Xanthomonas Oryzae Pv Research Articles

Pathotyping and Virulence Analysis of Xanthomonas oryzae pv. oryzae Causing Bacterial Blight of Rice in Tamil Nadu

Background-Bacterial leaf blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive diseases affecting rice production worldwide. Resistance breeding is considered a durable, effective, and eco-friendly approach to control BB. Several BB resistance (R) genes have been identified that confer resistance against various strains of Xoo. The dynamic nature of this pathogen needs proper knowledge of pathotype composition and its virulence among the diverse Xoo strains which is imperative for designing a resistance breeding program. Methods-In this study, we conducted an extensive survey to collect BB infected samples from diverse rice-growing regions of Tamil Nadu. Further, the samples were identified as Xoo through morphological and molecular identification methods. The pathotyping and virulence profiling of Xoo isolates was carried out on a set of rice differentials consisting of 22 near-isogenic lines (NILs) of IR24 possessing different BB resistance genes under glasshouse conditions during Kharif 2021-2022. Results-Based on the disease reaction in 22 rice BB differentials (IRBB lines), the Xoo isolates were grouped into six pathotypes (I II, III, IV, V, and VI). Further, the virulence analysis revealed that the near-isogenic lines possessing single R gene and gene pyramids were susceptible to about 20-88% and 4-20% respectively to Xoo isolates. R genes and their pyramids such as (Xa7, Xa21, Xa4+xa5+Xa21, Xa4+xa5+xa13 Xa4+xa13+Xa21, xa5+xa13+Xa21, and Xa4+Xa21+xa5+Xa21) were found to be effective against all the pathotypes in Tamil Nadu. The pathotype III was predominantly distributed (40%) over the Tamil Nadu. The isolates found in the pathotypes I and II are more virulent and in the pathotypes V, VI are less virulent. The current study identified the virulence nature of diverse Xoo isolates and the effectiveness of resistance (R) genes against the Xoo isolates. Therefore, the effective R genes identified in this study could be an effective source for resistance breeding program against BB in Tamil Nadu.

Activated Expression of Rice DMR6-like Gene OsS3H Partially Explores the Susceptibility to Bacterial Leaf Streak Mediated by Knock-Out OsF3H04g.

Downy Mildew Resistance 6-like (DMR6-like) genes are identified as salicylic acid (SA) hydroxylases and negative regulators of plant immunity. Previously, we identified two rice DMR6-like genes, OsF3H03g, and OsF3H04g, that act as susceptible targets of transcription activator-like effectors (TALEs) from Xanthomonas oryzae pv. oryzicola (Xoc), which causes bacterial leaf streak (BLS) in rice. Furthermore, all four homologs of rice DMR6-like proteins were identified to predominantly carry the enzyme activity of SA 5-hydroxylase (S5H), negatively regulate rice broad-spectrum resistance, and cause the loss of function of these OsDMR6s, leading to increased resistance to rice blast and bacterial blight (BB). Here, we curiously found that an OsF3H04g knock-out mutant created by T-DNA insertion, osf3h04g, was remarkedly susceptible to BLS and BB and showed an extreme reduction in SA content. OsF3H04g knock-out rice lines produced by gene-editing were mildly susceptible to BLS and reduced content of SA. To explore the susceptibility mechanism in OsF3H04g loss-of-function rice lines, transcriptome sequencing revealed that another homolog, OsS3H, had induced expression in the loss-of-function OsF3H04g rice lines. Furthermore, we confirmed that a great induction of OsS3H downstream and genomically adjacent to OsF3H04g in osf3h04g was primarily related to the inserted T-DNA carrying quadruple enhancer elements of 35S, while a slight induction was caused by an unknown mechanism in gene-editing lines. Then, we found that the overexpression of OsS3H increased rice susceptibility to BLS, while gene-editing mediated the loss-of-function OsS3H enhanced rice resistance to BLS. However, the knock-out of both OsF3H04g and OsS3H by gene-editing only neutralized rice resistance to BLS. Thus, we concluded that the knock-out of OsF3H04g activated the expression of the OsS3H, partially participating in the susceptibility to BLS in rice.

