Preferential mutagenesis of lacZ integrated at unique sites in the Escherichia coli chromosome

To study the variation in spontaneous mutation frequencies in different chromosomal domains, a mini-Mu-kan-lacZ ^?transposable element was constructed to insert the lacZ ^?(Trp570 → Opal) allele into many different loci in the Escherichia coli chromosome. Papillation on MacConkey lactose plates was used to screen for mini-Mu insertion mutants with elevated levels of spontaneous mutagenesis of lacZop → LacZ⁺ candidates were then screened for normal mutation frequencies in other genes. Two different insertion mutants with this enhanced mutagenesis phenotype were isolated from 14?000 colonies, and named plm-1 (preferential lacZmutagenesis) and plm-2. The frequency of LacZ^?→ LacZ⁺ mutations in these plm mutants was over 400-fold higher than that in isogenic strains containing mini-Mu-kan-lacZop insertions at other loci. Six Lac⁺ reversion (or suppression) mutations obtained from each of the two plm mutants were mapped by P1 transduction and all were found to be linked to the Kan^r gene in the mini-Mu-kan-lacZop, suggesting that a localized mutagenic event is responsible for the preferential mutagenesis. Furthermore, both the LacZ⁺→ LacZ^?and Kan^r→ Kan^s mutant frequencies of these Lac⁺ revertants were in the range of 10^?3 to 10^?2, indicating that this putative localized mutagenesis is neither allele nor gene specific. To identify the plm loci, the chromosomal regions flanking the mini-Mu insertion sites were cloned and sequenced. A computer-assisted database search of homologous sequences revealed that the plm-1 locus is identical to the mutS gene; the mini-Mu insertion most probably results in the production of a truncated MutS protein. We suggest that the enhanced lacZ mutation frequency in plm-1 may be associated with an active process involving the putative truncated MutS protein. The DNA sequence of the plm-2 locus matched a putative malate oxidoreductase gene located at 55.5 min of the E. coli chromosome.     

Site Specificity and Variability in the Mutator and Antimutator Effects of Phage T4 Gene 43 Mutants

Spontaneous, 2-aminopurine- and 5-bromouracil-induced mutations at six rII nonsense codons were studied in phage T4 strains possessing wild-type and mutant gene 43 alleles. The mutation pathways studied included interconversions and reversions of nonsense codons. The tsCB87 allele, which specifies an antimutator DNA polymerase, reduced base-analogue-induced mutation frequencies along all pathways. However, GC base pairs were less affected than AT base pairs. The frequency of spontaneous UAA→UAG conversions was also reduced by tsCB87, but that of spontaneous UAA→UGA conversions was often increased. Mutation in the presence of the mutator allele tsL56 was increased along all pathways, with no preference for either AT or GC base pairs. Mutation frequencies in the presence of the two mutant DNA polymerases were highly variable. A strong correlation was found between 2-aminopurine-induced mutation frequencies in ts⁺ and tsCB87 phage along the reversion and UAA→UAG (but not UAA→UGA) pathways.     

Simulation of X-Linked Selection in Drosophila

The change in gene frequency for two X-linked mutants, y and w, in a number of experiments was compared to that predicted from a genetic simulation program which utilized estimated differences in relative mating ability, fecundity, and viability. The simulation gave excellent predictions of gene frequency change even when experiments were started with different initial gene frequencies in the males and females or when the two loci were segregating simultaneously. The rate of elimination was slower when there were unequal initial gene frequencies than when males and females had equal initial gene frequencies. Simulation demonstrated that this was a general phenomenon when there is strong selection but that the opposite is true for weak selection. In two other experiments, the mating advantage of wild-type males was balanced by a fecundity advantage in mutant females. In all four replicates of both experiments, the mutant was maintained for several generations at the high initial frequency but then decreased quickly and was eliminated. Results obtained restarting one of these experiments with flies from a generation after the decline in gene frequency indicated that a linked gene and not frequency-dependent selection was responsible for the unpredictable gene-frequency change in the mutant. Using a least squares technique, it was found that a recessive fecundity locus 15 map units from the w locus gave the best fit for both experiments.     

