Digital Gene Expression Profiling Of Genes Related To Peanut Root-knot Nematode Resistance

Peanut is an important oilseed crop, edible and cash crop in the world.Peanut planting area is less than that of the rapeseed, and ranks second among oilcrops in our country. Peanut root-knot nematode disease (peanut nematode disease) is worldwidely distributed, and has occurred in almost all the countries and regions of growing peanut.Peanut nematode disease has occurred from south to north in china, and it is more serious in Shandong, Liaoning and Hebei provinces. Peanut nematode infestations cause devastating yield losses in normal20-30%,serious highly up to70-80%, even complete loss. In order to investigate the molecular machnism of peanut root-knot nematode resistance, we used the high-throughput tag-sequencing (Tag-seq) technology of Solexa Genome Analyzer platform to anlylize6peanut samples (D995C,D995I,D9910I,H225c,H225I,H2210I). The main results were as follows:1. The primary analysis showed that,4728183,4859235,4974812,4704398,4665294and4962367raw tags were obtained from digital gene expression libraries of H225C、D995C. H225I、D995、H2210I、and D9910I, respectively. After filtering dirty tags (low quality tags) from raw data,4499637,4438410,4770791,4520810,4508944and4731587clean tags were obtained,respectively. We analyzed the changes between distribution of total tags and distinct tags, discovering that small number categories of mRNA had very high abundance, while the rest majority retained at a very low level of expression. This conclusion accorded with that heterogeneity and redundancy, which were two significant characteristics of mRNA expression.2. Detection of DEGs(Differentially Expressed Genes). Analysis of DEGs showed that the number of DEGs between H225I and H2210I was4513, which was the most among the6digital gene expression libraries. And2885of those was upreulated and1628was downregulated.4225DEGs were obtained from H225I and H2210I, upregulated genes were2398, and downregulated genes were1827. DEGs between D995C and D995I were the least,799, among the6digital gene expression libraries, upregulated genes were390, and downregulated genes were409. It was observed that root-knot nematode infection increased with period after inoculation. As a result, stress of peanut roots and the total number of DEGs increased. This indicated that genes related to root-knot nematode resistance were initially expressed.3. Functional analysis of DEGs(differentially expressed genes)1) GO Functional Enrichment Analysis for D995C and D9910I DEGs was that differentially expressed genes significantly enriched ribonucleoprotein complex and structural molecule activity; Pathway Enrichment Analysis for D995C and D9910I DEGs was that differentially expressed genes significantly enriched ribosome metabolic pathways.2) GO Functional Enrichment Analysis for H225C and H2210I DEGs was that differentially expressed genes significantly enriched ribonucleoprotein complex organelle lumen,intracellular organelle lumen, ribosome ribosomal subunit,structural molecule activity,antioxidant activity, nuclear part,response to chemical stimulus,response to organic substance, response to endogenous stimulus,response to hormone stimulus and response to stress. Pathway Enrichment Analysis for H225C and H2210I DEGs was that differentially expressed genes significantly enriched ribosome metabolic pathways, Plant-pathogen interaction, Amino sugar and nucleotide sugar metabolism and Arginine and proline metabolism.3) GO Functional Enrichment Analysis for D9910I and H2210I DEGs was that differentially expressed genes significantly enriched organelle part, nuclear lumen,organelle lumen, intracellular organelle lumen,organelle membrane membrane-enclosed lumen,ribosome,ribosomal subunit,response to chemical stimulus,response to stimulus,response to organic substance, polyamine metabolic process,ethylene metabolic process,polyamine biosynthetic process, cellular biogenic amine biosynthetic process,response to endogenous stimulus,response to stress,response to metalion,response to inorganic substance,structural molecule activity, ribonucleoprotein complex and structural molecule activity; Pathway Enrichment Analysis for D9910I and H2210I DEGs was that differentially expressed genes significantly enriched ribosome metabolic pathways.4. Analysis of relevant resistant gene of peanut root-knot nematode showed that, After nematode infection, the number of RKN-induced transcripts coding for proteins was involved in plant stress/defense response, and abundancy of their expression was relatively higher in the H22than in the D99roots. But the number of RKN-induced transcripts coding for patatin proteins were comparatively higher in the D99than in the H22roots. Addtionaly, the number of RKN-induced transcripts coding for catalase proteins was higher in the H22. Enhanced catalase activity during a susceptible host-pathogen reaction probably compromises the H2O2-mediated growth and progress of hypersensitive disease resistance response initiated through cell wall-localized oxidative burst. In the H22and D99roots,11genes participated cytokinin regulated. Cytokinins had improved plant resistance of disease, coldness and drought in plant.4genes coding for transporter didn’t completely express in the D99roots,but express upregulatedly in the H22. This result indicated that the4genes may involded in establishment and formantin of giant cells.