Antioxidant activities and free amino acid content of rice responded to xanthomonas oryzae pv oryzae infection under phosphate starvation condition

Rice productivity strongly affects food security worldwide, especially in Asia, where rice is served as a staple food. However, rice productivity was threatened by numbers of environmental stresses, including Xanthomonas oryzae pv oryzae (Xoo) disease. Xoo is causing significant losses to rice production around the world. Furthermore, thanks to the significant function of phosphate (Pi) in nucleic acid and cell membrane structure, energy-transporting molecules, photosynthesis and respiration, a sufficient supply of Pi for rice plants is essential. Our previous studies had demonstrated the effect of low Pi in increasing Xoo tolerance in rice. In the present study, two-biochemical processes responsible for this tolerance were investigated by analyzing antioxidant enzyme activities and free amino acid profile produced by Xoo infected rice plants under Pi starvation and full Pi conditions. Two selected rice cultivars, G22 and G299, were used as plant materials. After two weeks of 6-week-old plants infected with Xoo, peroxidase and catalase activities in the plants under the low Pi condition were significant increased. Amino acids belonging to the glutamic, serine and pyruvate families, especially serine and proline accumulated the higher levels in plants under low Pi conditions compared to full Pi. In our two studied rice cultivars, the improvement in both antioxidant enzymes and free amino acid was found cultivar-dependence, the sensitive to low Pi G299 cultivar responsed stronger than the tolerant to low Pi G22 cultivar. The results from this study provide more detail about the possible mechanism how rice plants tolerant to Xoo under the Pi starvation condition and can suggest a strategy for green agriculture in dealing with Xoo infection by considering the interaction between Pi starvation and the Xoo response.

The potential of beneficial microbes to suppress the development of bacterial leaf blight in rice plants caused by Xanthomonas oryzae pv. oryzae

Abstract. Rahma H, Martinius, Khairul U, Rahmi F. 2023. The potential of beneficial microbes to suppress the development of bacterial leaf blight in rice plants caused by Xanthomonas oryzae pv. oryzae. Biodiversitas 24: 4209-4217. Xanthomonas oryzae pv. oryzae (Xoo) is caused bacterial leaf blight in rice plants. One technique for controlling the bacterial leaf blight that currently being developed is using beneficial microbes. The purpose of this study was to isolate and identified beneficial microbes that can suppress bacterial leaf blight development in rice plants. In the present study fifteen isolates of beneficial microbes were investigated for their potential as an antagonist against Xoo, the causal agent of bacterial leaf blight of rice plants. Four isolates, namely Act-SK2, Act-Mn2, Act-Hr21, and Act-Pha4, showed the ability to reduce the area under progress curve (AUDPC) values by 51.33, 51.00, 84.00, and 82.33, respectively. The effectiveness of AUDPC suppression ranged between 80%-88%. Two out of four isolates showed potential in reducing the severity of BLB disease by 3.65% (Act-Sk2) and 3.88% (Act-Mn2) as compared to control. The effectiveness of both isolates in reducing disease severity was 86.34% (Act-Sk2) and 85.48% (Act-Mn2). Furthermore, identification based on 16S rRNA gene sequence analysis showed that three isolates, namely Act-Sk2, Act-Hr21, and Act-Pha4, belong to Actinobacteria. Each isolate showed 99.68% similarities with Streptomyces sp. strain KS02 (Acc. No. AB373961, 99.84% with Streptomyces sp. strains Al-Dhabi-119 (Acc. No.MK675528), and 99.64% with Streptomyces griseus strain K 2 (Acc. No. MK811436). Isolate Act-Mn2 showed 100% similarity with Penicillium janthinellum strain CMV006C1 (Acc. No. MK450697). The results of this study indicate that the four microorganisms tested have potential to be developed as biological agents.

