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SUMMARY: Bacterial leaf streak (BLS), caused by Xanthomonas oryzae pv. oryzicola (Xoc), is a major bacterial disease in rice. Transcription activator‐like effectors (TALEs) from Xanthomonas can induce host susceptibility (S) genes and facilitate infection. However, knowledge of the function of Xoc TALEs in promoting bacterial virulence is limited. In this study, we demonstrated the importance of Tal10a for the full virulence of Xoc. Through computational prediction and gene expression analysis, we identified the hexokinase gene OsHXK5 as a host target of Tal10a. Tal10a directly binds to the gene promoter region and activates the expression of OsHXK5. CRISPR/Cas9‐mediated gene editing in the effector binding element (EBE) of OsHXK5 significantly increases rice resistance to Xoc, while OsHXK5 overexpression enhances the susceptibility of rice plants and impairs rice defense responses. Moreover, simultaneous editing of the promoters of OsSULTR3;6 and OsHXK5 confers robust resistance to Xoc in rice. Taken together, our findings highlight the role of Tal10a in targeting OsHXK5 to promote infection and suggest that OsHXK5 represents a potential target for engineering rice resistance to Xoc. [ABSTRACT FROM AUTHOR]

In order to give wide-ranging and long-lasting disease resistance that reduces rice output, breeding techniques are used such as the importance of selection assisted by markers and gene pyramiding. Bacterial leaf blight (BLB), which is carried on by the pathogen Xanthomonas oryzae pv. oryzae, is one such disease that significantly reduces rice yield. Numerous molecular marker techniques have already been developed because molecular markers are crucial for both marker-assisted selection and gene pyramiding. Currently, DNA-based markers, sometimes referred to as molecular markers, are the most frequently employed ones. Based on the methods used to find them, the molecular markers are divided into two main types. These markers are based on hybridization and polymerase chain reaction. The morphological (traditionally based) and biochemical (enzyme-based) markers are two more types of markers that are available. The best method for preventing rice BLB disease is host plant/varietal resistance. Gene pyramiding with the help of markers offers the potential to speed up breeding operations and ensure that the host plant's acquired resistance will last. This research explores the use, economic significance, constraints, and potential of marker-assisted selection and gene pyramiding for rice BLB disease resistance. [ABSTRACT FROM AUTHOR]

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight in rice. Polyhydroxyalkanoates (PHAs) consitute a diverse group of biopolyesters synthesized by bacteria under nutrient-limited conditions. The phaC gene is important for PHA polymerization. We investigated the effects of phaC gene mutagensis in Xoo strain PXO99A. The phaC gene knock-out mutant exhibited reduced swarming ability relative to that of the wild-type. Under conditions where glucose was the sole sugar source, extracellular polysaccharide (EPS) production by ΔphaC declined by 44.8%. ΔphaC showed weak hypersensitive response (HR) induction in the leaves of non-host Nicotiana tabacum, concomitant with downregulation of hpa1 gene expression. When inoculated in rice leaves by the leaf-clipping method, ΔphaC displayed reduced virulence in terms of lesion length compared with the wild-type strain. The complemented strain showed no significant difference from the wild-type strain, suggesting that the deletion of phaC in Xoo induces significant alterations in various physiological and biological processes. These include bacterial swarming ability, EPS production, transcription of hrp genes, and glucose metabolism. These changes are intricately linked to the energy utilization and virulence of Xoo during plant infection. These findings revealed involvement of phaC in Xoo is in the maintaining carbon metabolism by functioning in the PHA metabolic pathway. [ABSTRACT FROM AUTHOR]

Summary: The clade III subfamily of OsSWEETs includes transmembrane proteins necessary for susceptibility to bacterial blight (BB). These genes are targeted by the specific transcription activator‐like effector (TALE) of Xanthomonas oryzae pv. oryzae and mediate sucrose efflux for bacterial proliferation. However, the mechanism through which OsSWEETs regulate rice immunity has not been fully elucidated. Here, we demonstrated that the cytosolic carboxyl terminus of OsSWEET11a/Xa13 is required for complementing susceptibility to PXO99 in IRBB13 (xa13/xa13). Interestingly, the C‐terminus of ZmXa13, the maize homologue of OsSWEET11a/Xa13, could perfectly substitute for the C‐terminus of OsSWEET11a/Xa13. Furthermore, OsSWEET11a/Xa13 interacted with the high‐mobility group B1 (OsHMGB1) protein and the small heat shock‐like protein OsHsp20L through the same regions in the C‐terminus. Consistent with the physical interactions, knockdown or knockout of either OsHMGB1 or OsHsp20L caused an enhanced PXO99‐resistant phenotype similar to that of OsSWEET11a/OsXa13. Surprisingly, the plants in which OsHMGB1 or OsHsp20L was repressed developed increased resistance to PXO86, PXO61 and YN24, which carry TALEs targeting OsSWEET14/Xa41 or OsSWEET11a/Xa13. Additionally, OsHsp20L can interact with all six members of clade III OsSWEETs, whereas OsHMGB1 can interact with five other members in addition to OsSWEET12. Overall, we revealed that OsHMGB1 and OsHsp20L mediate conserved BB susceptibility by interacting with clade III OsSWEETs, which are candidates for breeding broad‐spectrum disease‐resistant rice. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bacterial virulence factors are involved in various biological processes and mediate persistent bacterial infections. Focusing on virulence factors of phytopathogenic bacteria is an attractive strategy and crucial direction in pesticide discovery to prevent invasive and persistent bacterial infection. Hence, discovery and development of novel agrochemicals with high activity, low‐risk, and potent anti‐virulence is urgently needed to control plant bacterial diseases. RESULTS: A series of novel β‐hydroxy pyridinium cation decorated pterostilbene derivatives were prepared and their antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) were systematacially assessed. Among these pterostilbene derivatives, compound 4S exhibited the best antibacterial activity against Xoo in vitro, with an half maximal effective concentration (EC50) value of 0.28 μg mL−1. A series of biochemical assays including scanning electron microscopy, crystal violet staining, and analysis of biofilm formation, swimming motility, and related virulence factor gene expression levels demonstrated that compound 4S could function as a new anti‐virulence factor inhibitor by interfering with the bacterial infection process. Furthermore, the pot experiments provided convinced evidence that compound 4S had the high control efficacy (curative activity: 71.4%, protective activity: 72.6%), and could be used to effectively manage rice bacterial leaf blight in vivo. CONCLUSION: Compounds 4S is an attractive virulence factor inhibitor with potential for application in treating plant bacterial diseases by suppressing production of several virulence factors. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Small non-coding RNAs (sRNAs) act as post-transcriptional regulators to participate in many cellular processes. Among these, sRNA trans217 has been identified as a key virulent factor associated with pathogenicity in rice, triggering hypersensitive reactions in non-host tobacco and facilitating the secretion of the PthXo1 effector in Xanthomonas oryzae pv. oryzae (Xoo) strain PXO99A. Elucidating potential targets and downstream regulatory genes is crucial for understanding cellular networks governing pathogenicity and plant resistance. To explore the targets regulated by sRNA trans217, transcriptome sequencing was carried out to assess differential expression genes (DEGs) between the wild-type strain PXO99A and a mutant lacking the sRNA fragment under both virulence-inducing or normal growth conditions. DEG analysis revealed that sRNA trans217 was responsible for diverse functions, such as type III secretion system (T3SS), glutamate synthase activity, and oxidative stress response. Three genes were selected for further investigation due to their significant differential expression and biological relevance. Deletion of PXO_RS08490 attenuated the pathogenicity of Xoo in rice and reduced the tolerance level of PXO99A to hydrogen peroxide. These findings suggest a regulatory role of sRNA trans217 in modulating bacterial virulence through multiple gene targets, either directly or indirectly. [ABSTRACT FROM AUTHOR]

