Early and specific gene expression triggered by rice resistance gene Pi33 in response to infection by ACE1 avirulent blast fungus

* Our view of genes involved in rice disease resistance is far from complete. Here we used a gene-for-gene relationship corresponding to the interaction between atypical avirulence gene ACE1 from Magnaporthe grisea and rice resistance gene Pi33 to better characterize early rice defence responses induced during such interaction. * Rice genes differentially expressed during early stages of Pi33/ACE1 interaction were identified using DNA chip-based differential hybridization and QRT-PCR survey of the expression of known and putative regulators of disease resistance. * One hundred genes were identified as induced or repressed during rice defence response, 80% of which are novel, including resistance gene analogues. Pi33/ACE1 interaction also triggered the up-regulation of classical PR defence genes and a massive down-regulation of chlorophyll a/b binding genes. Most of these differentially expressed genes were induced or repressed earlier in Pi33/ACE1 interaction than in the gene-for-gene interaction involving Nipponbare resistant cultivar. * Besides demonstrating that an ACE1/Pi33 interaction induced classical and specific expression patterns, this work provides a list of new genes likely to be involved in rice disease resistance.     

水稻穗发育功能基因对穗期氮肥的响应

为探讨氮肥对水稻(Oryza sativa)穗发育的调控作用, 使用高通量测序技术检测氮肥处理前后水稻叶片和幼穗组织中转录组的变化, 并从中筛选到大量差异表达基因。这些基因的功能涉及转录调控、激素代谢和信号转导、物质代谢和转运、胁迫响应、信号转导(受体)和蛋白质降解等。同时对目前克隆得到的穗发育相关基因进行分析, 发现在氮素穗肥的作用下, 部分重要功能基因的表达量发生了明显变化, 其中一些基因还参与调控水稻株高、抽穗期、分蘖和结实率等性状。对这些差异表达基因的功能研究有助于揭示氮素穗肥调控水稻每穗颖花数的分子机制。     

野生稻基因导入系W6023对白叶枯菌的抗谱及转录组差异表达基因分析

水稻白叶枯病是世界性水稻病害,严重威胁水稻的高产和稳产。为了挖掘水稻抗白叶枯病新基因,本研究对一个野生稻基因导入系W6023进行了白叶枯病多菌系接种鉴定及抗谱分析,发现W6023具有广谱抗病性。用强致病菌PXO99诱导W6023及其感病轮回亲本IR24后进行转录组测序,分别获得105644962和91022599条序列,通过GO注释及KEGG富集分析,发现差异表达基因主要富集在次生代谢产物的生物合成、植物激素信号转导及糖代谢途径等方面。在这些差异表达基因中,发现203个基因的表达有显著差异,其中在W6023中上调表达的基因有114个(56.2%),下调表达的有89个(43.8%),而且35.9%分布在第11染色体上。生物信息学分析发现在203个差异表达基因中有16个属于类抗病基因,如NBS-LRR等;14个直接或间接与水稻体内过氧化物的代谢相关,如编码过氧化物酶和金属硫蛋白等;6个编码抗病相关转录因子,如WRKY和NAC等;18个为信号传导相关基因,编码钙调素结合蛋白和萜类合成酶等。随机选择6个W6023中上调表达和3个IR24中上调表达的基因进行RT-PCR及qRT-PCR分析,结果与转录组测序结果一致,表明本研究获得的转录组测序数据结果是可靠的,为以后更深入挖掘W6023的抗病基因及分子机理研究提供了基础。     

Small RNAs and Gene Network in a Durable Disease Resistance Gene—Mediated Defense Responses in Rice

Accumulating data have suggested that small RNAs (sRNAs) have important functions in plant responses to pathogen invasion. However, it is largely unknown whether and how sRNAs are involved in the regulation of rice responses to the invasion of Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial blight, the most devastating bacterial disease of rice worldwide. We performed simultaneous genome-wide analyses of the expression of sRNAs and genes during early defense responses of rice to Xoo mediated by a major disease resistance gene, Xa3/Xa26, which confers durable and race-specific qualitative resistance. A large number of sRNAs and genes showed differential expression in Xa3/Xa26-mediated resistance. These differentially expressed sRNAs include known microRNAs (miRNAs), unreported miRNAs, and small interfering RNAs. The candidate genes, with expression that was negatively correlated with the expression of sRNAs, were identified, indicating that these genes may be regulated by sRNAs in disease resistance in rice. These results provide a new perspective regarding the putative roles of sRNA candidates and their putative target genes in durable disease resistance in rice.