of phytohormones. The present investigation was performed to evaluate the role of jasmonic acid (JA) and salicylic acid (SA) on two maize hybrids namely FH-1046 and YH-1898 against fall armyworm. Results showed that plant height, biomass and lengths, fresh and dry weight of root shoot which decreased with armyworm infestation improved with phytohormonal application. JA treatment resulted in a higher increase in all attributes as compared to SA treatment. Improvement in relative water contents, photosynthetic pigments and pronounced levels of phenol and proline accumulation were observed in infested plants after JA treatment. Infested plants recovered from oxidative stress as JA application activated and increased the antioxidant enzyme activity of superoxide dismutase, peroxidase and polyphenol oxidase activity in both FH-1046 and YH-1898 . The oxidative stress reduction in infested plants after JA treatment was also evident from a fair decrease in MDA and H2O2 in both varieties. The SA and JA mediated genes expression was studied and it was found that in FH1046 maize cultivar, JA dependent genes, particularly marker genes PR1 and Lox5 were highly expressed along with TPS10 and BBT12. Whereas SPI, WRKY28, ICS and PAL were shown to be activated upon SA application. Evidently, both JA and SA elicited a robust defensive response within the maize plants against the voracious S. frugiperda, which in consequence exerted a discernible influence over the pest's developmental trajectory and physiological dynamics. A decrease in detoxification enzyme activity of the insects was observed after feeding on treated plants. Moreover, it was recorded that the survival and weight gain of FAW feeding on phytohormone treated maize plants also decelerated. In conclusion, FH-1046 was found to be more tolerant than YH-1898 against fall armyworm infestation and 1 mM JA was more effective than 1 mM SA for alleviation of fall armyworm stress. Therefore, it was inferred that phytohormones regulated redox homeostasis to circumvent oxidative damage and mediate essential metabolic events in maize under stress. To our current understanding, this study is the very first presentation of induced resistance in maize against S. frugiperda with the phytohormonal application (JA and SA).

A glycine-rich nuclear effector VdCE51 of Verticillium dahliae suppresses plant immune responses by inhibiting the accumulation of GhTRXH2

Verticillium dahliae is an important soil-borne fungal pathogen that causes great yield losses in many cash crops. Effectors of this fungus are known to regulate plant immunity but the mechanism much remains unclear. A glycine-rich nuclear effector, VdCE51, was able to suppress immune responses in tobacco against Botrytis cinerea and Sclerotinia sclerotiorum. This effector was a required factor for full virulence of V. dahliae, and its nuclear localization was a requisite for suppressing plant immunity. The thioredoxin GhTRXH2, identified as a positive regulator of plant immunity, was a host target of VdCE51. Our findings show a virulence regulating mechanism whereby the secreted nuclear effector VdCE51 interferes with the transcription of PR genes, and the SA signaling pathway by inhibiting the accumulation of GhTRXH2, thus suppressing plant immunity.

Genome-wide characterization and expression analysis of the cultivated peanut AhPR10 gene family mediating resistance to Aspergillusflavus L.

The pathogenesis-related protein PR10 is essential for plant growth, development, and stress responses. In this study, PR10 genes in cultivated peanut (Arachis hypogaea L.) were systematically identified, after which their phylogenetic relationships, conserved motifs, gene structures, and syntenic relationships were analyzed. A total of 54 AhPR10 genes were identified. They were then divided into eight groups according to their phylogenetic relationships, which were supported by the characterization of gene structures and conserved motifs. Analyses of chromosomal distribution and synteny revealed that segmental duplications were critical for the expansion of the AhPR10 gene family. In addition, the identified AhPR10 genes had constitutive and inducible expression patterns. Notably, AhPR10-7, AhPR10-33, and AhPR10-41 may have crucial functions affecting the resistance of peanut to A. flavus. In vitro fungistatic experiments indicated that recombinant AhPR10-33 can effectively inhibit A. flavus mycelial growth. The study results provide useful insights for future research on AhPR10 functions that protect peanut from the detrimental effects of A. flavus.

