猕猴桃几丁质酶基因家族的鉴定和表达特征分析

Identification and Expression Characteristics of Chitinase Gene Families in Kiwifruit

摘要:

为探究几丁质酶基因家族(CHis)的特征和功能，从猕猴桃(Actinidia chinensis)中鉴定得到18个AcCHis基因。系统进化分析表明它们分别聚在GH18和GH19分支，可分为6小组，组内各成员间的保守结构域、基因结构、蛋白质结构具有较高的相似性。AcCHis基因启动子区域的顺式作用元件主要涉及激素响应、非生物胁迫应答和生长发育调控。18个AcCHis基因不均匀分布在12条染色体上，其中有5个基因发生了片段重复。AcCHis的表达可能受到miR172、miR408调控。AcCHis中，GH18与GH19成员在不同组织(成熟果、幼果、叶、茎、花)中的转录差异明显。在猕猴桃果实贮藏过程中，90.9%的GH18成员不表达或表达量较低；而71.4%的GH19成员呈现差异表达，其中猕猴桃果实中AcCHi8在25℃贮藏1周和4℃贮藏1~3周均上调表达，以4 ℃贮藏3周的表达量最大(为对照的188倍)，而果实浸泡ABA后在25 ℃贮藏1周的表达下调，推测AcCHis基因可能参与采后果实贮藏软化过程。

关键词:几丁质酶;猕猴桃;基因鉴定;基因表达

Abstract:

In order to explore the characteristics and functions of the chitinase gene family (CHis), eighteen AcCHi genes were identified from Actinidia chinensis. The phylogenetic analysis showed that they clustered in GH18 and GH19 clusters and were divided into 6 groups with high similarity in conserved domain, gene structure and protein structure among the members. The cis-acting elements of AcCHi genes promoter region were mainly involved in hormone response, abiotic stress response and growth and development regulation. The 18 AcCHi genes were unevenly distributed on 12 chromosomes, and 5 of them had fragment duplication. The expression of AcCHis might be regulated by miR172 and miR408. In AcCHis, the transcription of GH18 members and GH19 members in different tissues, such as mature fruit, young fruit, leaf, stem, flower, was significantly different. During the storage of kiwifruit fruit, 90.9% of GH18 members had no or low expression, however, 71.4% of GH19 members showed differential expression. The expression of AcCHi8 in fruits was up-regulated at 25 ℃ for 1 week and at 4 ℃ for 1 to 3 weeks, and the expression of AcCHi8 was the highest at 4 ℃ for 3 weeks (188 times to the control), while the expression of AcCHi8 was down-regulated at 25 ℃ for 1 week after ABA soaking. Therefore, it was suggested that AcCHi genes might be involved in the process of storage and softening of postharvest fruits.

Key words:Chitinase;Actinidia chinensis;Gene identification;Gene expression