Divya Dhanasekar, Sahu Nihar, Reddy P Sairam, Nair Suresh, Bentur J S
Agri Biotech Foundation, Rajendranagar, Hyderabad, 500030, India.
Present Address: Urbankisaan Farms Pvt Ltd, 4th Floor, 36 urban center, Rd. 36, CBI colony, Jubilee Hills, Hyderabad, 500033, India.
Rice (N Y). 2021 Mar 6;14(1):27. doi: 10.1186/s12284-021-00470-3.
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.
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.
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.
水稻是超过20亿人的主食。褐飞虱（BPH）和白背飞虱（WBPH）等稻飞虱在亚洲大部分水稻种植区同时出现，并通过取食和传播致病病毒导致大量减产。对害虫进行化学防治成本高昂且会造成生态灾难；培育抗性品种是一个可行的选择。但大多数此类努力都集中在褐飞虱上，假定这些品种对白背飞虱也有效。目前尚无关键研究来了解水稻对这两种稻飞虱的抗性，无论是共同抗性还是其他抗性。
我们的研究旨在通过对杂交组合TN1（感虫）和RP2068（抗病）衍生的重组自交系TR3RR在受到褐飞虱或白背飞虱侵染后进行RNA测序分析，来了解水稻品系RP2068对褐飞虱和白背飞虱的防御机制。结果显示，与未受侵染的植株相比，受褐飞虱侵染的植株中差异表达基因（DEG）的数量多于受白背飞虱侵染的植株。根据这些差异表达基因相对于褐飞虱和白背飞虱是上调（UP）还是下调（DN），可将其分为UPUP、DNDN、UPDN和DNUP组。基因本体分析，特别是对后两组成员的分析，揭示了植物对这两种稻飞虱的反应存在差异。miRNA的丰度及其靶基因的检测也表明，针对褐飞虱和白背飞虱，分别有不同的基因被抑制或诱导。通过使用一组五个遗传上相同但对这两种稻飞虱有不同反应的重组自交系，通过半定量和定量实时RT-PCR对27个基因的表达进行分析，验证了这些结果。结合通过涉及这27个基因的通路分析获得的数据，表达研究揭示了水稻RP2068对褐飞虱和白背飞虱的共同和差异反应。海藻糖生物合成、脯氨酸转运、甲基化是共同上调的关键通路；芥子油苷生物合成、对氧化应激的反应、蛋白水解、胞质分裂通路是共同下调的；光合作用、转录调控、肽的表达和转运以及防御相关通路仅在对白背飞虱的反应中上调；MYB转录因子介导的防御诱导仅针对褐飞虱。
在RP2068中，水稻对两种同域分布的稻飞虱：褐飞虱和白背飞虱的防御具有明显特征。因此，有意识地结合对这两种害虫的抗性对于有效的田间管理至关重要。
