Identification Of Chrysanthemum Gene Expression Profile And Microrna Involved In Aphid Resistance

Chrysanthemum(Chrysanthemum morifolium (Ramat.) Kitamura) is one of ten traditional famous flowers in China and one of four cut flowers in the world, enjoying a major share of the cut flower and flowering pot plant market worldwide. However, with the continuous expansion of the cut chrysanthemum production scale level and production intensification increasing, the chrysanthemum is rather susceptible to infection by a variety of pests, diseases and viruses, which can result in a loss in quality of the plant.Aphids are a major class of phloem feeders distributed worldwide. The infections usually take place in chrysanthemum from its seedling establishment to flowering stages. The aphids have the capability of highly efficient colonization and settlement, due to several biological characteristics. The economic impact of aphids is not just related to their direct removal of assimilate, but also their indirect action as vectors of viral pathogens which can result low and small plants, yellow leaves and leaf curling. Currently, chemical control was the major strategy for crop protection. However, the chemical pesticide not only incurred the economic and the environmental cost but also resulted in pesticide residue. Thus, it is important to place emphasis on the aphid resistance mechanisms exploring and the development of effective, non-chemical control strategies for managing insect pests affecting agronomic crops.In this study, we analyzed the regulation mechanisms involved in defense response to aphid and wounding by mRNA transcriptome and small RNA transcriptome, which was sequenced via Illumina high-throughput sequencing technology. We got a large amount of mRNA and small RNA sequence data and established the mRNA and small RNA transcriptome database of chrysanthemum leaves in aphid stress, wounding stress and normal condition. Furthermore, we found some transcription factor and microRNA involved in aphid-resistance such as WRKY and micro319a, micro393b-5p. The purpose of this study was to explore the aphid resistance mechanisms and find genes involved in resistance responses of chrysanthemum to aphid.it is important for the new aphid-resist germplasm of chrysanthemum development via genetic engineering.The main conclusions were as follows:(1) In the digital transcriptome database of chrysanthemum leaves in aphid stress, wounding stress and normal condition, there are7,215,860and7,319,841and7,363,292reads respectively. Comparison with non-aphid infested plants, aphid transcriptome database of infested plants chrysanthemum leaves, there are1,157differentially expressed genes in aphid stress, the number of up-regulated genes and down-regulated genes were995,162respectively; Comparison with non-aphid infested plants, mechanical stress transcriptome database of wounding chrysanthemum leaves, there are527differentially expressed genes in aphid stress, the number of up-regulated gene and down-regulated gene were487,40respectively; Comparison with mechanical wounding plants, aphid transcriptome database of infested plants chrysanthemum leaves, there are340differentially expressed genes in aphid stress, the number of up-regulated gene and down-regulated gene were213,127respectively.(2) Gene ontology enrichment analysis of differentially expressed genes show that there are2504,1013and666unigenes can be functionally annotated in non-aphid infested plants vs aphid stress plants, non-aphid infested plants vs wounding stress plants wounding stress plants vs aphid stress plants pair wise samples and KEGG pathway enrichment analysis of differentially expressed genes show that there are76,64and40pathway enriched in these three pair wise samples.(3) In small RNA annotation results of the three specimens, there are222,225and223conserved microRNA species. Differential expression analysis of these known microRNA species show that80microRNA differentially expressed, which contain39up-regulate and41down-regulate microRNA between aphid-stressed sample and the control; there are99microRNA differentially expressed, which contain49up-regulated and50down-regulated microRNA between wounding-stressed sample and the control; there are79microRNA differentially expressed, which contain39up-regulated and40down-regulated microRNA between aphid-stressed sample and wounding-stressed sample.(4) Target prediction of the Known microRNA differentially expressed were analyzed by Mireap.There are26differentially expressed microRNA whose target gene can be predicted between aphid-stressed sample and the control. The numbers of target gene and target location were141and145respectively. There are38differentially expressed microRNA whose target gene can be predicted between wounding-stressed sample and the control. The numbers of target gene and target location were156and159respectively. There are27differentially expressed microRNA whose target gene can be predicted between aphid-stressed sample and wounding-stressed sample. The numbers of target gene and target location were108and110respectively.