LuxR-type regulators play pivotal roles in regulating numerous bacterial processes, including bacterial motility and virulence, thereby exerting a significant influence on bacterial behavior and pathogenicity. Xanthomonas oryzae pv. oryzicola, a rice pathogen, causes bacterial leaf streak. Our research has identified VmsR, which is a response regulator of the two-component system (TCS) that belongs to the LuxR family. These findings of the experiment reveal that VmsR plays a crucial role in regulating pathogenicity, motility, biofilm formation, and the production of extracellular polysaccharides (EPSs) in Xoc GX01. Notably, our study shows that the vmsR mutant exhibits a reduced swimming motility but an enhanced swarming motility. Furthermore, this mutant displays decreased virulence while significantly increasing EPS production and biofilm formation. We have uncovered that VmsR directly interacts with the promoter regions of fliC and fliS, promoting their expression. In contrast, VmsR specifically binds to the promoter of gumB, resulting in its downregulation. These findings indicate that the knockout of vmsR has profound effects on virulence, motility, biofilm formation, and EPS production in Xoc GX01, providing insights into the intricate regulatory network of Xoc. [ABSTRACT FROM AUTHOR]

Xanthomonas oryzae pv. oryzae (Xoo), the causative agent of bacterial blight (BB), has developed a unique strategy to infect rice by hijacking the host's methylglyoxal (MG) detoxification pathway. This results in an over‐accumulation of MG, which facilitates tissue colonization and evasion of host's immune responses. While MG role in abiotic stresses is well‐documented, its involvement in biotic stresses has not been extensively explored. Recently, Fu et al. (2024) provided the first evidence of MG role in promoting Xoo pathogenesis in rice. This new virulence strategy contributes to the pathogen's remarkable adaptability and survival. In this mechanism of hijacking of MG detoxification pathway, Xoo induces OsWRKY62.1 to inhibit OsGLY II expression, leading to MG overaccumulation in infected rice cells. This excess MG hinders plant cell organelle function, creating a favorable environment for Xoo by compromising the rice defense system. In this article, we have presented our perspectives on how the BB pathogen adapts its virulence mechanisms to infect and cause disease in rice. [ABSTRACT FROM AUTHOR]

Enhancing carbohydrate export from source to sink tissues is considered to be a realistic approach for improving photosynthetic efficiency and crop yield. The rice sucrose transporters OsSUT1, OsSWEET11a and OsSWEET14 contribute to sucrose phloem loading and seed filling. Crucially, Xanthomonas oryzae pv. oryzae (Xoo) infection in rice enhances the expression of OsSWEET11a and OsSWEET14 genes, and causes leaf blight. Here we show that co‐overexpression of OsSUT1, OsSWEET11a and OsSWEET14 in rice reduced sucrose synthesis and transport leading to lower growth and yield but reduced susceptibility to Xoo relative to controls. The immunity‐related hypersensitive response (HR) was enhanced in the transformed lines as indicated by the increased expression of defence genes, higher salicylic acid content and presence of HR lesions on the leaves. The results suggest that the increased expression of OsSWEET11a and OsSWEET14 in rice is perceived as a pathogen (Xoo) attack that triggers HR and results in constitutive activation of plant defences that are related to the signalling pathways of pathogen starvation. These findings provide a mechanistic basis for the trade‐off between plant growth and immunity because decreased susceptibility against Xoo compromised plant growth and yield. Summary statement: The study reported in this manuscript concerns the emerging topic of the roles played by SWEET sugar transporters in plant immunity. The data reported in this manuscript show that overexpression of Clade III SWEET sucrose transporters OsSWEET11a and OsSWEET14 that are exploited by bacterial blight pathogen Xanthomonas oryzae pv. oryzae to acquire sugars for its propagation elicits immune responses and activates plant defence responses leading to enhanced resistance against bacterial as well as fungal pathogens. The findings obtained by the overexpression of OsSWEET11a and OsSWEET14 in rice show that sucrose transport occurs via an apoplastic route, and overexpression of these sugar transporters inhibits sucrose synthesis and transport, which explains the inverse relationships between plant growth and yield, and resistance to pathogens. Moreover, our results show that sucrose transport and pathogen responses are coupled processes, and provide evidence for the concept that pathogen‐induced starvation is linked to plant defence. Also, to the best of our knowledge this is the first study where we show that disease susceptibility genes OsSWEET11a and OsSWEET14 can lead to hypersensitive reaction leading to enhanced plant immunity. [ABSTRACT FROM AUTHOR]

Half of the world's population depends on rice for their calories. Protecting rice in the growth period from damage caused by phytopathogens is faced with a great challenge under the frequent extreme climate. To find novel fungicides to control rice diseases, 35 novel phenylthiazole‐1,3,4‐oxadiazole‐thioether (sulfone) derivatives were synthesized and evaluated for their efficacy against destructive fungal and bacterial diseases of rice. Bioassay results demonstrated that most of G‐series compounds possessed excellent antifungal and antibacterial activities. In particular, compounds G1 (EC50 = 2.22 μg/mL, R.s) and G7 (EC50 = 2.76 μg/mL, R.s) showed the most promising antifungal activities in vitro and exhibited superior protective and curative activities against rice sheath blight in vivo compared with commercial carbendazim. Surprisingly, compound G2 exhibited the remarkable antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo) with an EC50 value of 1.98 μg/mL, and demonstrated superior protective activity (88.08%) than thiodiazole copper (79.39%) against rice bacterial leaf blight at 200 μg/mL. The abovementioned results fully manifested that the phenylthiazole‐1,3,4‐oxadiazole‐sulfone structure, especially compounds G1 and G2, had the potential to develop as commercial agents for controlling rice fungal and bacterial diseases. [ABSTRACT FROM AUTHOR]

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Our study investigates the genetic mechanisms underlying the spotted leaf phenotype in rice, focusing on the spl43 mutant. This mutant is characterized by persistent reddish-brown leaf spots from the seedling stage to maturity, leading to extensive leaf necrosis. Using map-based cloning, we localized the responsible locus to a 330 Kb region on chromosome 2. We identified LOC_Os02g56000, named OsRPT5A, as the causative gene. A point mutation in OsRPT5A, substituting valine for glutamic acid, was identified as the critical factor for the phenotype. Functional complementation and the generation of CRISPR/Cas9-mediated knockout lines in the IR64 background confirmed the central role of OsRPT5A in controlling this trait. The qPCR results from different parts of the rice plant revealed that OsRPT5A is constitutively expressed across various tissues, with its subcellular localization unaffected by the mutation. Notably, we observed an abnormal accumulation of reactive oxygen species (ROS) in spl43 mutants by examining the physiological indexes of leaves, suggesting a disruption in the ROS system. Complementation studies indicated OsRPT5A's involvement in ROS homeostasis and catalase activity regulation. Moreover, the spl43 mutant exhibited enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo), highlighting OsRPT5A's role in rice pathogen resistance mechanisms. Overall, our results suggest that OsRPT5A plays a critical role in regulating ROS homeostasis and enhancing pathogen resistance in rice. [ABSTRACT FROM AUTHOR]

