Author: Jakub Pečenka
Internal reviewer: Joana G. Vicente
Expert reviewer:

Class: XopN
Family: XopN
Prototype: XopN (Xanthomonas euvesicatoria pv. euvesicatoria, ex Xanthomonas campestris pv. vesicatoria; strain 85-10)
RefSeq ID: NP_643095 (733 aa)
3D structure: unknown - similar to phosphatase 2a (pr65/A) (Roden et al., 2004).

XopN was identified in a genetic screen, using a Tn5-based transposon construct harboring the coding sequence for the HR-inducing domain of AvrBs2, but devoid of the effectors' T3SS signal, that was randomly inserted into the genome of X. campestris pv. vesicatoria (Xcv) strain 85-10. The XopN::AvrBs2 fusion protein triggered a Bs2-dependent hypersensitive response (HR) in pepper leaves (Roden et al., 2004).

Type III-dependent secretion was confirmed using a calmodulin-dependent adenylate cyclase reporter assay, with a ΔhrpF mutant strain serving as negative control (Roden et al., 2004).

Start codon of xopN was found downstream if a conserved cis-regulatory element, the plant-inducible promoter (PIP) box (TTCGG-N15-TTCTG). xopN is regulated by hrpX and hrpG genes (Cheong et al., 2013; Jiang et al., 2008).

qRT-PCR revealed that transcript levels of 15 out of 18 tested non-TAL effector genes (as well as the regulatory genes hrpG and hrpX) were significantly reduced in the Xanthomonas oryzae pv. oryzae ΔxrvC mutant compared with those in the wild-type strain PXO99^A , but this did not apply to xopN (Liu et al., 2016).

• XopN_Xcv is required for the pathogens' maximal growth in the leaf tissue of tomato and pepper plants (Roden et al., 2004).
• Its homolog XopN _Xcc was found as well to be required for full virulence on Chinese radish (Jiang et al., 2008).
• XopN has been shown to play a role in host defence systems causing the reduction of PAMP-triggered immune responses and reduce the callose deposition in the host tissue. Moreover the deletion of xopN open reading frame (ORF) reduced the Xcv strain virulence exhibited by lower bacterial spot symptoms occurrence (Kim et al., 2009).
• A ΔxopN–ΔxopQ double knock-out mutant in X. phaseoli pv. manihotis (Xpm) was less aggressive in the cassava host plant than its single mutation counterparts. In addition, in planta bacterial growth was reduced at 5 dpi in the double mutant with respect to the wild-type strain CIO151 and individual knock-out strains. The phenotype of the double mutant could be complemented when transforming a plasmid containing xopQ. These results confirmed that xopN and xopQ are functionally redundant in Xpm (Medina et al., 2017).

XopN was localized by confocal microscopy using fluorescent tagged fusion (yellow fluorescent protein [YFP]-XopN). [YFP]-XopN was localized throughout the plant cytoplasm and also associated with the plant plasma membrane (PM) (Kim et al., 2009).

Unknown – Kim et al. (2009) did not confirm that XopN is an enzyme (Kim et al., 2009).

XopN interact with two types of proteins in tomato: Tomato Atypical Receptor-like Kinase1 (TARK1) and four Tomato Fourteen-Three-Three isoforms (TFT1, TFT3, TFT5, and TFT6) (Kim et al., 2009).

Yes (e.g., X. campestris, X. citri, X. oryzae). Since the G+C content of the xopN gene is similar to that of the Xcv hrp gene cluster, it may be a member of a “core” group of Xanthomonas spp. effectors (Roden et al., 2004).

Yes (e.g., Pseudomonas spp.) (Kim et al., 2009).

Cheong H, Kim CY, Jeon JS, Lee BM, Sun Moon J, Hwang I (2013). Xanthomonas oryzae pv. oryzae type III effector XopN targets OsVOZ2 and a putative thiamine synthase as a virulence factor in rice. PloS ONE 8: e73346. DOI: 10.1371/journal.pone.0073346.

Jiang B, He Y, Cen W, Wei H, Jiang G, Jiang W, Hang X, Feng J, Lu G, Tang D, Tang J (2008). The type III secretion effector XopXccN of Xanthomonas campestris pv. campestris is required for full virulence. Res. Microbiol. 159: 216-220. DOI: 10.1016/j.resmic.2007.12.004

Kim JG, Li X, Roden JA, Taylor KW, Aakre CD, Su B, Landone S, Kirik A, Chen Y, Baranage G, Martin BG, Mudgett BM, McLane H (2009). Xanthomonas T3S effector XopN suppresses PAMP-triggered immunity and interacts with a tomato atypical receptor-like kinase and TFT1. Plant Cell 21: 1305-1323. DOI: 10.1105/tpc.108.063123

Kumar R, Soni M, Mondal KK (2016). XopN-T3SS effector of Xanthomonas axonopodis pv. punicae localizes to the plasma membrane and modulates ROS accumulation events during blight pathogenesis in pomegranate. Microbiol. Res. 193: 111-120. DOI: 10.1016/j.micres.2016.10.001 Information needs to be added to the profile.

Li S, Wang Y, Wang S, Fang A, Wang J, Liu L, Zhang K, Mao Y, Sun W (2015). The type III effector AvrBs2 in Xanthomonas oryzae pv. oryzicola suppresses rice immunity and promotes disease development. Mol. Plant Microbe Interact. 28: 869-880. DOI: 10.1094/MPMI-10-14-0314-R Information needs to be added to the profile.

Liu Y, Long J, Shen D, Song C (2016). Xanthomonas oryzae pv. oryzae requires H-NS-family protein XrvC to regulate virulence during rice infection. FEMS Microbiol. Lett. 363: fnw067. DOI: 10.1093/femsle/fnw067

Long J, Song C, Yan F, Zhou J, Zhou H, Yang B (2018). Non-TAL effectors from Xanthomonas oryzae pv. oryzae suppress peptidoglycan-triggered MAPK activation in rice. Front. Plant Sci. 9: 1857. doi: 10.3389/fpls.2018.01857 Information needs to be added to the profile.

Medina CA, Reyes PA, Trujillo CA, Gonzalez JL, Bejarano DA, Montenegro NA, Jacobs JM, Joe A, Restrepo S, Alfano JR, Bernal A (2018). The role of type III effectors from Xanthomonas axonopodis pv. manihotis in virulence and suppression of plant immunity. Mol. Plant Pathol. 19: 593-606. DOI:10.1111/mpp.12545

Roden JA, Belt B, Ross JB, Tachibana T, Vargas J, Mudgett MB (2004). A genetic screen to isolate type III effectors translocated into pepper cells during Xanthomonas infection. Proc. Natl. Acad. Sci. USA 101: 16624-16629. DOI: 10.1073/pnas.0407383101

Sinha D, Gupta MK, Patel HK, Ranjan A, Sonti RV (2013). Cell wall degrading enzyme induced rice innate immune responses are suppressed by the type 3 secretion system effectors XopN, XopQ, XopX and XopZ of Xanthomonas oryzae pv. oryzae. PLoS One 8: e75867. DOI: 10.1371/journal.pone.0075867 Information needs to be added to the profile.

Taylor KW, Kim JG, Su XB, Aakre CD, Roden JA, Adams CM, Mudgett MB (2012). Tomato TFT1 is required for PAMP-triggered immunity and mutations that prevent T3S effector XopN from binding to TFT1 attenuate Xanthomonas virulence. PLoS Pathog. 8: e1002768. DOI: 10.1371/journal.ppat.1002768 Information needs to be added to the profile.