Evolution And Expression Of The CKX Gene Family Identified From Fragaria Vesca

Fragaria vesca,as well known as wild strawberry,is a diploid plant(2 n = 2 x =14).Its genome is very small that is only about 240 MB.Because its growth cycle is short and it is easy to regenerate,it can be an ideal material for studies on the cultivated strawberry.So we studied strawberry genome which provides a huge advantage for strawberry breeding.In this study,we studied the composition and expression patterns of cytokinin oxidase(CKX)gene family in the Fragaria vesca variety ’Hawaii 4 ’.The main results are as follows:1.We defined eight FvCKX gene members,and named them as FvCKX1-FvCKX8 according to Liu et al.The length of the eight FvCKX genes ranged from 2008 to 3408 bp.They unequally distributed on four strawberry chromosomes.The coding sequences of all the FvCKX genes were disrupted by introns,with numbers varying from three to five.The predicted numbers of glycosylation sites in these eight genes were diverse,ranging from one to six.These FvCKX genes also had different numbers of amino acids,and their molecular weight,isoelectric point(pI)were also different.These FvCKX genesencoded polypeptides of 441 aa to 623 aa with predicted molecular weights ranging from 48648.5 KD to 69455.2 KD.The theoretical PI ranged from 5.01 to 8.60.Our data indicated that some motifs were all distributed in the eight genes such as motif 1,motif 2 and motif 9,but some only exsits in some of them.,for example,motif 15 only exists in genes FvCKX4 and FvCKX5.The FvCKX1/FvCKX2 and FvCKX6/FvCKX7 these two pair genes have the same motifs respectively.We also studied the cis-elements in promotersof eight FvCKXs(FvCKX1-FvCKX8)and seven AtCKXs(AtCKX1-AtCKX7).A series of cis-elements related with stresses and hormones were found in the promoter regions.The cis-elements of each gene were obviously different in their numbers and types.The different cis-elements might result in different functions in response to abiotic stresses and hormones.2.qRT-PCR results in the different tissues of Fragaria vesca showed that the expression patterns ofFvCKX gene family have differences.FvCKX4was mainly expressed in the reproductive organs(flowers,young fruit and mature fruit),especially in young fruit;while FvCKX5was mostly expressed in the vegetative organs(root,stem,leaf and stolon),especially in the root.TheFvCKX1,FvCKX6 and FvCKX8 genes are expressed in all the tissues,but their expression levels vary;and the expression of the three genes FvCKX2,FvCKX3 and FvCKX7is very low among all the tissues.3.According to the qRT-PCR results under the abiotic stresses,FvCKX gene expression patterns were different.Under ABA treatment,each member of FvCKX1-FvCKX8 in the leaves has an increased expression with different extents;the expression of FvCKX1,2,5 and 6 were decreased in the roots.Among all the FvCKX genes,the biggest expression change in response to all the stress treatments in leaves and roots was appeared as FvCKX6.Under the continuous high salt stress,the expression levels of FvCKX6 in leaf and root were significantly decreased.In addition,FvCKXl and FvCKX8 were also sensitive to the various stresses.The expression levels of the three genes FvCKX2,3 and 7 were weak under all the abiotic stresses,indicating that these genes may not beinduced by the above stress conditions,or they may be pseudo genes which have no function.Subsequent experiments are needed for verification.