BRRI31R is one of the Bangladesh's most promising restorer lines due to its abundant pollen producing capacity, strong restoring ability, good combining ability, high outcrossing rate and genetically diverse from cytoplasmic male sterile (CMS) line. But the drawback of this line is that it is highly susceptible to bacterial blight (BB) disease of rice caused by Xanthomonas oryzae pv. oryzae. The present study highlighted the pyramiding of effective BB resistance genes (xa5, xa13 and Xa21) into the background of BRRI31R, through marker–assisted backcrossing (MABC). Backcross progenies were confirmed and advanced based on the foreground selection of target genes. Pyramided lines were used for pathogenicity test against five Bangladeshi Xanthomonas oryzae (BXo) races (BXo93, BXo220, BXo822, BXo826, BXo887) and confirmed the dominant fertility restore genes, Rf3 and Rf4 and further validated against SNP markers for more confirmation of target resistance genes. All pyramided restorer lines consisted of Xa4 (in built), xa5, xa13, Xa21, and Chalk5 with two fertility restorer genes, Rf3, Rf4. and these restorer lines showed intermediate amylose content (<25%). Restorer lines BRRI31R-MASP3 and BRRI31R-MASP4 showed high levels of resistance against five virulent BXo races and SNP genotyping revealed that these lines also contained a blast resistance gene Pita races. Gene pyramided restorer lines, BRRI31R-MASP3 and BRRI31R-MASP4 can directly be used as a male parent for the development of new BB resistant hybrid rice variety or could be used as a replacement of restorer line of BRRI hybrid dhan5 and 7 to enhance the quality of hybrid seeds as well as rice production in Bangladesh. [ABSTRACT FROM AUTHOR]

Xanthomonas oryzae pv. oryzicola (Xoc) is a notorious plant pathogen. Like most bacterial pathogens, Xoc has evolved a complex regulatory network to modulate the expression of various genes related to pathogenicity. Here, we have identified TfmR, a transcriptional regulator belonging to the TetR family, as a key player in the virulence mechanisms of this phytopathogenic bacterium. We have demonstrated genetically that tfmR is involved in the hypersensitive response (HR), pathogenicity, motility and extracellular polysaccharide production of this phytopathogenic bacterium. Our investigations extended to exploring TfmR's interaction with RpfG and HrpX, two prominent virulence regulators in Xanthomonas species. We found that TfmR directly binds to the promoter region of RpfG, thereby positively regulating its expression. Notably, constitutive expression of RpfG partly reinstates the pathogenicity compromised by TfmR-deletion mutants. Furthermore, our studies revealed that TfmR also exerts direct positive regulation on the expression of the T3SS regulator HrpX. Similar to RpfG, sustained expression of HrpX partially restores the pathogenicity of TfmR-deletion mutants. These findings underscore TfmR's multifaceted role as a central regulator governing key virulence pathways in Xoc. Importantly, our research sheds light on the intricate molecular mechanisms underlying the regulation of pathogenicity in this plant pathogen. [ABSTRACT FROM AUTHOR]

SUMMARY: Rapid alkalinization factors (RALFs), belonging to a family of small secreted peptides, have been considered as important signaling molecules in diverse biological processes, including immunity. Current studies on RALF‐modulated immunity mainly focus on Arabidopsis, but little is reported in crop plants. The rice immune receptor XA21 confers immunity to the bacterial blight pathogen, Xanthomonas oryzae pv. oryzae (Xoo). Here, we pursued functional characterization of rice RALF26 (OsRALF26) up‐regulated by Xoo during XA21‐mediated immune response. When applied exogenously as a recombinant peptide, OsRALF26 induced a series of immune responses, including pathogenesis‐related genes (PRs) induction, reactive oxygen species (ROS) production, and callose deposition in rice and/or Arabidopsis. Transgenic rice and Arabidopsis overexpressing OsRALF26 exhibited significantly enhanced resistance to Xoo and Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), respectively. In yeast two‐hybrid, pull‐down assays, and co‐immunoprecipitation analyses, rice FER‐like receptor 1 (OsFLR1) was identified as a receptor of OsRALF26. Transient expression of OsFLR1 in Nicotiana benthamiana leaves displayed significantly increased ROS production and callose deposition after OsRALF26 treatment. Together, we propose that OsRALF26 induced by Xoo in an XA21‐dependent manner is perceived by OsFLR1 and may play a novel role in the enforcement of XA21‐mediated immunity. Significance Statement: In‐depth insights about rice immunity help us develop new strategy to protect economically important monocot crops from increasing numbers of pathogens. Here, by studying how rice rapid alkalinization factor 26 (OsRALF26), one of small secreted peptides, activates immune responses, we tried to broaden our understanding of the mechanism of the RALF perception in rice plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Xanthomonas oryzae pv. oryzae (Xoo) is often considered one of the most destructive bacterial pathogens causing bacterial leaf blight (BLB), resulting in significant yield and cost losses in rice. In this study, a series of novel derivatives containing the isopropanolamine moiety linked to various substituted phenols and piperazines were designed, synthesized and screened. RESULTS: Antibacterial activity results showed that most compounds had good inhibitory effects on Xoo, among which compound W2 (EC50 = 2.74 μg mL−1) exhibited the most excellent inhibitory activity, and W2 also had a certain curative effect (35.89%) on rice compared to thiodiazole copper (TC) (21.57%). Scanning electron microscopy (SEM) results indicated that compound W2 could cause rupture of the Xoo cell membrane. Subsequently, proteomics and quantitative real‐time polymerase chain reaction revealed that compound W2 affected the physiological processes of Xoo and may exert antibacterial activity by targeting the two‐component system pathway. Interestingly, W2 upregulated Xoo's methyltransferase to impact on its pathogenicity. CONCLUSION: The present study offers a promising phenolic‐piperazine‐sopropanolamine compound as an innovative antibacterial strategy by specifically targeting the two‐component system pathway and inducing upregulation of methyltransferase to effectively impact Xoo's pathogenicity. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious diseases of rice, and there is a lack of bactericides for controlling this disease. We previously found parthenolide (PTL) is a potential lead for developing bactericides against Xoo, and subunit F of respiratory chain complex I (NuoF) is an important target protein of PTL. However, the binding modes of PTL with NuoF need further elucidation. RESULTS: In this study, we obtained the crystal structure of Xoo NuoEF (complex of subunit E and F of respiratory chain complex I) with a resolution of 2.36 Å, which is the first report on the protein structure of NuoEF in plant‐pathogenic bacteria. The possible binding sites of PTL with NuoF (Cys105 and Cys187) were predicted with molecular docking and mutated into alanine using a base mismatch method. The mutated proteins were expressed in Escherichia coli and purified with affinity chromatography. The binding abilities of PTL with mutated proteins were investigated via pull‐down assay and BIAcore analysis, which revealed that double mutation of Cys105 and Cys187 in NuoF severely affected the binding ability of PTL with NuoF. In addition, the binding modes were further simulated with combined quantum mechanical/molecular mechanical calculations, and the results indicated that PTL may have a stronger binding with Cys105 than Cys187. CONCLUSION: NuoEF protein structure of Xoo was resolved, and Cys105 and Cys187 in NuoF are important binding sites of PTL. This study further clarified the action mechanism of PTL against Xoo, and will promote the innovation of bactericides targeting Xoo complex I. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Key message: OsICS1 but not OsICS1-L mediates the rice response to Xoo inoculation, with its overexpression increasing resistance against this pathogen. OsICS1 but not OsICS-L is directly upregulated by OsWRKY6. Rice (Oryza sativa) is a staple crop for about half of the global population and is particularly important in the diets of people living in Asia, Latin America, and Africa. This crop is continually threatened by bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo), which drastically reduces yields; therefore, it is needed to elucidate the plant's resistance mechanisms against Xoo. Isochorismate synthase (ICS1) generates salicylic acid (SA) and increases resistance against bacterial disease. The OsICS1 is differently annotated in rice genome databases and has not yet been functionally characterized in the context of Xoo infection. Here, we report that the expression of the OsICS1 is directly regulated by OsWRKY6 and increases plant resistance against Xoo. Inoculation with Xoo increased the expression of OsICS1 but not that of the long variant of OsICS1 (OsICS1-L). OsWRKY6 directly activated the OsICS1 promoter but not the OsICS1-L promoter. OsICS1 overexpression in rice increased resistance against Xoo through the induction of SA-dependent bacterial defense genes. These data show that OsICS1 promotes resistance against Xoo infection. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) yield, quality and resistance to various biotic and abiotic stresses are the major barriers of rice production worldwide. Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae, is a major cause of reduced yield in rice. In the present study, a set of 43 advance breeding lines along with 6 check varieties was evaluated for yield attributes, milling quality traits and BB resistance. The results indicated a significant variation for various morpho-physiological and milling traits. Disease screening was carried out in field at maximum tillering stage under artificial inoculation conditions. Based on pathogenicity test, 36 genotypes showed resistance to all the ten BB pathotypes prevalent in northern India (Punjab). Further, these lines were characterized for known BB resistance gene(s); Xa4, xa5, xa13 and Xa21 using linked molecular markers and molecular analysis showed a wide range of gene combinations and indicated the presence of single (6), two (23), and three (13) gene combinations while one line (PAU 5285-23-1-2) showed none of the known gene tested. The genotypes PAU 7261-19-1, PAU 6998-110-3-1, PAU 6516-11-1-2-1-1, PAU 6554-1-1-1-2-3, PAU 6970-18-1-3, PAU 6707-33-6-1-1-1-3 had significantly and consistently high yield with early maturity, semi dwarf, good tillering along with desirable quality traits. Moreover, these are resistant to all ten pathotypes of BB presently prevalent in the Punjab state. Therefore, it is recommended that these can be utilized further to identify and develop improved varieties with high yield, early to mid-maturity, desirable milling quality and BB resistance. [ABSTRACT FROM AUTHOR]