Molecular cloning and sequence analysis of the lysR gene from the extremely thermophilic eubacterium, Thermus thermophilus HB27

We have isolated a lysine-auxotrophic and kanamycin-resistant mutant from an extreme thermophile, Thermus thermophilus HB27. This mutant showed the lysA⁻ or lysR⁻ genotype since it could not grow on the minimal plate which contained diaminopimelic acid. Sequence analysis of the clones which could rescue the Lys⁻ mutant indicated the lysR gene. The lysR gene overlapped with the rimK gene for the modification enzyme of ribosomal protein S6. In the Lys⁻ mutant, the lysR gene was disrupted and the C-terminus region of the RimK protein was different from that of the wild-type, which contributed to the Lys⁻ and kanamycin-resistant phenotype. The deduced amino acid sequence of the lysR gene showed 20.9% identity with the LysR protein of Escherichia coli. The percentage of use of cytosine or guanine in the third letter of the codons in the lysR gene was only 67.4%. We also determined that the argC gene encoding N-acetyl-γ-glutamyl phosphate reductase and the argB gene encoding acetylglutamate kinase were located immediately upstream of the lysR gene.     

Characterization of the glnK-amtB Operon of Azotobacter vinelandii

To determine whether in Azotobacter vinelandii the P_II protein influences the regulation of nif gene expression in response to fluxes in the ammonium supply, the gene encoding P_II was isolated and characterized. Its deduced translation product was highly similar to P_II proteins from other organisms, with the greatest degree of relatedness being exhibited to the Escherichia coli glnK gene product. A gene designated amtB was found downstream of and was cotranscribed with glnK as in E. coli. The AmtB protein is similar to functionally characterized ammonium transport proteins from a few other eukaryotes and one other prokaryote. glnK and amtB comprise an operon. Attempts to isolate a stable glnK mutant strain were unsuccessful, suggesting that glnK, like glnA, is an essential gene in A. vinelandii. amtB mutants were isolated, and although growth on limiting amounts of ammonium was similar in the mutant and wild-type strains, the mutants were unable to transport [¹⁴C]methylammonium.     

Role of adipokinetic hormone and adenosine in the anti-stress response in Drosophila melanogaster

The role of adipokinetic hormone (AKH) and adenosine in the anti-stress response was studied in Drosophila melanogaster larvae and adults carrying a mutation in the Akh gene (Akh¹), the adenosine receptor gene (AdoR¹), or in both of these genes (Akh¹ AdoR¹ double mutant). Stress was induced by starvation or by the addition of an oxidative stressor paraquat (PQ) to food. Mortality tests revealed that the Akh¹ mutant was the most resistant to starvation, while the AdoR¹ mutant was the most sensitive. Conversely, the Akh¹ AdoR¹ double mutant was more sensitive to PQ toxicity than either of the single mutants. Administration of PQ significantly increased the Drome-AKH level in w¹¹¹⁸ and AdoR¹ larvae; however, this was not accompanied by a simultaneous increase in Akh gene expression. In contrast, PQ significantly increased the expression of the glutathione S-transferase D1 (GstD1) gene. The presence of both a functional adenosine receptor and AKH seem to be important for the proper control of GstD1 gene expression under oxidative stress, however, the latter appears to play more dominant role. On the other hand, differences in glutathione S-transferase (GST) activity among the strains, and between untreated and PQ-treated groups were minimal. In addition, the glutathione level was significantly lower in all untreated AKH- or AdoR-deficient mutant flies as compared with the untreated control w¹¹¹⁸ flies and further declined following treatment with PQ. All oxidative stress characteristics modified by mutations in Akh gene were restored or even improved by ‘rescue’ mutation in flies which ectopically express Akh. Thus, the results of the present study demonstrate the important roles of AKH and adenosine in the anti-stress response elicited by PQ in a D. melanogaster model, and provide the first evidence for the involvement of adenosine in the anti-oxidative stress response in insects.     

Genotypic diversity of the Killer Cell Immunoglobulin-like Receptors (KIR) and their HLA class I Ligands in a Saudi population

Killer Cell Immunoglobulin-like Receptors (KIR) have been used as good markers for the study of genetic predisposition in many diseases and in human genetic population dynamics. In this context, we have investigated the genetic diversity of KIR genes and their main HLA class I ligands in Saudi population and compared the data with other studies of neighboring populations. One hundred and fourteen randomly selected healthy Saudi subjects were genotyped for the presence or absence of 16 KIR genes and their HLA-C1, -C2, -Bw4^Thr80 and Bw4^Ile80 groups, using a PCR-SSP technique. The results show the occurrence of the framework genes (3DL2, 3DL3 and 2DL4) and the pseudogenes (2DP1 and 3DP1) at highest frequencies. All inhibitory KIR (iKIR) genes appeared at higher frequencies than activating genes (aKIR), except for 2DS4 with a frequency of 90.35%. A total of 55 different genotypes were observed appearing at different frequencies, where 12 are considered novel. Two haplotypes were characterized, AA and Bx (BB and AB), which were observed in 24.5% and 75.5% respectively of the studied group. The frequencies of iKIR + HLA associations were found to be much higher than aKIR + HLA. KIR genes frequencies in the Saudi population are comparable with other Middle Eastern and North African populations.     

