De Novo Transcriptomic Resources For Chrysanthemum Nankingense (Nakai) Tzvel.under Waterlogging And Breeding On Waterlogging Tolerance In Chrysanthemum

To gain transcriptomic resources to chrysanthemum and study the response of chrysanthemum to waterlogging on the transcriptome level preliminary,We performed waterlogging stress on Chrysanthemum nankingense(Nakai)Tzvel,and 3,6,12,24,48h after treatment,the samples of roots with waterlogging(J-W)and without(J-CK)were collected,and RNA of each sample was isolated independently.We have created transcriptome libraries of J-CK and J-W through a mixture of different samples,and sequenced with high throughput technology.After that,the filtered reads were assembled by de novo assembly,then,the transcriptome data were obtained and the differentially expressed genes(DEGs)between J-CK and J-W were analyzed.We also performed interspecific hybridization between C.zawadskii,which is tolerant to waterlogging,and C.morifolium 'Nannongyinshan',which is sensitive.The main conclusions as follows:(1)Illumina HiSeqTM 2000 platform was utilized to perform high-throughput sequencing.All 93,334 unigenes with an average length of 473 nt(nucleotide)and 149,184 and 164.392 contig with an average length of 219 and 276 nt respectively,were generated from 51.401,280 and 54,348,864 total primary reads after filtering and assembly.A total of 60,376 transcripts were annotated by comparison with non-redundant National Center for Biotechnology Information(NCBI)protein(NR),non-redundant NCBI nucleotide(NT),clusters of orthologous groups(COG),Gene Ontology(GO),and Kyoto Encyclopedia of Genes and Genomes(KEGG)databases after removing exogenous contaminated sequences.We searched the NCBI protein database with BLAST and found a total of 60,376 unigenes(64.69%)compared to at least one sequence(E-value<0.0001),homology found that existing public data and C.nankingense had the highest homology with species of Vitis vinifera,Ricinus communis,Populus trichocarpa,Glycine max.(2)Based on RPKM method,the research analyses of differentially expressed gene between J-CK and J-W,with 16,901 up-regulated and 14,700 down-regulated.According to GO classification and GO enrichment analysis of DEGs,4 GO terms were significantly enriched,including disaccharide metabolic process and glycoside metabolic process,structural constituent of cell wall and thiamine pyrophosphate binding molecular function.Analysis of KEGG pathway about DEGs found which accounted for the largest proportion of the top four were metabolic pathways,biosynthesis of secondary metabolites,plant-pathogen interaction and plant hormone signal transduction.Then,we analyzed expression of key enzymes gene in hormone signal transduction pathway of ABA and ethylene biosynthesis.Found that expression of 9-cis-epoxycarotenoid dioxygenase and abscisic-aldehyde oxidase gene,the key enzymes in ABA biosynthesis were up-regulated,most of xanthoxin dehydrogenase genes up-regulated too,and 1-aminocyclopropane-l-carboxylate synthase the key enzyme of ethylene synthesis dramatically up-regulated,with unigene40960_All and unigene32112_All fold up more than 12 times.The key enzymes in ABA and ethylene biosynthesis largely up-regulated under waterlogging,it will therefor promote the biosynthesis of ABA and ethylene,which two were proved to involved in responses to waterlogging.(3)Only one hybrid was obtained through interspecific hybridization between C.zawadskii(Herb.)Tzvel.and C.morifolium 'Nannongyinshan'.Morphological characteristics of the plant height,leaf length,leaf width,number of tubular florets and ray florets of the hybrid were between both parents,male specific bands and female specific bands both exist in the hybrid showed by SRAP molecular makers indicate the hybrid was real.The decrease of RWC and chl and the increase of MDA of the hybrid were significantly lower than 'Nannongyinshan',the activity of antioxidant enzymes of the hybrid were higher than 'Nannongyinshan'.It indicated that the hybrid was more tolerant than 'Nannongyinshan'.