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--- bacteria:t3e:xopl [2025/07/04 22:21] – jfpothier
+++ bacteria:t3e:xopl [2025/11/05 16:24] (current) – jfpothier
@@ Line 3: / Line 3: @@
 Author: [[https://www.researchgate.net/profile/Joana_Vicente2|Joana G. Vicente]]\\
 Internal reviewer: [[https://www.researchgate.net/profile/Joel_Pothier2|Joël F. Pothier]]\\
-Expert reviewer: [[https://www.researchgate.net/profile/Jessica-Erickson-9|Jessica L. Erickson]]
+Expert reviewer: [[https://www.researchgate.net/profile/Jessica-Erickson-9|Jessica L. Erickson]]\\
 Class: XopL\\
@@ Line 12: / Line 12: @@
 Examples of other sequences: XopL<sub>Xcc306</sub> [[https://www.ncbi.nlm.nih.gov/protein/21109412|21109412]] (//X. citri// pv. //citri//); XopL<sub>Xcc8004</sub> [[https://www.ncbi.nlm.nih.gov/protein/66575899|66575899]] (//X. campestris// pv. //campestris//)\\
 D structure: [[https://www.rcsb.org/structure/4FC9|4FC9]], [[https://www.rcsb.org/structure/4FCG|4FCG]] (Singer //et al//., 2013). Full-length XopL<sub>Xcv85-10</sub> did not crystallize but fragments XopL[aa 144–450] and XopL[aa 474–660] yielded crystals (Singer //et al//., 2013). The crystal structure of the N-terminal region of XopL showed the presence of a leucine-rich repeat (LRR) domain, that might serve as a protein-protein interaction module for ubiquitination target recognition (Singer //et al//., 2013). The protein represents a new class of E3 ubiquitin ligases.
 ===== Biological function =====
 === How discovered? ===
-XopL was first identified in //X. campestris// pv. //campestris// (//Xcc//) strain 8004 as a candidate T3E due to the presence of a plant-inducible promoter (PIP) box upstream of the CDS, //XC_4273// (Jiang //et al.//, 2009). The CDS //XC_4273//, re-called XopXccLR (LR = leucine-rich repeat) or XopL<sub>Xcc</sub> for the purposes of this article, in //Xcc// 8004 was suggested to be a T3E as it harboured a N-terminal region possessing a translocation signal that was able to target proteins into plant cells (Jiang //et al.//, 2009). It was also shown to be required for //Xcc// proliferation in hosts plant (Jiang //et al.//, 2009). It was only a few years later that the analysis of the genome sequence of //X.// //campestris// pv. //vesicatoria// (//Xcv//) strain 85-10 (synonymous with //X. euvesicatoria// 85-10; //Xe// 85-10) led to the identification of XCV3220 (//xopL<sub>Xe</sub>//) as a new T3E candidate gene and to its more complete characterization (Singer //et al//., 2013). XopL<sub>Xe</sub> was shown to have E3 ubiquitin ligase activity, conferred by a ligase domain with a novel fold (XL-box), capable of interacting with the plant host ubiquitination cascade (Singer //et al.//, 2023).
+XopL was first identified in //X. campestris// pv. //campestris// (//Xcc//) strain 8004 as a candidate T3E due to the presence of a plant-inducible promoter (PIP) box upstream of the CDS, //XC_4273// (Jiang //et al.//, 2009). The CDS //XC_4273//, re-called XopXccLR (LR = leucine-rich repeat) or XopL<sub>Xcc</sub> for the purposes of this article, in //Xcc// 8004 was suggested to be a T3E as it harboured a N-terminal region possessing a translocation signal that was able to target proteins into plant cells (Jiang //et al.//, 2009). It was also shown to be required for //Xcc// proliferation in hosts plant (Jiang //et al.//, 2009). It was only a few years later that the analysis of the genome sequence of //X. campestris// pv. //vesicatoria// (//Xcv//) strain 85-10 (synonymous with //X. euvesicatoria// 85-10; //Xe// 85-10) led to the identification of XCV3220 (//xopL<sub>Xe</sub>//) as a new T3E candidate gene and to its more complete characterization (Singer //et al//., 2013). XopL<sub>Xe</sub> was shown to have E3 ubiquitin ligase activity, conferred by a ligase domain with a novel fold (XL-box), capable of interacting with the plant host ubiquitination cascade (Singer //et al//., 2023).
 === (Experimental) evidence for being a T3E ===
-XopL<sub>Xcc</sub> possesses features that are typical of T3Es: the promoter region of the //xopL<sub>Xcc</sub>// gene contains a perfect plant inducible promoter (PIP) box followed by a 10 box similar sequence (TTCGC-N<sub>15</sub>-TTCGC-N<sub>31</sub>-ACGACA) and an LRR motif characteristic of T3Es in pathogenic bacteria (Yan //et al//., 2019). Using an AvrBs1 reporter fusion, XopL<sub>Xcc</sub> was shown to be translocated into plant cells in a //hrpF-// and //hpaB//-dependent manner (Jiang //et al//., 2009). XopL<sub>Xe</sub> also contains a PIP box (plant inducible promoter) in its promoter (TTCG-N<sub>16</sub>-TTCG; genome position 3669238-261) and co-regulation with the T3S system was confirmed by RT-PCR (Singer //et al.//, 2013). Type III-dependent secretion and translocation was confirmed by //in vitro//secretion and //in vivo//translocation assays (Singer //et al.//, 2013).