Functional characterization of AcWRKY94 in response to Pseudomonas syringae pv. actinidiae in kiwifruit

WRKY transcription factors are essential for coping with various biotic stresses. Pseudomonas syringae pv. actinidiae (Psa)-induced kiwifruit canker is a major problem restricting kiwifruit yield. Nevertheless, it's unclear how the kiwifruit WRKY genes respond to Psa. Through genome-wide identification, 112 WRKY members were found in ‘Hongyang’ genome in this work. Promoter analysis revealed that there were many cis-acting elements associated with stress responses in the AcWRKY gene's promoter region. According to transcriptomic analysis, 90 of the AcWRKY genes were differently expressed following Psa, salicylic acid (SA), or methyl jasmonate (MeJA) treatments. Almost all group III WRKYs were responsive to at least one of these treatments, with tissue-specific expression patterns. Quantitative RT-PCR study provided more evidence that Psa and SA treatments significantly induced the expression of the group III WRKY gene AcWRKY94, whereas MeJA treatment repressed it. AcWRKY94 was a transcriptionally active protein localized in the nucleus. Transient overexpression of AcWRKY94 in the leaves of ‘Hongyang’ enhanced the resistance of kiwifruit to Psa. Overexpression of AcWRKY94 in kiwifruit callus remarkably promoted the expression of PR and JAZ genes associated with SA and JA signals, respectively. These data imply that AcWRKY94 controls the signaling pathway dependent on SA and JA, thereby enhancing resistance to Psa. Taken together, this study establishes the basis for functional research on WRKY genes and provides important information for elucidating the resistance mechanism of kiwifruit canker disease.

Genome-wide analysis of the family 10 plant pathogenesis-related proteins in Pyrus bretschneideri and functional analysis of PbrMLP for Colletotrichum fructicola resistance

Pathogenesis-related (PR) genes are key regulators of plant adaptation responses to biotic and abiotic stresses. Family 10 PRs (PR10s, also known as major latex proteins) are usually induced by pathogens and environmental stresses. However, the evolutionary trajectory and functional divergence of the PR10 gene family in Chinese white pear (Pyrus bretschneideri ‘Dangshan Suli’) remain uncharacterized. The presence of 61 PR10s was detected across six Rosaceae species. The PR10 gene family was classified into two distinct groups by employing phylogenetic analysis and the taxonomic criteria of model plants. Interspecies synchrony revealed an ancient origin of the PR10 family in the six Rosaceae species, with 18 synchronic gene pairs. The expansion and evolution of the PR10 family were driven by various types of gene duplication events, with whole-genome duplication (WGD) being the primary mechanism. A candidate Colletotrichum fructicola (C. fructicola) resistance gene Pyrusbretschneiderimajor latex-like proteins (PbrMLP) belonging to the PR10 family was screened through transcriptomics and qRT-PCR. In addition, PbrMLP-silenced pear seedlings were more sensitive to C. fructicola than the controls. These results showed that PbrMLP is a candidate gene vital for anthracnose resistance in pears. These findings offer novel insights into the molecular mechanisms underlying the resistance to pear anthracnose infection in Rosaceae species and identify potential target genes for developing disease-resistant cultivars through genetic engineering.

Extraction optimization, physicochemical properties, and inhibitory effect against tobacco mosaic virus of the protein from discarded tobacco leaves

