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

文献类型： 外文期刊

第一作者： Wang, Congying

作者： Wang, Congying;Chen, Shen;Feng, Aiqing;Su, Jing;Wang, Wenjuan;Feng, Jinqi;Chen, Bing;Zhang, Meiying;Yang, Jianyuan;Zeng, Liexian;Zhu, Xiaoyuan

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关键词： Xa7; Map-based cloning; Rice bacterial blight; Durable resistance; TALE; Xanthomonas; Executor gene; Orphan gene; Gene origin; Genomic structural variation

期刊名称：RICE （ 影响因子：4.783； 五年影响因子：5.23 ）

ISSN： 1939-8425

年卷期： 2021 年 14 卷 1 期

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收录情况： SCI

摘要： 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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