Bacterial blight of rice is a devastating disease caused by the gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo). Chinese Xoo strain pathotypes IV, V, and IX are the major virulent Xoo strain types in South China sequentially from the 1990s to the present. Here, we report the isolation of GD0201 and GD0202, which belong to pathotypes IV and IX, respectively, and the complete genome sequence and transcriptomic analysis of GD0201 (IV), GD1358 (V), and GD0202 (IX). We found that resistance genes xa5, Xa23, and Xa27 confer strong resistance to all three Xoo strains, indicating that they are currently good choices for resistance rice breeding. The genome analysis reveals fewer TAL and non-TAL effector coding genes in GD0202 than in the other two strains, potentially contributing to its strong virulence. Transcriptomic analysis of ZH11 inoculated with the three Xoo strains strongly suggests that three Xoo strains for better infection repress the ethylene response factor (ERF) gene family members. Furthermore, weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) analysis revealed 14 hub genes potentially associated with rice response to the three Xoo strains. The expression of several hub genes was validated to be induced by all three Xoo strains, suggesting its role in bacterial blight disease response to Xoo strains. Genomic analysis of the Xoo strains belonging to pathotypes IV, V, and IX, identification of effectors and genes related to Xoo virulence in rice plants will provide insights into understanding the molecular mechanism underlying rice-Xoo interaction and the gene expression pattern in response to Xoo infection. [ABSTRACT FROM AUTHOR]

Bacterial leaf blight (BLB), among the most serious diseases in rice production, is caused by Xanthomonas oryzae pv. oryzae (Xoo). Xa23, the broadest resistance gene against BLB in rice, is widely used in rice breeding. In this study, the rice variety CBB23 carrying the Xa23 resistance gene was inoculated with AH28 and PXO99A to identify differentially expressed genes (DEGs) associated with the resistance. Transcriptome sequencing of the infected leaves showed 7997 DEGs between the two strains at different time points, most of which were up-regulated, including cloned rice anti-blight, peroxidase, pathology-related, protein kinase, glucosidase, and other coding genes, as well as genes related to lignin synthesis, salicylic acid, jasmonic acid, and secondary metabolites. Additionally, the DEGs included 40 cloned, five NBS-LRR, nine SWEET family, and seven phenylalanine aminolyase genes, and 431 transcription factors were differentially expressed, the majority of which belonged to the WRKY, NAC, AP2/ERF, bHLH, and MYB families. Metabolomics analysis showed that a large amount of alkaloid and terpenoid metabolite content decreased significantly after inoculation with AH28 compared with inoculation with PXO99A, while the content of amino acids and their derivatives significantly increased. This study is helpful in further discovering the pathogenic mechanism of AH28 and PXO99A in CBB23 rice and provides a theoretical basis for cloning and molecular mechanism research related to BLB resistance in rice. [ABSTRACT FROM AUTHOR]

The rice receptor kinase XA21 confers broad-spectrum resistance to Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of rice bacterial blight disease. To investigate the relationship between the expression level of XA21 and resulting resistance, we generated independent HA-XA21 transgenic rice lines accumulating the XA21 immune receptor fused with an HA epitope tag. Whole-genome sequence analysis identified the T-DNA insertion sites in sixteen independent T0 events. Through quantification of the HA-XA21 protein and assessment of the resistance to Xoo strain PXO99 in six independent transgenic lines, we observed that XA21-mediated resistance is dose dependent. In contrast, based on the four agronomic traits quantified in these experiments, yield is unlikely to be affected by the expression level of HA-XA21. These findings extend our knowledge of XA21-mediated defense and contribute to the growing number of well-defined genomic landing pads in the rice genome that can be targeted for gene insertion without compromising yield. [ABSTRACT FROM AUTHOR]

Background: Two-tiered plant immune responses involve cross-talk among defense-responsive (DR) genes involved in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI), effector-triggered immunity (ETI) and effector-triggered susceptibility (ETS). Bacterial leaf streak (BLS), caused by Xanthomonas oryzae pv. oryzicola (Xoc) is an important bacterial disease that causes serious threats to rice yield and quality. Transcriptomic profiling provides an effective approach for the comprehensive and large-scale detection of DR genes that participate in the interactions between rice and Xoc. Results: In this study, we used RNA-seq to analyze the differentially expressed genes (DEGs) in susceptible rice after inoculation with two naturally pathogenic Xoc strains, a hypervirulent strain, HGA4, and a relatively hypovirulent strain, RS105. First, bacterial growth curve and biomass quantification revealed that differential growth occurred beginning at 1 day post inoculation (dpi) and became more significant at 3 dpi. Additionally, we analyzed the DEGs at 12 h and 3 days post inoculation with two strains, representing the DR genes involved in the PTI and ETI/ETS responses, respectively. Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed on the common DEGs, which included 4380 upregulated and 4019 downregulated genes and 930 upregulated and 1383 downregulated genes identified for the two strains at 12 h post inoculation (hpi) and 3 dpi, respectively. Compared to those at 12 hpi, at 3 dpi the number of common DEGs decreased, while the degree of differential expression was intensified. In addition, more disease-related GO pathways were enriched, and more transcription activator-like effector (TALE) putative target genes were upregulated in plants inoculated with HGA4 than in those inoculated with RS105 at 3 dpi. Then, four DRs were randomly selected for the BLS resistance assay. We found that CDP3.10, LOC_Os11g03820, and OsDSR2 positively regulated rice resistance to Xoc, while OsSPX3 negatively regulated rice resistance. Conclusions: By using an enrichment method for RNA-seq, we identified a group of DEGs related to the two stages of response to the Xoc strain, which included four functionally identified DR genes. [ABSTRACT FROM AUTHOR]