Frequency distribution of PRNP polymorphisms in the Pakistani population

Prion diseases are neurodegenerative conditions caused by misfolding of a normal host-encoded prion protein (PrP^C) into pathogenic scrapie prion protein (PrP^Sc). In human prion diseases, the M129V prion protein polymorphism is known to confer susceptibility to the disease, determines PrP^Sc conformation and alters clinicopathological phenotypes. To date, all clinicopathologically confirmed cases of a variant form of Cruetzfeldt-Jacob disease (vCJD) have been 129MM homozygotes. There is also predominance of 129MM homozygotes in sporadic CJD (sCJD). No information regarding prion disorders is available from Pakistan. Although only invasive procedures like brain biopsy can confirm the diagnosis of prion disorders, testing a corresponding human population for variation in the prion protein gene (PRNP) may provide some insights into the presence of these disorders in a locality. The current study therefore aimed at exploring the genetic susceptibility of Pakistani population to CJD. A total of 909 unrelated individuals including 221 hemophiliacs representing all 4 major provinces of Pakistan were screened for M129V polymorphism and insertions or deletions of octapeptide repeats (OPRIs/OPRDs) using Polymerase Chain Reaction coupled with Restriction Fragment Length Polymorphism (PCR-RFLP). Concordance of the results of some PCR-RFLP reactions was also confirmed by dideoxy automated Sanger sequencing. The frequencies of M129V alleles (129M and 129V) and genotypes (129MM, 129MV and 129VV) were found in all 909 individuals to be 0.7101, 0.2899, 0.5270, 0.3663 and 0.1067, respectively. Deletion of 1 octapeptide repeat (1-OPRD) was detected in heterozygous state in PRNP of 10 individuals and in homozygous state in 1 individual. An insertion of 3 octapeptide repeats (3-OPRI) was found in 1 individual and an insertion of 1 octapeptide repeat (1-OPRI) in two individuals. Both 3-OPRI and 1-OPRI were present in heterozygous state and were linked to 129M allele. There were no significant χ² differences between M129V allelic and genotypic frequencies of healthy individuals and hemophiliacs. However, M129V allelic and genotypic frequencies differed significantly between Pakistani population and East Asian and Western populations. Non-significant χ² differences between M129V frequencies of healthy individuals and hemophiliacs suggest that individuals manifesting single gene disorders may provide naturally randomized samples for studies aiming at surveying the genetic variation. The combined excess of 129MM and 129VV homozygosity and the presence of 3-OPRI in 1 individual imply that Pakistani population is susceptible to prion disorders. Cases of prion disorders may exist in Pakistan, albeit at lower annual prevalence than other countries where life expectancy is greater than 65 years.     

Distribution of polymorphic variants of the <Emphasis Type="Italic">GSTP1</Emphasis> gene involved in biotransformation of xenobiotics in Tundra Nenets and Nganasans in comparison to Russians

The first study on the frequencies of polymorphic variants of the GSTP1 gene encoding glutathione-S-transferase P1 in Tundra Nenets and Nganasan populations was performed. The subject of the study was the single nucleotide polymorphisms rs1695 (Ile105Val substitution in the protein sequence) and rs1138272 (Ala114Val substitution) that had previously been shown to be associated with cancer and other multifactorial diseases. The data for Tundra Nenets of the Yamalo-Nenets autonomous okrug, Nganasans of the Taimyr Peninsula, and Russian residents of the Northern Siberia were compared. The frequencies of the mutant 105Val and 114Val variants were 10.8% and 0.8% in Nganasans, 23.7% and 4.8% in Nenets, and 35.8% and 9.1% in Russian population samples, respectively. The differences within all pairs of populations were significant for each allele. These differences may characterize the population-level susceptibility to cancer and other multifactorial diseases.     

