猕猴桃Aux/IAA基因家族的鉴定与表达

Identification and Expression Analysis of Aux/IAA Gene Family in Actinidia chinensis

在猕猴桃全基因组范围内鉴定生长素/吲哚乙酸(Aux/IAA)基因家族,利用生物信息学方法分析其理化性质、结构特征及共线性关系等,并采用实时荧光定量PCR分析Aux/IAA家族基因在不同组织及部分家族成员在外源激素胁迫下的表达模式,为揭示该家族基因在猕猴桃发育过程中的功能奠定基础。结果表明:(1)猕猴桃基因组含有50个Aux/IAA家族基因,编码氨基酸序列介于125~391 aa,蛋白分子量介于14.06~42.48 kD,等电点介于4.33~9.51;Aux/IAA家族基因不均匀的分布于21条不同染色体上,且分布最多的23号染色体上含有11个基因;聚类分析将其分为9个亚族。(2)大部分Aux/IAA家族基因含有4个不同的保守结构域,多数成员均含有Ⅱ、Ⅲ和Ⅳ结构域,部分基因缺失Ⅰ结构域;基因结构分析表明该家族基因包含1~5个内含子;基因组内序列分析发现该家族基因含有23对重复基因对,包括20对片段重复和3对串联重复;与拟南芥的组间共线性分析发现有36个基因与拟南芥基因存在共线性关系。(3)亚细胞预测显示该家族基因大部分定位于细胞核;启动子顺式作用元件分析发现该家族启动子包含光、激素以及响应生物与非生物胁迫等相关作用元件。(4)实时荧光定量PCR分析表明,Aux/IAA家族基因有组织表达特异性,各成员对外源激素响应的时间和强度不同,绝大多数基因在激素处理的早期下调表达,而AcIAA1a和AcIAA18a相对表达量呈现上调表达,响应模式的差异也说明了Aux/IAA家族各个基因在调控猕猴桃发育过程中功能上的差异性。研究认为,猕猴桃Aux/IAA家族基因具有功能多样性,且存在基因复制现象的基因部分表现出组织表达模式相似性,推测在功能上可能有冗余,在进化过程中该基因可能受到环境胁迫而导致序列的缺失或基因复制。

The Actinidia chinensis Aux/IAA gene family was identified and analyzed by bioinformatics in this study.Their physicochemical properties,structural characteristics,synteny relationships were analyzed by bioinformatics,tissue-specific expression patterns and exogenous hormones stress responses were also analyzed by qRT-PCR,which lay the foundation for elucidation the biological function of Aux/IAA family during kiwifruit development.The results showed that:(1)50 Aux/IAA candidate genes were identified in the A.chinensis genome and they were located on twenty-one chromosomes,and with Chr 23 residing the largest number of 11 Aux/IAA genes(AcIAAs).The amino acid size,molecular weight,and isoelectric point ranged from 125-391 aa,14.06-42.48 kD,4.33-9.51,and 0-5,respectively.Phylogenetic analysis divided these genes into nine subfamilies.(2)Most AcIAAs contained 4 different conservative domains,most of the members containⅡ,ⅢandⅣdomains,and some genes lackⅠdomain.There were 1-5 introns in the AcIAA genes based on the gene structure analysis.Also,23 pairs of AcIAA genes were found underwent segment duplications,which including 20 pairs of fragment repeats and 3 pairs of tandem repeats.Moreover,thirty-six pairs orthologous gene were observed between A.chinensis and Arabidopsis.(3)Stress responses,hormone response and tissure specific related cis-elements were abundant in the promoter region of the AcIAA genes.Subcellular localization analysis indicated that most AcIAA located in the cell nuclear.(4)qPCR analysis showed AcIAAs showed tissue-specific expression,and differential response time and intensity under exogenous hormones treatment.Most of the genes were down-regulated at the early stage of treatment,while the gene AcIAA1a and AcIAA18a were up-regulated.The difference of response mode showed that the Aux/IAA family genes may had different functions during the regulation of A.chinensis development.The research suggests that Aux/IAA family genes have functional diversity in A.chinensis,and some of the genes with gene duplication show similarity in tissue expression patterns.It is speculated that there may be redundancy in function of Aux/IAA genes,or gene sequence deletion or gene duplication due to environmental stress in the evolutionary process of A.chinensis.