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875000.8593MicroRNA miR171b Positively Regulates Resistance to Huanglongbing of Citrus. Huanglongbing (HLB) is one of the most severe citrus diseases in the world, causing huge economic losses. However, efficient methods of protecting citrus from HLB have not yet been developed. microRNA (miRNA)-mediated regulation of gene expression is a useful tool to control plant diseases, but the miRNAs involved in regulating resistance to HLB have not yet been identified. In this study, we found that miR171b positively regulated resistance to HLB in citrus. Upon infection with HLB bacteria, the bacteria were detected in the second month in the control plants. However, in the miR171b-overexpressing transgenic citrus plants, the bacteria could not be detected until the 24th month. RNA-seq data indicated that multiple pathways, such as photosynthesis, plant-pathogen interaction, the MAPK signaling pathway, etc., might be involved in improving the resistance to HLB in miR171b-overexpressing plants compared with the control. Finally, we determined that miR171b could target SCARECROW-like (SCL) genes to downregulate their expression, which then led to promoted resistance to HLB stress. Collectively, our results demonstrate that miR171b plays a positive regulatory role in resistance to citrus HLB, and provides a new insight into the role of miRNAs in the adaptation of citrus to HLB stress.202336982808
874710.8491An endolysin gene from Candidatus Liberibacter asiaticus confers dual resistance to huanglongbing and citrus canker. The most damaging citrus diseases are Huanglongbing (HLB) and citrus canker, which are caused by Candidatus Liberibacter asiaticus (CaLas) and Xanthomonas citri pv. citri (Xcc), respectively. Endolysins from bacteriophages are a possible option for disease resistance in plant breeding. Here, we report improvement of citrus resistance to HLB and citrus canker using the LasLYS1 and LasLYS2 endolysins from CaLas. LasLYS2 demonstrated bactericidal efficacy against several Rhizobiaceae bacteria and Xcc, according to inhibition zone analyses. The two genes, driven by a strong promoter from Cauliflower mosaic virus, 35S, were integrated into Carrizo citrange via Agrobacterium-mediated transformation. More than 2 years of greenhouse testing indicated that LasLYS2 provided substantial and long-lasting resistance to HLB, allowing transgenic plants to retain low CaLas titers and no obvious symptoms while also clearing CaLas from infected plants in the long term. LasLYS2 transgenic plants with improved HLB resistance also showed resistance to Xcc, indicating that LasLYS2 had dual resistance to HLB and citrus canker. A microbiome study of transgenic plants revealed that the endolysins repressed Xanthomonadaceae and Rhizobiaceae populations in roots while increasing Burkholderiaceae and Rhodanobacteraceae populations, which might boost the citrus defense response, according to transcriptome analysis. We also found that Lyz domain 2 is the key bactericidal motif of LasLYS1 and LasLYS2. Four endolysins with potential resistance to HLB and citrus canker were found based on the structures of LasLYS1 and LasLYS2. Overall, the work shed light on the mechanisms of resistance of CaLas-derived endolysins, providing insights for designing endolysins to develop broad-spectrum disease resistance in citrus.202337719271
5820.8461A Conserved Basal Transcription Factor Is Required for the Function of Diverse TAL Effectors in Multiple Plant Hosts. Many Xanthomonas bacteria use transcription activator-like effector (TALE) proteins to activate plant disease susceptibility (S) genes, and this activation contributes to disease. We recently reported that rice basal transcription factor IIA gamma subunit, OsTFIIAγ5, is hijacked by TALE-carrying Xanthomonas oryzae infecting the plants. However, whether TFIIAγs are also involved in TALE-carrying Xanthomonas-caused diseases in other plants is unknown. Here, molecular and genetic approaches were used to investigate the role of TFIIAγs in other plants. We found that TFIIAγs are also used by TALE-carrying Xanthomonas to cause disease in other plants. The TALEs of Xanthomonas citri pv. citri (Xcc) causing canker in citrus and Xanthomonas campestris pv. vesicatoria (Xcv) causing bacterial spot in pepper and tomato interacted with corresponding host TFIIAγs as in rice. Transcriptionally suppressing TFIIAγ led to resistance to Xcc in citrus and Xcv in pepper and tomato. The 39th residue of OsTFIIAγ5 and citrus CsTFIIAγ is vital for TALE-dependent induction of plant S genes. As mutated OsTFIIAγ5(V 39E), CsTFIIAγ(V 39E), pepper CaTFIIAγ(V 39E), and tomato SlTFIIAγ(V 39E) also did not interact with TALEs to prevent disease. These results suggest that TALE-carrying bacteria share a common mechanism for infecting plants. Using TFIIAγ(V 39E)-type mutation could be a general strategy for improving resistance to TALE-carrying pathogens in crops.201729163628
