Xa7, a new executor R gene that confers durable and broad-spectrum resistance to bacterial blight disease in rice

Chen, Xifeng; Liu, Pengcheng; Mei, Le; He, Xiaoling; Chen, Long; Liu, Hui; Shen, Shurong; Ji, Zhandong; Zheng, Xiangqun; Zhang, Yuchen; Gao, Zhenyu; Zeng, Dali; Qian, Qian; Ma, Bo

doi:10.1016/j.xplc.2021.100143

Cited by 68 publications

(107 citation statements)

References 63 publications

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“…In addition to our work, two recently published papers also identified the gene encoding a 113-amino-acid protein and validated its function as Xa7 (Chen et al 2021 ; Luo et al 2021 ). The three independent research groups adopted different research strategies to identify the functional Xa7 gene from the large SV region.…”

Section: Discussionsupporting

confidence: 63%

“…It took almost two decades for multiple groups to molecularly clone Xa7 because of a large genomic structural variation (SV) present in this gene mapping region (Chen et al 2021 ; Luo et al 2021 , two papers published during the preparation of this manuscript). Many types of SVs exist in the genome, such as deletions, duplications, copy-number variants, insertions, inversions, and translocations.…”

Section: Discussionmentioning

confidence: 99%

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Xa7, a Small Orphan Gene Harboring Promoter Trap for AvrXa7, Leads to the Durable Resistance to Xanthomonas oryzae Pv. oryzae

Wang

Shen

Feng

et al. 2021

Rice

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Background The rice (Oryza sativa) gene Xa7 has been hypothesized to be a typical executor resistance gene against Xanthomonas oryzae pv. oryzae (Xoo), and has conferred durable resistance in the field for decades. Its identity and the molecular mechanisms underlying this resistance remain elusive. Results Here, we filled in gaps of genome in Xa7 mapping locus via BAC library construction, revealing the presence of a 100-kb non-collinear sequence in the line IRBB7 compared with Nipponbare reference genomes. Complementary transformation with sequentially overlapping subclones of the BACs demonstrated that Xa7 is an orphan gene, encoding a small novel protein distinct from any other resistance proteins reported. A 27-bp effector binding element (EBE) in the Xa7 promoter is essential for AvrXa7-inducing expression model. XA7 is anchored in the endoplasmic reticulum membrane and triggers programmed cell death in rice and tobacco (Nicotiana benthamiana). The Xa7 gene is absent in most cultivars, landraces, and wild rice accessions, but highly homologs of XA7 were identified in Leersia perrieri, the nearest outgroup of the genus Oryza. Conclusions Xa7 acts as a trap to perceive AvrXa7 via EBEAvrXa7 in its promoter, leading to the initiation of resistant reaction. Since EBEAvrXa7 is ubiquitous in promoter of rice susceptible gene SWEET14, the elevated expression of which is conducive to the proliferation of Xoo, that lends a great benefit for the Xoo strains retaining AvrXa7. As a result, varieties harboring Xa7 would show more durable resistance in the field. Xa7 alleles analysis suggests that the discovery of new resistance genes could be extended beyond wild rice, to include wild grasses such as Leersia species.

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Section: Discussionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Xa7, a Small Orphan Gene Harboring Promoter Trap for AvrXa7, Leads to the Durable Resistance to Xanthomonas oryzae Pv. oryzae

Wang

Shen

Feng

et al. 2021

Rice

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“…The genes Lr34 and Lr67 conferring leaf rust resistance in wheat 16,17 , and Xa7, Xa10, Xa23, Xa27, and Bs4 (executor genes) conferring resistance to Xanthomonas sp. in rice and pepper 70,85 , also encode proteins with multiple transmembrane helices. While Lr34 and Lr67 are race-non-specific, executor genes are race-specific.…”

Section: Molecular Function Of the Rph3 Proteinmentioning

confidence: 99%

“…The cell death can be directly prompted by Rph3 protein or indirectly via triggering a defence pathway. Previous work has shown that the executor genes (Xa7, Xa10, Xa23, Bs3, and Bs4C) trigger cell death in both their host (rice or pepper) and N. benthamiana [51][52][53]75,85 . Although Xa27 was reported to triggers cell death only in rice 54 , we found that it does trigger cell death in N. benthamiana when driven by the MasΩ promoter, suggesting that expression level is essential for function.…”

Section: Molecular Function Of the Rph3 Proteinmentioning

confidence: 99%

“…While Lr34 and Lr67 are race-non-specific, executor genes are race-specific. Cloned executor genes encode small proteins (113 -342 aa) that are predicted to contain transmembrane helices [52][53][54]75,85 . The Bs3 protein shows a high level of similarity to flavin monooxygenases 76 , whereas the other executor proteins and RPH3 showed no significant sequence homology to any known resistance protein 53,85 .…”

Section: Molecular Function Of the Rph3 Proteinmentioning

confidence: 99%

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The barley leaf rust resistance gene Rph3 encodes a putative executor protein

Dinh

Singh

Cruz

et al. 2021

Preprint

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Host resistance is considered the most effective means to control plant diseases; however, individually deployed resistance genes are often rapidly overcome by pathogen adaptation. Combining multiple effective resistance genes is the optimal approach to durable resistance, but the lack of functional markers for resistance genes has hampered implementation. Leaf rust, caused by Puccinia hordei, is an economically significant disease of barley, but only a few major Resistance genes to P. hordei (Rph) have been cloned. In this study, gene Rph3 was isolated by positional cloning and confirmed by mutational analysis and transgenic complementation. The Rph3 gene, which originated from wild barley and was first introgressed into cultivated Egyptian germplasm, encodes a unique transmembrane resistance protein that differs from all known plant disease resistance proteins at the amino acid sequence level. Genetic profiles of diverse accessions indicated limited genetic diversity in Rph3 in domesticated germplasm, and higher diversity in wild barley from the Eastern Mediterranean region. Expression profiling using P. hordei isolates with contrasting pathogenicity for the Rph3 host locus showed that the Rph3 gene was expressed only in interactions with Rph3-avirulent isolates, a phenomenon also observed for transcription activator-like effector-dependent genes known as executors conferring resistance to Xanthomonas spp. Like the known transmembrane executors such as Bs3 and Xa7 heterologous expression of Rph3 in N. benthamiana induced a cell death response. Given that Rph3 shares several features with executor genes, it seems likely that P. hordei contains effectors similar to the transcription activator-like effectors that target host executor genes. The isolation of Rph3 highlights convergent evolutionary processes in diverse plant-pathogen interaction systems, where similar defence mechanisms evolved independently in monocots and dicots and provide evidence for executor genes in the Triticeae tribe.

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Action mechanism of the potential biocontrol agent Brevibacillus laterosporus SN19-1 against Xanthomonas oryzae pv. oryzae causing rice bacterial leaf blight

Su,

Wan,

Gao

et al. 2023

Arch Microbiol

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Xa7, a new executor R gene that confers durable and broad-spectrum resistance to bacterial blight disease in rice

Cited by 68 publications

References 63 publications

Xa7, a Small Orphan Gene Harboring Promoter Trap for AvrXa7, Leads to the Durable Resistance to Xanthomonas oryzae Pv. oryzae

Xa7, a Small Orphan Gene Harboring Promoter Trap for AvrXa7, Leads to the Durable Resistance to Xanthomonas oryzae Pv. oryzae

The barley leaf rust resistance gene Rph3 encodes a putative executor protein

Action mechanism of the potential biocontrol agent Brevibacillus laterosporus SN19-1 against Xanthomonas oryzae pv. oryzae causing rice bacterial leaf blight

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