Molecular analysis of broad-spectrum induced resistance in rice by the green leaf volatile Z-3-hexenyl acetate.

Green leaf volatiles (GLVs), volatile organic compounds released by plants upon tissue damage, are key signaling molecules in plant immunity. The ability of exogenous GLV application to trigger an induced resistance (IR) phenotype against arthropod pests has been widely reported, but its effectiveness against plant pathogens is less well understood. In this study, we combined mRNA sequencing-based transcriptomics and phytohormone measurements with multispectral imaging-based precision phenotyping to gain insights into the molecular basis of Z-3-hexenyl acetate-induced resistance (Z-3-HAC-IR) in rice. Furthermore, we evaluated the efficacy of Z-3-HAC-IR against a panel of economically significant rice pathogens: Pyricularia oryzae, Rhizoctonia solani, Xanthomonas oryzae pv. oryzae, Cochliobolus miyabeanus, and Meloidogyne graminicola. Our data revealed rapid induction of jasmonate metabolism and systemic induction of plant immune responses upon Z-3-HAC exposure, as well as a transient allocation cost due to accelerated chlorophyll degradation and nutrient remobilization. Z-3-HAC-IR proved effective against all tested pathogens except for C. miyabeanus, including against the (hemi)biotrophs M. graminicola, X. oryzae pv. oryzae, and P. oryzae. The Z-3-HAC-IR phenotype was lost in the jasmonate (JA)-deficient hebiba mutant, which confirms the causal role of JA in Z-3-HAC-IR. Together, our results show that GLV exposure in rice induces broad-spectrum, JA-mediated disease resistance with limited allocation costs, and may thus be a promising alternative crop protection approach.

Fine mapping and sequence analysis reveal a promising candidate gene encoding a novel NB-ARC domain derived from wild rice (Oryza officinalis) that confers bacterial blight resistance.

Bacterial blight disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious constraints in rice production. The most sustainable strategy to combat the disease is the deployment of host plant resistance. Earlier, we identified an introgression line, IR 75084-15-3-B-B, derived from Oryza officinalis possessing broad-spectrum resistance against Xoo. In order to understand the inheritance of resistance in the O. officinalis accession and identify genomic region(s) associated with resistance, a recombinant inbred line (RIL) mapping population was developed from the cross Samba Mahsuri (susceptible to bacterial blight) × IR 75084-15-3-B-B (resistant to bacterial blight). The F2 population derived from the cross segregated in a phenotypic ratio of 3: 1 (resistant susceptible) implying that resistance in IR 75084-15-3-B-B is controlled by a single dominant gene/quantitative trait locus (QTL). In the F7 generation, a set of 47 homozygous resistant lines and 47 homozygous susceptible lines was used to study the association between phenotypic data obtained through screening with Xoo and genotypic data obtained through analysis of 7K rice single-nucleotide polymorphism (SNP) chip. Through composite interval mapping, a major locus was detected in the midst of two flanking SNP markers, viz., Chr11.27817978 and Chr11.27994133, on chromosome 11L with a logarithm of the odds (LOD) score of 10.21 and 35.93% of phenotypic variation, and the locus has been named Xa48t. In silico search in the genomic region between the two markers flanking Xa48t identified 10 putatively expressed genes located in the region of interest. The quantitative expression and DNA sequence analysis of these genes from contrasting parents identified the Os11g0687900 encoding an NB-ARC domain-containing protein as the most promising gene associated with resistance. Interestingly, a 16-bp insertion was noticed in the untranslated region (UTR) of the gene in the resistant parent, IR 75084-15-3-B-B, which was absent in Samba Mahsuri. The association of Os11g0687900 with resistance phenotype was further established by sequence-based DNA marker analysis in the RIL population. A co-segregating PCR-based INDEL marker, Marker_Xa48, has been developed for use in the marker-assisted breeding of Xa48t.