Differentially expressed genes in the ovary of the sixth day of pupal “Ming” lethal egg mutant of silkworm, Bombyx mori

The “Ming” lethal egg mutant (l-e^m) is a vitelline membrane mutant in silkworm, Bombyx mori. The eggs laid by the l-e^m mutant lose water, ultimately causing death within an hour. Previous studies have shown that the deletion of BmEP80 is responsible for the l-e^m mutation in silkworm, B. mori. In the current study, digital gene expression (DGE) was performed to investigate the difference of gene expression in ovaries between wild type and l-e^m mutant on the sixth day of the pupal stage to obtain a global view of gene expression profiles using the ovaries of three l-e^m mutants and three wild types. The results showed a total of 3,463,495 and 3,607,936 clean tags in the wild type and the l-e^m mutant libraries, respectively. Compared with those of wild type, 239 differentially expressed genes were detected in the l-e^m mutant, wherein 181 genes are up-regulated and 58 genes are down-regulated in the mutant strain. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis results showed that no pathway was significantly enriched and three pathways are tightly related to protein synthesis among the five leading pathways. Moreover, the expression profiles of eight important differentially expressed genes related to oogenesis changed. These results provide a comprehensive gene expression analysis of oogenesis and vitellogenesis in B. mori which facilitates understanding of both the specific molecular mechanism of the 1-e^m mutant and Lepidopteran oogenesis in general.     

Lambda CIN-1, a New Mutation Which Enhances Lysogenization by Bacteriophage Lambda, and the Genetic Structure of the Lambda CY Region

Seven lambda cy mutants have been mapped within a small region located approximately halfway between the rightward boundary of the imm⁴³⁴ region and the lambda cII gene. The seven mutants lie at four sites separated by a total distance of about 12 nucleotide pairs, as estimated from recombination frequencies. Six of the seven mutants lie on the right side of the cy fine structure map, spanning a total distance of about 3–5 nucleotide pairs. Lying approximately 11–21 nucleotide pairs to the left of the leftmost cy mutant is a newly described mutation called cin-1, for c independent. The cin-1 mutation allows some lysogenization when coupled with any cy, cII or cIII mutant, but not when coupled with a defective cI gene. The cin-1 mutation, like cy mutants, has a cis-dominant action upon the cI gene in mixed infections. The observation that λimm⁴³⁴ cin-1 cy2001 lysogenizes efficiently, but not λimm⁴³⁴ cin-1 cy2001 cII68 nor any other λimm⁴³⁴ cin-1 cy derivative, is interpreted to mean that all of the cy mutants on the right side of the cy fine structure map inactivate a binding site for cII/cIII function, but that cy2001, the single mutant on the left side of the cy fine structure map, does not inactivate that binding site.     

Characterisation of the glnK-amtB operon and the involvement of AmtB in methylammonium uptake in Azorhizobium caulinodans

This work reports the characterisation of the Azorhizobium caulinodans amtB gene, the deduced protein sequence of which shares similarity to those of several ammonium transporters. amtB is located downstream from glnK, a glnB-like gene. It is cotranscribed with glnK from an NtrC- and σ⁵⁴-dependent promoter. glnK and amtB insertion mutant strains have been isolated. Methylammonium uptake was assayed in these strains and in other mutant strains in which the regulation of nitrogen metabolism is impaired. Our data suggest that the AmtB protein is an ammonium transporter, which is mainly regulated by NtrC in response to nitrogen availability.     

Double-strand break repair and genetic recombination in topoisomerase and primase mutants of bacteriophage T4

The effects of primase and topoisomerase II deficiency on the double-strand break (DSB) repair and genetic recombination in bacteriophage T4 were studied in vivo using focused recombination. Site-specific DSBs were induced by SegC endonuclease in the rIIB gene of one of the parents. The frequency/distance relationship was determined in crosses of the wild-type phage, topoisomerase II mutant amN116 (gene 39), and primase mutant E219 (gene 61). Ordinary two-factor (i × j) and three-factor (i k × j) crosses between point rII mutations were also performed. These data provide information about the frequency and distance distribution of the single-exchange (splice) and double-exchange (patch) events. In two-factor crosses ets1 × i, the topoisomerase and primase mutants had similar recombinant frequencies in crosses at ets1–i distances longer than 1000 bp, comprising about 80% of the corresponding wild-type values. They, however, differ remarkably in crosses at shorter distances. In the primase mutant, the recombinant frequencies are similar to those in the wild-type crosses at distances less than 100 bp, being a bit diminished at longer distances. In two-factor crosses ets1 × i of the topoisomerase mutant, the recombinant frequencies were reduced ten-fold at the shortest distances. In three-factor crosses a6 ets1 × i, where we measure patch-related recombination, the primase mutant was quite proficient across the entire range of distances. The topoisomerase mutant crosses demonstrated virtually complete absence of rII⁺ recombinants at distances up to 33 bp, with the frequencies increasing steadily at longer distances. The data were interpreted as follows. The primase mutant is fully recombination-proficient. An obvious difference from the wild-type state is some shortage of EndoVII function leading to prolonged existence of HJs and thus stretched out ds-branch migration. This is also true for the topoisomerase mutant. However, the latter is deficient in the ss-branch migration step of the DSB repair pathway and partially deficient in HJ initiation. In apparent contradiction to their effects on the DSB-induced site-specific recombination, the topoisomerase and primase mutants demonstrated about 3–8-fold increase in the recombinant frequencies in the ordinary crosses, with the recombination running exclusively via patches. This implies that most of the spontaneous recombination events are not initiated by dsDNA ends in these mutants.     

