Development and mapping of SSR markers linked to resistance-gene homologue clusters in common bean

Common bean is an important but often a disease-susceptible legume crop of temperate,subtropical and tropical regions worldwide. The crop is affected by bacterial, fungal and viral pathogens. The strategy of resistance-gene homologue(RGH) cloning has proven to be an efficient tool for identifying markers and R(resistance) genes associated with resistances to diseases. Microsatellite or SSR markers can be identified by physical association with RGH clones on large-insert DNA clones such as bacterial artificial chromosomes(BACs). Our objectives in this work were to identify RGH-SSR in a BAC library from the Andean genotype G19833 and to test and map any polymorphic markers to identify associations with known positions of disease resistance genes. We developed a set of specific probes designed for clades of common bean RGH genes and then identified positive BAC clones and developed microsatellites from BACs having SSR loci in their end sequences. A total of 629 new RGH-SSRs were identified and named BMr(bean microsatellite RGH-associated markers). A subset of these markers was screened for detecting polymorphism in the genetic mapping population DOR364 × G19833. A genetic map was constructed with a total of 264 markers,among which were 80 RGH loci anchored to single-copy RFLP and SSR markers. Clusters of RGH-SSRs were observed on most of the linkage groups of common bean and in positions associated with R-genes and QTL. The use of these new markers to select for disease resistance is discussed.

Nature of Gene Action and Maternal Effects for Pod Borer, <i>Helicoverpa armigera</i>Resistance and Grain Yield in Chickpea, <i>Cicer arietinum</i>

Information on mechanisms and inheritance of resistance is critical to plan an effective strategy to breed for resistance to insect pests. Therefore, we evaluated a diverse array of chickpea genotypes (eight desi and one kabuli) with varying levels of resistance to the pod borer, Helicoverpa armigera to gain an understanding of the nature of gene action and possible maternal effects. The test genotypes were crossed in all possible combinations for a full diallel. The 72 F1s (36 direct and 36 reciprocal crosses) along with the parents were evaluated for resistance to H. armigera under field conditions, and for antibiosis mechanism of resistance (larval survival and larval weight gain) by using detached leaf assay under laboratory conditions, and grain yield under un-protected conditions in the field. Additive gene action governed the inheritance of resistance to H. armigera, while non-additive type of gene action was predominant for inheritance of antibiosis component of resistance (larval survival and larval weight) and grain yield. Greater magnitude of σ2 A(17.39 and 1.42) than σ2 D (3.93 and 1.21) indicated the preponderance of σ2 Ain inheritance of resistance to pod borer, H. armigera under laboratory and field conditions, respectively. There were no maternal effects for inheritance of resistance to pod borer and grain yield. Lines with significant gca effects for pod borer damage and grain yield were identified for further use in the resistance breeding program. The implications of the inheritance pattern of pod borer resistance and grain yield are discussed in the context of strategies to enhance pod borer resistance and grain yield in chickpea.

Studies on the temporal,structural,and interacting features of the clubroot resistance gene Rcr1 using CRISPR/Cas9-based systems

Clubroot disease is a severe threat to Brassica crops globally,particularly in western Canada.Genetic resistance,achieved through pyramiding clubroot resistance(CR)genes with different modes of action,is the most important strategy for managing the disease.However,studies on the CR gene functions are quite limited.In this study,we have conducted investigations into the temporal,structural,and interacting features of a newly cloned CR gene,Rcr1,using CRISPR/Cas9 technology.For temporal functionality,we developed a novel CRISPR/Cas9-based binary vector,pHHIGR-Hsp18.2,to deliver Rcr1 into a susceptible canola line(DH12075)and observed that early expression of Rcr1 is critical for conferring resistance.For structural functionality,several independent mutations in specific domains of Rcr1 resulted in loss-offunction,highlighting their importance for CR phenotype.In the study of the interacting features of Rcr1,a cysteine protease gene and its homologous allele in canola were successfully disrupted via CRISPR/Cas9 as an interacting component with Rcr1 protein,resulting in the conversion from clubroot resistant to susceptible in plants carrying intact Rcr1.These results indicated an indispensable role of these two cysteine proteases in Rcr1-mediated resistance response.This study,the first of its kind,provides valuable insights into the functionality of Rcr1.Further,the new vector p HHIGR-Hsp18.2 demonstrated an inducible feature on the removal of add-on traits,which should be useful for functional genomics and other similar research in brassica crops.

