柑橘扩张蛋白(EXP)基因家族的鉴定及其在橙类汁胞膨大中的表达模式

Identification of the citrus expansin(EXP)gene family and its expression patterns during orange juice sac expansion

以柑橘属橘类(克里曼丁橘)、橙类(甜橙)、柚类(晚白柚)为研究对象,应用生物信息学方法对柑橘扩张蛋白(EXP)基因家族成员进行鉴定,对其进化发育、结构特征、顺式作用元件和共线性进行分析;研究‘黔阳冰糖橙’和‘纽荷尔脐橙’汁胞膨大变化过程中EXP基因的表达模式。结果从橙类(甜橙)、橘类(克里曼丁橘)、柚类(晚白柚)中分别鉴定出30、32和26个扩张蛋白成员;橙类、橘类和柚类分别含有7对、8对和5对片段重复,橘类和柚类分别含有1对串联重复,推测在EXP基因进化过程中以片段重复为主;监测膨大期不同品种甜橙果实发现,‘纽荷尔脐橙’单个汁胞体积显著大于‘黔阳冰糖橙’的,且随着果实的膨大,单个汁胞体积差异逐渐增加;基因表达分析结果显示,CsEXPA6、CsEXPA9、CsEXPA12、CsEXPA15在甜橙果实汁胞组织中高度表达;果实膨大期CsEXPA6和CsEXPA15在‘纽荷尔脐橙’汁胞中的表达量显著高于‘黔阳冰糖橙’的,CsEXPA6、CsEXPA15的表达与汁胞体积呈极显著正相关,推测CsEXPA6、CsEXPA15可能通过调控汁胞膨大影响果实大小。

In this study,three oranges,tangerine(Clementine),orange(sweet orange)and pummelo(Wanbaiyou)were used raw material to identify EXP family members with bioinformatics methods.Their evolutionary development,structural characteristics,cis-acting elements,collinearity and the expression patterns of EXP in the process of juice sac expansion of‘Qianyang bingtang orange’and‘Newhall navel orange’were analyzed.The results revealed that 32,30 and 26 dilatorin members were identified from tangerine(Clementine),orange(sweet orange)and pummelo(Wanbaiyou),respectively.The results of collinearity analysis showed that oranges,tangerines and pummelos contained 7 pairs,8 pairs and 5 pairs of fragment repeats,respectively,while oranges and pomelo contained 1 pair of tandem repeats,respectively,speculating that fragment repeat events played a major role in the evolution of the EXP gene.The monitoring of sweet orange fruits at the expansion phase among different varieties showed that the individual juice sac volume of‘Newhall navel orange’was significantly larger than that of‘Qianyang bingtang orange’.Furthermore,as the fruits expansion,the difference in individual juice sac volume gradually increased.Gene expression analysis showed that CsEXPA6,CsEXPA9,CsEXPA12 and CsEXPA15 were highly expressed in the juice sac tissues of orange fruits.The expression levels of CsEXPA6 and CsEXPA15 in the juice sacs of‘Newhall navel orange’were significantly higher than those of‘Qianyang bingtang orange’during the fruit expansion stage,and the expressions of CsEXPA6 and CsEXPA15 were significantly positively correlated with the increase of juice cell volume,suggesting that CsEXPA6 and CsEXPA15 might affect fruit size formation by regulating juice sac expansion.