Comparative Genomic And Expression Analysis Of The WRKY ? Gene Family In Poplar, Grape, Arabidopsis And Rice

WRKY ? genes have significant functions in regulating plant development and resistance.In plant,WRKY gene family has been studied in many species,however,there still lack a comprehensive analysis of WRKY ? genes in the woody plant species poplar,three representative lineages of flowering plant species are incorporated in most analyses: Arabidopsis,Vitis vinifera and Oryza sativa.Populus,as a large and long-lived woody plant,had a different life history compared with Arabidopsis,grape and rice,and is likely to be more complex with respect to development and gene regulation networks.In this study,the four species of WRKY ? were analyzed,a comprehensive analysis including their chromosomal location,phylogeny,gene structure,conversed motifs,conserved microsynteny and gene duplication,the Ks and the expression profiling analysis of poplar WRKY ? genes were also performed.Through the research we obtained following results:1.We first identified members of the WRKY ? gene family in Populus,Vitis vinifera,Arabidopsis and Oryza sativa.Although the distribution of the WRKY ? genes were diverse,their genetic features and biochemical properties apparently tended toward identify.Physical parameters including length,molecular weight,and isoelectric point for each of the predicted WRKY ? protein were tended toward identify.2.A multiple sequence alignment of the 57 WRKY ? genes were performed and then an unrooted phylogenetic tree were constructed.The result indicated that the WRKY ? proteins can be divided into four clades.Based on the phylogenetic analysis,two pairs of orthologous genes were identified among the WRKY ? genes: PtrWRKY54/ VvWRKY42,and PtrWRKY30/ VvWRKY52.Most genes in the WRKY ? gene family are represented by paralogous pairs.3.We generated exon/intron organization maps from the coding sequences of each WRKY ? gene.These genes contain different numbers of exon/intron,and the exon/intron structure of some orthologous and paralogous gene pairs were also different.This data indicated that both exon/intron loss and gain has occurred during the evolution of the WRKY ? gene family.The motif analysis obvious that some of the closely-related proteins share common motif profiles.This analysis predicted that all WRKY ? genes contain the functional divergence.4.By microsynteny analysis,we found that the duplicated regions were more conserved between poplar and grape than Arabidopsis or rice.Each intraspecies were independent duplication events except to the whole-genome duplication event.We dated their duplications by Ks analysis of poplar WRKY ? genes and demonstrated that all the blocks were formed after the divergence of monocots and dicots.Our results indicated that the majority of WRKY ? genes of poplar were expanded by large-scale gene duplication.Strong purifying selection has played a key role in the maintenance of WRKY ? genes in poplar.5.Populus trichocarpa(Nanlin 95)tissue expression pattern analysis of the WRKY ? genes in poplar revealed that five(PtrWRKY30?-54?-55?-63?-90)were most highly expressed in the xylem.We also performed quantitative real-time reverse transcription PCR analysis of WRKY ? genes in poplar treated with salicylic acid,polyethylene glycerol 6000 and abscisic acid to explore their stress-related expression patterns,the results demonstrated that most of the PtrWRKY? were obviously inducible.