Studies On The Virulence And Midgut Transcriptome Of Nilaparvata Lugens(St(?)l) Population Reared On Rice Resistant Variety IR56

The brown planthopper(BPH), Nilaparvata lugens(St(?)l)(Hemiptera: Delphacidae), is the important pest of rice in Asia. Through feeding rice and transmit virus, BPH damaged rice plants and caused loss of rice quality and yield each year. Cultivation of resistant rice varieties is one of the most important ways to control the BPH. However with the promotion and planting of resistant varieties, these resistant varieties gradually lost the resistance and a fast change in virulence of BPH made that could produce the new population adapted to resistant varieties. This is the most critical problem in the BPH control management.Insect herbivore midgut, containing various digestive enzymes, detoxifying enzymes and sugar metabolism related enzymes, has been reported to play an important role in plant-herbivore interactions, including in plant defense and herbivore virulence. Based on IR56 population that continuous forced feeding more than 40 generations resistant rice IR56(including Bph3 insect-resistant genes) compared TN1 population that feed on TN1 rice(no insect-resistant genes), we studied the virulence and midgut transcriptome of IR56 population. The main results are as follows:1. Virulence of IR56 population: After over 40 generation continuous stress feeding on IR56 rice, it has initially formed a new virulence population- IR56 population. IR56 population has the strong ability to damage rice, and can grow and reproduce on IR56 to complete the generation and development. We can clear distinguish between IR56 population and TN1 population by the nymphal development, newly emerged adult body weight, honeydew excretion, adult weight gain, adult longevity, number of single female eggs laid and feeding duration time with in 6h.2. Analysis of IR56 population in midgut transcriptome: We sequenced the midgut transcriptomes of TN1 and IR56 population of BPH. In total, 45,587 unigenes generated from the midgut of these populations. 21,368 unigenes were annotated among all unigenes and 22,665 unigenes were obtained coding sequence by sequence alignment and prediction software. Gene ontology annotations indicated that most of the genes related to "metabolism", "cells", "combine" and "transfer" in the midgut. The numbers of genes those expression level lower in IR56 populations were more than of TN1 population in the midgut. These lower genes may relate to the change in virulence that BPH can adapt to IR56 resistant rice varieties.3. Cloning and expression level validation of important differentially expressed genes in midgut transcriptomes: We screened differentially expressed genes relating to digestion, detoxification and sugar metabolism in midgut transcriptomes and successfully cloned 18 important differentially expressed genes of them. From quantitative validation of differentially expressed genes in midgut transcriptomes, we found 13 genes that were differentially expressed in midgut of different populations.Then, through quantitative validation of these genes in midgut and female after exchanging host, we found that there were the expression level of three genes(Nl51、Nl76、Nl20369) were significant difference between the host varieties and the expression level of two genes(Nl32990、Nl42468) were significantly decreased of IR56 population in IR56 rice variety. We speculated that these genes may be associated with BPH of IR56 population adapt to IR56 resistant rice. Whether these genes associated with the change in BPH, we need further research to study genic functions and verify the relationship between genes and the change of BPH virulene.