Plant proteins have been attracting increasing attention due to their significant antiviral activity against tobacco mosaic virus (TMV). This paper aimed to investigate the tobacco endogenous protein and the anti-TMV effects. Firstly, the extraction of protein from discarded tobacco leaves (DTLP) was optimized by response surface methodology (RSM). The maximum DTLP yield reached to 8.32 % under the condition of solid-liquid ratio 1:19, temperature 60 °C and pH 12. DTLP was rich in hydrophilic amino acids, such as aspartic acid (8.08 ± 0.34 g/100 g) and glutamic acid (8.02 ± 0.42 g/100 g). DTLP structure was compact and stable with a denaturation temperature of 99.7 °C. Furthermore, the anti-TMV experiments revealed that DTLP showed inactive and protective activities against TMV with inhibitory rates (79.2 % and 75.4 %, respectively) at 500 µg/mL, and inhibited the polymerization of TMV-CP to damage TMV particles. In addition, DTLP increased the expressions of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and phenylalanine ammonia lyase (PAL) in tobacco leaves by 1.55, 1.18, 9.13 and 2.92 times, respectively. Transcriptomics further verified that DTLP increased the expressions of TGA, WRKY, and PR1 genes for up-regulating the salicylic acid (SA) and pathogenesis-related proteins (PRs), thereby improving the system resistance of tobacco plants. Therefore, DTLP could be potentially developed as an alternative drug to treat plant viral diseases due to its broad-spectrum anti-TMV activity.

Genome-wide analysis of salicylic acid and jasmonic acid signalling marker gene families in wheat.

Jasmonic acid (JA) and salicylic acid (SA) phytohormone pathways are important regulators of stress tolerance. Knowledge regarding the diversity, phylogeny and functionality of wheat genes involved in JA and SA response is limited. Using Arabidopsis, rice and wheat genomic and wheat disease transcriptomic data, we deduced the size, phylogenetic diversity and pathogen-responsiveness of seven hormone-responsive gene families, and thus selected 14 candidates as potential hormone responsive gene markers. Gene-specific expression studies assessed the impact of exogenous JA and SA on their transcriptional activation in leaves of two distinct wheat cultivars. RNAseq data were interrogated to assess their disease responsiveness and tissue-specific expression. This study elucidated the number, phylogeny and pathogen-responsiveness of wheat genes from seven families, including 12 TaAOS, 6 TaJAMyb, 256 TaWRKY group III, 85 TaPR1, 205 TaPR2, 76 TaPR3 and 124 TaPR5. This included the first description of the wheat AOS, JAMyb, PR2, PR3 and PR5 gene families. Gene expression studies delineated TaAOS1-5B and TaJAMyb-4A as JA-responsive in leaves, but not significantly responsive to SA treatment, while TaWRKY45-B was a SA- but not a JA-responsive marker. Other candidate genes were either unresponsive or non-specific to SA or JA. Our findings highlight that all seven gene families are greatly expanded in wheat as compared to other plants (up to 7.6-fold expansion), and demonstrate disparity in the response to biotic stress between some homoeologous and paralogous sequences within these families. The SA- and JA-responsive marker genes identified herein will prove useful tools to monitor these signalling pathways in wheat.

Tomato SlWRKY3 Negatively Regulates Botrytis cinerea Resistance via TPK1b.

Botrytis cinerea is considered the second most important fungal plant pathogen, and can cause serious disease, especially on tomato. The TPK1b gene encodes a receptor-like kinase that can positively regulate plant resistance to B. cinerea. Here, we identified a tomato WRKY transcription factor SlWRKY3 that binds to the W-box on the TPK1b promoter. It can negatively regulate TPK1b transcription, then regulate downstream signaling pathways, and ultimately negatively regulate tomato resistance to B. cinerea. SlWRKY3 interference can enhance resistance to B. cinerea, and SlWRKY3 overexpression leads to susceptibility to B. cinerea. Additionally, we found that B. cinerea can significantly, and rapidly, induce the upregulation of SlWRKY3 expression. In SlWRKY3 transgenic plants, the TPK1b expression level was negatively correlated with SlWRKY3 expression. Compared with the control, the expression of the SA pathway marker gene PR1 was downregulated in W3-OE plants and upregulated in W3-Ri plants when inoculated with B. cinerea for 48 h. Moreover, SlWRKY3 positively regulated ROS production. Overall, SlWRKY3 can inhibit TPK1b transcription in tomato, and negatively regulate resistance to B. cinerea by modulating the downstream SA and ROS pathways.

Search for biocontrol agents among endophytic lipopeptide-synthesizing bacteria Bacillus spp. to protect wheat plants against Greenbug aphid (Schizaphis graminum).