874530.8444Enhanced resistance to seed-transmitted bacterial diseases in transgenic rice plants overproducing an oat cell-wall-bound thionin. Bacterial attack is a serious agricultural problem for growth of rice seedlings in the nursery and field. The thionins purified from seed and etiolated seedlings of barley are known to have antimicrobial activity against necrotrophic pathogens; however, we found that no endogenous rice thionin genes alone are enough for resistance to two major seed-transmitted phytopathogenic bacteria, Burkholderia plantarii and B. glumae, although rice thionin genes constitutively expressed in coleoptile, the target organ of the bacteria. Thus, we isolated thionin genes from oat, one of which was overexpressed in rice. When wild-type rice seed were germinated with these bacteria, all seedlings were wilted with severe blight. In the seedling infected with B. plantarii, bacterial staining was intensively marked around stomata and intercellular spaces. However, transgenic rice seedlings accumulating a high level of oat thionin in cell walls grew almost normally with bacterial staining only on the surface of stomata. These results indicate that the oat thionin effectively works in rice plants against bacterial attack.200212059099
874640.8443Enhanced Resistance to Fungal and Bacterial Diseases Due to Overexpression of BSR1, a Rice RLCK, in Sugarcane, Tomato, and Torenia. Sugarcane smut caused by Sporisorium scitamineum is one of the most devastating sugarcane diseases. Furthermore, Rhizoctonia solani causes severe diseases in various crops including rice, tomato, potato, sugar beet, tobacco, and torenia. However, effective disease-resistant genes against these pathogens have not been identified in target crops. Therefore, the transgenic approach can be used since conventional cross-breeding is not applicable. Herein, the overexpression of BROAD-SPECTRUM RESISTANCE 1 (BSR1), a rice receptor-like cytoplasmic kinase, was conducted in sugarcane, tomato and torenia. BSR1-overexpressing tomatoes exhibited resistance to the bacteria Pseudomonas syringae pv. tomato DC3000 and the fungus R. solani, whereas BSR1-overexpressing torenia showed resistance to R. solani in the growth room. Additionally, BSR1 overexpression conferred resistance to sugarcane smut in the greenhouse. These three BSR1-overexpressing crops exhibited normal growth and morphologies except in the case of exceedingly high levels of overexpression. These results indicate that BSR1 overexpression is a simple and effective tool for conferring broad-spectrum disease resistance to many crops.202336835053
4250.8436Suppression of the rice fatty-acid desaturase gene OsSSI2 enhances resistance to blast and leaf blight diseases in rice. Fatty acids and their derivatives play important signaling roles in plant defense responses. It has been shown that suppressing a gene for stearoyl acyl carrier protein fatty-acid desaturase (SACPD) enhances the resistance of Arabidopsis (SSI2) and soybean to multiple pathogens. In this study, we present functional analyses of a rice homolog of SSI2 (OsSSI2) in disease resistance of rice plants. A transposon insertion mutation (Osssi2-Tos17) and RNAi-mediated knockdown of OsSSI2 (OsSSI2-kd) reduced the oleic acid (18:1) level and increased that of stearic acid (18:0), indicating that OsSSI2 is responsible for fatty-acid desaturase activity. These plants displayed spontaneous lesion formation in leaf blades, retarded growth, slight increase in endogenous free salicylic acid (SA) levels, and SA/benzothiadiazole (BTH)-specific inducible genes, including WRKY45, a key regulator of SA/BTH-induced resistance, in rice. Moreover, the OsSSI2-kd plants showed markedly enhanced resistance to the blast fungus Magnaporthe grisea and leaf-blight bacteria Xanthomonas oryzae pv. oryzae. These results suggest that OsSSI2 is involved in the negative regulation of defense responses in rice, as are its Arabidopsis and soybean counterparts. Microarray analyses identified 406 genes that were differentially expressed (>or=2-fold) in OsSSI2-kd rice plants compared with wild-type rice and, of these, approximately 39% were BTH responsive. Taken together, our results suggest that induction of SA-responsive genes, including WRKY45, is likely responsible for enhanced disease resistance in OsSSI2-kd rice plants.200919522564