+XopL<sub>Xcc</sub> possesses features that are typical of T3Es: the promoter region of the //xopL<sub>Xcc</sub>// gene contains a perfect plant inducible promoter (PIP) box followed by a 10 box similar sequence (TTCGC-N<sub>15</sub>-TTCGC-N<sub>31</sub>-ACGACA) and an LRR motif characteristic of T3Es in pathogenic bacteria (Yan //et al//., 2019). Using an AvrBs1 reporter fusion, XopL<sub>Xcc</sub> was shown to be translocated into plant cells in a //hrpF-// and //hpaB//-dependent manner (Jiang //et al//., 2009). XopL<sub>Xe</sub> also contains a PIP box (plant inducible promoter) in its promoter (TTCG-N<sub>16</sub>-TTCG; genome position 3669238-261) and co-regulation with the T3S system was confirmed by RT-PCR (Singer //et al.//, 2013). Type III-dependent secretion and translocation was confirmed by //in vitro// secretion and //in vivo// translocation assays (Singer //et al//., 2013).
 === Regulation ===
 The //xopL// <sub>Xcc8004</sub> gene contains a PIP box and was shown to be controlled by //hrpG// and //hrpX// (Jiang et al., 2009).
-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 //xopL//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99<sup>A</sup>  (Liu //et al.//, 2016).
+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 //xopL//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99<sup>A</sup>  (Liu //et al//., 2016).
 The expression of //xopL<sub>Xcc</sub>// gene is positively regulated by HrpG/HrpX (Yan //et al//., 2019).
 === Phenotypes ===
-  * XopL<sub>//Xe//</sub>  from //X. euvesicatoria//  85-10 (previously referred to as //X. campestris// pv. //euvesicatoria//; //Xcv//) displays E3 ubiquitin ligase activity (Singer //et al.//, 2013).
+  * XopL<sub>//Xe//</sub> from //X. euvesicatoria// 85-10 (previously referred to as //X. campestris// pv. //euvesicatoria//; //Xcv//) displays E3 ubiquitin ligase activity (Singer //et al//., 2013).
-  * XopL//<sub>Xe</sub>// inhibits expression of the elf18- and flg22-induced defense gene pNHL10 in //Arabidopsis// mesophyll protoplasts independent of E3 ligase function (Singer //et al.//, 2013).
+  * XopL//<sub>Xe</sub>// inhibits expression of the elf18- and flg22-induced defense gene pNHL10 in //Arabidopsis// mesophyll protoplasts independent of E3 ligase function (Singer //et al//., 2013).
   * XopL//<sub>Xe</sub>// suppresses ABA responsive reporter //pRD29b:GUS// and PTI reporter //pFRK1:LUC// in //Arabidopsis// protoplasts (Popov //et al//., 2016).
   * XopL//<sub>Xcc</sub>// interferes with innate immunity (Yan //et al.//, 2019; Huang //et al.//, 2024a) and SA signaling in //Arabidopsis// (Huang //et al.//, 2024).
   * XopL//<sub>Xe</sub>// triggers cell death in //Nicotiana benthamiana// in an E3 ligase dependant manner (Singer //et al.//, 2013). XopL<sub>Xoc</sub> from //X. oryzae// pv. //oryzicola// and XopL<sub>Xoo</sub> from //X. oryzae// pv. //oryzae// PX099A also cause cell death in this model (Ma //et al.//, 2020).
   * Distantly related XopL homolog XopL//<sub>Xcc</sub>// from //Xcc// 8004 failed to cause plant cell death. (Ortmann //et al.//, 2023).
-  * XopL//<sub>Xcc</sub>// is required for full virulence and growth of //Xcc// 8004 in the host plant Chinese radish (Jiang //et al.//, 2009) but not in //Arabidopsis// (Huang et al, 2024). However a mutant for 17 effectors (Δ//17E//) supplemented with //xopL<sub>Xcc</sub> // did grow better than Δ//17E//.
+  * XopL//<sub>Xcc</sub>// is required for full virulence and growth of //Xcc// 8004 in the host plant Chinese radish (Jiang //et al.//, 2009) but not in //Arabidopsis// (Huang //et al.//, 2024). However a mutant for 17 effectors (Δ//17E//) supplemented with //xopL<sub>Xcc</sub>// did grow better than Δ//17E//.
   * XopL//<sub>Xcc</sub>// constitutive overexpression in //Arabidopsis// led to enhanced //Xcc// 8004 virulence and suppressed callose deposition and oxidative burst (Huang //et al.//, 2024).
   * XopL//<sub>Xe</sub>// is required for full virulence of //Xe// 85-10 on tomato (Leong et al., 2022).