Xanthomonas oryzae pv. oryzae (Xoo) injects major transcription activator-like effectors (TALEs) into plant cells to activate susceptibility (S) genes for promoting bacterial leaf blight in rice. Numerous resistance (R) genes have been used to construct differential cultivars of rice to identify races of Xoo, but the S genes were rarely considered. Different edited lines of rice cv. Kitaake were constructed using CRISPR/Cas9 gene-editing, including single, double and triple edits in the effector-binding elements (EBEs) located in the promoters of rice S genes OsSWEET11a, OsSWEET13 and OsSWEET14. The near-isogenic lines (NILs) were used as tracers to detect major TALEs (PthXo1, PthXo2, PthXo3 and their variants) in 50 Xoo strains. The pathotypes produced on the tracers determined six major TALE types in the 50 Xoo strains. The presence of the major TALEs in Xoo strains was consistent with the expression of S genes in the tracers, and it was also by known genome sequences. The EBE editing had little effect on agronomic traits, which was conducive to balancing yield and resistance. The rice-tracers generated here provide a valuable tool to track major TALEs of Xoo in Asia which then shows what rice cultivars are needed to combat Xoo in the field. [ABSTRACT FROM AUTHOR]

Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is a widespread and destructive disease in rice production. Previously, we cloned an executor R gene, Xa7, which confers durable and broad-spectrum resistance to BB. Here, we further confirmed that the transcription activator-like effector (TALE) AvrXa7 in Xoo strains could directly bind to the effector-binding element (EBE) in the promoter of the Xa7 gene. Other executor R genes (Xa7, Xa10, Xa23, and Xa27) driven by the promoter of the Xa7 gene could be activated by AvrXa7 and trigger the hypersensitive response (HR) in tobacco leaves. When the expression of the Xa23 gene was driven by the Xa7 promoter, the transgenic rice plants displayed a similar resistance spectrum as the Xa7 gene, demonstrating that the disease resistance characteristics of executor R genes are mainly determined by their induction patterns. Xa7 gene is induced locally by Xoo in the infected leaves, and its induction not only inhibited the growth of incompatible strains but also enhanced the resistance of rice plants to compatible strains, which overcame the shortcomings of its race-specific resistance. Transcriptome analysis of the Xa7 gene constitutive expression in rice plants displayed that Xa7-mediated disease resistance was related to the biosynthesis of lignin and thus enhanced resistance to Xoo. Overall, our results provided novel insights and important resources for further clarifying the molecular mechanisms of the executor R genes. [ABSTRACT FROM AUTHOR]

In this study, a series of novel difluoromethyl pyrazole derivatives were synthesized and their structures were confirmed by 1H NMR, 13C NMR, and HRMS techniques. Subsequently, their antifungal activities in vitro against Mucor fragilis (M. fragilis), Trichoderma atroviride (T. atroviride), and Mucor bainieri (M. bainieri) at concentrations of 50 and 100 μg/mL were evaluated using the mycelium growth rate assay. Bioactivity results showed that the target compounds revealed lower antifungal activities against M. fragilis, T. atroviride, and M. bainieri than those of prochloraz and carbendazim. Additionally, the antibacterial activities against Xanthomonas axonopodis pv. citri (Xac) and Xanthomonas oryzae pv. oryzicola (Xoo) were determined using the turbidimeter test method. The bioassay results demonstrated that some of the target compounds exhibited moderate to good antibacterial activities. Notably, 2-methoxyphenyl 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylate displayed superior antibacterial effects against Xoo and Xac with inhibition rates of 62, 86 and 53, 80%, respectively, compared to those of thiodiazole copper. [ABSTRACT FROM AUTHOR]

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. Result: 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. [ABSTRACT FROM AUTHOR]

Bacterial blight is a destructive disease in rice caused by Xanthomonas oryzae pv. oryzae (Xoo). Single resistance genes often have limitations in providing broad-spectrum resistance, as pathogens continuously evolve and vary. Breeding rice varieties with multiple disease resistance genes has proven to be an effective strategy for controlling bacterial blight. In this study, a single Cas9/gRNA construct was used to target the homologous sequences of Xa13 and Xa25 genes through destroying the target gene function, creating bacterial blight resistance in five rice varieties. These materials provide promising germplasm resources for the development of rice varieties with durable resistance to bacterial blight. [ABSTRACT FROM AUTHOR]

Summary: Plants have intricate mechanisms that tailor their defence responses to pathogens. WRKY transcription factors play a pivotal role in plant immunity by regulating various defence signalling pathways. Many WRKY genes are transcriptionally activated upon pathogen attack, but how their functions are regulated after transcription remains elusive. Here, we show that OsWRKY7 functions as a crucial positive regulator of rice basal immunity against Xanthomonas oryzae pv. oryzae (Xoo). The activity of OsWRKY7 was regulated at both translational and post‐translational levels. Two translational products of OsWRKY7 were generated by alternative initiation. The full‐length OsWRKY7 protein is normally degraded by the ubiquitin–proteasome system but was accumulated following elicitor or pathogen treatment, whereas the alternate product initiated from the downstream in‐frame start codon was stable. Both the full and alternate OsWRKY7 proteins have transcriptional activities in yeast and rice cells, and overexpression of each form enhanced resistance to Xoo infection. Furthermore, disruption of the main AUG in rice increased the endogenous translation of the alternate stabilized form of OsWRKY7 and enhanced bacterial blight resistance. This study provides insights into the coordination of alternative translation and protein stability in the regulation of plant growth and basal defence mediated by the OsWRKY7 transcription factor, and also suggests a promising strategy to breed disease‐resistant rice by translation initiation control. [ABSTRACT FROM AUTHOR]

Diverse bacterial and fungal pathogens attack plants, causing biotic stress and severe yield losses globally. These losses are expected to become more serious as climate change improves conditions for many pathogens. Therefore, identifying genes conferring broad-spectrum disease resistance and elucidating their underlying mechanisms provides important resources for plant breeding. WRKY transcription factors affect plant growth and stress responses. However, the functions of many WRKY proteins remain to be elucidated. Here, we demonstrated the role of rice (Oryza sativa) WRKY group III transcription factor OsWRKY65 in immunity. OsWRKY65 localized to the nucleus and acted as transcriptional repressor. Genetic and molecular functional analyses showed that OsWRKY65 increases resistance to the fungal pathogen Fusarium fujikuroi through downregulation of GA signaling and upregulation of JA signaling. Moreover, OsWRKY65 modulated the expression of the key genes that confer susceptibility or resistance to Xanthomonas oryzae pv. oryzae to enhance immunity against the pathogen. In particular, OsWRKY65 directly bound to the promoter region of OsSWEET13 and repressed its expression. Taken together, our findings demonstrate that the OsWRKY65 enhances resistance to fungal and bacterial pathogens in rice. [ABSTRACT FROM AUTHOR]

Abstract The aim of the present work is to biosynthesize Chitosan nanoparticles (CTNp) using tea (Camellia sinensis) extract, with potent antimicrobial properties towards phytopathogens of rice. Preliminary chemical analysis of the extract showed that they contain carbohydrate as major compound and uronic acid indicating the nature of acidic polysaccharide. The structure of the isolated polysaccharide was analyzed through FTIR and 1H NMR. The CTNp was prepared by the addition of isolated tea polysaccharides to chitosan solution. The structure and size of the CTNp was determined through FTIR and DLS analyses. The surface morphology and size of the CTNp was analysed by SEM and HRTEM. The crystalinity nature of the synthesized nanoparticle was identified by XRD analysis. The CTNp exhibited the antimicrobial properties against the most devastating pathogens of rice viz., Pyricularia grisea, Xanthomonas oryzae under in vitro condition. CTNp also suppressed the blast and blight disease of rice under the detached leaf assay. These results suggest that the biosynthesized CTNp can be used to control the most devastating pathogens of rice.

