Effect Of Aluminum Ions On Hydrangea Anthocyanin Synthesis And HmCHS Gene Expression

Hydrangea macrophylla is a ornamental shrub of Saxifragaceae family.Because of its bright color and great flowers of fine traits,it has become a popular materials in landscaping and floral decoration.At present,there are a large number of literature to prove that change of H.macrophylla sepal from red to blue is mainly caused by the free aluminum ions in the substrate.The study of H.macrophylla sepal color is also focused on the analysis of anthocyanin composition and the effect of aluminum ions on the physiological characteristics of the growth.So far,research on effect of aluminum ions on hydrangea anthocyanin synthesis and relational gene expression has not been reported,among hydrangea different color and different tissues anthocyanin related genes also have not been reported.This experiment is to study the effect of aluminum ion on hydrangea sepal color through different aspects,to provide a theoretical basis for the molecular breeding for color of H.macrophylla.In this experiment,3 cultivars H.macrophylla ‘Broad Blue' ‘Magical Jewel'‘Schneeball' were used as experimental materials,aluminum ions were applied to the treatment group and the substrate pH was adjusted around 4.5.Water was applied to the substrate of the control group and the pH was 7.0.The effect of aluminum ions on the phenotype of sepal color,the content of anthocyanin and the relative expression of HmCHS gene in different growth stages were analyzed by RHS Colour Chart,anthocyanin extraction,RNA extraction and real-time fluorescence quantitative PCR.As well as,the difference of anthocyanin content and gene expression among 3 cultivars,the relational gene expression between sepal and leaves,the genetic relationship of H.macrophylla with other species were analyzed and compared.The main conclusions are as follows:(1)2 colored cultivars ‘Broad Blue' and ‘Magical Jewel',after treatment with aluminum ions,were blue sepal;in the neutral control condition were red sepal.‘Schneeball' do not change the color keep the stable white sepal.It is proved that aluminum ion is an important factor affecting the color change of H.macrophylla.(2)2 colored cultivars were affected by aluminum ions,promoted the ‘Broad blue' but suppressed the ‘Magical Jewel' anthocyanin synthesis at the same time.‘Schneeball' were not affected by aluminum ions as a white sepal cultivar.The results showed that the effect of aluminum ion on the synthesis of anthocyanins was different.The possible reasons were transcription factors and related structural genes could affect the synthesis of anthocyanins,and it was also possible that the absorption of aluminum ions in different varieties was inconsistent.(3)The effect of aluminum ion on the HmCHS gene of the two varieties of ‘Broad blue' and‘Magical Jewel' was inhibited,but there was no significant effect on the ‘Schneeball'.It is estimated that aluminum ion may specifically act on the expression of HmCHS gene of colored cultivars in a certain period.This may be related to the mechanism which anthocyanins synthesis is regulated by multiple genes.(4)Aluminum ions could promote the expression of HmCHS in leaves of ‘Broad blue',which had little effect on the expression of ‘Magical Jewel' and ‘Schneeball'.Colored cultivars with different performance may be anthocyanin induction mechanism in leaves of different cultivars is different.(5)The difference of HmCHS expression among 3 cultivars in the initial period was not significant,probably because the HmCHS expression in this period was not regulated by the external environment.With the flowers unfolded,colored cultivars HmCHS expression increased and white variety downed.(6)The expression of HmCHS gene in the sepal was always higher than that in the leaf and expression of HmCHS in the sepal was continuously up-regulated,the leaves decreased in 2colored cultivars ‘Broad blue' and ‘Magical Jewel'.In white cultivar,the expression level of HmCHS in the leaves was higher than that in the sepal.Maybe the HmCHS in the sepal was regulated by the feedback inhibition of the product,which inhibited the expression of HmCHS in the sepal.Sepal and leaves within the HmCHS expression were graduallydecreased to zero in ‘Schneeball'.(7)By comparing the amino acid sequences of CHS gene in ten species out of Hydrangea,it was found that Hydrangea macrophylla HmCHS gene was more closely to Rosa chinensis RcCHS gene and Rhododendron simsii RsCHS gene in genetic relationship.And it has relatively distant relationship with Dendranthema morifolium and Arabidopsis thaliana.