Effects of the Fhb1 gene on Fusarium head blight resistance and agronomic traits of winter wheat

The gene Fhb1 has been used in many countries to improve wheat Fusarium head blight(FHB) resistance. To make better use of this gene in the Yellow-Huai River Valleys Winter Wheat Zone(YHWZ), the most important wheat-producing region of China, it is desirable to elucidate its effects on FHB resistance and agronomic traits in different genetic backgrounds. Based on a diagnostic marker for Fhb1, six BC2 populations were developed by crossing dwarf-male-sterile(DMS)-Zhoumai 16 to three Fhb1 donors(Ningmai 9, Ningmai 13, and Jianyang 84) and backcrossing to Zhoumai 16 and Zhoumai16’s derivative cultivars(Lunxuan 136 and Lunxuan 13) using marker-assisted backcross breeding. The progenies were assessed for FHB resistance and major agronomic traits.The Fhb1 alleles were identified using the gene-specific molecular marker. The plants with the Fhb1-resistant genotype(Fhb1-R) in these populations showed significantly fewer infected spikelets than those with the Fhb1-susceptible genotype(Fhb1-S). When Lunxuan 136 was used as the recurrent parent, Fhb1-R plants showed significantly fewer infected spikelets per spike than Fhb1-R plants produced using Lunxuan 13 as the recurrent parent, indicating that the genetic backgrounds of Fhb1 influence the expression of FHB resistance. Fhb1-R plants from the DMS-Zhoumai 16/Ningmai 9//Zhoumai 16/3/Lunxuan 136 population showed the highest FHB resistance among the six populations and a significantly higher level of FHB resistance than the moderately susceptible control Huaimai 20. No significant phenotypic differences between Fhb1-R and Fhb1-S plants were observed for the eight agronomic traits investigated. These results suggest that it is feasible to improve FHB resistance of winter wheat withoutreducing yield potential by introgressing Fhb1 resistance allele into FHB-susceptible cultivars in the YHWZ.

Conventional and Molecular Approaches towards Genetic Improvement in Pigeonpea for Insects Resistance

Pigeonpea [Cajanus cajan (L.) Millspaugh] is an important food legume of the semi-arid tropics (SAT) sustaining livelihood of millions of people. Stagnant and unstable yield per hectare all over the world is the characteristic feature of this crop. This is primarily ascribed to its susceptibility/sensitivity to a number of biotic and abiotic factors. Among biotic factors, insects such as pod borer (Helicoverpa armigera), pod fly (Melanoagromyza obtusa) and spotted borer (Maruca vitrata) substantially damage the crop and result in significant economic losses. Management of these insects by genetic means has always been considered environment friendly approach. However, genetic improvement has always been impeded by limited genetic variability in the primary gene pool of pigeonpea. Wild species present in the secondary and tertiary gene pools have been reported to carry resistance for such insects. However, transfer of resistance through conventional backcrossing has not been much successful. It calls for gene introgression through marker assisted backcrossing (MABC) or advanced backcross breeding (AB breeding). In this review, we have attempted to assess the progress made through conventional and molecular breeding and suggested the ways to move further towards genetic enhancement for insects resistance in

Seedling and adult plant resistance to leaf rust in 46 Chinese bread wheat landraces and 39 wheat lines with known Lr genes

Wheat leaf rust,caused by Puccinia triticina(Pt),is an important foliar disease that has an important influence on wheat yield.The most economic,safe and effective way to control the disease is growing resistant cultivars.In the present study,a total of 46 wheat landraces and 34 wheat lines with known Lr(leaf rust resistance)genes were inoculated with 16Pt pathotypes for postulating seedling resistance gene(s)in the greenhouse.These cultivars and five wheat differential lines with adult plant resistance(APR)genes(Lr12,Lr22b,Lr34,Lr35 and Lr37)were also evaluated for identification of slow rusting resistance in the field trials in Baoding,Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons.Furthermore,10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes.Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage.Nonetheless,Lr1 was detected only in Hongtangliangmai.The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance.Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46.Lr genes namely,Lr9,Lr19,Lr24,Lr28,Lr29,Lr47,Lr51 and Lr53 were effective at the whole plant stage.Lr18,Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage.Lr34 as a slowing rusting gene showed good resistance in the field.Four race-specific APR genes Lr12,Lr13,Lr35 and Lr37 conferred good resistance in the field experiments.Seven race-specific genes,Lr2b,Lr2c,Lr11,Lr16,Lr26,Lr33 and LrB had lost resistance.The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.