The aim of the present work is to biosynthesize Chitosan nanoparticles (CTNp) using tea (Camellia sinensis) extract, with potent antimicrobial properties towards phytopathogens of rice. Preliminary chemical analysis of the extract showed that they contain carbohydrate as major compound and uronic acid indicating the nature of acidic polysaccharide. The structure of the isolated polysaccharide was analyzed through FTIR and 1H NMR. The CTNp was prepared by the addition of isolated tea polysaccharides to chitosan solution. The structure and size of the CTNp was determined through FTIR and DLS analyses. The surface morphology and size of the CTNp was analysed by SEM and HRTEM. The crystalinity nature of the synthesized nanoparticle was identified by XRD analysis. The CTNp exhibited the antimicrobial properties against the most devastating pathogens of rice viz., Pyricularia grisea, Xanthomonas oryzae under in vitro condition. CTNp also suppressed the blast and blight disease of rice under the detached leaf assay. These results suggest that the biosynthesized CTNp can be used to control the most devastating pathogens of rice. [ABSTRACT FROM AUTHOR]

A series of novel quinazolinone derivatives containing glycosides were designed and synthesized. The biological activities test found that this series of compounds had good antibacterial activities. Among all target compounds, compounds 1 and 15 showed good antibacterial activity in vitro against Pseudomonas syringae pv. actinidiae (Psa), with an EC50 value of 48.7 mg/L, 45.6 mg/L, respectively, which better than thiodiazole copper (54.6 mg/L) and zinc thiazole (49.2 mg/L). Compounds 15 and 23 showed good in vitro antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo) at a concentration of 100 mg/L, with inhibition rates of 79.3% and 77.1%, respectively, which better than thiodiazole copper (71.8%). In addition, compound 15 can cause significant deformation of cell surface. [ABSTRACT FROM AUTHOR]

SYAUP-491 is a novel alkyl sulfonamide. In this study, in vivo and in vitro tests were performed along with a proteomic analysis to determine the effects and underlying mechanisms of the antibacterial activity of SYAUP-491 against the causative agent of bacterial leaf blight in rice. The antibacterial test results suggested that SYAUP-491 exhibited significant activities against Xanthomonas oryzae pv. oryzae (Xoo) in vitro and in vivo. The minimal EC50 values reached 6.96 μg/mL and the curative activity reached 74.1%. Detailed studies demonstrated that SYAUP-491 altered membrane permeability and caused morphological changes. Based on proteomics results, SYAUP-491 might inhibit bacterial protein synthesis. SYAUP-491 may disrupt and alter cell membrane permeability and could further act on ribosomes in the bacterial body. Given the above results, SYAUP-491 could serve as a new lead compound in the research of antibacterial control of plant pathogenic bacterial disease. [ABSTRACT FROM AUTHOR]

Pest disasters which occurs on crops is a serious problem that not only cause crop yield loss or even crop failure but can also spread a number of plant diseases.Sulfonate derivatives have been widely used in insecticide and fungicide research in recent years. On this basis, a series of sulfonate derivatives bearing an amide unit are synthesized and the biological activities are evaluated. The bioassay results showed that compounds A8, A13, A16, B1, B3, B4, B5, B10, B12 − 20, C3, C5, C9, C10, C14, C15, C17 and C19 showed 100% activity at a concentration of 500 µg/mL against the Plutella xylostella (P. xylostella). Among them, B15 which contains a thiadiazole sulfonate structure still shows 100% activity at 50 µg/mL concentration against P. xylostella and had the lowest median lethal concentration (LC50) (7.61 µg/mL) among the target compounds. Further mechanism studies are conducted on compounds with better insecticidal activity. Molecular docking results shows that B15 formed hydrophobic interactions π-π and hydrogen bonds with the indole ring of Trp532 and the carboxyl group of Asp384, respectively, with similar interaction distances or bond lengths as those of diflubenzuron. Moreover, chitinase inhibition assays are performed to further demonstrate its mode of action. In addition, the anti-bacterial activity of the series of compounds is also tested and the results showed that the series of compounds has moderate biological activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), with inhibition rates of 91%, 92% and 92%, 88% at the concentration of 100 µg/mL, respectively. Our study indicates that B15 can be used as a novel insecticide for crop protection. [ABSTRACT FROM AUTHOR]

Herein, a series of novel 4-chromanone-derived compounds incorporating an acylhydrazone moiety was synthesized and their structures were confirmed using 1H NMR, 13C NMR, and HRMS technologies. Bioassay results demonstrated that some of the target compounds exhibited moderate to good antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicolaby (Xoc), as well as antifungal activities against Lasiodiplodia theobromae (L. theobromae) and Fusarium proliferatum (F. proliferatum). [ABSTRACT FROM AUTHOR]

A total of eighteen novel 2-(1H-indol-1-yl)-N-(5-phenyl-1,3,4-thiadiazol-2-yl) acetamide derivatives were synthesized through the condensation reaction of 2-(1H-indol-1-yl) acetic acid and 5-phenyl1,3,4-thiadiazol-2-amine via fragment-based design strategy. The target compounds were subjected to screening for antibacterial activity against Xanthomonas oryzae pv. Oryzae, Xanthomonas axonopodis pv. Citri and Pseudomonas syringae pv. Actinidiae. The preliminary antibacterial evaluation of the target compounds showed that some target compounds possessed moderate to good activities against Xoo and Xac. Among them, compound 3p exhibited best inhibition effects against Xoo (77.85% and 62.15%, respectively) and Xac (52.51% and 36.48%, respectively) at 100 lg/mL and 50 lg/mL, which were superior to Thiodiazole-copper and Bismerthiazol. To the best of our knowledge, it is the first report on the design, synthesis, and antibacterial evaluation of novel indole-derived compounds containing 1,3,4-thiadiazole and amide moieties. [ABSTRACT FROM AUTHOR]