51560.8428The Streptomyces peucetius dpsY and dnrX genes govern early and late steps of daunorubicin and doxorubicin biosynthesis. The Streptomyces peucetius dpsY and dnrX genes govern early and late steps in the biosynthesis of the clinically valuable antitumor drugs daunorubicin (DNR) and doxorubicin (DXR). Although their deduced products resemble those of genes thought to be involved in antibiotic production in several other bacteria, this information could not be used to identify the functions of dpsY and dnrX. Replacement of dpsY with a mutant form disrupted by insertion of the aphII neomycin-kanamycin resistance gene resulted in the accumulation of UWM5, the C-19 ethyl homolog of SEK43, a known shunt product of iterative polyketide synthases involved in the biosynthesis of aromatic polyketides. Hence, DpsY must act along with the other components of the DNR-DXR polyketide synthase to form 12-deoxyaklanonic acid, the earliest known intermediate of the DXR pathway. Mutation of dnrX in the same way resulted in a threefold increase in DXR production and the disappearance of two acid-sensitive, unknown compounds from culture extracts. These results suggest that dnrX, analogous to the role of the S. peucetius dnrH gene (C. Scotti and C. R. Hutchinson, J. Bacteriol. 178:73167321, 1996), may be involved in the metabolism of DNR and/or DXR to acid-sensitive compounds, possibly related to the baumycins found in many DNR-producing bacteria.19989573189
874970.8425Analysis of Defense-Related Gene Expression in Citrus Hybrids Infected by Xylella fastidiosa. Resistance to Xylella fastidiosa was evaluated in 264 hybrids of crosses between Murcott tangor (Citrus reticulata × Citrus sinensis) and Pera sweet orange (C. sinensis) under field conditions. Uninfected hybrids were grafted with buds collected from Pera sweet orange plants infected with X. fastidiosa, forming a plant with two scions (i.e., hybrid branches and Pera sweet orange branches). From these plants, we chose 10 genotypes with three biological replicates. We evaluated gene expression, bacterial multiplication, and citrus variegated chlorosis (CVC) symptom development in both scions. X. fastidiosa was not detected in most hybrid scions and none showed disease symptoms. In contrast, all Pera sweet orange scions were infected with X. fastidiosa and expressed symptoms of CVC. We quantified the expression of 12 defense-related genes by qPCR comparing resistant to susceptible scions. We suggest that some of these genes are involved in resistance of the hybrids to X. fastidiosa, since their expression was significantly higher in the resistant hybrid scions than in tolerant hybrids and scions originated from CVC symptomatic Pera sweet orange buds. However, we note that these data should be interpreted carefully, as the plant genotypes tested are related but necessarily distinct (hybrids of C. reticulata and C. sinensis, in relation to a C. sinensis control). A principal component analysis revealed a relationship between the expression of these genes and hybrid scions, and between scions that originated from infected buds and the presence of the bacteria and plant symptoms. Multiyear field trials are necessary to develop plant resistance to X. fastidiosa. While the experimental design used here had limitations, it allowed us to identify a set of genes potentially involved in Citrus sp. resistance to this pathogen. Future work on the role of these genes in plant defenses to X. fastidiosa infection is necessary to confirm their importance in the displayed resistance phenotype.201930480473
2180.8424miR159a modulates poplar resistance against different fungi and bacteria. Trees are inevitably attacked by different kinds of pathogens in their life. However, little is known about the regulatory factors in poplar response to different pathogen infections. MicroRNA159 (miR159) is a highly conserved microRNA (miRNA) in plants and regulates plant development and stress responses. Here, transgenic poplar overexpressing pto-miR159a (OX-159) showed antagonistic regulation mode to poplar stem disease caused by fungi Cytospora chrysosperma and bacteria Lonsdalea populi. OX-159 lines exhibited a higher susceptibility after inoculation with bacterium L. populi, whereas enhanced disease resistance to necrotrophic fungi C. chrysosperma compared with wild-type (WT) poplars. Intriguingly, further disease assay found that OX159 line rendered the poplar susceptible to hemi-biotrophic fungi Colletotrichum gloeosporioide, exhibiting larger necrosis and lower ROS accumulation than WT lines. Transcriptome analyses revealed that more down-regulated differentially expressed genes with disease-resistant domains in OX-159 line compared with WT line. Moreover, the central mediator NPR1 of salicylic acid (SA) pathway showed a decrease in expression level, while jasmonic acid/ethylene (JA/ET) signal pathway marker genes ERF, as well as PR3, MPK3, and MPK6 genes showed an increase level in OX159-2 and OX159-5 compared with WT lines. Further spatio-temporal expression analysis revealed JA/ET signaling was involved in the dynamic response process to C. gloeosporioides in WT and OX159 lines. These results demonstrate that overexpression of pto-miR159a resulted in the crosstalk changes of the downstream hub genes, thereby controlling the disease resistance of poplars, which provides clues for understanding pto-miR159a role in coordinating poplar-pathogen interactions.202337494825
80790.8416Transcriptomic analysis of Saccharomyces cerevisiae upon honokiol treatment. Honokiol (HNK), one of the main medicinal components in Magnolia officinalis, possesses antimicrobial activity against a variety of pathogenic bacteria and fungi. However, little is known of the molecular mechanisms underpinning the antimicrobial activity. To explore the molecular mechanism of its antifungal activity, we determined the effects of HNK on the mRNA expression profile of Saccharomyces cerevisiae using a DNA microarray approach. HNK markedly induced the expression of genes related to iron uptake and homeostasis. Conversely, genes associated with respiratory electron transport were downregulated, mirroring the effects of iron starvation. Meanwhile, HNK-induced growth deficiency was partly rescued by iron supplementation and HNK reacted with iron, producing iron complexes that depleted iron. These results suggest that HNK treatment induced iron starvation. Additionally, HNK treatment resulted in the upregulation of genes involved in protein synthesis and drug resistance networks. Furthermore, the deletion of PDR5, a gene encoding the plasma membrane ATP binding cassette (ABC) transporter, conferred sensitivity to HNK. Overexpression of PDR5 enhanced resistance of WT and pdr5Δ strains to HNK. Taken together, these findings suggest that HNK, which can be excluded by overexpression of Pdr5, functions in multiple cellular processes in S. cerevisiae, particularly in inducing iron starvation to inhibit cell growth.201728499955
33100.8415Transgenic Silkworms Overexpressing Relish and Expressing Drosomycin Confer Enhanced Immunity to Multiple Pathogens. The sericulture industry faces substantial economic losses due to severe pathogenic infections caused by fungi, viruses, and bacteria. The development of transgenic silkworms against specific pathogens has been shown to enhance disease resistance against a particular infection. A single gene or its products that can confer protection against multiple pathogens is required. In an attempt to develop silkworms with enhanced immunity against multiple pathogens, we generated transgenic silkworm lines with an overexpressed NF-kB transcription factor, Relish 1, under two different promoters. Separately, a potent anti-fungal gene, Drosomycin, was also expressed in transgenic silkworms. Both Relish 1 and Drosomycin transgenic silkworms had single copy genomic integration, and their mRNA expression levels were highly increased after infection with silkworm pathogens. The overexpression of the Relish 1 in transgenic silkworms resulted in the upregulation of several defense-related genes, Cecropin B, Attacin, and Lebocin, and showed enhanced resistance to Nosema bombycis (microsporidian fungus), Nucleopolyhedrovirus (BmNPV), and bacteria. The Drosomycin expressing transgenic silkworms showed elevated resistance to N. bombycis and bacteria. These findings demonstrate the role of Relish 1 in long-lasting protection against multiple pathogens in silkworms. Further, the successful introduction of a foreign gene, Drosomycin, also led to improved disease resistance in silkworms.202235098482