Beneficial endophytic bacteria can suppress the development of insect pests through direct antagonism, with the help of metabolites, or indirectly by the induction of systemic resistance through the regulation of hormonal signaling pathways. Lipopeptides are bacterial metabolites that exhibit direct antagonistic activity against many organisms, including insects. Also, lipopeptides are able to trigger induced systemic resistance (ISR) in plants against harmful organisms, but the physiological mechanisms of their action are just beginning to be studied. In this work, we studied ten strains of bacteria isolated from the tissues of wheat and potatoes. Sequencing of the 16S rRNA gene showed that all isolates belong to the genus Bacillus and to two species, B. subtilis and B. velezensis. The genes for lipopeptide synthetase - surfactin synthetase (Bs_srf ), iturin synthetase (Bs_ituA, Bs_ituB) and fengycin synthetase (Bs_fenD) - were identified in all bacterial isolates using PCR. All strains had high aphicidal activity against the Greenbug aphid (Schizaphis graminum Rond.) due to the synthesis of lipopeptides, which was proven using lipopeptide-rich fractions (LRFs) isolated from the strains. Endophytic lipopeptide-synthesizing strains of Bacillus spp. indirectly affected the viability of aphids, the endurance of plants against aphids and triggered ISR in plants, which manifested itself in the regulation of oxidative metabolism and the accumulation of transcripts of the Pr1, Pr2, Pr3, Pr6 and Pr9 genes due to the synthesis of lipopeptides, which was proven using LRF isolated from three strains: B. subtilis 26D, B. subtilis 11VM, and B. thuringiensis B-6066. We have for the first time demonstrated the aphicidal effect of fengycin and the ability of the fengycin-synthesizing strains and isolates, B. subtilis Ttl2, Bacillus sp. Stl7 and B. thuringiensis B-6066, to regulate components of the pro-/antioxidant system of aphid-infested plants. In addition, this work is the first to demonstrate an elicitor role of fengycin in triggering a systemic resistance to S. graminum in wheat plants. We have discovered new promising strains and isolates of endophytes of the genus Bacillus, which may be included in the composition of new biocontrol agents against aphids. One of the criteria for searching for new bacteria active against phloem-feeding insects can be the presence of lipopeptide synthetase genes in the bacterial genome.

SA and NHP glucosyltransferase UGT76B1 affects plant defense in both SID2- and NPR1-dependent and independent manner

Key messageThe small-molecule glucosyltransferase loss-of-function mutant ugt76b1 exhibits both SID2- or NPR1-dependent and independent facets of enhanced plant immunity, whereupon FMO1 is required for the SID2 and NPR1 independence.The small-molecule glucosyltransferase UGT76B1 inactivates salicylic acid (SA), isoleucic acid (ILA), and N-hydroxypipecolic acid (NHP). ugt76b1 loss-of-function plants manifest an enhanced defense status. Thus, we were interested how UGT76B1 genetically integrates in defense pathways and whether all impacts depend on SA and NHP. We study the integration of UGT76B1 by transcriptome analyses of ugt76b1. The comparison of transcripts altered by the loss of UGT76B1 with public transcriptome data reveals both SA-responsive, ISOCHORISMATE SYNTHASE 1/SALICYLIC ACID INDUCTION DEFICIENT 2 (ICS1/SID2)- and NON EXPRESSOR OF PR GENES 1 (NPR1)-dependent, consistent with the role of UGT76B1 in glucosylating SA, and SA-non-responsive, SID2/NPR1-independent genes. We also discovered that UGT76B1 impacts on a group of genes showing non-SA-responsiveness and regulation by infections independent from SID2/NPR1. Enhanced resistance of ugt76b1 against Pseudomonas syringae is partially independent from SID2 and NPR1. In contrast, the ugt76b1-activated resistance is completely dependent on FMO1 encoding the NHP-synthesizing FLAVIN-DEPENDENT MONOOXYGENASE 1). Moreover, FMO1 ranks top among the ugt76b1-induced SID2- and NPR1-independent pathogen responsive genes, suggesting that FMO1 determines the SID2- and NPR1-independent effect of ugt76b1. Furthermore, the genetic study revealed that FMO1, ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), SID2, and NPR1 are required for the SA–JA crosstalk and senescence development of ugt76b1, indicating that EDS1 and FMO1 have a similar effect like stress-induced SA biosynthesis (SID2) or the key SA signaling regulator NPR1. Thus, UGT76B1 influences both SID2/NPR1-dependent and independent plant immunity, and the SID2/NPR1 independence is relying on FMO1 and its product NHP, another substrate of UGT76B1.

