Incompatible Interactions Between Crucifers andXanthomonas campestrisInvolve a Vascular Hypersensitive Response: Role of thehrpXLocus

Kamoun, Sophien; Kamdar, H. V.; Tola, Elisabetta; Kado, Clarence I.

doi:10.1094/mpmi-5-022

Cited by 95 publications

(74 citation statements)

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“…This would allow the bacterium to access nutrients -as it is known that companion cells transport sugars and amino acids into and out of the sieve elements -or use the T3SS to suppress plant defences at this location. In support of the latter is the observation that a functional HrpX, the HrpB orthologue in X. campestris, is required to inhibit a hypersensitive response at the vascular level in crucifers (Kamoun et al, 1992). Similarly, degeneration of cells flanking the protoxylem has also been observed in tomato plants challenged with an hrpB-mutated R. solanacearum strain (Vasse et al, 2000).…”

Section: Discussionmentioning

confidence: 87%

A luminescent reporter evidences active expression of Ralstonia solanacearum type III secretion system genes throughout plant infection

et al. 2012

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Although much is known about the signals that trigger transcription of virulence genes in plant pathogens, their prevalence and timing during infection are still unknown. In this work, we address these questions by analysing expression of the main pathogenicity determinants in the bacterial pathogen Ralstonia solanacearum. We set up a quantitative, non-invasive luminescent reporter to monitor in planta transcription from single promoters in the bacterial chromosome. We show that the new reporter provides a real-time measure of promoter output in vivo -either after re-isolation of pathogens from infected plants or directly in situ -and confirm that the promoter controlling exopolysaccharide (EPS) synthesis is active in bacteria growing in the xylem. We also provide evidence that hrpB, the master regulator of type III secretion system (T3SS) genes, is transcribed in symptomatic plants. Quantitative RT-PCR assays demonstrate that hrpB and type III effector transcripts are abundant at late stages of plant infection, suggesting that their function is required throughout disease. Our results challenge the widespread view in R. solanacearum pathogenicity that the T3SS, and thus injection of effector proteins, is only active to manipulate plant defences at the first stages of infection, and that its expression is turned down when bacteria reach high cell densities and EPS synthesis starts. INTRODUCTIONDuring infection, pathogens deploy a tightly regulated genetic program to overcome the host natural defences and mobilize metabolic resources to their benefit (Grant et al., 2006;Mudgett, 2005). This program, leading to the appearance of disease symptoms, is still unknown for most pathosystems, although many genes involved in infection have been described and their expression measured in culture.Ralstonia solanacearum is an excellent model to study gene regulation, as the pathways controlling its pathogenicity genes have been characterized in detail (Schell, 2000). This soil-borne b-proteobacterium is the causative agent of bacterial wilt on a wide range of plant hosts, including economically important species such as tomato, potato, peanut and eggplant (Hayward, 2000). R. solanacearum invades plants through root wounds and rapidly colonises the xylem vessels, where it multiplies extensively and produces large amounts of exopolysaccharide (EPS) (Kao et al., 1992;Vasse et al., 2000). EPS accumulation in the vascular system and the ensuing collapse of the water flow causes the wilting symptoms and eventually plant death.Coevolution with its various hosts has led to the emergence of a large number of virulence-promoting genes in R. solanacearum (Poueymiro & Genin, 2009;Schell, 2000). The main pathogenicity determinant is the type III secretion system (T3SS), encoded by the hrp cluster and conserved in most Gram-negative pathogens (van Gijsegem et al., 1995). The T3SS translocates some 70 bacterial effector proteins directly into the host cells (Occhialini et al., 2005;Poueymiro & Genin, 2009) to suppress host defence respons...