516110.8415Role of Iron-Containing Alcohol Dehydrogenases in Acinetobacter baumannii ATCC 19606 Stress Resistance and Virulence. Most bacteria possess alcohol dehydrogenase (ADH) genes (Adh genes) to mitigate alcohol toxicity, but these genes have functions beyond alcohol degradation. Previous research has shown that ADH can modulate quorum sensing in Acinetobacter baumannii, a rising opportunistic pathogen. However, the number and nature of Adh genes in A. baumannii have not yet been fully characterized. We identified seven alcohol dehydrogenases (NAD(+)-ADHs) from A. baumannii ATCC 19606, and examined the roles of three iron-containing ADHs, ADH3, ADH4, and ADH6. Marker-less mutation was used to generate Adh3, Adh4, and Adh6 single, double, and triple mutants. Disrupted Adh4 mutants failed to grow in ethanol-, 1-butanol-, or 1-propanol-containing mediums, and recombinant ADH4 exhibited strongest activity against ethanol. Stress resistance assays with inorganic and organic hydroperoxides showed that Adh3 and Adh6 were key to oxidative stress resistance. Virulence assays performed on the Galleria mellonella model organism revealed that Adh4 mutants had comparable virulence to wild-type, while Adh3 and Adh6 mutants had reduced virulence. The results suggest that ADH4 is primarily involved in alcohol metabolism, while ADH3 and ADH6 are key to stress resistance and virulence. Further investigation into the roles of other ADHs in A. baumannii is warranted.202134576087
8748120.8412Heterologous Expression of the Constitutive Disease Resistance 2 and 8 Genes from Poncirus trifoliata Restored the Hypersensitive Response and Resistance of Arabidopsis cdr1 Mutant to Bacterial Pathogen Pseudomonas syringae. Huanglongbing (HLB), also known as citrus greening, is the most destructive disease of citrus worldwide. In the United States, this disease is associated with a phloem-restricted bacterium, Candidatus Liberibacter asiaticus. Commercial citrus cultivars are susceptible to HLB, but Poncirus trifoliata, a close relative of Citrus, is highly tolerant of HLB. Isolating P. trifoliata gene(s) controlling its HLB tolerance followed by expressing the gene(s) in citrus is considered a potential cisgenic approach to engineering citrus for tolerance to HLB. Previous gene expression studies indicated that the constitutive disease resistance (CDR) genes in P. trifoliata (PtCDRs) may play a vital role in its HLB tolerance. This study was designed to use Arabidopsis mutants as a model system to confirm the function of PtCDRs in plant disease resistance. PtCDR2 and PtCDR8 were amplified from P. trifoliata cDNA and transferred into the Arabidopsis cdr1 mutant, whose resident CDR1 gene was disrupted by T-DNA insertion. The PtCDR2 and PtCDR8 transgenic Arabidopsis cdr1 mutant restored its hypersensitive response to the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) expressing avrRpt2. The defense marker gene PATHOGENESIS RELATED 1 (PR1) expressed at much higher levels in the PtCDR2 or PtCDR8 transgenic cdr1 mutant than in the non-transgenic cdr1 mutant with or without pathogen infection. Multiplication of Pst DC3000 bacteria in Arabidopsis was inhibited by the expression of PtCDR2 and PtCDR8. Our results showed that PtCDR2 and PtCDR8 were functional in Arabidopsis and played a positive role in disease resistance and demonstrated that Arabidopsis mutants can be a useful alternate system for screening Poncirus genes before making the time-consuming effort to transfer them into citrus, a perennial woody plant that is highly recalcitrant for Agrobacterium or biolistic-mediated transformation.202032629813
6078130.8409Genomic Insights into Cyanide Biodegradation in the Pseudomonas Genus. Molecular studies about cyanide biodegradation have been mainly focused on the hydrolytic pathways catalyzed by the cyanide dihydratase CynD or the nitrilase NitC. In some Pseudomonas strains, the assimilation of cyanide has been linked to NitC, such as the cyanotrophic model strain Pseudomonas pseudoalcaligenes CECT 5344, which has been recently reclassified as Pseudomonas oleovorans CECT 5344. In this work, a phylogenomic approach established a more precise taxonomic position of the strain CECT 5344 within the species P. oleovorans. Furthermore, a pan-genomic analysis of P. oleovorans and other species with cyanotrophic strains, such as P. fluorescens and P. monteilii, allowed for the comparison and identification of the cioAB and mqoAB genes involved in cyanide resistance, and the nitC and cynS genes required for the assimilation of cyanide or cyanate, respectively. While cyanide resistance genes presented a high frequency among the analyzed genomes, genes responsible for cyanide or cyanate assimilation were identified in a considerably lower proportion. According to the results obtained in this work, an in silico approach based on a comparative genomic approach can be considered as an agile strategy for the bioprospection of putative cyanotrophic bacteria and for the identification of new genes putatively involved in cyanide biodegradation.202438674043