Genome-wide analysis of polyphenol oxidase gene family in Solanum tuberosum and functional identification of StuPPO9 in regulating tolerance to Phytophthora infestans

Polyphenol oxidase (PPO) is the key enzyme involved in the enzymatic browning of potato tubers. However, the understanding of its other functions, as well as the underlying molecular mechanisms, is still limited. StuPPO9 was predicted as an inducible gene in response to disease defense and cell rescue, as analyzed using the EST database. In this study, an identification and evolutionary analysis of PPOs in Solanum tuberosum was conducted. A total of 10 members of StuPPOs were identified and their gene structure, protein motifs, chromosomal location, and tissue distribution were further investigated. QRT-PCR analysis indicated that most PPOs were induced or inhibited under hormone treatments, and StuPPO9 showed the highest expression level when induced by Phytophthora infestans. Therefore, StuPPO9, the only one located on chromosome 2, was selected for further study. The StuPPO9 overexpressing Nicotiana benthamiana transgenic line effectively slowed down the growth of P. infestans and showed more tolerance compared to the wild type (WT). Moreover, the molecular markers NtHin1 and PR genes were significantly upregulated in the transgenic tobacco than in WT under P. infestans infection. This study will provide a basis and reference for future research on the roles of StuPPO9 in disease defense.

Relative Expression of Genes Elicited by Clonostachys rosea in Pinus radiata Induces Systemic Resistance

Radiata pine is one of the most commonly planted tree species in Chile due to its fast growth and desirable wood and pulp properties. However, its productivity is hampered by several diseases. Pitch canker disease (PCC) caused by Fusarium circinatum, is considered the most damaging disease to the pine forest industry. Several control measures have been established, with biological control emerging as an environmentally friendly and effective way for F. circinatum control. Previous studies support the value of Clonostachys rosea in reducing PCC damage, with evidence suggesting a potential induced systemic resistance (ISR) triggered in radiata pines by this agent. Ten-month-old radiata pine plants were pre-treated with C. rosea on a substrate at 8 and 1 days before inoculation with F. circinatum on the stem tip, and expression levels were determined for DXS1, LOX, PAL, and PR3 genes 24 h later. Lesion length was 45% lower on plants pre-treated with C. rosea and infected with F. circinatum compared to non-pre-treated and infected plants. Additionally, LOX and PR3 were induced 23 and 62 times more, respectively, in comparison to untreated plants. Our results indicate that C. rosea causes an ISR response in pre-treated plants, significantly increasing the expression of resistance genes and reducing lesion length.

Changes in Physiological Traits, Gene Expression and Phytochemical Profile of Mentha piperita in Response to Elicitor.