Identification of QTLs for Blast, Bacterial Blight, and Planthopper Resistance Using SNP-Based Linkage Maps from Two Recombinant Inbred Rice Lines

Rice is the most significant global food security. Several biotic factors limit rice production, breeding biotic-resistant rice has, therefore, become an increasingly important goal. Two elite rice lines, IR71033-121-15 (IR71033) and IR57514-PMI-5-B-1-2 (IR57514), provide potential genes for biotic stress resistance traits. In this study, genotyping by sequencing (GBS) for single nucleotide polymorphism (SNP)-based linkage map construction was used to detect quantitative trait loci (QTLs) for blast (BL), bacterial blight (BB), whitebacked planthopper (WBPH), and brown planthopper (BPH) resistance. IR71033 was derived from Oryza minuta and carried BL, BB, WBPH, and BPH resistance QTLs. IR57514 is a well-adapted rainfed lowland line that carries BL and BB resistance QTLs. Two sets of recombinant inbred line (RIL) populations derived from crosses of KDML105 × IR71033 and KDML105 × IR57514 were used to dissect the genetic basis of disease and insect pest resistance. The RIL populations were evaluated for BL, BB, WBPH, and BPH resistance from 2016 to 2018 at four rice research centers in Thailand. From these, we identified a large number of SNPs through GBS and constructed high-resolution linkage maps. By combining phenotypic evaluation with the GBS data, a total of 24 QTLs on four chromosomes were detected that confered pest resistance and explained 7.3% - 61.4% of the phenotypic variance. These findings should facilitate identifying novel resistance genes and applying marker-assisted selection for resistance to the four major rice pests investigated here. These strategies will improve the resilience and reliability of rice varieties adapted to the low-yielding environment of rainfed lowland areas worldwide.

Current Status of Conventional and Molecular Interventions for Blast Resistance in Rice

Pyricularia oryzae anamorph of Magnaporthe oryzae is one of the most notorious fungal pathogens causing severe economic loss in rice production worldwide. Various methods, viz. cultural, biological and molecular approaches, are utilized to counteract this pathogen. Moreover, some tolerant or resistant rice varieties have been developed with the help of breeding programmes. Isolation and molecular characterization of different blast resistance genes now open the gate for new possibilities to elucidate the actual allelic variants of these genes via various molecular breeding and transgenic approaches. However, the behavioral pattern of this fungus breakups the resistance barriers in the resistant or tolerant rice varieties. This host-pathogen barrier will be possibly countered in future research by comparative genomics data from available genome sequence data of rice and M. oryzae for durable resistance. Present review emphasized fascinating recent updates, new molecular breeding approaches, transgenic and genomics approaches(i.e. mi RNA and genome editing) for the management of blast disease in rice. The updated information will be helpful for the durable, resistance breeding programme in rice against blast pathogen.

Molecular mapping of stripe rust resistance gene YrH9017 in wheat-Psathyrostachys huashanica introgression line H9017-14-16-5-3

Several new stripe rust pathogen races emerged in the wheat growing regions of China in recent years.These races were virulent to most of the designated wheat seedling resistance genes.Thus,it is necessary and worthwhile to identify new valuable resistant materials for the sake of diversifying resistant sources,pyramiding different resistance genes and achieving durable resistance.Here,we identified the resistance gene,temporarily designated as YrH9017,in wheat-Psathyrostachys huashanica introgression line H9017-14-16-5-3.A total of 146 F2 plants and their derived F2:3 families in a cross of Mingxian 169 and H9017-14-16-5-3 were used to evaluate seedling stripe rust response and as a mapping population.Finally,we constructed a genetic map including eight simple sequence repeat(SSR) markers and expressed sequence tag(EST) markers.YrH9017 was located on the long arm of chromosome 2A and closely linked with two EST-sequence tagged site(EST-STS) markers BG604577 and BE471201 at 1.3 and 1.8 cM distance,respectively.The two closest markers could be used for marker-assisted selection of YrH9017 in breeding.

