NolX of
 Sinorhizobium fredii
 USDA257, a Type III-Secreted Protein Involved in Host Range Determination, Is Localized in the Infection Threads of Cowpea (
 Vigna unguiculata
 [L.] Walp) and Soybean (
 Glycine max
 [L.] Merr.) Nodules

Krishnan, Hari B.

doi:10.1128/jb.184.3.831-839.2002

Cited by 54 publications

(37 citation statements)

References 34 publications

(48 reference statements)

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“…Moreover, HrpF can form pores in artificial lipid bilayers, consistent with it acting as a translocator (11). HrpF has homology with NolX, a type III secreted protein from Sinorhizobium fredii whose function is unknown (42,54).…”

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confidence: 96%

“…However, a PSI-BLAST iteration 2 search queried with HrpK indicated that HrpK was similar to the X. campestris pv. vesicatoria HrpF putative translocator (E value, 6eϪ14) (11), the type III secreted PopF1 (E value, 7eϪ 7) and PopF2 (E value, 0.27) from Ralstonia solanacearum, and NolX (E value, 2eϪ7), a type III secreted protein from S. fredii (54). Huguet and colleagues (42) identified two regions in HrpF with similarity to a single region in NolX.…”

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confidence: 99%

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The hrpK Operon of Pseudomonas syringae pv. tomato DC3000 Encodes Two Proteins Secreted by the Type III (Hrp) Protein Secretion System: HopB1 and HrpK, a Putative Type III Translocator

2005

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Pseudomonas syringae is a gram-negative bacterial plant pathogen that is dependent on a type III protein secretion system (TTSS) and the effector proteins it translocates into plant cells for pathogenicity. The P. syringae TTSS is encoded by hrp-hrc genes that reside in a central region of a pathogenicity island (Pai). Flanking one side of this Pai is the exchangeable effector locus (EEL). We characterized the transcriptional expression of the open reading frames (ORFs) within the EEL of P. syringae pv. tomato DC3000. One of these ORFs, PSPTO1406 (hopB1) is expressed in the same transcriptional unit as hrpK. Both HopB1 and HrpK were secreted in culture and translocated into plant cells via the TTSS. However, the translocation of HrpK required its C-terminal half. HrpK shares low similarity with a putative translocator, HrpF, from Xanthomonas campestris pv. vesicatoria. DC3000 mutants lacking HrpK were significantly reduced in disease symptoms and multiplication in planta, whereas DC3000 hopB1 mutants produced phenotypes similar to the wild type. Additionally, hrpK mutants were reduced in their ability to elicit the hypersensitive response (HR), a programmed cell death associated with plant defense. The reduced HR phenotype exhibited by hrpK mutants was complemented by hrpK expressed in bacteria but not by HrpK transgenically expressed in tobacco, suggesting that HrpK does not function inside plant cells. Further experiments identified a C-terminal transmembrane domain within HrpK that is required for HrpK translocation. Taken together, HopB1 is a type III effector and HrpK plays an important role in the TTSS and is a putative type III translocator.

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confidence: 96%

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confidence: 99%

The hrpK Operon of Pseudomonas syringae pv. tomato DC3000 Encodes Two Proteins Secreted by the Type III (Hrp) Protein Secretion System: HopB1 and HrpK, a Putative Type III Translocator

2005

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“…Genes responsible for the biosynthesis of the rhizobial T3SS are organized in the tts region, which also contains genes that encode secreted proteins collectively known as nodulation outer proteins (Nops). To date, eight secreted proteins have been identified: NopA, NopB, NopC, NopD, NopL, NopM, NopP and NopX (Ausmees et al, 2004;Bartsev et al, 2003;Deakin et al, 2005;Krishnan, 2002;Lorio et al, 2004;Rodrigues et al, 2007;Saad et al, 2005;Skorpil et al, 2005). Recently, eight proteins have been found to be type III-secreted in B. japonicum; one of them, GunA2, has been identified as an endoglucanase (Süss et al, 2006).…”