Peppermint (Mentha piperita) is a perennial medicinal plant containing active ingredients that can be used for treating liver and prostate cancers, acute respiratory infections, allergies, digestive problems, neuralgia, and migraines. The objective of this research is to investigate the expression of essential genes in the menthol pathway of Mentha piperita, including Pulegone reductase (Pr), Menthofuran synthase (Mfs), and limonene synthase (Ls) using qPCR, physiological analysis and essential oil composition in response to methyl jasmonate (MeJA) (0.5mM) elicitation. Physiological analysis showed that 0.5mM MeJA triggers defensive responsiveness in Mentha piperita by increasing superoxide dismutase (SOD) and Peroxidase (POD) enzymesactivity. The highest transcript levels of Pr and Mfs genes were observed during 8 and 12h after treatment respectively, but following 24h, they were down-regulated. Essential oil analysis indicated that the percentage of constituents in the essential oil was changed using MeJA at 48h and 96h after post-treatment. Effective antimicrobial compounds, α-pinene, β-pinene, linalool and methyl acetate, were induced after 48h. A non-significant positive relationship was detected between menthol content, and expression of the Pr and Mfs genes. Due to the significant change in the expression of Pr and Mfs genes in the menthol pathway, role of Pr gene in directing the pathway to the valuable compound menthol and deviation of the menthol pathway to the menthofuran as an undesirable component of essential oil by Mfs gene, it can be deduced that they are the most critical genes in response to MeJA treatment, which are appropriate candidates for metabolite engineering. In addition, MeJA improved defensive responsiveness and percentage of some constituents with antimicrobial properties in Mentha piperita.

Cadmium toxicity promotes hormonal imbalance and induces the expression of genes involved in systemic resistances in barley.

Cadmium (Cd) is a widely distributed pollutant that adversely affects plants' metabolism and productivity. Phytohormones play a vital role in the acclimation of plants to metal stress. On the other hand, phytohormones trigger systemic resistances, including systemic acquired resistance (SAR) and induced systemic resistance (ISR), in plants in response to biotic interactions. The present study aimed to investigate the possible induction of SAR and ISR pathways in relation to the hormonal alteration of barley seedlings in response to Cd stress. Barley seedlings were exposed to 1.5mgg-1 Cd in the soil for three days. The nutrient content, oxidative status, phytohormones profile, and expression of genes involved in SAR and ISR pathways of barley seedlings were examined. Cd accumulation resulted in a reduction in the nutrient content of barley seedlings. The specific activity of superoxide dismutase and the hydrogen peroxide content significantly increased in response to Cd toxicity. Abscisic acid, jasmonic acid, and ethylene content increased under Cd exposure. Cd treatment resulted in the upregulation of NPR1, PR3, and PR13 genes in SAR pathways. The transcripts of PAL1 and LOX2.2 genes in the ISR pathway were also significantly increased in response to Cd treatment. These findings suggest that hormonal-activated systemic resistances are involved in the response of barley to Cd stress.

Enhancing Botrytis disease management in tomato plants: insights from a Pseudomonas putida strain with biocontrol activity.

This study explores the biocontrol potential of Pseudomonas putida Z13 against Botrytis cinerea in tomato plants, addressing challenges posed by the pathogen's fungicide resistance. The aims of the study were to investigate the in vitro and in silico biocontrol traits of Z13, identify its plant-colonizing efficacy, evaluate the efficacy of different application strategies against B. cinerea in planta, and assess the capacity of Z13 to trigger induced systemic resistance (ISR) in plants. The in vitro experiments revealed that Z13 inhibits the growth of B. cinerea, produces siderophores, and exhibits swimming and swarming activity. Additionally, the Z13 genome harbors genes that encode compounds triggering ISR, such as pyoverdine and pyrroloquinoline quinone. The in planta experiments demonstrated Z13's efficacy in effectively colonizing the rhizosphere and leaves of tomato plants. Therefore, three application strategies of Z13 were evaluated against B. cinerea: root drenching, foliar spray, and the combination of root drenching and foliar spray. It was demonstrated that the most effective treatment of Z13 against B. cinerea was the combination of root drenching and foliar spray. Transcriptomic analysis showed that Z13 upregulates the expression of the plant defense-related genes PR1 and PIN2 upon B. cinerea inoculation. The results of the study demonstrated that Z13 possesses significant biocontrol traits, such as the production of siderophores, resulting in significant plant protection against B. cinerea when applied as a single treatment to the rhizosphere or in combination with leaf spraying. Additionally, it was shown that Z13 root colonization primes plant defenses against the pathogen.

INDUCER OF CBF EXPRESSION 1 promotes cold-enhanced immunity by directly activating salicylic acid signaling.