MODELING INTENSITY OF BACTERIAL LEAF BLIGHT ON RICE PLANTS DUE TO INFLUENCE OF ABIOTIC FACTORS IN BABAKSARI VILLAGE, GRESIK

Rice plants is the main food crop in Indonesia. Gresik is one of the ten highest rice producing regions in East Java Province, Indonesia. Rice production in Babaksari Village, Gresik Regency reaches 646 tonnes/year. One of the obstacles in rice production is bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae. This disease can cause yield loss reaching 15-80%. The development of bacterial leaf blight in rice can be caused by several factors, one of which is abiotic factors. This study aims to determine how far the influence exerted by abiotic factors (air humidity, soil pH, and air temperature) on the intensity of bacterial leaf blight. The research was conducted using a survey method, diagonal random sampling, and interviews with farmers in Petissari Hamlet and Sariwonorejo Hamlet, Babaksari Village, Dukun District, Gresik Regency. From the results of this study it was found that the three abiotic factors simultaneously had a significant effect on the intensity of bacterial leaf blight with the regression model obtained, namely: (1) Petissari: Y = -0.050 + 0.587X1 +1.378X2 – 0.789X3; and (2) Sariwonorejo: Y = 8.464 - 3.044X1 +3.745X2 + 1.854X3. The results of path analysis showed that the abiotic factor that had the highest direct effect on the intensity of bacterial leaf blight was soil pH.

Synthesis and bioactivity evaluation of novel acetamide-derived compounds bearing a methylsulfonyl unit

This study reports the synthesis and structural characterization of a series of novel acetamide-derived compounds containing a methylsulfonyl unit. The in vitro antibacterial activity results demonstrated that compound 2-((4-fluorophenyl)sulfonyl)-N-(4-(methylsulfonyl)phenyl)acetamide (6b) exhibited superior antibacterial activities against Xanthomonas oryzae pv. oryzicolaby (Xoc), Xanthomonas oryzae pv. oryzae (Xoo), and Xanthomonas axonopodis pv. citri (Xac) at 100 μg/mL concentration, with the inhibition rates of 86.24%, 81.59%, and 75.65%, respectively, compared to Bismerthiazol and Thiodiazole copper. Meanwhile, the in vitro antifungal activities of all target compounds were found to be lower against Mucor fragilis (M. fragilis), Mucor bainieri (M. bainieri), and Trichoderma atroviride (T. atroviride) at 50 μg/mL concentration, with the inhibition rates of 0–45.21%, 0–30.24%, and 0–12.65%, respectively, compared to Carbendazim. Moreover, bioassay results of the target compounds against prostate cancer (PC3), hepatocellular carcinoma (HepG2), and leukemia (K562) cells at 10 μM concentration demonstrated that, compared to 5-fluorouracil, compound 2-((4-fluorophenyl)thio)-N-(4-(methylsulfonyl)phenyl)acetamide (4c) illustrated obvious antitumor activity (56.87%) against K562. This work first highlights the effect of the modification of the acetamide-derived compounds bearing a methylsulfonyl unit on the bioactivity evaluation.

Synthesis, antibacterial and antifungal activity of myricetin derivatives containing piperidine and amide fragments.

