Allelic diversity in an NLR gene BPH9 enables rice to combat planthopper variation.
Friday, 2016/11/04 | 07:42:08
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Zhao Y, Huang J, Wang Z, Jing S, Wang Y, Ouyang Y, Cai B, Xin XF, Liu X, Zhang C, Pan Y, Ma R, Li Q, Jiang W, Zeng Y, Shangguan X, Wang H, Du B, Zhu L, Xu X, Feng YQ, He SY, Chen R, Zhang Q, He G. Proc Natl Acad Sci U S A. 2016 Oct 24. pii: 201614862. [Epub ahead of print] AbstractBrown planthopper (BPH), Nilaparvata lugens Stål, is one of the most devastating insect pests of rice (Oryza sativa L.). Currently, 30 BPH-resistance genes have been genetically defined, most of which are clustered on specific chromosome regions. Here, we describe molecular cloning and characterization of a BPH-resistance gene, BPH9, mapped on the long arm of rice chromosome 12 (12L). BPH9 encodes a rare type of nucleotide-binding and leucine-rich repeat (NLR)-containing protein that localizes to the endomembrane system and causes a cell death phenotype. BPH9 activates salicylic acid- and jasmonic acid-signaling pathways in rice plants and confers both antixenosis and antibiosis to BPH. We further demonstrated that the eight BPH-resistance genes that are clustered on chromosome 12L, including the widely used BPH1, are allelic with each other. To honor the priority in the literature, we thus designated this locus as BPH1/9 These eight genes can be classified into four allelotypes, BPH1/9-1, -2, -7, and -9 These allelotypes confer varying levels of resistance to different biotypes of BPH. The coding region of BPH1/9 shows a high level of diversity in rice germplasm. Homologous fragments of the nucleotide-binding (NB) and leucine-rich repeat (LRR) domains exist, which might have served as a repository for generating allele diversity. Our findings reveal a rice plant strategy for modifying the genetic information to gain the upper hand in the struggle against insect herbivores. Further exploration of natural allelic variation and artificial shuffling within this gene may allow breeding to be tailored to control emerging biotypes of BPH.
See http://www.pnas.org/content/early/2016/10/21/1614862113.long
Fig. 1. Map-based cloning and functional characterization of BPH9. (A) NIL-BPH9 shows a high level of resistance to BPH at the seedling stage. (B) Two-host choice test showing more BPH insects settling on 9311 than on NIL-BPH9 plants (n = 15). (C) Body weight gain and images of BPH insects feeding on NIL-BPH9 and 9311 plants for 2 d. All data are means ± SEM. **P < 0.01 (Student’s t test). (D) Mapping of BPH9 to the interval between the molecular markers RM28486 and RM28438 on chromosome 12L. LOD, logarithm of odds; PEV, phenotypic variance explained by the locus. (E) Delimiting BPH9 to the genomic region flanked by InD2 and RsaI. The numbers below the line indicate the numbers of recombinants between adjacent markers. (F) Identifying and sequencing of the two fosmid clones of Pokkali genomic library to obtain the 68-kb sequence of the BPH9 region and identifying R1 and R2 as candidates for BPH9. (G) BPH-resistance assay of transgenic lines harboring the BPH9-genomic region (15.6 kb). The lines 23p65-14 and 23p24-23 are two independent transgenic lines. (H) BPH resistance assay of transgenic lines harboring the BPH9 cDNA construct. POK1–POK3 are three independent transgenic lines. Kasalath and TN1, susceptible variety. |
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