Transduction of Fas gene or Bcl-2 antisense RNA sensitizes cultured drug resistant gastric cancer cells to chemotherapeutic drugs

AIM To compare the expression level of Fas gene and Bcl-2 gene in gastric cancer cells SGC7901 and gastric cancer MDR (multidrug resistant) cells SGC7901/VCR, to transduce Fas cDNA and Bcl-2 antisense nucleic acid into SGC7901/VCR cells respectively, and to observe the expression of two genes in transfectants and non-transfectants as well as their drug sensitivity.METHODS Eukaryotic expression vector pBK-Fas cDNA and pDOR-anti Bcl-2 were constructed and transfected into SGC7901/VCR cells by lipofectamine, respectively. Northern blot and Western blot were used to detect the expression of mRNA and protein in SGC7901/VCR and SGC7901 cells and transfectants, and drug sensitivity of transfectants for VCR, CDDP and 5-FU was analyzed with MTT assay.RESULTS After gene transfection, 80 for Fas and 120 for antisense Bcl-2 drug-resistant clones were selected from 2×105 cells, transfection rate being 0.04% and 0.06%. Two clones of SGC7901 Fas/VCR cells and SGC7901 anti Bcl-2/VCR cells were randomly selected for further incubation. Hybridization results showed that the expression level of Fas mRNA and protein in SGC7901/VCR cells was much lower, but that of Bcl-2 mRNA and protein was higher than that in SGC7901 cells. The expression of Fas mRNA and protein in SGC7901 Fas/VCR cells was higher, and of Bcl-2 mRNA and protein was lower in SGC7901 anti Bcl-2/VCR cells than that in non-transfectants. MTT assay showed that transfectants were more sensitive to VCR, CDDP, 5-FU than non-transfectants.CONCLUSION Bcl-2 gene displayed high expression while Fas gene had low expression in drug resistant gastric cancer cells. Expression of Bcl-2 protein was effectively blocked in SGC7901 anti Bcl-2/VCR cells by gene transfection. In contrast, the expression of Fas mRNA and protein in SGC7901 Fas/VCR cells increased. Fas gene and Bcl-2 antisense nucleic acid transfection sensitized drug resistant gastric cancer cells to chemotherapeutic drugs. These results suggest cell apoptosis plays an important role in the mechanism of MDR, and enhancing apoptosis might reverse MDR.

Identification and fine mapping of two blast resistance genes in rice cultivar 93-11

Rice blast, caused by Magnaporthe oryzae, is a major disease of rice almost worldwide. The Chinese indica cultivar 93-11 is resistant to numerous isolates of the blast fungus in China, and can be used as broad-spectrum resistance resource, particularly in japonica rice breeding programs. In this study, we identified and mapped two blast resistance genes, Pi60(t) and Pi61(t), in cv. 93-11 using F2 and F3 populations derived from a cross between the susceptible cv. Lijiangxintuanheigu(LTH) and resistant cv. 93-11 and inoculated with M. oryzae isolates from different geographic origins. Pi60(t) was delimited to a 274 kb region on the short arm of chromosome 11, flanked by InDel markers K1-4 and E12 and cosegregated with InDel markers B1 and Y10. Pi61(t) was mapped to a 200 kb region on the short arm(near the centromere) of chromosome 12, flanked by InDel markers M2 and S29 and cosegregating with InDel marker M9. In the 274 kb region of Pi60(t), 93-11 contains six NBS-LRR genes including the two Pia/ PiCO39 alleles(BGIOSGA034263 and BGIOSGA035032) which are quite close to the two Pia/ PiCO39 alleles(SasRGA4 and SasRGA5) in Sasanishiki and CO39, with only nine amino acids differing in the protein sequences of BGIOSGA035032 and SasRGA5. In the 200 kb region of Pi61(t), 93-11 contains four NBS-LRR genes, all of which show high identities in protein sequence with their corresponding NBS-LRR alleles in susceptible cv. Nipponbare. Comparison of the response spectra and physical positions between the target genes and other R genes in the same chromosome regions indicated that Pi60(t) could be Pia/PiCO39 or its allele, whereas Pi61(t) appears to be different from Pita, Pita-2, Pi19(t), Pi39(t) and Pi42(t) in the same R gene cluster. DNA markers tightly linked to Pi60(t) and Pi61(t) will enable marker-assisted breeding and map-based cloning.