Oxidative phosphorylation in Escherichia coli K-12: The genetic and biochemical characterisation of a strain carrying a mutation in the uncB gene

1. A mutant strain of Escherichia coli unable to grow with succinate as sole carbon source was isolated. This mutant was found to carry a mutation in a gene (designated uncB) mapping at about minute 73.5 on the E. coli chromosome and close to the uncA gene which is probably the structural gene for (Mg²⁺,Ca²⁺)-stimulated ATPase.2. The uncB401 allele was transduced into two other strains of E. coli and the transductants compared with the parent strains.3. Strains carrying the uncB401 allele have low aerobic growth yields when grown on limiting concentrations of glucose, but unlike mutations in the uncA gene, mutations in the uncB gene do not impair anaerobic growth on a glucose-mineral salts medium.4. Oxidase activities in membranes from the normal strains and strains carrying the uncB401 allele were similar.5. Measurement of P/O ratios indicated that a mutation in the uncB gene causes uncoupling of phosphorylation associated with electron transport with d-lactate as substrate.6. (Mg²⁺,Ca²⁺)-stimulated ATPase activities in the normal strains and in strains carrying the uncB401 allele are similar.7. Estimation of the energy-linked and non-energy-linked transhydrogenase activities in membrane preparations from both the normal and mutant strains indicated that the protein affected by a mutation in the uncB gene is essential for the functioning of the ATP-dependent energy-linked transhydrogenase.8. It is concluded that two proteins, specified by the uncA and uncB genes, are essential for phosphorylation coupled to d-lactate oxidation and also for the energy-linked transhydrogenase activity using ATP as the energy source.     

Aluminum-sensitive mutants of Saccharomyces cerevisiae

We are developing budding yeast, Saccharomyces cerevisiae, as a genetic system for the study of tolerance to the trivalent aluminum cation (Al³⁺). We have isolated eight mutants that are more sensitive to Al³⁺ than the wild type. Each mutant represented a different complementation group. A number of the mutants were pleiotropic, and showed defects in other stress responses, changes in tolerance to other metal cations, or abnormal morphology. Two mutants also showed increased dependence on supplemental Mg²⁺ and Ca²⁺. One mutant with a relatively specific sensitivity to Al³⁺ was chosen for molecular complementation. Normal Al³⁺ tolerance was restored by expression of the MAP kinase gene SLT2. Strains carrying deletions of the SLT2 gene, or of the gene for the corresponding MAP kinase–kinase SLK1, showed sensitivity to Al³⁺. These results indicate that the SLT2 MAP kinase signal transduction pathway is required for yeast to sense and respond to Al³⁺ stress.     

Natural Selection Mediated Association of the Duffy (FY) Gene Polymorphisms with Plasmodium vivax Malaria in India