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confidence: 99%

Regulation and symbiotic significance of nodulation outer proteins secretion in Sinorhizobium fredii HH103

et al. 2008

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In this work we show that the Sinorhizobium fredii HH103 ttsI gene is essential for the expression of the tts genes and secretion of nodulation outer proteins (Nops). Moreover, we demonstrate for the first time, to our knowledge, that the nod box preceding ttsI is necessary for Nops secretion. TtsI is responsible for the transcriptional activation of nopX, nopA, rhcJ and rhcQ. We confirm that the S. fredii HH103 ttsI gene is activated by NodD1 and repressed by NolR. In contrast, NodD2 is not involved in the regulation of ttsI expression. Despite the dependence of expression of both ttsI and nodA on NodD1 and flavonoids, clear differences in the capacity of some flavonoids to activate these genes were found. The expression of the ttsI and nodA genes was also sensitive to differences in the pH of the media. Secretion of Nops in the ttsI mutant could not be complemented with a DNA fragment containing the ttsI gene and its nod box, but it was restored when a plasmid harbouring the ttsI, rhcC2 and y4xK genes was transferred to the mutant strain. The symbiotic effect of Nops secretion was host-dependent but independent of the type of nodule formed by the host legume. Nops are beneficial in the symbiosis with Glycine max and Glycyrrhiza uralensis, and detrimental in the case of the tropical legume Erythrina variegata.

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“…HrpF displays similarity to NolX (recently renamed NopX [63]), a TTSS-secreted protein of S. fredii and Rhizobium sp. strain NGR234 (34,42,51). However, the possible role of NopX as a translocator has not yet been studied.…”

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PopF1 and PopF2, Two Proteins Secreted by the Type III Protein Secretion System of Ralstonia solanacearum , Are Translocators Belonging to the HrpF/NopX Family

et al. 2006

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Ralstonia solanacearum GMI1000 is a gram-negative plant pathogen which contains an hrp gene cluster which codes for a type III protein secretion system (TTSS). We identified two novel Hrp-secreted proteins, called PopF1 and PopF2, which display similarity to one another and to putative TTSS translocators, HrpF and NopX, from Xanthomonas spp. and rhizobia, respectively. They also show similarities with TTSS translocators of the YopB family from animal-pathogenic bacteria. Both popF1 and popF2 belong to the HrpB regulon and are required for the interaction with plants, but PopF1 seems to play a more important role in virulence and hypersensitive response (HR) elicitation than PopF2 under our experimental conditions. PopF1 and PopF2 are not necessary for the secretion of effector proteins, but they are required for the translocation of AvrA avirulence protein into tobacco cells. We conclude that PopF1 and PopF2 are type III translocators belonging to the HrpF/NopX family. The hrpF gene of Xanthomonas campestris pv. campestris partially restored HRinducing ability to popF1 popF2 mutants of R. solanacearum, suggesting that translocators of R. solanacearum and Xanthomonas are functionally conserved. Finally, R. solanacearum strain UW551, which does not belong to the same phylotype as GMI1000, also possesses two putative translocator proteins. However, although one of these proteins is clearly related to PopF1 and PopF2, the other seems to be different and related to NopX proteins, thus showing that translocators might be variable in R. solanacearum.

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NolX of Sinorhizobium fredii USDA257, a Type III-Secreted Protein Involved in Host Range Determination, Is Localized in the Infection Threads of Cowpea ( Vigna unguiculata [L.] Walp) and Soybean ( Glycine max [L.] Merr.) Nodules

Cited by 54 publications

References 34 publications

The hrpK Operon of Pseudomonas syringae pv. tomato DC3000 Encodes Two Proteins Secreted by the Type III (Hrp) Protein Secretion System: HopB1 and HrpK, a Putative Type III Translocator

The hrpK Operon of Pseudomonas syringae pv. tomato DC3000 Encodes Two Proteins Secreted by the Type III (Hrp) Protein Secretion System: HopB1 and HrpK, a Putative Type III Translocator

Regulation and symbiotic significance of nodulation outer proteins secretion in Sinorhizobium fredii HH103

PopF1 and PopF2, Two Proteins Secreted by the Type III Protein Secretion System of Ralstonia solanacearum , Are Translocators Belonging to the HrpF/NopX Family

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