Preliminary evaluation of resistance genes in rice against bacterial leaf blight in Guilan Province—Iran

The reactions of rice bacterial leaf blight races were identified in Guilan province—Iran on 12 near-isogenic lines and 14 pyramiding lines from International Network for Genetic Evaluation of rice (INGER) and 8 local and improved Iranian varieties were evaluated under natural photoperiod condition in the field. Inoculation was done at panicle initiation by clipping the sterilized scissors in the bacterial suspension to booting stage. Scoring of inoculated plants was made 21 days after inoculation. Infection levels of pyramiding lines containing two to five resistance genes, expect, IRBB53 and IRBB61 with respectively resistance gene combination, Xa5 + Xa13 and Xa4 + Xa5 + Xa7, were not so clear. Among near-isogenic lines IRBB1, IRBB2, IRBB4 and IRBB10 carrying resistance gene Xa1, Xa2, Xa4 and Xa10 were susceptible;IRBB8, IRBB11, IRBB3, IRBB5 and IRBB13 were moderately susceptible;(having resistance gene Xa8, Xa11, Xa3, Xa5 and Xa13) IRBB14, IRBB21 and IRBB7 with respectively resistance gene Xa14, Xa21 and Xa7 were moderately resistance to bacterial blight. Furthermore, most of the time gene combinations support the strategy of pyramiding appropriate resistance gene. Local varieties were more susceptible than improved varieties to leaf blight disease. Among local varieties, Tarom was the most susceptible. And also, there were no significant differences among improved varieties and all of them were moderately resistance.

Core and variable antimicrobial resistance genes in the gut microbiomes of Chinese and European pigs

Monitoring the prevalence of antimicrobial resistance genes(ARGs)is vital for addressing the global crisis of antibiotic-resistant bacterial infections.Despite its importance,the characterization of ARGs and microbiome structures,as well as the identification of indicators for routine ARG monitoring in pig farms,are still lacking,particularly concerning variations in antimicrobial exposure in different countries or regions.Here,metagenomics and random forest machine learning were used to elucidate the ARG profiles,microbiome structures,and ARG contamination indicators in pig manure under different antimicrobial pressures between China and Europe.Results showed that Chinese pigs exposed to high-level antimicrobials exhibited higher total and plasmid-mediated ARG abundances compared to those in European pigs(P<0.05).ANT(6)-Ib,APH(3')-IIIa,and tet(40)were identified as shared core ARGs between the two pig populations.Furthermore,the core ARGs identified in pig populations were correlated with those found in human populations within the same geographical regions.Lactobacillus and Prevotella were identified as the dominant genera in the core microbiomes of Chinese and European pigs,respectively.Forty ARG markers and 43 biomarkers were able to differentiate between the Chinese and European pig manure samples with accuracies of 100%and 98.7%,respectively.Indicators for assessing ARG contamination in Chinese and European pigs also achieved high accuracy(r=0.72-0.88).Escherichia flexneri in both Chinese and European pig populations carried between 21 and 37 ARGs.The results of this study emphasize the importance of global collaboration in reducing antimicrobial resistance risk and provide validated indicators for evaluating the risk of ARG contamination in pig farms.

Turnip mosaic virus pathogenesis and host resistance mechanisms in Brassica

Turnip mosaic virus(TuMV)is a devastating potyvirus pathogen that infects a wide variety of both cultivated and wild Brassicaceae plants.We urgently need more information and understanding of TuMV pathogenesis and the host responses involved in disease development in cruciferous crops.TuMV displays great versatility in viral pathogenesis,especially in its replication and intercellular movement.Moreover,in the coevolutionary arms races between TuMV and its hosts,the virus has evolved to co-opt host factors to facilitate its infection and counter host defense responses.This review mainly focuses on recent advances in understanding the viral factors that contribute to the TuMV infection cycle and the host resistance mechanism in Brassica.Finally,we propose some future research directions on TuMV pathogenesis and control strategies to design durable TuMV-resistant Brassica crops.

Mobile genetic elements facilitate the transmission of antibiotic resistance genes in multidrug-resistant Enterobacteriaceae from duck farms

Multidrug-resistant(MDR)Enterobacteriaceae critically threaten duck farming and public health.The phenotypes,genotypes,and associated mobile genetic elements(MGEs)of MDR Enterobacteriaceae isolated from 6 duck farms in Zhejiang Province,China,were investigated.A total of 215 isolates were identified as Escherichia coli(64.65%),Klebsiella pneumoniae(12.09%),Proteus mirabilis(10.23%),Salmonella(8.84%),and Enterobacter cloacae(4.19%).Meanwhile,all isolates were resistant to at least two antibiotics.Most isolates carried tet(A)(85.12%),blaTEM(78.60%)and sul1(67.44%)resistance genes.Gene co-occurrence analysis showed that the resistance genes were associated with IS26 and integrons.A conjugative IncFII plasmid pSDM004 containing all the above MGEs was detected in Proteus mirabilis isolate SDM004.This isolate was resistant to 18 antibiotics and carried the blaNDM-5 gene.MGEs,especially plasmids,are the primary antibiotic resistance gene transmission route in duck farms.These findings provide a theoretical basis for the rational use of antibiotics in farms which are substantial for evaluating public health and food safety.