Continuous use of synthetic bactericides and fungicides is causing pathogens to develop resistance, resulting in increased use of pesticides and affecting food security. The green pesticides derived from natural products could reduce or avoid 'pesticide hazards' caused by synthetic pesticides as a result of their unique mechanism of action. Therefore, it is of great significance to create green pesticides with novel structures. Herein, 30 novel myricetin derivatives containing piperidine and amide fragments were designed and synthesized using active group splicing. Among them, compound Z30 had excellent inhibitory effect against Xanthomonas oryzae pv. Oryzae (Xoo) with the half effective concentration (EC50 ) of 2.7 μg mL-1 . Compound Z26 not only exhibited better antibacterial activity against Xaxonopodis pv. Citri (Xac) with EC50 of 3.9 μg mL-1 , but also displayed higher antifungal activity against Rhizoctonia solani (Rs) with EC50 of 8.3 μg mL-1 . In vivo experiments proved that Z30 against bacterial blight of rice and Z26 against rice blast exhibits significant protective and curative effect. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Z26 and Z30 could change the integrity of cell wall and membrane of pathogen Xoo, Xac and Rs, resulting in cytoplasmic leakage and eventually death. Enzymatic assay, molecular docking and molecular dynamics simulations (MDs) indicated that Z26 could be used as a potential succinate dehydrogenase inhibitor (SDHI). Z26 and Z30 significantly reduced the pathogenicity of the pathogens, which provided a new idea and direction for the development of green pesticides. © 2023 Society of Chemical Industry.

Co-expression of four penaeidins in transgenic rice seeds: an alternative strategy for substitute antibiotic agricultural products.

The co-expression of multiple antimicrobial peptides (AMPs) in genetically modified (GM) crops can give plants a broader antibacterial spectrum and lower the pathogen risk of drug resistance. Therefore, four penaeidins (shrimp-derived AMPs) were fused and encoded in an artificial gene (PEN1234), driven by the seed-specific promoter Pzein, with the aim of co-expression in seeds of transgenic rice. The resistant rice plants, acquired via Agrobacterium-mediated transformation and glufosinate screening, were identified by PCR and the modified disk-diffusion method, and eight GM lines with high AMP content in the seeds were obtained. Among them, the PenOs017 line had the largest penaeidin content, at approximately 251-300μg/g in seeds and 15-47μg/g in roots and leaves. The AMPs in the seeds kept their antibacterial properties even after the seed had been boiled in hot water and could significantly inhibit the growth of methicillin-resistant Staphylococcus aureus, and AMPs in the leaves could effectively inhibit Xanthomonas oryzae pv. Oryzae. The results indicate that PenOs017 seeds containing AMPs are an ideal raw-material candidate for antibiotic-free food and feed, and may require fewer petrochemical fungicides or bactericides for disease control during cultivation than conventional rice.

Bio-functionalized nickel-silica nanoparticles suppress bacterial leaf blight disease in rice (Oryza sativa L.).

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastative diseases that threatens rice plants worldwide. Biosynthesized nanoparticle (NP) composite compounds have attracted attention as environmentally safe materials that possess antibacterial activity that could be used in managing plant diseases. During this study, a nanocomposite of two important elements, nickel and silicon, was biosynthesized using extraction of saffron stigmas (Crocus sativus L.). Characterization of obtained nickel-silicon dioxide (Ni-SiO2) nanocomposite was investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission/Scanning electron microscopy (TEM/SEM), and energy-dispersive spectrum (EDS). Antibacterial activities of the biosynthesized Ni-SiO2 nanocomposite against Xoo were tested by measuring bacterial growth, biofilm formation, and dead Xoo cells. The bacterial growth (OD600) and biofilm formation (OD570) of Xoo treated with distilled water (control) was found to be 1.21 and 1.11, respectively. Treatment with Ni-SiO2 NPs composite, respectively, reduced the growth and biofilm formation by 89.07% and 80.40% at 200 μg/ml. The impact of obtained Ni-SiO2 nanocomposite at a concentration of 200 μg/ml was assayed on infected rice plants. Treatment of rice seedlings with Ni-SiO2 NPs composite only had a plant height of 64.8cm while seedlings treated with distilled water reached a height of 45.20cm. Notably, Xoo-infected seedlings treated with Ni-SiO2 NPs composite had a plant height of 57.10cm. Furthermore, Ni-SiO2 NPs composite sprayed on inoculated seedlings had a decrease in disease leaf area from 43.83% in non-treated infected seedlings to 13.06% in treated seedlings. The FTIR spectra of biosynthesized Ni-SiO2 nanocomposite using saffron stigma extract showed different bands at 3,406, 1,643, 1,103, 600, and 470 cm-1. No impurities were found in the synthesized composite. Spherically shaped NPs were observed by using TEM and SEM. EDS revealed that Ni-SiO2 nanoparticles (NPs) have 13.26% Ni, 29.62% Si, and 57.11% O. Xoo treated with 200 µg/ml of Ni-SiO2 NPs composite drastically increased the apoptosis of bacterial cells to 99.61% in comparison with 2.23% recorded for the control. The application of Ni-SiO2 NPs significantly improved the vitality of rice plants and reduced the severity of BLB.