-  * XopL//<sub>Xap</sub>// supports //X. axonopodis //pv.// punicae //multiplication in pomegranate by suppressing plant immune responses including plant cell death (Soni //et al//., 2017).
+  * XopL//<sub>Xap</sub>// supports //X. axonopodis// pv. //punicae// multiplication in pomegranate by suppressing plant immune responses including plant cell death (Soni //et al//., 2017).
-  * Transient expression of XopL//<sub>Xe</sub> //, led to a nearly complete elimination of stromules and the relocation of plastids to the nucleus and further characterization revealed that the E3 ligase activity is essential for the two plastid phenotypes (//Erickson et al//., 2018).
+  * Transient expression of XopL//<sub>Xe</sub>//, led to a nearly complete elimination of stromules and the relocation of plastids to the nucleus and further characterization revealed that the E3 ligase activity is essential for the two plastid phenotypes (//Erickson et al//., 2018).
-  * //Xe //85-10 suppresses host autophagy by utilizing type-III effector XopL//<sub>Xe</sub> //. Intriguingly, XopL//<sub>Xe</sub>// is targeted for degradation by defense-related selective autophagy mediated by NBR1/Joka2, revealing a complex antagonistic interplay between XopL and the host autophagy machinery (Leong// et al.//, 2022).
+  * //Xe//85-10 suppresses host autophagy by utilizing type-III effector XopL//<sub>Xe</sub>//. Intriguingly, XopL//<sub>Xe</sub>// is targeted for degradation by defense-related selective autophagy mediated by NBR1/Joka2, revealing a complex antagonistic interplay between XopL and the host autophagy machinery (Leong //et al.//, 2022).
 === Localization ===
 Several localization patterns have been reported for XopL proteins in epidermal cells with some strain dependent differences. XopLs are most often tagged at the C-terminus, with the exception of the studies by Leong //et al//., 2022 and Yan //et al.//, 2019.
-  * __Cytosolic localization__ has been reported for XopL//<sub>Xe</sub>// (Erickson //et al.//, 2018), XopL//<sub>Xcc</sub>// (Yan //et al//., 2019; Ortmann //et al//. 2023), XopL<sub>//Xoo//</sub> (Ma //et al//., 2020; Ortmann //et al//., 2023), and XopL//<sub>Xac</sub> //  from //X. citri// pv. //citri// (Ortmann et al. 2023) in //N. benthamiana//.
+  * __Cytosolic localization__ has been reported for XopL//<sub>Xe</sub>// (Erickson //et al.//, 2018), XopL//<sub>Xcc</sub>// (Yan //et al//., 2019; Ortmann //et al//. 2023), XopL<sub>//Xoo//</sub> (Ma //et al//., 2020; Ortmann //et al//., 2023), and XopL//<sub>Xac</sub>// from //X. citri// pv. //citri// (Ortmann et al. 2023) in //N. benthamiana//.
-  * __Nuclear localization__ was reported for XopL//<sub>Xe</sub>//, XopL<sub>//Xcc//</sub> (Yan //et al.//, 2019; Ortmann //et al//., 2023) and XopL//<sub>Xac</sub>// in //N. benthamiana// (Ortmann et al. 2023), but not for XopL//<sub>Xoo</sub>// in //N. benthamiana// or XopL//<sub>Xap</sub>// from //X. axonopodis// pv. //punicae// in //Arabidopsis// protoplasts (Soni //et al.//, 2017; Ortmann //et al.,// 2023).
+  * __Nuclear localization__ was reported for XopL//<sub>Xe</sub>//, XopL<sub>//Xcc//</sub> (Yan //et al.//, 2019; Ortmann //et al//., 2023) and XopL//<sub>Xac</sub>// in //N. benthamiana// (Ortmann et al. 2023), but not for XopL//<sub>Xoo</sub>// in //N. benthamiana// or XopL//<sub>Xap</sub>// from //X. axonopodis// pv. //punicae// in //Arabidopsis// protoplasts (Soni //et al.//, 2017; Ortmann //et al//., 2023).
   * __Plasma membrane localization__ has been reported for XopL<sub>//Xap//</sub> transiently expressed in //N. benthmiana// (Soni //et al//., 2017) and XopL//<sub>Xcc</sub>// expressed in //Arabidopsis// protoplasts (Huang //et al//. 2024b; Yan //et al.// , 2019) and //N. benthamiana// leaves (Yan //et al//., 2019).
   * __Microtubule localization__ has been reported for XopL//<sub>Xe</sub>//, XopL<sub>//Xoo//</sub> and XopL//<sub>Xac</sub>//, whereas the distantly related XopL//<sub>Xcc</sub>// failed to localize to microtubules in //N. benthamiana// (Ortmann //et al.//, 2023).
   * __Autophagosome localization__ has been reported for XopL//<sub>Xe</sub>// (co-localizes with autophagy markers RFP-ATG8e and SH3P2-RFP; Leong //et al//., 2022).
 === Enzymatic function ===

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