Brown planthopper (BPH), Nilaparvata lugens St?l, 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.
水稻是世界上最重要的糧食作物之一，褐飛虱是隨水稻而生專門取食水稻的害蟲。在自然界中，為了抵抗褐飛虱取食，水稻進(jìn)化出了抗蟲性；而褐飛虱則形成能克服水稻抗性的生物型群體，水稻反過來又產(chǎn)生出新的抗性來對(duì)抗褐飛虱。如此周而復(fù)始，二者形成協(xié)同進(jìn)化關(guān)系，使得在傳統(tǒng)農(nóng)業(yè)中褐飛虱不會(huì)對(duì)水稻造成重大危害。
本文克隆了水稻第12染色體長(zhǎng)臂上的一個(gè)抗褐飛虱基因BPH9，并發(fā)現(xiàn)此前定位在該染色體區(qū)段上的7個(gè)抗褐飛虱基因均是BPH9的等位基因。正是由于BPH9的等位變異使得水稻可以抵抗褐飛虱不同生物型群體，因此揭示了抗蟲基因等位變異是水稻應(yīng)對(duì)褐飛虱種群變異的重要策略。該論文還分析了BPH9基因在水稻群體中分化和演化特點(diǎn)。基于BPH9等位型在野生稻和栽培稻中的分布，發(fā)現(xiàn)人類抗蟲育種實(shí)踐重演了自然選擇進(jìn)化過程，即等位型1是在野生稻中最早出現(xiàn)的抗蟲等位型，也是第一個(gè)應(yīng)用于現(xiàn)代抗蟲育種的等位型，隨后是等位型2。等位型7和等位型9則是新近發(fā)掘的等位型，對(duì)三種生物型的褐飛虱均表現(xiàn)為抗性，在今后的水稻抗蟲育種中具有重要利用價(jià)值。論文發(fā)表前，抗褐飛虱基因BPH9已經(jīng)獲得發(fā)明專利授權(quán)，利用BPH9培育的抗蟲新種質(zhì)已在全國(guó)各育種單位廣泛應(yīng)用。