48140.8403Priming of the Arabidopsis pattern-triggered immunity response upon infection by necrotrophic Pectobacterium carotovorum bacteria. Boosted responsiveness of plant cells to stress at the onset of pathogen- or chemically induced resistance is called priming. The chemical β-aminobutyric acid (BABA) enhances Arabidopsis thaliana resistance to hemibiotrophic bacteria through the priming of the salicylic acid (SA) defence response. Whether BABA increases Arabidopsis resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) is not clear. In this work, we show that treatment with BABA protects Arabidopsis against the soft-rot pathogen Pcc. BABA did not prime the expression of the jasmonate/ethylene-responsive gene PLANT DEFENSIN 1.2 (PDF1.2), the up-regulation of which is usually associated with resistance to necrotrophic pathogens. Expression of the SA marker gene PATHOGENESIS RELATED 1 (PR1) on Pcc infection was primed by BABA treatment, but SA-defective mutants demonstrated a wild-type level of BABA-induced resistance against Pcc. BABA primed the expression of the pattern-triggered immunity (PTI)-responsive genes FLG22-INDUCED RECEPTOR-LIKE KINASE 1 (FRK1), ARABIDOPSIS NON-RACE SPECIFIC DISEASE RESISTANCE GENE (NDR1)/HAIRPIN-INDUCED GENE (HIN1)-LIKE 10 (NHL10) and CYTOCHROME P450, FAMILY 81 (CYP81F2) after inoculation with Pcc or after treatment with purified bacterial microbe-associated molecular patterns, such as flg22 or elf26. PTI-mediated callose deposition was also potentiated in BABA-treated Arabidopsis, and BABA boosted Arabidopsis stomatal immunity to Pcc. BABA treatment primed the PTI response in the SA-defective mutants SA induction deficient 2-1 (sid2-1) and phytoalexin deficient 4-1 (pad4-1). In addition, BABA priming was associated with open chromatin configurations in the promoter region of PTI marker genes. Our data indicate that BABA primes the PTI response upon necrotrophic bacterial infection and suggest a role for the PTI response in BABA-induced resistance.201322947164
328150.8402Multiresistance genes of Rhizobium etli CFN42. Multidrug efflux pumps of bacteria are involved in the resistance to various antibiotics and toxic compounds. In Rhizobium etli, a mutualistic symbiont of Phaseolus vulgaris (bean), genes resembling multidrug efflux pump genes were identified and designated rmrA and rmrB. rmrA was obtained after the screening of transposon-generated fusions that are inducible by bean-root released flavonoids. The predicted gene products of rmrAB shared significant homology to membrane fusion and major facilitator proteins, respectively. Mutants of rmrA formed on average 40% less nodules in bean, while mutants of rmrA and rmrB had enhanced sensitivity to phytoalexins, flavonoids, and salicylic acid, compared with the wild-type strain. Multidrug resistance genes emrAB from Escherichia coli complemented an rmrA mutant from R. etli for resistance to high concentrations of naringenin.200010796024
8423160.8402Horizontal Gene Transfer From Bacteria and Plants to the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis. Arbuscular mycorrhizal fungi (AMF) belong to Glomeromycotina, and are mutualistic symbionts of many land plants. Associated bacteria accompany AMF during their lifecycle to establish a robust tripartite association consisting of fungi, plants and bacteria. Physical association among this trinity provides possibilities for the exchange of genetic materials. However, very few horizontal gene transfer (HGT) from bacteria or plants to AMF has been reported yet. In this study, we complement existing algorithms by developing a new pipeline, Blast2hgt, to efficiently screen for putative horizontally derived genes from a whole genome. Genome analyses of the glomeromycete Rhizophagus irregularis identified 19 fungal genes that had been transferred between fungi and bacteria/plants, of which seven were obtained from bacteria. Another 18 R. irregularis genes were found to be recently acquired from either plants or bacteria. In the R. irregularis genome, gene duplication has contributed to the expansion of three foreign genes. Importantly, more than half of the R. irregularis foreign genes were expressed in various transcriptomic experiments, suggesting that these genes are functional in R. irregularis. Functional annotation and available evidence showed that these acquired genes may participate in diverse but fundamental biological processes such as regulation of gene expression, mitosis and signal transduction. Our study suggests that horizontal gene influx through endosymbiosis is a source of new functions for R. irregularis, and HGT might have played a role in the evolution and symbiotic adaptation of this arbuscular mycorrhizal fungus.201829887874
