Comparative Transcriptome Analysis of Two Rice Varieties in Response to Rice Stripe Virus and Small Brown Planthoppers during Early Interaction

Rice stripe, a virus disease, transmitted by a small brown planthopper (SBPH), has greatly reduced production of japonica rice in East Asia, especially in China. Although we have made great progress in mapping resistance genes, little is known about the mechanism of resistance.By de novo transcriptome assembling, we gained sufficient transcript data to analyze changes in gene expression of early interaction in response to SBPH and RSV infection in rice. Respectively 648 and 937 DEGs were detected from the disease-resistant (Liaonong 979) and the susceptible (Fengjin) varieties, most of which were up-regulated. We found 37 genes related to insect resistance, which mainly included genes for jasmonate-induced protein, TIFY protein, lipoxygenase, as well as trypsin inhibitor genes and transcription factor genes. In the interaction process between RSV and rice, 87 genes were thought to be related to RSV resistance; these primarily included 12 peroxidase biosynthesis genes, 12 LRR receptor-like protein kinase genes, 6 genes coding pathogenesis-related proteins, 4 glycine-rich cell wall structural protein genes, 2 xyloglucan hydrolase genes and a cellulose synthase. The results indicate that the rice-pathogen interaction happened both in disease-resistant and susceptible varieties, and some genes related to JA biosynthesis played key roles in the interaction between SBPHs and rice. When rice was infected by RSV a hypersensitive reaction (HR) in the disease-resistant variety was suppressed, which resulted from an increase in peroxidase expression and down-regulation of LRR receptor-like protein kinase and pathogenesis-related proteins, while, the changes of peroxidase biosynthesis, glycine-rich cell wall structural protein, cellulose synthase and xyloglucan endotransglucosylase/hydrolase could lead to the strengthening of physical barriers of rice, which may be an important resistance mechanism to RSV in rice.

水稻条纹叶枯病（Rice stripe）是一种由灰飞虱（small brown planthopper, SBPH）传播的病毒病害，已在东亚地区大幅降低粳稻产量，在中国尤为严重。尽管我们在抗病基因定位方面已取得显著进展，但对其抗病机制仍知之甚少。本研究通过从头转录组组装（de novo transcriptome assembling）获取了足量转录组数据，用以分析水稻在响应灰飞虱与水稻条纹病毒（Rice stripe virus, RSV）侵染的早期互作过程中的基因表达变化。分别从抗病品种辽农979与感病品种丰锦中检测到648个和937个差异表达基因（differentially expressed genes, DEGs），其中绝大多数呈上调表达。本研究共发现37个与抗虫相关的基因，主要包括茉莉酸诱导蛋白基因、TIFY蛋白基因、脂氧合酶（lipoxygenase）基因，以及胰蛋白酶抑制剂基因与转录因子（transcription factor）基因。在水稻与RSV互作过程中，共有87个基因被认为与RSV抗病性相关；这些基因主要包含12个过氧化物酶（peroxidase）生物合成基因、12个富含亮氨酸重复序列受体样蛋白激酶（LRR receptor-like protein kinase）基因、6个病程相关蛋白（pathogenesis-related proteins, PR）编码基因、4个甘氨酸富集型细胞壁结构蛋白基因、2个木葡聚糖水解酶（xyloglucan hydrolase）基因以及1个纤维素合酶基因。研究结果表明，抗病与感病品种中均发生了水稻-病原物互作，且部分与茉莉酸（jasmonate, JA）生物合成相关的基因在灰飞虱与水稻的互作中发挥关键作用。当水稻被RSV侵染时，抗病品种的过敏反应（hypersensitive reaction, HR）受到抑制，这源于过氧化物酶表达上调，以及富含亮氨酸重复序列受体样蛋白激酶与病程相关蛋白的下调表达；而与此同时，过氧化物酶生物合成、甘氨酸富集型细胞壁结构蛋白、纤维素合酶以及木葡聚糖内转糖苷酶/水解酶（xyloglucan endotransglucosylase/hydrolase）的变化可增强水稻的物理屏障，这或许是水稻抗RSV的重要抗病机制之一。