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Author: Leonor Martins
Internal reviewer: Jaime Cubero
Expert reviewer:
Class: XopF
Family: XopF1, XopF2, XopF3
Prototype: XopF (Xanthomonas euvesicatoria aka Xanthomonas campestris pv. vesicatoria; strain 85-10)
RefSeq ID: XopF1 WP_011346095.1 (670 aa), XopF2 AAV74205.1 (667 aa)
3D structure: Unknown
XopF1 and XopF2 were identified by a genetic screen using AvrBs2 as a reporter protein (Roden et al., 2004).
Xcv XopF1::AvrBs2 proteins triggered avrBs2-dependent hypersensitive response (HR) during infection in Bs2-resistant pepper leaves. Fragments of the xopF1 gene are located within the hrp cluster of many Xanthomonas spp., although a complete ORF is present only in the Xcv and Xanthomonas oryzae pv. oryzae (Xoo) hrp clusters (Roden et al., 2004). XopF1 belongs to the class A effectors (Büttner et al., 2006). XopF2 is 59% identical and 68% similar to XopF1 when analysed with the pairwise BLAST algorithm. xopF2 appears to be co-transcribed with ORF1. ORF1 analysis revealed characteristics shared by type III chaperones, and is suggested to encode an Xcv chaperone (Roden et al., 2004).
RT-PCR analysis revealed xopF1 is regulated by hrpG and hrpX and that xopF1, hpaD, hpaI belong to the same operon. Upstream there is a PIP box which provides binding site for HrpX (Büttner et al., 2007).
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), including xopF, were significantly reduced in the Xanthomonas oryzae pv. oryzae ΔxrvC mutant compared with those in the wild-type strain PXO99A (Liu et al., 2016).
XopF2 localizes in the Golgi apparatus, while XopF1 has been found in cytoplasm (Popov et al., 2016) and plasma membrane (Mondal et al., 2016). XopF1 is encoded within hrp region, between hpaB and hrpF, while XopF2 is encoded elsewhere in the bacterial chromosome (Roden et al., 2004; Büttner et al., 2007).
Unknown.
XopF1 secretion and translocation is T3SS-dependent; HpaH, HpaC and T3S chaperone HpaB are required for efficient secretion XopF1 (Büttner et al., 2006, 2007).
Yes (e.g., X. arboricola, X. bromi, X. citri, X. oryzae, X. euvesicatoria, X. translucens, X. vasicola). Since the G+C content of the xopF1 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).
Unknown.
Büttner D, Lorenz C, Weber E, Bonas U (2006). Targeting of two effector protein classes to the type III secretion system by a HpaC- and HpaB-dependent protein complex from Xanthomonas campestris pv. vesicatoria. Mol. Microbiol. 59: 513-527. DOI: 10.1111/j.1365-2958.2005.04924.x
Büttner D, Noël L, Stuttmann J, Bonas U (2007). Characterization of the nonconserved hpaB-hrpF region in the hrp pathogenicity island from Xanthomonas campestris pv. vesicatoria. Mol. Plant Microbe Interact. 20: 1063-1074. DOI: 10.1094/MPMI-20-9-1063
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
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
Mondal K K, Verma G, Manju, Junaid A, Mani C (2016). Rice pathogen Xanthomonas oryzae pv. oryzae employs inducible hrp-dependent XopF type III effector protein for its growth, pathogenicity and for suppression of PTI response to induce blight disease. Eur. J. Plant Pathol. 144: 311-323. DOI: 10.1007/s10658-015-0768-7
Popov G, Fraiture M, Brunner F, Sessa G (2016). Multiple Xanthomonas euvesicatoria type III effectors inhibit flg22-triggered immunity. Mol. Plant Microbe Interact. 29: 651-660. DOI: 10.1094/MPMI-07-16-0137-R
Roden J, Belt B, Ross J, Tachibana T, Vargas J, Mudgett M (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