Cold stress affects plant immune responses, and this process may involve the salicylic acid (SA) signaling pathway. However, the underlying mechanism by which low-temperature signals coordinate with SA signaling to regulate plant immunity remains unclear. Here, we found that low temperatures enhanced the disease resistance of Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000. This process required INDUCER OF CBF EXPRESSION 1 (ICE1), the core transcription factor in cold-signal cascades. ICE1 physically interacted with NONEXPRESSER OF PATHOGENESIS-RELATED GENES 1 (NPR1), the master regulator of the SA signaling pathway. Enrichment of ICE1 on the PATHOGENESIS-RELATED GENE 1 (PR1) promoter and its ability to transcriptionally activate PR1 were enhanced by NPR1. Further analyses revealed that cold stress signals cooperate with SA signals to facilitate plant immunity against pathogen attack in an ICE1-dependent manner. Cold treatment promoted interactions of NPR1 and TGACG-BINDING FACTOR 3 (TGA3) with ICE1 and increased the ability of the ICE1-TGA3 complex to transcriptionally activate PR1. Together, our results characterize a critical role of ICE1 as an indispensable regulatory node linking low-temperature-activated and SA-regulated immunity. Understanding this crucial role of ICE1 in coordinating multiple signals associated with immunity broadens our understanding of plant-pathogen interactions.

Genome-wide analysis of NPR1-like genes in citrus species and expression analysis in response to citrus canker (Xanthomonas axonopodis pv. citri).

Citrus fruits, revered for their nutritional value, face significant threats from diseases like citrus canker, particularly impacting global citrus cultivation, notably in Pakistan. This study delves into the critical role of NPR1-like genes, the true receptors for salicylic acid (SA), in the defense mechanisms of citrus against Xanthomonas axonopodis pv. citri (Xcc). By conducting a comprehensive genome-wide analysis and phylogenetic study, the evolutionary dynamics of Citrus limon genes across diverse citrus cultivars are elucidated. Structural predictions unveil conserved domains, such as the BTB domain and ankyrin repeat domains, crucial for the defense mechanism. Motif analysis reveals essential conserved patterns, while cis-regulatory elements indicate their involvement in transcription, growth, response to phytohormones, and stress. The predominantly cytoplasmic and nuclear localization of NPR1-like genes underscores their pivotal role in conferring resistance to various citrus species. Analysis of the Ks/Ka ratio indicates a purifying selection of NPR1-like genes, emphasizing their importance in different species. Synteny and chromosomal mapping provide insights into duplication events and orthologous links among citrus species. Notably, Xac infection stimulates the expression of NPR1-like genes, revealing their responsiveness to pathogenic challenges. Interestingly, qRT-PCR profiling post-Xac infection reveals cultivar-specific alterations in expression within susceptible and resistant citrus varieties. Beyond genetic factors, physiological parameters like peroxidase, total soluble protein, and secondary metabolites respond to SA-dependent PR genes, influencing plant characteristics. Examining the impact of defense genes (NPR1) and plant characteristics on disease resistance in citrus, this study marks the inaugural investigation into the correlation between NPR1-associated genes and various plant traits in both susceptible and resistant citrus varieties to citrus bacterial canker.

Brevipalpus yothersiBaker (Tenuipalpidae) development in sweet orange plants is influenced by previous mite infestation and the presence of shelters.

Citrus leprosis is the most important viral disease affecting citrus. The disease is caused predominantly by CiLV-C and is transmitted by Brevipalpus yothersi Baker mites. This study brings some insight into the colonization of B. yothersi in citrus [(Citrus × sinensis (L.) Osbeck (Rutaceae)] previously infested by viruliferous or non-viruliferous B. yothersi. It also assesses the putative role of shelters on the behavior of B. yothersi. Expression of PR1 and PR4 genes, markers of plant defense mechanisms, were evaluated by RT-qPCR to correlate the role of the plant hormonal changes during the tri-trophic virus-mite-plant interplay. A previous infestation with either non-viruliferous and viruliferous mites positively influenced oviposition and the number of adult individuals in the resulting populations. Mite populations were higher on branches that had received a previous mite infestation than branches that did not. There was an increase in the expression of PR4, a marker gene in the jasmonic acid (JA) pathway, in the treatment with non-viruliferous mites, indicating a response from the plant to their feeding. Conversely, an induced expression of PR1, a marker gene in the salicylic acid (SA) pathway, was observed mainly in the treatment with viruliferous mites, which suggests the activation of a plant response against the pathogen. The earlier mite infestation, as well as the presence of leprosis lesions and a gypsum mixture as artificial shelters, all fostered the growth of the B. yothersi populations after the second infestation, regardless of the presence or absence of CiLV-C. Furthermore, it is suggested that B. yothersi feeding actually induces the JA pathway in plants. At the same time, the CiLV-C represses the JA pathway and induces the SA pathway, which benefits the mite vector.

