Identification And Characterization Of Ethylene Responsive Factors In Fragaria Vesca

Ethylene responsive transcription factors(ERFs)play important roles in plant development,hormone signaling,as well as in the response to biotic and abiotic stresses,which is a subfamily of AP2/ERF transcription factors superfamily.ERF transcription factors have already been identified and systematically analyzed in arabidopsis,rice and poplar.However,ERF gene family is few reported in strawberry.Moreover,the sequenced genome of strawberry will support the molecular research of strawberry.As strawberry is a nutrient-rich fruit which has economic value,researchs of ERF gene family in strawberry could do great contribution to the strawberry breeding or offer scientific guidance to improve strawberry stress resistance.In this study,according to identified ERF family genes in arabidopsis,a comprehensive computational analysis identified in strawberry(Fragaria vesca)via bioinformatics.A total of 91 ERF genes were identified and divided into 11 groups based on topology of phylogenetic tree.Moreover,both the motif analysis of ERF protein and the classify of ERF family genes in arabidopsis support the grouping of FvERF genes in strawberry.We further classified ERF family genes into two type based on the relationship between FvERFs and AtERFs:I)one FvERF gene formed a single-gene branch,II)a cluster of FvERF genes formed a branch.We performed chromosome location and MCScan analyses to investigate possible expansion mechanisms of ERF gene.As a result of these analyses,Type II FvERF genes could be traced back to specific tandem duplicate,segmental duplicate and dispered duplicate,suggesting that the three duplicate mechanism was an main contributor in the specfic expansion of the ERF gene family.What is interesting is that among the Type I FvERF genes that did not undergo recent expansions,some of which reside in tandem repeats on the chromosomes as well.These FvERF genes could be derived from ancient tandem duplicates before the split of A.thaliana and F.vesca,and were maintained in tandem in F.vesca.At least 31(34.1%of all 91)FvERF genes could be traced back to ancient tandem duplicates,suggesting that tandem duplication was also play an important role in the ancient expansion of the ERF gene family.Analysis of motif distributed in FvERF proteins and intron/exon structure FvERF genes show that ancient tandem FveERFs have diverged at the level of protein structure and gene structure,which may evolved different function.To investigate the expression profiles of FvERF genes,we analyzed their transcriptome data in flower and early-stage fruit development.Therefore,the FvERF genes might have more extensive expression during the development of flowers than early-stage fruits.In addition,either the FvERFS among different groups or the ones within a same group showed different expression patterns at various stages or tissues.This suggested that even the members of a same FvERF group appeared to play differential roles during reproductive development of F.vesca.Compared to the non-tandem/clustered FvERFs within same groups,a higher proportion of tandem or clustered FvERFs showed similar expression patterns in flower or early-stage fruit development.In addition,we found that tandem and clustered genes were enriched in the FvERFs lowly expressed in most stages/tissues.However,the clustered FvERFs,including the lineage-specific tandem ones,did not displayed higher proportion than the ancient tandem FvERFs.To further investigate the expression of the tandem FvERFs in fruit ripening of F.vesca,we selected 14 genes,including 5 lineage-specific tandem and 9 ancient tandem FvERFs,for qPCR analyses in four ripening stages.The qPCR results suggested that the tandem FvERF genes were consistently expressed throughout the fruit development and ripening stages of F.vesca,and the overall expression levels of the lineage-specific tandem FvERFs were lower than those of the ancient tandem FvERFs.ERF transcription factors play important roles in response to abiotic stresses.We treated the F.vesca seedlings with cold and dehydration stresses and characterized the expression of the above 14 lineage-specific and ancient tandem FvERFs.As a result,the overall expression levels of the lineage-specific tandem FvERFs were much lower than those of the ancient tandem FvERFs.Furthermore,the lineage-specific tandem FvERFs exhibited similar response patterns to cold or dehydration stress,whereas the members in each of all the four ancient FvERFs tandems displayed different expression variations under at least one of the two stress conditions.In summary,we identified and classify ERF gene family in strawberry and reveal expression pattern of ERF gene in flowers and fruit,which laid the foundation for the futher study of ERF gene in strawberry.In addition,we found that tandem genes are constantly low-expressed duiring fruit development and maturation,but increased or decreased under abiotic stress,indicating that tandem replicating genes responded to abiotic stress.lt provide reference for screen of stress resistance gene in strawberry.