Preliminary Localization of Resistance Gene against Tomato Gray Mold in Xinjiang

The genetic linkage map of F1 progeny of tomato variety " TS-107" and susceptible cultivar " TS-100" in Xinjiang was constructed. The inheritance of resistance genes against gray mold in disease-resistant cultivar " TS-107" was studied. Genetic mapping of resistance genes through Bulked Segregation Analysis( SSA) and Simple Sequence Recognition( SSR) markers provided germplasm resources for resistance breeding against gray mold. The results showed that the resistance of tomato " TS-107" to gray mold was controlled by a dominant gene. Eleven SSR polymorphic markers were screened and the gene was located between LGVII markers SSR12510 and ECM123 by linkage analysis. There was a partial segregation phenomenon in the No. 327 and No. 328 markers with significant difference,and the two markers had partial segregation sites.

<i>Escherichia coli</i>Harbouring Resistance Genes, Virulence Genes and Integron 1 Isolated from Athi River in Kenya

Rivers can act as reservoirs of highly resistant strains and facilitate the dissemination of resistance, virulence and integron 1 genes. A cross-sectional study was carried out where 318 water samples were collected (53 from each site) and from the samples, 318 E. coli isolates were analysed for resistance genes, virulence genes and integron 1 using Polymerase Chain Reaction. 22% of the isolates had blaTEM, 33% had blaCTX-M and 28% had blaCMY. Prevalence of typical Enteropathogenic E. coli strains (carrying both eae and bfp genes) was 5% while the prevalence of atypical Enteropathogenic E. coli (carying only eae) was 1.8%. The prevalence of Enteroaggregative E. coli carrying the aggr genes was 11%. The prevalence of Enterotoxigenic E. coli encoding only lt toxin was 16 (5%) and while those carrying only st toxin was 6.9%. The prevalence of Enteroinvasive E. coli strains encoding as IpaH was 5% while that of strains, adherent invasive E. coli, carrying adherent invasive gene inv was 8.7%. 36% isolates were positive for class 1 integrons which were mostly isolated near the sewage effluent from waste treatment plant. Anthropogenic activities and close proximity to sewage treatment plant were found to play a key role in pollution of water body and accumulation of resistance and virulence genes. These results suggest that waste treatment plant may act as reservoir of resistance, virulence and integron 1 genes and is a potential risk to human and animal health in the region.

Analysis of The Correlation Between inhA Gene Mutation and Resistance to Protionamide in Drug-Resistant Mycobacterium Tuberculosis

Objective: To investigate the characteristics of katG and inhA gene mutations in multidrug-resistant tuberculosis (MDR-TB), pre-extensively drug-resistant tuberculosis (preXDR-TB), and their correlation with resistance to protionamide (Pto). Methods: A total of 229 patients with MDR-TB and pre-XDR-TB diagnosed in the Eighth Affiliated Hospital of Xinjiang Medical University from January 2020 to February 2024 were selected to analyze the characteristics of katG and inhA mutations in MTB clinical isolates and their correlation with Pto resistance. Results: The mutation rate of katG (with or without inhA mutation) was 85.2%. The mutation rates in MDR-TB and pre-XDR-TB were 87.4% (125/143) and 81.4% (70/86), respectively. The mutation rate of inhA (including katG mutation) was 14.8% (34/229), which was 12.6% (18/143) and 18.6% (16/86) in MDR-TB and pre-XDR-MTB, respectively. There was no difference in mutation (P > 0.05). Conclusion: The total resistance rate to Pto in 229 strains was 8.7% (20/229), which was 8.4% (12/143) and 9.3% (8/86) in MDR-TB and pre-XDR-TB, respectively. Among the inhA mutant strains, 13 were resistant to the Pto phenotype, and the resistance rate was 65% (13/20). In MDR-TB and pre-XDR-TB strains resistant to Pto, inhA gene mutations occurred in 66.7% (6/9) and 63.6% (7/11), respectively. The resistance rates of MDR-MTB and pre-XDR-TB strains without inhA gene mutation to Pto were 2.4% (3/125) and 5.7% (4/70), respectively.