Hedychium coronarium flower extract modulates rice plant photosystem II and antioxidant enzymes activity to induce resistance against bacterial blight

Rice Bacterial Blight (BB), which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is deemed as one of the most severe diseases that can afflict rice crops. Agricultural practices have often relied upon bactericides to reduce BB infections. The excessive utilization of conventional bactericides in past years has led to environmental contamination and elevated bacterial resistance. However, plant elicitors are ecologically safe biological pesticides, have been demonstrated to enhance plant disease resistance by inducing defense-related enzymes and restoring photosynthetic efficiency. We tested the efficacy of Hedychium coronarium methanol extract (ME) and aqueous extract (AE) and found that they improved protection against BB disease by inducing resistance to the pathogen. However, the control group exhibited significantly higher membrane damage due to greater Xoo infections and necrosis. Additionally, the occurrence of various antimicrobial compounds was identified in the extract by using the gas chromatography-mass spectrometry (GC-MS). Subsequently, the in vitro antibacterial property of the extract was confirmed, as the higher zone of inhibition was observed with ME against Xoo. Molecular docking study further revealed that certain metabolites, such as mucic acid and 3-phenyllactic acid of H. coronarium, could target the d-alanine d-alanine ligase A (DdlA) and Peptide deformylase (PDF) proteins of Xoo, thereby hindering its growth. Thus, priming rice plants with H. coronarium flower extract could induce defense responses by modulating photosystem II and enzymatic antioxidants. Therefore, it could be a promising source of antimicrobial metabolites.

Identification of QTLs Conferring Resistance to Bacterial Diseases in Rice.

Bacterial panicle blight, bacterial leaf streak, and bacterial brown stripe are common bacterial diseases in rice that represent global threats to stable rice yields. In this study, we used the rice variety HZ, Nekken and their 120 RIL population as experimental materials. Phenotypes of the parents and RILs were quantitatively analyzed after inoculation with Burkholderia glumae, Xanthomonas oryzae pv. oryzicola, and Acidovorax avenae subsp. avenae. Genetic SNP maps were also constructed and used for QTL mapping of the quantitative traits. We located 40 QTL loci on 12 chromosomes. The analysis of disease resistance-related candidate genes in the QTL regions with high LOD value on chromosomes 1, 3, 4, and 12 revealed differential expression before and after treatment, suggesting that the identified genes mediated the variable disease resistance profiles of Huazhan and Nekken2. These results provide an important foundation for cloning bacterial-resistant QTLs of panicle blight, leaf streak, and brown stripe in rice.

Genetic Structure and TALome Analysis Highlight a High Level of Diversity in Burkinabe Xanthomonas Oryzae pv. oryzae Populations

