Background

Rice is staple food for over two billion people. Planthoppers like BPH and WBPH occur together in most of rice growing regions across Asia and cause extensive yield loss by feeding and transmission of disease-causing viruses. Chemical control of the pest is expensive and ecologically disastrous; breeding resistant varieties is an acceptable option. But most of such efforts are focused on BPH with an assumption that these varieties will also be effective against WBPH. No critical studies are available to understand rice resistance, common or otherwise, against these two planthoppers.

Results

Our studies aimed to understand the defense mechanisms in rice line RP2068 against BPH and WBPH through RNA sequencing analysis of a RIL line TR3RR derived from the cross TN1 (susceptible) and RP2068 (resistant) after infestation with BPH or WBPH. Results revealed higher number of differentially expressed genes (DEGs) in BPH infested plants than in WBPH infested plants when compared with the uninfested plants. These DEGs could be grouped into UPUP, DNDN, UPDN and DNUP groups based on whether the DEGs were up (UP) or down (DN) regulated against BPH and WBPH, respectively. Gene ontology analysis, specially of members of the last two groups, revealed differences in plant response to the two planthoppers. Abundance of miRNAs and detection of their target genes also indicated that separate sets of genes were suppressed or induced against BPH and WBPH. These results were validated through the analysis of expression of 27 genes through semi-quantitative and quantitative real-time RT-PCR using a set of five RILs that were genetically identical but with different reaction against the two planthoppers. Coupled with data obtained through pathway analysis involving these 27 genes, expression studies revealed common and differential response of rice RP2068 against BPH and WBPH. Trehalose biosynthesis, proline transport, methylation were key pathways commonly upregulated; glucosinolate biosynthesis, response to oxidative stress, proteolysis, cytokinesis pathways were commonly down regulated; photosynthesis, regulation of transcription, expression and transport of peptides and defense related pathways were exclusively upregulated against WBPH; MYB transcription factor mediated defense induction was exclusive to BPH.

Conclusion

Rice defense against the two sympatric planthoppers: BPH and WBPH has distinct features in RP2068. Hence, a conscious combination of resistance to these two pests is essential for effective field management.

中文翻译：

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RNA测序揭示差异表达的水稻基因，其功能与RP2068和TN1杂交产生的RIL中对BPH和WBPH的防御相关

背景

大米是超过20亿人的主食。BPH和WBPH等飞虱在亚洲大多数稻米种植地区同时发生，并通过致病病毒的喂养和传播造成大量的产量损失。化学控制害虫是昂贵的，并且在生态上是灾难性的。育种抗性品种是可以接受的选择。但是，大多数此类努力都集中在BPH上，并假设这些变种也将对WBPH有效。没有关键的研究可以了解水稻对这两种飞虱的抗性，无论是普通的还是其他的。

结果

我们的研究旨在通过对BPH或WBPH侵染后源自交叉TN1（易感）和RP2068（抗性）的RIL系TR3RR进行RNA测序分析，了解水稻RP2068对BPH和WBPH的防御机制。结果表明，与未侵染植物相比，BPH侵染植物中差异表达基因（DEGs）的数量高于WBPH侵染植物中的差异表达基因（DEG）的数量。根据DEG分别针对BPH和WBPH进行上调（UP）还是下调（DN），可以将这些DEG分为UPUP，DNDN，UPDN和DNUP组。基因本体分析，特别是最后两组的成员，揭示了植物对两种飞虱反应的差异。miRNA的丰富性及其靶基因的检测还表明，针对BPH和WBPH的不同基因集受到抑制或诱导。这些结果通过使用一组五个RIL的半定量和实时定量RT-PCR分析27个基因的表达而得到验证，这五个RIL的基因相同，但对两个飞虱的反应却不同。结合通过涉及这27个基因的途径分析获得的数据，表达研究揭示了水稻RP2068对BPH和WBPH的共同和差异反应。海藻糖的生物合成，脯氨酸转运，甲基化是通常被上调的关键途径。芥子油苷的生物合成，对氧化应激的反应，蛋白水解，胞质分裂途径通常被下调；光合作用，转录的调节，肽的表达和运输以及防御相关的途径被专门针对WBPH上调。

结论

水稻对两种同胞飞虱的防御：BPH和WBPH在RP2068中具有独特的功能。因此，对这两种有害生物的有意识抗药性组合对于有效的田间管理至关重要。