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Author: Ralf Koebnik
Internal reviewer:
Expert reviewer: WANTED!

Class: XopM
Family: XopM
Prototype: XCV0442 (Xanthomonas euvesicatoria pv. euvesicatoria, ex Xanthomonas campestris pv. vesicatoria; strain 85-10)

RefSeq ID: WP_011346113.1
3D structure: Unknown

Biological function

How discovered?

xopM Xee85-10 was identified as a candidate T3E gene based on the presence of a PIP box in the promoter region and its conservation in other plant pathogens (Schulze et al., 2012). XopM was also discovered as a T3E in Xee 85-10 using a machine-learning approach (Teper et al ., 2016).

(Experimental) evidence for being a T3E

Xanthomonas bacteria containing a translational fusion between XopM and an N-terminally truncated variant of AvrBs3 were shown by imumunodetection with an AvrBs3-specific antibody to secrete the chimeric protein into the culture medium in a T3SS-dependent manner (Schulze et al., 2012).

To test for T3SS-dependent translocation into plant cells, Xee 85-10 expressing the XopM-AvrBs3 chimeric protein was inoculated into leaves of AvrBs3-responsive pepper plants (ECW-30R) and the near-isogenic susceptible pepper line ECW, which lacks the Bs3 resistance gene. Bacteria expressing the XopM1–520-AvrBs3delta2 chimeric protein induced the hypersensitive response (HR) in ECW-30R, but not in ECW. As expected, no HR induction was observed in plants infected with a strain mutated in the T3SS gene hrcV (Schulze et al., 2012).


Expression of xopM Xee85-10 was shown to be controlled by both HrpG and HrpX (Schulze et al., 2012).


The Xee 85-10 strain deleted in xopM showed no difference in the induction of disease symptoms on pepper plants compared to the wild-type strain 85-10 (Schulze et al., 2012).

To identify defense reactions, mediated by xopM, leaves of pepper ECW, Nicotiana benthamiana and N. tabacum, the latter two being nonhost plants of Xee 85-10, were inoculated with Agrobacterium strains mediating the in planta expression of the effector gene fused to GFP. In this assay, XopM elicited a cell death reaction in N. benthamiana at 3–5 dpi (Schulze et al., 2012).



Enzymatic function


Interaction partners



In xanthomonads

xopM is typically encoded next to the hrp gene cluster and considered a core effector gene in several Xanthomonas species (Jiang et al., 2009; Merda et al., 2017; Pesce et al., 2017).

In other plant pathogens/symbionts

Yes (Acidovorax, Pseudomonas, and Ralstonia) (Schulze et al., 2012; Pesce et al., 2017)


Jiang W, Jiang BL, Xu RQ, Huang JD, Wei HY, Jiang GF, Cen WJ, Liu J, Ge YY, Li GH, Su LL, Hang XH, Tang DJ, Lu GT, Feng JX, He YQ, Tang JL (2009). Identification of six type III effector genes with the PIP box in Xanthomonas campestris pv. campestris and five of them contribute individually to full pathogenicity. Mol. Plant Microbe Interact. 22: 1401-1411. DOI: 10.1094/MPMI-22-11-1401

Pesce C, Jacobs JM, Berthelot E, Perret M, Vancheva T, Bragard C, Koebnik R (2017). Comparative genomics identifies a novel conserved protein, HpaT, in proteobacterial type III secretion systems that do not possess the putative translocon protein HrpF. Front. Microbiol. 8: 1177. DOI: 10.3389/fmicb.2017.01177

Merda D, Briand M, Bosis E, Rousseau C, Portier P, Barret M, Jacques MA, Fischer-Le Saux M (2017). Ancestral acquisitions, gene flow and multiple evolutionary trajectories of the type three secretion system and effectors in Xanthomonas plant pathogens. Mol. Ecol. 26: 5939-5952. DOI: 10.1111/mec.14343

Schulze S, Kay S, Büttner D, Egler M, Eschen-Lippold L, Hause G, Krüger A, Lee J, Müller O, Scheel D, Szczesny R, Thieme F, Bonas U (2012). Analysis of new type III effectors from Xanthomonas uncovers XopB and XopS as suppressors of plant immunity. New Phytol. 195: 894-911. DOI: 10.1111/j.1469-8137.2012.04210.x

Teper D, Burstein D, Salomon D, Gershovitz M, Pupko T, Sessa G (2016). Identification of novel Xanthomonas euvesicatoria type III effector proteins by a machine-learning approach. Mol. Plant Pathol. 17: 398-411. DOI: 10.1111/mpp.12288

bacteria/t3e/xopm.txt · Last modified: 2023/12/07 10:57 by rkoebnik