BACKGROUND: To address the challenges of food security for the ever‐increasing population, the emergence of nanotechnology provides an alternate technology of choice for the production of safer pesticides which serves as a substitute for conventional fertilizer. The antidrug resistance of Xanthomonas oryzae pv. oryzae (Xoo) and build‐up of chemicals in the environment has made it necessary to find alternative safe techniques for effective disease management. Hence, in this study, copper oxide nanoparticles (CuONPs) were produced by green synthesis using a Hibiscus rosa‐sinensis L. flower extract. RESULTS: The characterization of CuONPs using ultraviolet–visible spectrophotometry, scanning electron microscopy with an energy‐dispersive spectrum profile, Fourier transform infrared spectroscopy, and X‐ray diffraction ascertained the presence of CuONPs, which were nanorods of 28.1 nm. CuONPs significantly obstructed the growth and biofilm development of Xoo by 79.65% and 79.17% respectively. The antibacterial mechanism of CuONPs was found to result from wounding the cell membrane, giving rise to an exodus of intracellular content and generation of oxidative reactive oxygen species that invariably inhibited Xoo respiration and growth. A toxicity study under greenhouse conditions revealed that CuONPs significantly increased growth variables and the biomass of rice, and reduced bacterial leaf blight. Application of CuONPs on Arabidopsis improved the chlorophyll fluorescence parameters; the ΦPSII was significantly increased by 152.05% in comparison to the control. CONCLUSION: Altogether, these results suggest that CuONPs in low concentration (200.0 μg mL−1) are not toxic to plants and can serve as nano‐fertilizers and nano‐pesticides. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Bacterial leaf blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), represents a significant threat to rice (Oryza sativa) production. Induce plant resistance has emerged as a promising control strategy. The extract of Tapak Liman (Elephantopus scaber) has been considered a promising agent due to its antimicrobial properties, with several of its compounds showing its potential as inducers of plant resistance. This study aimed at elucidating the impact of Tapak Liman extract on the expression of resistance Xa4 gene in rice that plays a crucial role in the synthesis mechanism leading to cell wall thickening. To explore this effect, we analyzed Xa4 gene expression using the reverse transcriptionpolymerase chain reaction (RT-PCR) technique, followed by a semi-quantitative descriptive analysis. Our results demonstrate that the application of Tapak Liman extracts at a concentration of 10 mg/ml significantly upregulates Xa4 gene expression in the IR64 compared with other concentrations, 1 mg/ml or 5 mg/ml. Furthermore, the observed higher expression of the Xa4 gene persists until 5 days after pathogen inoculation, which is also implicated with a less developed lesion on rice leaves by 76% compared with the control. [ABSTRACT FROM AUTHOR]

Background: Alternative polyadenylation (APA) is an important pattern of post-transcriptional regulation of genes widely existing in eukaryotes, involving plant physiological and pathological processes. However, there is a dearth of studies investigating the role of APA profile in rice leaf blight. Results: In this study, we compared the APA profile of leaf blight-susceptible varieties (CT 9737-613P-M) and resistant varieties (NSIC RC154) following bacterial blight infection. Through gene enrichment analysis, we found that the genes of two varieties typically exhibited distal poly(A) (PA) sites that play different roles in two kinds of rice, indicating differential APA regulatory mechanisms. In this process, many disease-resistance genes displayed multiple transcripts via APA. Moreover, we also found five polyadenylation factors of similar expression patterns of rice, highlighting the critical roles of these five factors in rice response to leaf blight about PA locus diversity. Conclusion: Notably, the present study provides the first dynamic changes of APA in rice in early response to biotic stresses and proposes a possible functional conjecture of APA in plant immune response, which lays the theoretical foundation for in-depth determination of the role of APA events in plant stress response and other life processes. [ABSTRACT FROM AUTHOR]

Key message: OsMKK1, a MAPK gene, positively regulates rice Xa21-mediated resistance response and also plays roles in normal growth and development process of rice. The mitogen-activated protein kinase (MAPK) cascade was highly conserved among eukaryotes, which played crucial roles in plant responses to pathogen infection. Bacterial blight is the most devastating bacterial disease. Xa21 confers broad-spectrum resistance to Xanthomonas oryzae pv. Oryzae (Xoo). This study identified that the transcription level of OsMKK1 was up-regulated in resistant response against Xoo, thus overexpression (OsMKK1-OX) and RNA interference (OsMKK1-RNAi) transgenic rice lines under the background of Xa21 was constructed. Compared with recipient control plants 4021, the OsMKK1-OX lines significantly enhanced disease resistance to Xoo, on the contrary, the resistance of OsMKK1-RNAi lines was weakened, demonstrated that OsMKK1 played a positive role in Xa21-mediated disease resistance pathway. A number of pathogenesis-related proteins, including PR1A, PR2 and PR10A showed enhanced expression in OsMKK1-OX lines, supported that these PR genes may be regulated by OsMKK1 to participate in the defense responses. In addition, the agronomic traits of OsMKK1 transgenic plants were affected. Overall, these results revealed the role of OsMKK1 in Xa21-mediated resistance against Xoo and in the normal growth and development process in rice. [ABSTRACT FROM AUTHOR]

Mesoporous silica nanoparticles (MSNs) can be used as carrier materials for the controlled release of pesticides while reducing their negative environmental impact. In this study, we screened an active ingredient, p-cymene (PC), with an excellent inhibitory effect on rice bacterial blight. Subsequently, the PC was successfully loaded onto MSNs via physisorption (PC@MSNs). PC@MSNs, characterized by a regular spherical shape, smooth surface, and an MSN average size of 262.9 nm, achieved an 8.6% drug loading capacity. The release kinetics of the PC from the PC@MSNs demonstrated a sustained release (288 h) pattern influenced by drug diffusion. The efficacy of the PC@MSNs against Xanthomonas oryzae pv. Oryzae paralleled those of PC. Acute toxicity assays revealed that the PC@MSNs were less toxic to aquatic life (LC50 = 257.867 mg/L) and that the formulation showed no adverse effects on rice seedling growth. In summary, these results suggest that PC@MSNs can broaden PC's scope of application in managing rice diseases. [ABSTRACT FROM AUTHOR]

A series of twenty one novel compounds derived from indole-3-acetic acid, the structure of which includes 1,3,4-thiadiazole, thioether, and amide moieties were designed, synthesized, and evaluated for their in vitro antibacterial activity against three bacterial strains. The bioassay results showed that among the synthesized compounds, N-{5-[(2-fluorobenzyl)sulfanyl]-1,3,4-thiadiazol-2-yl}-3-(1H-indol-3-yl)-propanamide demonstrated the best inhibition rate against Pseudomonas syringae pv. actinidiae and N-{5-[(4-chlorobenzyl)sulfanyl]-1,3,4-thiadiazol-2-yl}-3-(1H-indol-3-yl)propanamide possessed the best inhibition rate against Xanthomonas oryzae pv. oryzae and Xanthomonas axonopodis pv. citri, in all cases superior to that of bactericides thiodiazole copper and bismerthiazol. [ABSTRACT FROM AUTHOR]

Rice bacterial leaf streak (BLS), caused by Xanthomonas oryzae pv. oryzicola (Xoc), is a worldwide destructive rice bacterial disease, and seriously affects the global rice industry. Effective integrated management measures for BLS depend on the timely and proper detection of Xoc. Here, two highly specific and super-sensitive monoclonal antibodies (MAbs) against Xoc were first prepared using the cultured Xoc RS105 as an immunogen. Then, two serological assays, Dot enzyme-linked immunosorbent assay (Dot-ELISA) and Colloidal gold immunochromatographic strip (CGICS), were developed for the super-sensitive and broad-spectrum detection of Xoc in homogenates prepared from field-collected rice plants. The newly created Dot-ELISA and CGICS assays can detect ten different Xoc strains from various provinces in China and other countries without cross-reactivity with the other ten tested plant bacteria. Furthermore, Dot-ELISA and CGICS can detect Xoc in bacterial suspensions diluted up to 9.78 × 103 CFU/mL and 4.88 × 103 CFU/mL, respectively, or in rice plant tissue homogenates diluted up to 1:51,200 (w/v, g/mL). Surprisingly, both Dot-ELISA and CGICS serological assays were more sensitive than the conventional PCR. Additionally, analysis results using field-collected rice samples showed that the newly created Dot-ELISA and CGICS were reliable in detecting Xoc in rice tissues. Thus, the two serological assays were highly valuable and effective for the diagnosis of rice bacterial leaf streak in rice-grown areas and for inspection and quarantine of Xoc. [ABSTRACT FROM AUTHOR]