Bacterial Leaf Blight of rice (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major threat for food security in many rice growing countries including Burkina Faso, where the disease was first reported in the 1980’s. In line with the intensification of rice cultivation in West-Africa, BLB incidence has been rising for the last 15 years. West-African strains of Xoo differ from their Asian counterparts as they (i) are genetically distant, (ii) belong to new races and, (iii) contain reduced repertoires of Transcription Activator Like (TAL) effector genes. In order to investigate the evolutionary dynamics of Xoo populations in Burkina Faso, 177 strains were collected from 2003 to 2018 in three regions where BLB is occurring. Multilocus VNTR Analysis (MLVA-14) targeting 10 polymorphic loci discriminated 24 haplotypes and showed that Xoo populations were structured according to their geographical localization and year of collection. Considering their major role in Xoo pathogenicity, we assessed the TAL effector repertoires of the 177 strains upon RFLP-based profiling. Surprisingly, an important diversity was revealed with up to eight different RFLP patterns. Finally, comparing neutral vs. tal effector gene diversity allowed to suggest scenarios underlying the evolutionary dynamics of Xoo populations in Burkina Faso, which is key to rationally guide the deployment of durably resistant rice varieties against BLB in the country.

Design, synthesis, and antimicrobial evaluation of 2-aminothiazole derivatives bearing the 4-aminoquinazoline moiety against plant pathogenic bacteria and fungi.

To find more effective agricultural antibiotics, a class of new 2-aminothiazole derivatives containing the 4-aminoquinazoline moiety were synthesized and evaluated for their antimicrobial properties against the phytopathogenic bacteria and fungi of agricultural importance. All the target compounds were fully characterized by 1 H NMR, 13 C NMR, and HRMS spectra. The bioassay results showed that compound F29 with a 2-pyridinyl substituent exhibited an outstanding antibacterial effect against Xanthomonas oryzae pv. oryzicola (Xoc) in vitro, having an EC50 (half maximal effective concentration) value as low as 2.0 μg/mL (over 30-fold more effective than the commercialized agrobactericide Bismerthiazol, with an EC50 value of 64.3 μg/mL). Additionally, compound F8 with a 2-fluorophenyl group demonstrated a good inhibitory activity towards the bacterium Xanthomonas axonopodis pv. citri (Xac), around 2-fold more active than Bismerthiazol in terms of their EC50 values (22.8 vs 71.5 μg/mL). Interestingly, this compound also demonstrated a notable fungicidal effect against Phytophthora parasitica var. nicotianae, with a largely comparable EC50 value to the commercialized fungicide Carbendazim. Finally, the mechanistic studies revealed that compound F29 exerted its antibacterial effects by increasing the permeability of bacterial membranes, reducing the release of extracellular polysaccharides, and triggering morphological changes of bacterial cells. Compound F29 held the promising potential as a lead compound for developing more efficient bactericides to fighting against Xoc. This article is protected by copyright. All rights reserved.

Induction of Bacterial Leaf Blight (Xanthomonas oryzae pv. oryzae) Resistance in Rice by Potential Endophytic Bacterial Consortium

Induction of Bacterial Leaf Blight (Xanthomonas oryzae pv. oryzae) Resistance in Rice by Potential Endophytic Bacterial Consortium

Xoo-responsive transcriptome reveals the role of the circular RNA133 in disease resistance by regulating expression of OsARAB in rice

Upon Xanthomonas oryzae pv. oryzae (Xoo) infection of rice leaves, the invasion induces systematic expression changes for both the coding genes and the non-coding genes, allowing the plant to make corresponding responses. However, the roles of circular RNAs (circRNAs) in rice defending against Xoo remain largely unknown. To address this question, we conducted a whole-transcriptomic analysis to systematically screen the differentially expressed (DE) mRNAs and non-coding RNAs (ncRNAs) in rice responding to Xoo infection. Our results revealed a total of 4076 DE mRNAs, 89 DE long non-coding RNAs (lncRNAs), 82 DE microRNAs (miRNAs), and 14 DE circRNAs identified from Xoo-infected rice plants at 48 h post inoculation. Three circRNAs (ciR52, ciR298, and ciR133) were found to be able to form circular RNAs, and their expression was induced by Xoo infection. ciR133 was found to repress the expression of its parental gene OsARAB (putative arabinofuranosidase gene) during Xoo infection. Overexpression of ciR133 and mutation of OsARAB enhanced rice resistance against Xoo, without compromising main agronomic traits. Our data suggest that circRNAs are associated with rice response to Xoo infection, providing a potential strategy for breeding Xoo-resistant rice plants by manipulating ciR133 and OsARAB.