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Section: Discussionmentioning

confidence: 87%

A luminescent reporter evidences active expression of Ralstonia solanacearum type III secretion system genes throughout plant infection

et al. 2012

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“…Mutant strains defective in flagella organization or motility were constructed by marker-integration mutagenesis (Kamoun et al, 1992a). Using the sequence information shown in Fig.…”

Section: Generation Of Flagella-defective Mutantsmentioning

confidence: 99%

**Characterization of flagella genes of Agrobacterium tumefaciens, and the effect of a bald strain on virulence**

Chesnokova

Coutinho

Khan

et al. 1997

Molecular Microbiology

104

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Because the 54 promoter is associated with genes regulated by physiological changes in various bacteria, the flaC gene might be similarly regulated in response to A. tumefaciens responding to host plant stimuli. Virulence studies showed that the bald strain was consistently reduced in virulence below that of the parental wild-type strain by at least 38%. The difference is statistically significant and suggests that the flagella may play a role in facilitating virulence.

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“…Nine races of Xcc have been identified to date from pathogenicity tests based on the interaction between differential cultivars and races [5][6][7][8][9]. [7] reported that the appearance of race 1 and 4 was predominant worldwide and other races, 2, 3, 5 and 6, were rare.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Positions of QTLs Conferring Resistance to Xanthomonas campestris pv. campestris in Brassica oleracea

Tonu¹,

Doullah²,

Shimizu³

et al. 2013

AJPS

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Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) is possibly the most important disease of Brassica worldwide. To compare chromosomal positions of Xcc resistance loci in Brassica oleracea between the present and published studies and to develop marker assisted selection (MAS) to resistance against Xcc race 1, we constructed a B. oleracea map, including pW, pX and BoCL markers that were closely linked to previously reported Xcc resistance QTLs. We also analyzed Xcc resistance QTLs by improving our previously reported map derived from the cross of a susceptible double-haploid line (GC P09) with a resistant double-haploid line (Reiho P01). In the nine linkage groups obtained (C1-C9), the major QTL, XccBo(Reiho)2, was derived from Reiho with a maximum LOD score (7.7) in C8. The QTL (LOD 4.4) located in C9, XccBo(GC)1 was derived from the susceptible GC. The other QTL (LOD 4.4), XccBo(Reiho)1, was found in C5. Based on common markers, it was possible to compare our finding Xcc resistance QTLs with the B. oleraceaXcc loci reported by previous authors; XccBo(Reiho)1 and XccBo(GC)1 may be identical to the Xcc resistance QTLs reported previously or a different member contained in the same resistance gene cluster. Our map includes public SSR markers linked to Xcc resistance genes that will promote pyramiding Xcc resistance genes in B. oleracea. The present study will also contribute to a better understanding of genetic control of Xcc resistance.

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Incompatible Interactions Between Crucifers andXanthomonas campestrisInvolve a Vascular Hypersensitive Response: Role of thehrpXLocus

Cited by 95 publications

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A luminescent reporter evidences active expression of Ralstonia solanacearum type III secretion system genes throughout plant infection

A luminescent reporter evidences active expression of Ralstonia solanacearum type III secretion system genes throughout plant infection

**Characterization of flagella genes of Agrobacterium tumefaciens, and the effect of a bald strain on virulence**

Comparison of Positions of QTLs Conferring Resistance to <i>Xanthomonas campestris</i> pv. <i>campestris</i> in <i>Brassica oleracea</i>

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Incompatible Interactions Between Crucifers andXanthomonas campestrisInvolve a Vascular Hypersensitive Response: Role of thehrpXLocus

Cited by 95 publications

References 0 publications

A luminescent reporter evidences active expression of Ralstonia solanacearum type III secretion system genes throughout plant infection

A luminescent reporter evidences active expression of Ralstonia solanacearum type III secretion system genes throughout plant infection

Characterization of flagella genes of Agrobacterium tumefaciens, and the effect of a bald strain on virulence

Comparison of Positions of QTLs Conferring Resistance to &lt;i&gt;Xanthomonas campestris&lt;/i&gt; pv. &lt;i&gt;campestris&lt;/i&gt; in &lt;i&gt;Brassica oleracea&lt;/i&gt;

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**Characterization of flagella genes of Agrobacterium tumefaciens, and the effect of a bald strain on virulence**

Comparison of Positions of QTLs Conferring Resistance to <i>Xanthomonas campestris</i> pv. <i>campestris</i> in <i>Brassica oleracea</i>