8764170.8401Transgenic citrus expressing synthesized cecropin B genes in the phloem exhibits decreased susceptibility to Huanglongbing. Expression of synthesized cecropin B genes in the citrus phloem, where Candidatus Liberibacter asiaticus resides, significantly decreased host susceptibility to Huanglongbing. Huanglongbing (HLB), associated with Candidatus Liberibacter asiaticus bacteria, is the most destructive disease of citrus worldwide. All of the commercial sweet orange cultivars lack resistance to this disease. The cationic lytic peptide cecropin B, isolated from the Chinese tasar moth (Antheraea pernyi), has been shown to effectively eliminate bacteria. In this study, we demonstrated that transgenic citrus (Citrus sinensis Osbeck) expressing the cecropin B gene specifically in the phloem had a decreased susceptibility to HLB. Three plant codon-optimized synthetic cecropin B genes, which were designed to secrete the cecropin B peptide into three specific sites, the extracellular space, the cytoplasm, and the endoplasmic reticulum, were constructed. Under the control of the selected phloem-specific promoter GRP1.8, these constructs were transferred into the citrus genome. All of the cecropin B genes were efficiently expressed in the phloem of transgenic plants. Over more than a year of evaluation, the transgenic lines exhibited reduced disease severity. Bacterial populations in transgenic lines were significantly lower than in the controls. Two lines, in which bacterial populations were significantly lower than in others, showed no visible symptoms. Thus, we demonstrated the potential application of the phloem-specific expression of an antimicrobial peptide gene to protect citrus plants from HLB.201727866312
504180.8400Activation of Dithiolopyrrolone Antibiotics by Cellular Reductants. Dithiolopyrrolone (DTP) natural products are broad-spectrum antimicrobial and anticancer prodrugs. The DTP structure contains a unique bicyclic ene-disulfide that once reduced in the cell, chelates metal ions and disrupts metal homeostasis. In this work we investigate the intracellular activation of the DTPs and their resistance mechanisms in bacteria. We show that the prototypical DTP holomycin is reduced by several bacterial reductases and small-molecule thiols in vitro. To understand how bacteria develop resistance to the DTPs, we generate Staphylococcus aureus mutants that exhibit increased resistance to the hybrid DTP antibiotic thiomarinol. From these mutants we identify loss-of-function mutations in redox genes that are involved in DTP activation. This work advances the understanding of how DTPs are activated and informs development of bioreductive disulfide prodrugs.202539665630
605190.8399Conservation and diversity of the IrrE/DdrO-controlled radiation response in radiation-resistant Deinococcus bacteria. The extreme radiation resistance of Deinococcus bacteria requires the radiation-stimulated cleavage of protein DdrO by a specific metalloprotease called IrrE. DdrO is the repressor of a predicted radiation/desiccation response (RDR) regulon, composed of radiation-induced genes having a conserved DNA motif (RDRM) in their promoter regions. Here, we showed that addition of zinc ions to purified apo-IrrE, and short exposure of Deinococcus cells to zinc ions, resulted in cleavage of DdrO in vitro and in vivo, respectively. Binding of IrrE to RDRM-containing DNA or interaction of IrrE with DNA-bound DdrO was not observed. The data are in line with IrrE being a zinc peptidase, and indicate that increased zinc availability, caused by oxidative stress, triggers the in vivo cleavage of DdrO unbound to DNA. Transcriptomics and proteomics of Deinococcus deserti confirmed the IrrE-dependent regulation of predicted RDR regulon genes and also revealed additional members of this regulon. Comparative analysis showed that the RDR regulon is largely well conserved in Deinococcus species, but also showed diversity in the regulon composition. Notably, several RDR genes with an important role in radiation resistance in Deinococcus radiodurans, for example pprA, are not conserved in some other radiation-resistant Deinococcus species.201728397370