Effect Concentration of Teak Leaf Extract on the Diameter of the Inhibitory Zone Xanthomonas oryzae

Indonesia is an agricultural country with the majority of the population working in the agricultural sector. According to the Central Statistics Agency of Indonesia, rice production in 2022 is estimated at 9.58 million tons, down by 0.04 million tons or 0.41 percent compared to 2021 which was around 9.62 million tons. The rise and fall of rice production was influenced by several problems. One of the causes of the delay in rice production is leaf blight caused by Xanthomonas oryzae pv. oryzae reducing rice yields by 30-40%. This research was to examine the use of teak leaf extract in inhibiting the growth of X. oryzae bacteria. The results showed that there was an effect of various concentrations of teak leaf extract (Tectona grandis) on the inhibition zone of X. oryzae. The effective concentration of teak leaf extract in inhibiting Xanthomonas oryzae bacteria is 20%.

Discovery and Structural Optimization of 1,2,3,4-Tetrahydro-β-carbolines as Novel Reactive Oxygen Species Inducers for Controlling Intractable Plant Bacterial Diseases.

Nowadays, reactive oxygen species (ROS) have been acknowledged as promising bactericidal targets against pesticide-resistant bacteria. Herein, to further excavate more excellent ROS inducers, simple 1,2,3,4-tetrahydro-β-carboline derivatives containing a 3-aminopropanamide moiety were prepared and assessed for their antibacterial potency. Notably, three promising compounds displayed significant antibacterial potency. Compound I29 exhibits excellent in vitro bioactivity, with an EC50 value of 5.73 μg/mL, and admirable in vivo activities (protective activity of 55.74% and curative activity of 65.50%) toward Xanthomonas oryzae pv. oryzae. Compound I16 has good activity in vitro, with an EC50 of 3.43 μg/mL, and outstanding bioactivities in vivo (protective activity of 92.50% and curative activity of 59.68%) against Xanthomonas axonopodis pv. citri. Compound I6 shows excellent in vitro bioactivity (EC50 = 2.86 μg/mL) and significant protective activity (94.02%) for preventing Pseudomonas syringae pv. actinidiae. Antibacterial mechanism investigations indicate that these compounds disrupt the balance of the redox system to kill bacteria. These simple 1,2,3,4-tetrahydro-β-carboline derivatives are promising leads to the discovery of bactericidal agents.

Photoinduced palladium-catalyzed 1,3-diene-selective fluoroalkylamination compounds as potential bactericidal agent against Xanthomonas oryzae pv. oryzae

A series of photoinduced palladium-catalyzed 1,3-diene-selective fluoroalkylamination derivatives was rationally synthesized based on diversity-oriented synthesis via cross coupling of 1,3-dienes, amines and fluoroalkyl iodides. The reaction featured good function group tolerance and a broad substrate scope, which could be extended to the late-stage modification of bioactive molecules. Bactericidal activity of all the compounds against Xanthomonas oryzae pv. oryzae (Xoo) was evaluated. Among them, compound E14 showed significant activity against Xanthomonas oryzae pv. oryzae (Xoo) with half maximal effective concentration (EC50) value of 6.61 µmol/mL. In pot experiments, the results showed that E14 could control rice bacterial blight with protective and curative efficiencies of 37.5% and 63.2% at 200 µg/mL, respectively. Additionally, a plausible mechanism for antibacterial behavior of E14 was proposed by electron microscopy, flow cytometry, reactive oxygen species detection, and biofilm assay. In current work, it can promote the development of photoinduced palladium-catalyzed 1,3-diene-selective fluoroalkyl amination compounds as prospective antibacterial agent bearing an intriguing mode of action.