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Molecular analysis of avirulence gene avrRpt2 and identification of a putative regulatory sequence common to all known Pseudomonas syringae avirulence genes.

ABSTRACT: The avrRpt2 locus from Pseudomonas syringae pv. tomato causes virulent strains of P. syringae to be avirulent on some, but not all, lines of Arabidopsis thaliana and Glycine max (soybean). We determined the DNA sequence of the avrRpt2 locus and identified the avrRpt2 gene as a 768-bp open reading frame encoding a putative 28.2-kDa protein. Deletion analysis and transcription studies provided further evidence that this open reading frame encodes AvrRpt2. We found that the avrRpt2 gene also has avirulence activity in P. syringae pathogens of Phaseolus vulgaris (common bean), suggesting that disease resistance genes specific to avrRpt2 are functionally conserved among diverse plant species. The predicted AvrRpt2 protein is hydrophilic and contains no obvious membrane-spanning domains or export signal sequences, and there was no significant similarity of AvrRpt2 to sequences in the GenBank, EMBL, or Swiss PIR data bases. A comparison of the avrRpt2 DNA sequence to nine other P. syringae avirulence genes revealed a highly conserved sequence, GGAACCNA-N14-CCACNNA, upstream of the translation initiation codon. This motif is located 6 to 8 nucleotides upstream of the transcription start site in all four P. syringae avirulence genes for which a transcription start site has been determined, suggesting a role as a binding site for a novel form of RNA polymerase. Regulation of avrRpt2 was similar to other P. syringae avirulence genes; expression was high in minimal medium and low in rich medium and depended on the hrpRS locus and an additional locus at the opposite end of the hrp cluster of P. syringae pv. tomato.

SUBMITTER: Innes RW

PROVIDER: S-EPMC204939 | biostudies-other | 1993 Aug

REPOSITORIES: biostudies-other

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Molecular analysis of avirulence gene avrRpt2 and identification of a putative regulatory sequence common to all known Pseudomonas syringae avirulence genes.

Innes R W RW Bent A F AF Kunkel B N BN Bisgrove S R SR Staskawicz B J BJ

Journal of bacteriology 19930801 15

The avrRpt2 locus from Pseudomonas syringae pv. tomato causes virulent strains of P. syringae to be avirulent on some, but not all, lines of Arabidopsis thaliana and Glycine max (soybean). We determined the DNA sequence of the avrRpt2 locus and identified the avrRpt2 gene as a 768-bp open reading frame encoding a putative 28.2-kDa protein. Deletion analysis and transcription studies provided further evidence that this open reading frame encodes AvrRpt2. We found that the avrRpt2 gene also has av ...[more]

PMID: 8335641

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Project description:BACKGROUND:Pseudomonas syringae is an important plant pathogen, which could adapt many different environmental conditions. Under the nutrient-limited and other stress conditions, P. syringae produces nucleotide signal molecules, i.e., guanosine tetra/pentaphosphate ((p)ppGpp), to globally regulate gene expression. Previous studies showed that (p) ppGpp played an important role in regulating virulence factors in P. syringae pv. tomato DC3000 (PstDC3000) and P. syringae pv. syringae B728a (PssB728a). Here we present a comparative transcriptomic analysis to uncover the overall effects of (p)ppGpp-mediated stringent response in P. syringae. RESULTS:In this study, we investigated global gene expression profiles of PstDC3000 and PssB728a and their corresponding (p)ppGpp0 mutants in hrp-inducing minimal medium (HMM) using RNA-seq. A total of 1886 and 1562 differentially expressed genes (DEGs) were uncovered between the (p)ppGpp0 mutants and the wild-type in PstDC3000 and PssB728a, respectively. Comparative transcriptomics identified 1613 common DEGs, as well as 444 and 293 unique DEGs in PstDC3000 and PssB728a, respectively. Functional cluster analysis revealed that (p) ppGpp positively regulated a variety of virulence-associated genes, including type III secretion system (T3SS), type VI secretion system (T6SS), cell motility, cell division, and alginate biosynthesis, while negatively regulated multiple basic physiological processes, including DNA replication, RNA processes, nucleotide biosynthesis, fatty acid metabolism, ribosome protein biosynthesis, and amino acid metabolism in both PstDC3000 and PssB728a. Furthermore, (p) ppGpp had divergent effects on other processes in PstDC3000 and PssB728a, including phytotoxin, nitrogen regulation and general secretion pathway (GSP). CONCLUSION:In this study, comparative transcriptomic analysis reveals common regulatory networks in both PstDC3000 and PssB728a mediated by (p) ppGpp in HMM. In both P. syringae systems, (p) ppGpp re-allocate cellular resources by suppressing multiple basic physiological activities and enhancing virulence gene expression, suggesting a balance between growth, survival and virulence. Our research is important in that due to similar global gene expression mediated by (p) ppGpp in both PstDC3000 and PssB728a, it is reasonable to propose that (p) ppGpp could be used as a target to develop novel control measures to fight against important plant bacterial diseases.

Dataset Information

Molecular analysis of avirulence gene avrRpt2 and identification of a putative regulatory sequence common to all known Pseudomonas syringae avirulence genes.

Publications

Molecular analysis of avirulence gene avrRpt2 and identification of a putative regulatory sequence common to all known Pseudomonas syringae avirulence genes.

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