The Relationship of Methyl Jasmonate Enhanced Powdery Mildew Resistance in Wheat and the Expressions of 9 Disease Resistance Related Genes

[Objective] This study was carried out to determine the induction effect of jasmonic acid（JA）on powdery mildew resistance in wheat,the activation effect on the expressions of plant disease resistance related genes,and to investigate the relationship between the induced resistance and the gene expression patterns.[Method] Three powdery mildew susceptible cultivars of ＂Chinese Spring＂,＂Pumai 9＂ and ＂Zhoumai 18＂ typically representing different phenotypes in the field were employed.The powdery mildew was assessed by detached leaf assay,and real time quantitative RT-PCR was used to determine the expression patterns of 9 disease resistance related genes of PR1（PR1.1）,PR2（β,1-3 glucanase）,PR3（chitinase）,PR4（wheatwin1）,PR5（thaumatin-like protein）,PR9（TaPERO,peroxidase）,PR10,TaGLP2a（germin-like）and Ta-JA2（jasmonate-induced protein）in leaf of the three cultivars.[Result] MeJA application enhanced the powdery mildew resistances of ＂Chinese Spring＂,＂Pumai 9＂ and ＂Zhoumai 18＂.The induced powdery mildew resistance could be detected from 12 h to 96 h after MeJA treatment,and the peak value was at 24 h.Though there were differences between the three cultivars,MeJA significantly effect on the expressions of the 8 disease resistance related genes except TaGLP2a,and the peak values were at 12 h,24 h or 48 h after treatments.The strongest activation of MeJA was on PR9 and PR1 that their expressions could reach more than 100 times of the untreated samples.MeJA strongly activated PR2、PR4、PR5、PR3、PR10 and Ta-JA2,their expression could reach 10 to 70 times,and there was almost no activation effect on TaGLP2a.The induced powdery mildew resistance positively correlated with the induced expressions of the 8 disease related genes.[Conclusion] The induced powdery mildew resistance positively correlated with the induced expressions of the disease related genes.Jasmonate signalling plays a role in defence against Blumeria graminis f.sp.tritici.and future manipulation of this pathway may improve powdery mildew resistance in wheat.

Suppression of P-gp induced multiple drug resistance in a drug resistant gastric cancer cell line by overexpression of Fas

AIM To observe the drug sensitizing effect andrelated mechanisms of fas gene transduction onhuman drug-resistant gastric cancer cellSGC7901/VCR(resistant to Vincristine).METHODS The cell cycle alteration wasobserved by FACS.The sensitivity of gastriccancer cells to apoptosis was determined by invitro apoptosis assay.The drug sensitization ofcells to several anti-tumor drugs was observedby MTT assay.Immunochemical method wasused to show expression of P-gp and Topo Ⅱ ingastric cancer cells.RESULTS Comparing to SGC7901 and pBK-SGC7901/VCR,fas-SGC7901/VCR showeddecreasing G2 cells and increasing S cells,theG2 phase fraction of pBK-SGC7901/VCR wasabout 3.0 times that of fas-SGC7901/VCR,but Sphase fraction of fas-SGC7901/VCR was about1.9 times that of pBK-SGC7901/VCR,indicatingS phase arrest of fas-SGC7901/VCR.FACS alsosuggested apoptosis of fas-SGC7901/VCR,fas-SGC7901/VCR was more sensitive to apoptosisinducing agent VM-26 than pBK-SGC7901/VCR.MTT assay showed increased sensitization offas-SGC7901/VCR to DDP,MMC and 5-FU,butsame sensitization to VCR according to pBK-SGC7901/VCR.SGC7901,pBK-SGC7901/ VCRand fas-SGC7901/VCR had positively stainedTopo Ⅱ equally.P-gp staining in pBK- SGC7901/VCR was stronger than in SG07901,but there was little staining of P-gp in fas.SGC7901/VCR.CONCLUSION fas gene transduction couldreverse the MDR of human drug-resistant gastriccancer cell SGC7901/VCR to a degree,possiblybecause of higher sensitization to apoptosis anddecreased expression of P-gp.