欧洲报春细胞液pH对花色形成的作用机理初探

Effects of Cell Sap pH on the Flower Color Formation in Primula vulgaris

为研究欧洲报春花瓣细胞液p H对花色形成的作用机理,以粉、红、白、黄、蓝5个花色欧洲报春的花瓣为材料,采用便携式色差仪、平面型pH计以及UPLC技术对其花色值(CIE L*a*b*)、细胞液p H值及花色素的成分及含量进行测定。结果表明,细胞液pH值以红色花瓣最低(5.07),粉、白、黄色花瓣次之,蓝色花瓣最高(6.33)。红、粉、蓝色品种花瓣中花青苷含量较高,白色和黄色品种花瓣中类黄酮含量最高。同时花瓣细胞液pH值与蓝色品种特有的5种花青苷(飞燕草素3–葡萄糖苷、报春色素苷、矮牵牛–7–甲氧基–3,5–二葡萄糖苷、锦葵素–3–葡糖苷和报春色素–4’–丙二酸酯)的含量呈显著正相关。红、粉和蓝色品种花瓣花色素提取液的颜色随着外界缓冲液pH的增大而逐渐变浅,并最终变为黄色;在可见光区的最大吸收波长发生红移。通过分析可能调控欧洲报春pH的6个基因表达量及其与花瓣细胞液pH值的相关性,发现PvPH4在蓝色花瓣中显著高表达,并与花瓣细胞液p H值呈显著正相关;其编码的蛋白质保守结构域是属于Ca2+/H+逆向转运超家族(Cha Asuperfamily)的caca2,并且蛋白质三级结构建模显示其与液泡钙离子转运体相似度最高(39%)。因此推测PvPH4通过编码Ca2+/H+转运跨膜蛋白,影响花瓣细胞液p H值,进而影响花色。

To study the mechanism of cell sap pH on flower color formation in Primula vulgaris,petals of pink,red,white,yellow and blue were used as materials. The flower color indices were measured using CIE L*a*b* system,and the cell sap pH values in different colored petals were measured by planar pH meter. Furthermore,the composition and content of anthocyanin,flavonoids and carotenoid were assessed qualitatively and quantitatively by UPLC. And then,the color change and absorbance change of cell sap in different external buffer solutions were observed using UV spectrophotometer. The results showed that cell sap pH value was the lowest in red(5.07),followed by pink,white and yellow,and the highest in blue petal(6.33). The anthocyanidins were accumulated abundantly in pink,red and blue petals while the contents of flavonoids were the highest in white and yellow petals. Meanwhile,the cell sap pH values showed significantly positive correlations with the content of delphinidin-3-glucoside,hirsutin,petunidin-7-methoxy-3,5-diglucoside,malvidin-3-glucoside and hirsutin-4’-malonate,which all were specific in blue petals. Moreover,there was a bathochromic shift in the visible light region of the maximum absorption peak of pink,red and blue cultivars’ petal pigment extracting solution,and the color of pigment extracting solution of pink,red and blue petals was fading gradually with the increasing of buffer solution pH,and then turned into yellow. In addition,based on the results from expression profiles,the correlation between cell sap pH and gene expression,and the bioinformatics analysis,the relative expression of PvPH4 in blue petals was significantly higher than those in the other four colored petals. Furthermore,the relative expression of PvPH4 showed significantly positive correlation with cell sap pH. The conserved domain of PvPH4 was caca2,which belonged to Cha A superfamily. And the tertiary structure modeling of the protein showed that the similarity to the vacuolar calcium ion transporter was 39%. Thus,PvPH4 may play a role on flower color by encoding vacuolar calcium ion transporter to influence the petal cell sap pH.