Aims: The objective of the study was to isolate bacteriophages and conduct a comprehensive analysis of their potential against Xanthomonas oryzae pv. oryzae (Xoo) strains in the Mekong Delta, Vietnam. Methodology and results: Twelve Xoo strains were isolated from rice fields located in the Mekong Delta, Vietnam. Among these strains, three strains Xoo L019, L020 and L024, showed the highest disease index of bacterial blight. Four phages specific to Xoo were isolated from soil, water and leaf samples, and their morphologies were determined. In a test against 12 Xoo strains, phage L541, MLA23 or W41 could infect 10 of the 12 Xoo strains, while phage LBH01 could infect 8 of the 12 Xoo strains. The stability of the phages to pH, organic solvents, UV-A and UV-B was also evaluated. Conclusion, significance and impact of study: The initial characterization of the phages indicates their potential as biocontrol agents against bacterial blight in rice. The study is one of the very first studies about Xoo phages in rice in Vietnam. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa) being among the most important food crops in the world is also susceptible to various bacterial and fungal diseases that are the major stumbling blocks in the way of increased production and productivity. The bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae and the sheath blight disease caused by Rhizoctonia solani are among the most devastating diseases of the rice crop. In spite of the availability of array of chemical control, there are chances of development of resistance. Thus, there is a need for the nanotechnological intervention for management of disease in the form of copper and silver nano-composites. The copper (CuNPs) and silver nanoparticles (AgNPs) were synthesized using green route and characterized using different high throughput techniques, i.e., UV–Vis, FT-IR, DLS, XRD, FE-SEM, TEM. The particle size and zeta potential of synthesized CuNPs and AgNPs were found 273 nm and − 24.2 mV; 95.19 nm and − 25.5 mV respectively. The nanocomposite of CuNPs and AgNPs were prepared having particle size in the range of 375–306 nm with improved stability (zeta potential − 54.7 to − 39.4 mV). The copper and silver nanoparticle composites evaluated against Xanthomonas oryzae pv. oryzae and Rhizoctonia solani were found to have higher antibacterial (inhibition zone 13 mm) and antifungal activities (77%) compared to only the copper nanoparticle (8 mm; 62% respectively). Net house trials of nano-composite formulations against the bacterial blight of rice also corroborated the potential of nanocomposite formulation. In silico studies were carried out selecting two disease-causing proteins, peptide deformylase (Xanthomonas oryzae) and pectate lyase (Rhizoctonia solani) to perform the molecular docking. Interaction studies indicatedthat both of these proteins generated better complex with CuNPs than AgNPs. The study suggested that the copper and silver nano-composites could be used for developing formulations to control these devastating rice diseases. [ABSTRACT FROM AUTHOR]

To effectively control the infection of plant pathogens, we designed and synthesized a series of phenylthiazole derivatives containing a 1,3,4-thiadiazole thione moiety and screened for their antibacterial potencies against Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, as well as their antifungal potencies against Sclerotinia sclerotiorum, Rhizoctonia solani, Magnaporthe oryzae and Colletotrichum gloeosporioides. The chemical structures of the target compounds were characterized by 1H NMR, 13C NMR and HRMS. The bioassay results revealed that all the tested compounds exhibited moderate-to-excellent antibacterial and antifungal activities against six plant pathogens. Especially, compound 5k possessed the most remarkable antibacterial activity against R. solanacearum (EC50 = 2.23 μg/mL), which was significantly superior to that of compound E1 (EC50 = 69.87 μg/mL) and the commercial agent Thiodiazole copper (EC50 = 52.01 μg/mL). Meanwhile, compound 5b displayed the most excellent antifungal activity against S. sclerotiorum (EC50 = 0.51 μg/mL), which was equivalent to that of the commercial fungicide Carbendazim (EC50 = 0.57 μg/mL). The preliminary structure-activity relationship (SAR) results suggested that introducing an electron-withdrawing group at the meta-position and ortho-position of the benzene ring could endow the final structure with remarkable antibacterial and antifungal activity, respectively. The current results indicated that these compounds were capable of serving as promising lead compounds. [ABSTRACT FROM AUTHOR]

Stability and delivery are major challenges associated with exogenous double‐stranded RNA (dsRNA) application into plants. We report the encapsulation and delivery of dsRNA in cationic poly‐aspartic acid‐derived polymer (CPP6) into plant cells. CPP6 stabilizes the dsRNAs during long exposure at varied temperatures and pH, and protects against RNase A degradation. CPP6 helps dsRNA uptake through roots or foliar spray and facilitates systemic movement to induce endogenous gene silencing. The fluorescence of Arabidopsis GFP‐overexpressing transgenic plants was significantly reduced after infiltration with gfp‐dsRNA‐CPP6 by silencing of the transgene compared to plants treated only with gfp‐dsRNA. The plant endogenous genes flowering locus T (FT) and phytochrome interacting factor 4 (PIF4) were downregulated by a foliar spray of ft‐dsRNA‐CPP6 and pif4‐dsRNA‐CPP6 in Arabidopsis, with delayed flowering and enhanced biomass. The rice PDS gene targeted by pds‐dsRNA‐CPP6 through root uptake was effectively silenced and plants showed a dwarf and albino phenotype. The NaCl‐induced OsbZIP23 was targeted through root uptake of bzip23‐dsRNA‐CPP6 and showed reduced transcripts and seedling growth compared to treatment with naked dsRNA. The negative regulators of plant defence SDIR1 and SWEET14 were targeted through foliar spray to provide durable resistance against bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo). Overall, the study demonstrates that transient silencing of plant endogenous genes using polymer‐encapsulated dsRNA provides prolonged and durable resistance against Xoo, which could be a promising tool for crop protection and for sustaining productivity. [ABSTRACT FROM AUTHOR]

Auxin plays a pivotal role in the co‐evolution of plants and microorganisms. Xanthomonas oryzae pv. oryzicola (Xoc) stands as a significant factor that affects rice yield and quality. However, the current understanding of Xoc's capability for indole 3‐acetic acid (IAA) synthesis and its mechanistic implications remains elusive. In this study, we performed a comprehensive genomic analysis of Xoc strain RS105, leading to the identification of two nitrilase enzyme family (NIT) genes, designated as AKO15524.1 and AKO15829.1, subsequently named NIT24 and NIT29, respectively. Our investigation unveiled that the deletion of NIT24 and NIT29 resulted in a notable reduction in IAA synthesis capacity within RS105, thereby impacting extracellular polysaccharide production. This deficiency was partially ameliorated through exogenous IAA supplementation. The study further substantiated that NIT24 and NIT29 have nitrilase activity and the ability to catalyse IAA production in vitro. The lesion length and bacterial population statistics experiments confirmed that NIT24 and NIT29 positively regulated the pathogenicity of RS105, suggesting that NIT24 and NIT29 may regulate Xoc invasion by affecting IAA synthesis. Furthermore, our analysis corroborated mutant strains, RS105_ΔNIT24 and RS105_ΔNIT29, which elicited the outbreak of reactive oxygen species, the deposition of callose and the upregulation of defence‐related gene expression in rice. IAA exerted a significant dampening effect on the immune responses incited by these mutant strains in rice. In addition, the absence of NIT24 and NIT29 affected the growth‐promoting effect of Xoc on rice. This implies that Xoc may promote rice growth by secreting IAA, thus providing a more suitable microenvironment for its own colonization. In summary, our study provides compelling evidence for the existence of a nitrilase‐dependent IAA biosynthesis pathway in Xoc. IAA synthesis‐related genes promote Xoc colonization by inhibiting rice immune defence response and affecting rice growth by increasing IAA content in Xoc. [ABSTRACT FROM AUTHOR]