The Type III Effector XopAM from //Xanthomonas//

Author: Ralf Koebnik Expert reviewer: WANTED!

Class: XopAM
Family: XopAM
Prototype: XopXccR1/XC_3160 (Xanthomonas campestris pv. campestris; strain 8004) (Jiang et al., 2009)
GenBank ID: AAY50204.1 (2031 aa)
RefSeq ID: WP_012438997.1 (2049 aa)
3D structure: Unknown

The xopAM gene in X. campstris pv. campestris strain 8004 (Xcc8004) was identified as a candidate T3E due to the presence of a PIP box (TTCGB-N₁₅-TTCGB) within the upstream sequence of its putative translational start codon (Jiang et al., 2009).

Using the HR-inducing domain AvrBs1_59-445 as a type-3 translocation reporter, the N-terminal region of XopAM_Xcc8004 was found to act as a type 3 secretion signal, since the translational reporter fusion triggered a Bs1-specific hypersensitive response in a hrpF- and hpaB-dependent manner (Jiang et al., 2009).

Using a promoterless β-glucuronidase (gus) gene as a transcriptional reporter, xopAM _Xcc8004 was found to be under control of HrpG and HrpX (Jiang et al., 2009).

Mutagenesis of type III effectors in X. campestris pv. campestris (Xcc) confirmed that xopAM functions as a second avirulence gene on plants of the Arabidopsis Col-0 ecotype (Guy et al., 2013).

Deletion of xopAM from Xcc reduced its virulence in cruciferous crops but increased virulence in Arabidopsis (Arabidopsis thaliana) Col-0, indicating that XopAM may perform opposite functions depending on the host species (Xie et al., 2023).

XopAM_Xcc is a lipase that may target the cytomembrane (Xie et al., 2023).

XopAM_Xcc is a lipase that may target the cytomembrane and this activity might be enhanced by its membrane-targeted protein XOPAM-ACTIVATED RESISTANCE 1 (AMAR1) in Arabidopsis Col-0 (Xie et al., 2023).

Binding of XopAM_Xcc to XOPAM-ACTIVATED RESISTANCE 1 (AMAR1) induced an intense hypersensitive response that restricted Xcc proliferation (Xie et al., 2023).

Yes (e.g., Pseudomonas syringae, Ralstonia solanacearum) (Mukaihara et al., 2004; Kvitko et al., 2009)

Guy E, Genissel A, Hajri A, Chabannes M, David P, Carrere S, Lautier M, Roux B, Boureau T, Arlat M, Poussier S, Noël LD (2013). Natural genetic variation of Xanthomonas campestris pv. campestris pathogenicity on Arabidopsis revealed by association and reverse genetics. mBio 4: e00538-12. DOI: 10.1128/mBio.00538-12. Erratum in: MBio (2013) 4: e00978-13.

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

Kvitko BH, Park DH, Velásquez AC, Wei CF, Russell AB, Martin GB, Schneider DJ, Collmer A (2009). Deletions in the repertoire of Pseudomonas syringae pv. tomato DC3000 type III secretion effector genes reveal functional overlap among effectors. PLoS Pathog. 5: e1000388. DOI: 10.1371/journal.ppat.1000388

Mukaihara T, Tamura N, Murata Y, Iwabuchi M (2004). Genetic screening of Hrp type III-related pathogenicity genes controlled by the HrpB transcriptional activator in Ralstonia solanacearum. Mol. Microbiol. 54: 863-875. DOI: 10.1111/j.1365-2958.2004.04328.x

Xie Q, Wei B, Zhan Z, He Q, Wu K, Chen Y, Liu S, He C, Niu X, Li C, Tang C, Tao J (2023). Arabidopsis membrane protein AMAR1 interaction with type III effector XopAM triggers a hypersensitive response. Plant Physiol., in press. DOI: 10.1093/plphys/kiad478