A novel lectin receptor kinase gene, AtG-LecRK-I.2, enhances bacterial pathogen resistance through regulation of stomatal immunity in Arabidopsis

The S-locus lectin receptor kinases (G-LecRKs) have been suggested as receptors for microbe/damage-associated molecular patterns (MAMPs/DAMPs) and to be involved in the pathogen defense responses, but the functions of most G-LecRKs in biotic stress response have not been characterized. Here, we identified a member of this family, G-LecRK-I.2, that positively regulates flg22- and Pseudomonas syringae pv. tomato (Pst) DC3000-induced stomatal closure. G-LecRK-I.2 was rapidly phosphorylated under flg22 treatment and could interact with the FLS2/BAK1 complex. Two T-DNA insertion lines, glecrk-i.2–1 and glecrk-i.2–2, had lower levels of reactive oxygen species (ROS) and nitric oxide (NO) production in guard cells, as compared with the wild-type Col-0, under Pst DC3000 infection. Also, the immunity marker genes CBP60g and PR1 were induced at lower levels under Pst DC3000 hrcC- infection in glecrk-i.2–1 and glecrk-i.2–2. The GUS reporter system also revealed that G-LecRK-I.2 was expressed only in guard cells. We also found that G-LecRK-I.2 could interact H+-ATPase AHA1 to regulate H+-ATPase activity in the guard cells. Taken together, our results show that G-LecRK-I.2 plays an important role in regulating stomatal closure under flg22 and Pst DC3000 treatments and in ROS and NO signaling specifically in guard cells.

Potential of different species of actinobacteria in the management of Meloidogyne javanica.

Root-knot nematodes (RKN) are one of the most harmful soil-borne plant pathogens in the world. Actinobacteria are known phytopathogen control agents. The aim of this study was to select soil actinobacteria with control potential against the RKN (Meloidogyne javanica) in tomato plants and to determine mechanisms of action. Ten isolates were tested and a significant reduction was observed in the number of M. javanica eggs, and galls 46days after infestation with the nematode. The results could be explained by the combination of different mechanisms including parasitism and induction of plant defense response. The M. javanica eggs were parasited by all isolates tested. Some isolates reduced the penetration of juveniles into the roots. Other isolates using the split-root method were able to induce systemic defenses in tomato plants. The 4L isolate was selected for analysis of the expression of the plant defense genes TomLoxA, ACCO, PR1, and RBOH1. In plants treated with 4L isolate and M. javanica, there was a significant increase in the number of TomLoxA and ACCO gene transcripts. In plants treated only with M. javanica, only the expression of the RBOH1 and PR1 genes was induced in the first hours after infection. The isolates were identified using 16S rRNA gene sequencing as Streptomyces sp. (1A, 3F, 4L, 6O, 8S, 9T, and 10U), Kribbella sp. (5N), Kitasatospora sp. (2AE), and Lentzea sp. (7P). The efficacy of isolates from the Kitasatospora, Kribbella, and Lentzea genera was reported for the first time, and the efficacy of Streptomyces genus isolates for controlling M. javanica was confirmed. All the isolates tested in this study were efficient against RKN. This study provides the opportunity to investigate bacterial genera that have not yet been explored in the control of M. javanica in tomatoes and other crops.