The Duffy (Fy) antigens act as receptors for chemokines as well as for Plasmodium vivax to invade human RBCs. A recent study has correlated the occurrence of the FY*A allele of Duffy gene with decreased susceptibility to vivax malaria, but no epidemiological correlation between the distribution of FY*A allele and incidences of vivax malaria has been established so far. Furthermore, if such correlations exist, whether natural selection has mediated the association, is an important question. Since India is highly endemic to P. vivax malaria with variable eco-climatic and varying vivax malaria epidemiology across different regions, such a question could well be answered in Indians. For this, we have genotyped the FY gene at the −33^rd and the 125^th nucleotide positions in 250 Indians sampled from six different zonal plus one tribal population covering the whole of India and studied possible correlations with eco-climatic and vivax malaria incidences. No FY*O allele was found, however, both the FY*A and FY*B alleles forming FY*A/FY*A, FY*A/FY*B and FY*B/FY*B genotypes were widely distributed among Indians. Five out of seven population samples significantly deviated from the Hardy-Weinberg equilibrium expectation, and two alleles (FY*A and FY*B) and the homozygote genotype, FY*B/FY*B were clinally distributed over the population coordinates. Furthermore, vivax malaria incidences over the past five years were significantly negatively and positively associated with the frequencies of the FY*A and FY*B alleles, respectively. The Northern Indians were highly differentiated from the other zonal population samples at the FY gene, as evidenced from the reconstructed Neighbor-Joining phylogenetic tree. The results specify the role of natural selection in the distribution of FY gene polymorphism in India. Furthermore, the hypotheses on the part of the FY*A allele in conferring protection to vivax malaria could be validated following population genetic studies in a vivax malaria epidemiological setting, such as India.     

Gene polymorphism of the renin-angiotensin system in six ethnogeographic regions of Belarus

The insertion/deletion polymorphism of the angiotensin-converting enzyme gene (ACE) and the T174M polymorphism of the angiotensinogen gene (AGT) have been studied in six ethnogeographic regions of Belarus. Significant intrapopulation differences in ACE genotype frequencies have been found for the northern and eastern regions (the Dvina and Dnepr basins, respectively). Significant differences in the AGT genotype frequencies have been found between populations of the Dnepr basin and populations of all other Belarusian regions. The allele and genotype frequencies of the genes studied in the Belarusian population and populations of other regions of the world have been compared. The frequencies of the insertion (I) and deletion (D) alleles of the ACE gene in the Belarusian population are 50.7 and 49.3%, respectively, which is similar to these frequencies in European countries. The frequency of the M allele of the AGT gene in Belarus is 16.6%, which is higher than its frequency in populations of European, African, and Asian origins.     

A novel polymorphism of apolipoprotein A-IV is the result of an asparagine to serine substitution at residue 127

We have identified a hitherto genetic polymorphism of apolipoprotein A-IV (apo-IV). The molecular basis for this polymorphism is an A to G substitution at nucleotide 1687 resulting in an Asn to Ser change of amino acid 127. The frequencies of the two apoA-IV alleles (designated apoA-IV^127Asn and apoA-IV^127Ser), determined by Hinc II restriction analysis of PCR amplified exon three of the apoA-IV gene, were 0.788 and 0.212, respectively, in a Finnish population sample. Allele frequencies of another polymorphism due to a Thr to Ser substitution at amino acid 347 were determined using Hinf I restriction analysis. The allele frequencies were 0.823 for apoA-IV^347Thr and 0.177 for apoA-IV^247Ser. None of the apoA-IV polymorphisms (apoA-IV_{127:Asn→Ser}, apoA-IV_{347:Thr→Ser} and apoA-IV_{360:Gln→His}) had any effect of plasma lipid and lipoprotein concentrations in cohorts of dyslipidemic men and in a population sample of normolipidemic controls. There was also no association between the history of previous myocardial infarction and any of the apoA-IV alleles.     

A phcA− marker-free mutant of Ralstonia solanacearum as potential biocontrol agent of tomato bacterial wilt

A phcA⁻ mutant of Ralstonia solanacearum strain ZJ3721 was created in a marker-free method. Expression of virulence-associated genes such as xpsR, egl, tek and epsE was significantly suppressed in the phcA⁻ mutant. The ability of the mutant to control tomato bacterial wilt was evaluated by potting experiment. Results showed that application of mutant with wild type (WT) at the same time only delayed the development of wilt for about one day and the population of WT in tomato rhizosphere soil was nearly 70-fold higher than that of the mutant, resulting in a 90% disease incidence at last, as high as that of control. If the phcA⁻ mutant was applied three days earlier than WT pathogen, tomato wilt disease incidence was only 6%, 80% lower than that of control and population of WT was about 0.5-fold as much as that of mutant. Under hydroponic conditions, phcA⁻ mutant significantly triggered the expressions of genes in salicylic acid pathway but inhibited the expressions of genes in jasmonic acid (JA) and ethylene (ET) pathways. The expressions of PR-1a and GluA genes (salicylic acid pathway) in phcA⁻ mutant were 66-fold and 7.5-fold higher than in WT pathogen after three days of inoculation.